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1
Deerenberg, Sirik. "Stereogenic phosphorus containing phosphine-phosphite ligands in asymmetric catalysis". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/57171.
Testo completo
2
Gudmunsen, David. "The synthesis, coordination chemistry and catalytic applications of phosphinite, phosphonite and phosphite ligands containing perfluoroalkyl substituents". Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30048.
Testo completoAbstract (sommario):
A review is presented of the development and application of liquid-liquid biphase systems in homogeneous catalysis and the concept and application of fluorous biphase systems (FBS) in catalysis. Novel monodentate phosphorus(III) ligands of general formula PhxP(OC6H4-4-C6F,3)3.x and PhCHF-* (x = 0, 1 or 2), and the phosphite ligands P(OC6H4-4-C8Fl7)3, P(OC6H4-4-C10F2i)3, P(OC6H4-3-C6F13)3 and P(OC6H4-2-C6Fi3)3 have been synthesised and fully characterised by 'H, 19F and 3,P{1H} NMR spectroscopy, mass spectrometry and elemental analysis. The monodentate phosphinite, phosphonite and phosphite ligands (L) have been reacted with a variety of transition metal complexes to form complexes of the type cis- and trans- MC 2L2 (M = Pt, Pd), cw- PtCl2(PEt3)L , M(n5-C5Me5)Cl2L (M = Ir, Rh) and RI1CIL3 . The complexes have been isolated and characterised using analytical techniques including H, 19F and 31P{!H} NMR spectroscopy, mass spectrometry, IR spectroscopy, X-ray crystallography and elemental analysis. The steric and electronic influences of the perfluoroalkyl substituents on the chemical and physical properties of the metal complexes have been assessed by comparison of their spectroscopic and structural data with that for their related protio complexes. Preliminary catalytic studies involving P(OC6H4-4-C6Fi3)3 as a modifying ligand in the rhodium-catalysed hydroformylation of 1-hexene and 1-nonene under FBS conditions have been undertaken. The influence of the perfluoroalkyl substituents on the rate of reaction, product selectivity and catalyst/product separation has been examined. The synthesis of bidentate phosphonite and phosphite ligands containing perfluoroalkyl substituents has been investigated. The derivatised bidentate phosphonite ligands (C6F13-4-C6H40)2PCH2CH2P(OC6H4-4-C6F, 3)2 and {5,5' - (C6F13)2-2,2,-02C,2H6}PCH2CH2P{2,2,-02C,2H6-5,5,-(C6F13)2} (L-L) have been reacted with transition metal complexes to form coordination complexes of the type PtCl2(L-L) and Rh(u-C1)(L-L)]2.
3
Auckland, Clare. "The dilution of phosphite in rapidly growing plants and how soil and plant phosphate levels interact with phosphite and its ability to control Phytophthora cinnamomi". Thesis, Auckland, Clare (2002) The dilution of phosphite in rapidly growing plants and how soil and plant phosphate levels interact with phosphite and its ability to control Phytophthora cinnamomi. Honours thesis, Murdoch University, 2002. https://researchrepository.murdoch.edu.au/id/eprint/32633/.
Testo completoAbstract (sommario):
The soil borne plant pathogen Phytophthora cinnamomi has irreversibly altered the make-up and diversity of the plant communities found in Australia. Recently, the fungicide phosphite has been used to effectively reduce the impact of this pathogen in natural plant communities. However, little is known (a) about how rapidly phosphite is diluted in the tissues of rapidly growing plants and (b) how soil and plant phosphate levels interact with phosphite and its ability to induce host-resistant responses when challenged by P. cinnamomi. This study examined the effects of different phosphite rates (0, 24 and 48 kg/ha phosphite) applied as a mist application on three size classes of Banksia grand is, as well as the interaction of phosphate status on two Eucalyptus marginata forest vegetation types differing in soil phosphate status with phosphite. It also examined, under controlled glasshouse conditions, the effects different soil phosphate levels had on in planta phosphite and phosphate levels in B. hookeriana, and the subsequent control of P. cinnamomi.
This study was the first to look at the role of phosphate in the soil and the plant, and its interaction with phosphite and the subsequent control of P. cinnamomi in planta. Results from the field trial indicated that phosphate in the soil did not play a role in the reducing the uptake of phosphite by the plant. It did suggest that stem and root colonisation was increased when phosphate in the soil was more plentiful. Further research is needed into this area.
This study was also the first to look at the distribution of phosphite in planta. The highest concentration of phosphite was in the leaves, followed by the stem and then roots. Ph9sphite in the plant tissue was found to increase as the phosphite applied to 5 the plants increased. Plants classed as seedlings showed more phytotoxic symptoms than the intermediate and semi-mature plants. The concentration of phosphite in the roots of the intermediate sized plants was more than double the amount found in the seedling and semi-mature plants. The concentration of phosphite in the whole plant, as well as in the leaves and stems per plant, increased as the plant size increased. This was supported by results that showed that as the dry weight of the leaves increased so did the amount of phosphite in the leaves. The same was seen with the dry weights of the stems and roots that correlated with phosphite in the stem and the roots, respectively.
Lesions and P. cinnamomi colonisation in the stems of non-phosphite treated plants were more than double those in stems of plants treated with 24 and 48 kg/ha phosphite. There was very little difference in the visible lesion lengths and P. cinnamomi colonisation between plants treated with 24 and 48 kglha of phosphite even though plants sprayed with 48 kg/ha phosphite had significantly more phosphite in their tissues than plants sprayed with 24kg/ha phosphite. This suggests that the phosphite in the plant may have been metabolised into another substance and that this substance was acting on the pathogen and/or the plant to reduce colonisation. This was further supported by no observed correlation between phosphite in the plant tissue and the extent of colonisation or visible stem lesion caused by P. cinnamomi. This was contradictory to other results in this study (Chapter 2) that clearly showed that phosphite did restrict the colonisation of the pathogen. Further research is needed into the mode of action of phosphite.
In the glasshouse trial, a non-invasive inoculation technique failed to infect B. hookeriana plants with the pathogen. However, this is likely due to very high ambient temperatures experienced during the trial, since a preliminary trial 18 days earlier resulted in extensive colonisation of all plants inoculated. As phosphate levels increased, stem colonisation by the pathogen increased in the presence of phosphite. There was no difference in the concentration of phosphite in the leaves. As phosphite applied increased, so did the concentration of phosphite in the root tissue.
This study shows that phosphate does interact with phosphite and the subsequent expression of P. cinnamomi, and as phosphate levels increased in planta so did the extent of colonisation by the pathogen. The exact nature of this interaction is still unknown and further research is required to better understand the nature of this relationship.
4
Phung, Quang Linh. "Synthèse de ligands chiraux de type phosphine-phosphite et phosphine-carbène N-hétérocyclique pour la catalyse asymétrique". Rouen, 2005. http://www.theses.fr/2005ROUES033.
Testo completoAbstract (sommario):
La catalyse organométallique est une méthode de choix pour la synthèse de composés chiraux. Afin d'atteindre une selectivité et efficacité élevées en catalyse asymétrique, plusieurs paramètres réactionnels doivent être optimisés, parmi lesquels le choix et la structure du ligand sont sans doute les points les plus importants. Nous avons développé deux familles de ligands bidentates de type phosphine-phosphite et phosphine-carbène N-hétérocyclique. Ces deux séries de ligands possèdent une caractéristique structurale commune, à savoir un centre asymétrique adjacent à la phosphine. Cette proximité du centre stéréogène et de l'atome de phosphore pourrait avoir un effet positif sur l'énantiodiscrimination. Les ligands phosphine-phosphites ont été testés en hydrogénation (ee jusqu'à 84%) et hydroformylation (pas d'induction asymétrique) asymétriques catalysées par le rhodium. Les ligands phosphine-carbènes N-hétérocycliques ont été testés en hydrogénation et hydrosilylation asymétriques catalysées à l'iridium (pas d'induction asymétrique), et avec des résultats prometteurs dans le couplage de Suzuki-MiyauraCatalytic asymmetric synthesis using organometallic reagents has become one of the most active areas of research in modern organic synthesis. To achieve the highest levels of reactivity and selectivity in catalytic enantioselective reactions, several reactions parameters must be optimized. Among them, the selection and design of the chiral ligand is perhaps the most crucial step. We have developed two families of bidentate ligands : phosphine-phosphite and phosphine N-heterocyclic carbene. These two series of ligands have a chiral center to the α-position next to the phosphine moiety. This stereogenic α-position could be of great importance since the phosphorus atom is directly associated with the transition metal in the asymmetric reaction. Phosphine-phosphite ligands were tested in the Rh-catayzed asymmetric hydrogenation (ee up to 84%) and hydroformylation (no asymmetric induction). Phosphine N-heterocyclic carbene ligands were tested in the Ir-catalyzed asymmetric hydrogenation and hydrosilylation (no asymmetric induction), and with promising results in the Suzuki-Miyaura cross-coupling reaction
5
Meiswinkel, Andreas. "Chirale Monophosphite als effiziente Liganden für die asymmetrische Hydrierung". [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968943152.
Testo completo
6
Passays, Johan. "Nouveaux ligands mixtes de type phosphore / carbène N-hétérocyclique : synthèse et applications en catalyse asymétrique". Thesis, Rouen, INSA, 2011. http://www.theses.fr/2011ISAM0008.
Testo completoAbstract (sommario):
Une méthode simple et efficace a été développée pour la préparation de ligands bifonctionnels associant les motifs phosphine ou phosphite d'une part, et carbène Nhétérocyclique(NHC) ou imidazolium d'autre part. Dans un premier temps, une série de ligands diphénylphosphine-carbène chiraux portant un centre stéréogène en a de la phosphinea été développée à partir b-hydroxyesters. Une famille de ligands a ainsi été développée afin d'évaluer l'influence de l'encombrement stérique de différents groupements alkyles en a de la phosphine et de la nature des groupements aromatiques portés sur l'imidazole sur leur activité catalytique. L’étude s’est ensuite étendue à la synthèse de ligands de type dialkylphosphine carbène et phosphite-carbène. Ces différents ligands ont été complexés avec des métaux tels que l’iridium ou le rhodium de manière à en étudier l’activité en hydrogénation asymétriqueA straightforward method for the preparation of new bidentate ligands containing aphosphine or a phosphite and a carbene function was developed. Different phosphorus-imidazolium compounds were prepared according to this method. First, diphenylphosphine-NHC ligands featuring a stereogenic center a to the phosphine were synthesized from b-hydroxyesters. This strategy was then extended to the preparation of phosphite-imidazoliumand dialkylphosphine-imidazolium compounds. Complexation of these phosphorus-NHCligands with different metals like Ir or Rh was performed in order to study there catalytic properties in asymmetric hydrogenation
7
李慧敏 e Huai-min Li. "Photochemical studies of binuclear platinum and rhodium complexes withbridging isocyanide, phosphite and phosphine ligands". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31231603.
Testo completo
8
Sampson, Jacqueline Marie. "The extent of phosporus redox chemistry in west central Florida waters". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4939.
Testo completoAbstract (sommario):
Phosphorus (P) has long been acknowledged as a vital nutrient for living organisms and is a key factor responsible for the fresh water eutrophication. Our understanding of the phosphorus cycle has been limited by: (1) the common assumption that all P in the environment occurs primarily as phosphates and (2) by the limited analytical methods available to identify P speciation. In an attempt to understand the distribution and chemistry of phosphorus within a freshwater system we must be able to identify individual P species. To this end, we used a coupled High Performance Liquid Chromatograph (HPLC) - Inductively Coupled Plasma Mass Spectrometer (ICPMS) to determine concentrations of orthophosphate (+5), phosphite (+3) and hypophosphite (+1) in aqueous samples using methods modified from IC techniques developed by Ivey & Foster (2005) and Pech, et al. (2009) and Atlas et al. (in prep). The identification of different P species provides insight pertaining to contamination, bioavailability and sustainability within a freshwater system.
Thirty-two individual water samples were collected from six different bodies of freshwater in the Tampa Bay area between the months of November 2012 to March 2013. The freshwater samples collected were from river and pond/swamp water locations. Two sampling sites were chosen at each location. At each site, one sample was collected from the water's surface and a second sample was collected from the sediment pore water. When depth was sufficient a third sample was obtained from the midpoint between the surface and sediment.
Analytical results show that redox reactions of P occur in all freshwater samples collected as identified by HPLC-ICP-MS analysis. Our data show that the distribution and concentration of reduced P is controlled primarily by pH, and secondarily by water circulation, ORP and sediment type. Our results also imply biologic influence as a potential primary control of reduced P flux. Additional samples must be collected in order to quantify and differentiate the processes controlling P speciation. The ability to identify P speciation raises many questions concerning the validity of current methods used to measure P; other forms of reduced P may be present. Additional sample analysis will be necessary to determine how and if reduced forms of P affect the P cycle.
9
Horiuti, Toshihide. "Studies on Enantioselective Addition to C=C Bonds Catalyzed by Transition Metal-Phosphine-Phosphite Complexes". Kyoto University, 1997. http://hdl.handle.net/2433/202317.
Testo completo
10
Li, Huai-min. "Photochemical studies of binuclear platinum and rhodium complexes with bridging isocyanide, phosphite and phosphine ligands /". [Hong Kong] : University of Hong Kong, 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12428541.
Testo completo
11
Philippon, David. "Lubrification par la phase gazeuse : tribochimie des additifs phosphorés et boratés". Phd thesis, Ecole Centrale de Lyon, 2007. http://tel.archives-ouvertes.fr/tel-00280892.
Testo completoAbstract (sommario):
La formulation des lubrifiants utilisés dans l'automobile est complexe du fait du nombre important d'additifs mélangés aux huiles de base. Pour orienter le choix des formulateurs, il est non seulement nécessaire de connaître le mécanisme d'action de chaque additif mais aussi les interactions entre ces additifs. Pour mieux appréhender ces mécanismes, une démarche originale a été mise en place dans cette étude. Celle-ci consiste à simuler expérimentalement la lubrification en régime limite par la lubrification en phase gazeuse. Pour cela, des molécules de faible poids moléculaire modélisant les différents constituants d'un lubrifiant ont été introduites sous ultravide. Ce type d'expérience a pu être réalisé grâce au développement d'un nouveau Tribomètre à Environnement Contrôlé (TEC) connecté à un système d'analyse de surface. Cette technique permet de simplifier le système tribologique et d'étudier in situ les tribofilms formés en phase gazeuse par des analyses de surface (XPS/AES). Différentes molécules ont été étudiées : triméthylborate (TMB), triméthylphosphite (TMPi) et triméthylphosphate (TMPa) modélisant respectivement les additifs boratés et phosphorés des lubrifiants de transmission. Cette simulation expérimentale a pu être validée en comparant les résultats en phase gazeuse avec ceux obtenus en phase liquide. Des observations en microscopie optique et des analyses chimiques ont mis en évidence la formation de tribofilms. Les expériences réalisées en présence de TMB ont permis de confirmer les résultats de la littérature sur la formation d'un tribofilm non sacrificiel de borates de type « minéral ». Les expériences réalisées avec les molécules phosphorées ont permis de montrer la différence entre les phosphates et les phosphites, notamment la formation d'un composé de type phosphure de fer en présence de TMPi. Les analyses in situ sur les tribofilms obtenus en présence de TMPi ont permis de déterminer le mécanisme de formation du composé phosphure de fer. La réalisation de mélanges de gaz a permis également de mettre en avant les effets de synergie et d'antagonisme entre les additifs
12
Minguet, Sébastien. "Nouveaux ligands bifonctionnels potentiellement hémilabiles de type phosphite-phosphonate ou phosphite-éther : : synthèse et évaluation en catalyse". Rennes 1, 2005. http://www.theses.fr/2005REN1S026.
Testo completoAbstract (sommario):
Si la coordination métal-ligand est au centre de la catalyse homogène, le processus de décoordination se révèle très important pour permettre l’incorporation de substrats au sein du complexe. Les ligands dits « hémilabiles » facilitent le second processus. Après avoir mené un examen bibliographique approfondi, nous nous sommes orientés vers l’étude de ligands bifonctionnels de type phosphite-oxygène. Deux familles de ligands ont ainsi été développées : les phosphite-phosphonate et les phosphite-éther. Parallèlement, l’utilisation de réactifs optiquement actifs a permis de synthétiser une série de ligands chiraux. Au total, 20 ligands ont été isolés et caractérisés. Ces ligands ont été testés sur la réaction d’hydroformylation du styrène catalysée par des complexes de rhodium. Les ligands phosphite-phosphonate se positionnent parmi les meilleurs ligands bifonctionnels décrits, en terme d’activité et de sélectivité dans ces conditions de catalyse
13
Djiele, Ngameni Patrice. "Phosphane and Phosphite Silver(I) Complexes: Synthesis, Reaction Chemistry and their Use as CVD Precursors". Doctoral thesis, [S.l. : s.n.], 2005. http://archiv.tu-chemnitz.de/pub/2005/0008.
Testo completo
14
au, M. King@murdoch edu, e Michaela King. "The phosphite responsive transcriptome of phytophthora cinnamomi". Murdoch University, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20080526.104656.
Testo completoAbstract (sommario):
Phosphite has been used to effectively control the soil borne plant pathogen Phytophthora cinnamomi in many horticultural crops, forest trees and natural ecosystems. However, the molecular mechanisms behind phosphite action on this pathogen are poorly understood.
Several studies have shown that phosphite inhibits growth and zoospore production of P. cinnamomi and in addition induces significant physiological and metabolic changes in the mycelium. As an approach to understanding the mechanisms and relevance of these changes in the pathogen, the effect of phosphite on gene expression was investigated using microarray analysis. To construct the microarray, RNA was extracted from phosphite-treated (40 ug/ml) mycelium of P. cinnamomi isolate MP 80. The chosen phosphite concentration inhibited the mycelial growth by 70% but provided sufficient mycelium for RNA extractions after 4 days growth at 25C.
The mRNA was reverse transcribed into cDNA and cloned into lambda to construct a library consisting of 2 million pfu of which 80 % were recombinant phage. The inserts were sequenced for a random selection of clones from the library. The nucleotide sequences generated revealed a range of different P. cinnamomi genes being expressed and demonstrated that the cDNA library provided a good representation of the transcripts expressed in P. cinnamomi. The types of genes found to be expressed in the mycelium of P. cinnamomi included genes encoding GTP binding proteins involved in vesicle transport, structural proteins involved in maintaining cell membrane integrity,elicitors, phosphatases and ribosomal proteins.
Over nine thousand cDNA transcripts were randomly selected from the cDNA library and prepared by PCR amplification and purification for microarray construction. Custom made cDNA arrays containing 9216 cDNA transcripts were constructed and probed with RNA from untreated mycelium and mycelium grown in medium with 40 ug/ml phosphite.
Two genes, EF-1 alpha and cinnamomin gene, identified by qRT-PCR as being constitutively expressed were also positioned on the arrays as positive controls. In the process of identifying constitutively expressed genes, qRT PCR revealed that phosphite down-regulated a gene encoding ubiquitin-conjugating enzyme, a component of the ubiquitin/proteasome pathway involved in the removal of abnormal and short lived-regulatory proteins and rate limiting enzymes.
From the arrays a further seventy-two transcripts with altered patterns in gene expression (fold change > 2) were identified. The majority of the cDNA transcripts spotted on the array were down-regulated with changes in gene expression ranging from 2- to 3.5-fold. Thirty-two cDNA transcripts were up-regulated with changes in gene expression ranging from 2- to 16-fold. Characterisation by sequencing revealed that the most highly induced transcripts coded for ADP-ribosylation factors, an ABC cassette transporter and a glycosyl transferase. A transcript encoding a vitamin B6 biosynthesis protein was also identified as up-regulated by 2.9-fold. In contrast, the down-regulated transcripts coded for cellulose synthase I, annexin, glutamine synthetase, metallothionein and an alternative oxidase. The results are discussed in terms of possible roles and mechanism(s) of phosphite action within the mycelium of P.cinnamomi.
This work is the first comprehensive screen for phosphite regulated-gene expression in P. cinnamomi and represents a significant step towards an understanding of the mode of action of phosphite on this organism. This thesis provides valuable information on the molecular interaction between phosphite and P. cinnamomi, which in future studies may stimulate the discovery of novel methods and cellular targets for the control of plant pathogenic Oomycetes.
15
Marsault, Eric. "Diastereoselective synthesis of phosphite triesters and phosphorothioates". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0027/NQ30333.pdf.
Testo completo
16
Marsault, Eric. "Diastereoselective synthesis of phosphite triesters and phosphorothioates". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42091.
Testo completoAbstract (sommario):
The diastereoselective synthesis of phosphite triesters and related phosphorothioate triesters and diesters has been investigated, with the goal of synthesizing diastereomerically pure DNA phosphorothioates.Towards this end, the elaboration of a new heterobicyclic structure, imidazo-oxazaphosphorine such as 56, is reported. This unstable intermediate led to the highly diastereoselective synthesis of simple phosphite triesters upon reaction with various alcohols.
Two new types of sterically hindered chiral oxazaphosphorinanes 135 and 146 were then synthesized from cholesterol and camphor respectively. These structures, derived from $ gamma$-aminoalcohols possessing a tertiary alcohol function, could be isolated and characterized. They revealed very reactive in acidic conditions and led to rearrangements.
Finally, oxazaphosphorinane 188 derived from 1,2-O-isopropylidene-D-xylofuranose, was synthesized and characterized. The introduction of a participating group adjacent to the leaving phosphorothioate group led to the fast release of the phosphorothioate moiety. This new chiral auxiliary was successfully used as a precursor in the diastereoselective synthesis of a T-T phosphorothioate dimer, in a diastereomeric ratio of 28.5:1.* ftn*Please refer to dissertation for diagrams.
17
King, Michaela. "The phosphite responsive transcriptome of phytophthora cinnamomi". Thesis, King, Michaela (2007) The phosphite responsive transcriptome of phytophthora cinnamomi. PhD thesis, Murdoch University, 2007. https://researchrepository.murdoch.edu.au/id/eprint/132/.
Testo completoAbstract (sommario):
Phosphite has been used to effectively control the soil borne plant pathogen Phytophthora cinnamomi in many horticultural crops, forest trees and natural ecosystems. However, the molecular mechanisms behind phosphite action on this pathogen are poorly understood.
Several studies have shown that phosphite inhibits growth and zoospore production of P. cinnamomi and in addition induces significant physiological and metabolic changes in the mycelium. As an approach to understanding the mechanisms and relevance of these changes in the pathogen, the effect of phosphite on gene expression was investigated using microarray analysis. To construct the microarray, RNA was extracted from phosphite-treated (40 ug/ml) mycelium of P. cinnamomi isolate MP 80. The chosen phosphite concentration inhibited the mycelial growth by 70% but provided sufficient mycelium for RNA extractions after 4 days growth at 25C.
The mRNA was reverse transcribed into cDNA and cloned into lambda to construct a library consisting of 2 million pfu of which 80 % were recombinant phage. The inserts were sequenced for a random selection of clones from the library. The nucleotide sequences generated revealed a range of different P. cinnamomi genes being expressed and demonstrated that the cDNA library provided a good representation of the transcripts expressed in P. cinnamomi. The types of genes found to be expressed in the mycelium of P. cinnamomi included genes encoding GTP binding proteins involved in vesicle transport, structural proteins involved in maintaining cell membrane integrity,elicitors, phosphatases and ribosomal proteins.
Over nine thousand cDNA transcripts were randomly selected from the cDNA library and prepared by PCR amplification and purification for microarray construction. Custom made cDNA arrays containing 9216 cDNA transcripts were constructed and probed with RNA from untreated mycelium and mycelium grown in medium with 40 ug/ml phosphite.
Two genes, EF-1 alpha and cinnamomin gene, identified by qRT-PCR as being constitutively expressed were also positioned on the arrays as positive controls. In the process of identifying constitutively expressed genes, qRT PCR revealed that phosphite down-regulated a gene encoding ubiquitin-conjugating enzyme, a component of the ubiquitin/proteasome pathway involved in the removal of abnormal and short lived-regulatory proteins and rate limiting enzymes.
From the arrays a further seventy-two transcripts with altered patterns in gene expression (fold change > 2) were identified. The majority of the cDNA transcripts spotted on the array were down-regulated with changes in gene expression ranging from 2- to 3.5-fold. Thirty-two cDNA transcripts were up-regulated with changes in gene expression ranging from 2- to 16-fold. Characterisation by sequencing revealed that the most highly induced transcripts coded for ADP-ribosylation factors, an ABC cassette transporter and a glycosyl transferase. A transcript encoding a vitamin B6 biosynthesis protein was also identified as up-regulated by 2.9-fold. In contrast, the down-regulated transcripts coded for cellulose synthase I, annexin, glutamine synthetase, metallothionein and an alternative oxidase. The results are discussed in terms of possible roles and mechanism(s) of phosphite action within the mycelium of P.cinnamomi.
This work is the first comprehensive screen for phosphite regulated-gene expression in P. cinnamomi and represents a significant step towards an understanding of the mode of action of phosphite on this organism. This thesis provides valuable information on the molecular interaction between phosphite and P. cinnamomi, which in future studies may stimulate the discovery of novel methods and cellular targets for the control of plant pathogenic Oomycetes.
18
King, Michaela. "The phosphite responsive transcriptome of Phytophthora cinnamomi /". King, Michaela (2007) The phosphite responsive transcriptome of phytophthora cinnamomi. PhD thesis, Murdoch University, 2007. http://researchrepository.murdoch.edu.au/132/.
Testo completoAbstract (sommario):
Phosphite has been used to effectively control the soil borne plant pathogen Phytophthora cinnamomi in many horticultural crops, forest trees and natural ecosystems. However, the molecular mechanisms behind phosphite action on this pathogen are poorly understood.
Several studies have shown that phosphite inhibits growth and zoospore production of P. cinnamomi and in addition induces significant physiological and metabolic changes in the mycelium. As an approach to understanding the mechanisms and relevance of these changes in the pathogen, the effect of phosphite on gene expression was investigated using microarray analysis. To construct the microarray, RNA was extracted from phosphite-treated (40 ug/ml) mycelium of P. cinnamomi isolate MP 80. The chosen phosphite concentration inhibited the mycelial growth by 70% but provided sufficient mycelium for RNA extractions after 4 days growth at 25C.
The mRNA was reverse transcribed into cDNA and cloned into lambda to construct a library consisting of 2 million pfu of which 80 % were recombinant phage. The inserts were sequenced for a random selection of clones from the library. The nucleotide sequences generated revealed a range of different P. cinnamomi genes being expressed and demonstrated that the cDNA library provided a good representation of the transcripts expressed in P. cinnamomi. The types of genes found to be expressed in the mycelium of P. cinnamomi included genes encoding GTP binding proteins involved in vesicle transport, structural proteins involved in maintaining cell membrane integrity,elicitors, phosphatases and ribosomal proteins.
Over nine thousand cDNA transcripts were randomly selected from the cDNA library and prepared by PCR amplification and purification for microarray construction. Custom made cDNA arrays containing 9216 cDNA transcripts were constructed and probed with RNA from untreated mycelium and mycelium grown in medium with 40 ug/ml phosphite.
Two genes, EF-1 alpha and cinnamomin gene, identified by qRT-PCR as being constitutively expressed were also positioned on the arrays as positive controls. In the process of identifying constitutively expressed genes, qRT PCR revealed that phosphite down-regulated a gene encoding ubiquitin-conjugating enzyme, a component of the ubiquitin/proteasome pathway involved in the removal of abnormal and short lived-regulatory proteins and rate limiting enzymes.
From the arrays a further seventy-two transcripts with altered patterns in gene expression (fold change > 2) were identified. The majority of the cDNA transcripts spotted on the array were down-regulated with changes in gene expression ranging from 2- to 3.5-fold. Thirty-two cDNA transcripts were up-regulated with changes in gene expression ranging from 2- to 16-fold. Characterisation by sequencing revealed that the most highly induced transcripts coded for ADP-ribosylation factors, an ABC cassette transporter and a glycosyl transferase. A transcript encoding a vitamin B6 biosynthesis protein was also identified as up-regulated by 2.9-fold. In contrast, the down-regulated transcripts coded for cellulose synthase I, annexin, glutamine synthetase, metallothionein and an alternative oxidase. The results are discussed in terms of possible roles and mechanism(s) of phosphite action within the mycelium of P.cinnamomi.
This work is the first comprehensive screen for phosphite regulated-gene expression in P. cinnamomi and represents a significant step towards an understanding of the mode of action of phosphite on this organism. This thesis provides valuable information on the molecular interaction between phosphite and P. cinnamomi, which in future studies may stimulate the discovery of novel methods and cellular targets for the control of plant pathogenic Oomycetes.
19
Kollehn, Daniel. "Genetic analysis of phosphite sensitivity in Arabidopsis thaliana". Thesis, Kollehn, Daniel (2018) Genetic analysis of phosphite sensitivity in Arabidopsis thaliana. PhD thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/43074/.
Testo completoAbstract (sommario):
Application of phosphite to plants is used to manage oomycete diseases. However, the mode of action is not fully understood and together with a lack of alternative control methods, and increased resistance to phosphite, an in-depth investigation was warranted. Arabidopsis thaliana was used as a model to investigate the response to phosphite by looking at changes to relevant genes by ethyl methanesulphonate mutant analysis and by natural genetic variation between accessions.
The ethyl methanesulphonate analysis resulted in a phosphite tolerant mutant with a significantly altered root phenotype. However, this was lost after out- and backcrosses and hence the mutation remains unknown. The presence of natural genetic variation between different accessions was shown and highlights that the phosphate starvation response can be used to investigate responses to phosphite. Notably, this study was the first to examine long-term exposure to phosphite in A. thaliana, allowing phosphate usage efficiency instead of variation on phosphate/phosphite uptake competition to be examined in detail. Out of 18 accessions screened, two contrasting accessions Bur-0 and Col-0 were shown to be suitable to investigate genetic variation, leading to the identification of highly significant quantitative trait loci’s. In turn, locally acting phosphate distribution and recycling genes were shown to respond differently to phosphite between accessions. These candidate genes were further investigated and hypothesised to increase phosphate use efficiency resulting in better plant growth.
This study confirmed differences in the sensing and the distinction between phosphate and phosphite between accessions. Furthermore, the phosphate and phosphite status of the vacuole in the shoot and selective sequestration was shown to be involved in systematic phosphate starvation response regulation and signalling of adaptations in root development. Additionally, the highest measured gene induction was measured for the Pathogen Resistance1 gene in Col-0, proving a direct link between phosphate starvation response and pathogen defence. This further underlines the appropriateness of phosphite application against oomycete pathogens.
20
au, 30365216@student murdoch edu, e Mee-Hua Wong. "Phosphite induces morphological and molecular changes in Phytophthora species". Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20070717.155119.
Testo completoAbstract (sommario):
The influence of the chemical phosphite on Phytophthora species was investigated by
studying the morphological and molecular changes induced by phosphite.
In vitro experiments were conducted to study the effects of phosphite on five isolates of
each of five species of Phytophthora grown in low phosphate defined medium. Sensitivity
to phosphite varied greatly among the five isolates of each species and resulted in a
significant interaction between isolate and phosphite effect. The EC50 values ranged from
less than 5 to 10 ìg/ml for P. cinnamomi, to 13 ìg/ml for P. nicotianae, to 27 ìg/ml for P.
citricola, to 24 ìg/ml for P. palmivora and to 49 ìg/ml for P. capsici.
Phosphite concentrations from 5 to 100 ìg/ml caused different degrees of morphological
changes. Mycelial growth of all species was significantly suppressed by phosphite at 5
ìg/ml while at 100 ìg/ml there was hyphal lysis. Swelling of hyphae with stunted sidebranches
and shrinking of cytoplasm from hyphal tips and hyphal walls were characteristic
changes observed. Phosphite also retarded the development and caused distortion and lysis
of chlamydospores, sporangia and zoospores. Zoosporogenesis was also adversely
affected.
Differential display reverse transcription-PCR was used to study changes in gene
expression in P. cinnamomi induced in response to phosphite stress. The differential
conditions were simulated by growth on a defined medium with and without phosphite
amendment. This technique resulted in the isolation of 34 putative differentially expressed
cDNA fragments which were cloned and sequenced. Nucleotide sequences of 26 of these
cDNA clones were generated. BLASTX analysis of these nucleotide sequences against the
NCBI database revealed that 18 exhibited homology to gene sequences encoding known
proteins involved in various biological processes. The remaining eight showed homology to
either hypothetical or unknown or unnamed proteins.
The expression level of four of these cDNA clones were further analysed by real-time
quantitative RT-PCR using SYBR Green 1 assay. Three candidate endogenous reference
genes namely, tubulin, cyclophilin and actin were evaluated to determine their expression
level under the influence of phosphite. None of these genes were significantly regulated by
phosphite. As tubulin had the highest expression among the three, it was chosen as the
endogenous reference gene. Amplification efficiencies between the reference gene and
each of the target genes were validated and found to be approximately equal or within 5%
of each other. The relative gene expression between the phosphite-treated and untreated
samples can thus be determined using the comparative CT (ÄÄCT) method. One of the
cDNA clones, CP6 which showed differential expression of three-fold was up-regulated.
The remaining three were constitutively expressed. CP6 which encodes 1564 nucleotides
showed sequence homology, at the amino acid level with proteophosphoglycans from
Leishmania major.
This study demonstrated the growth inhibition and morphological deformities caused by
phosphite in Phytophthora species. It also illustrated the use of a modified DDRT-PCR
method to study genes expressed in phosphite stress regulation. The application of real-time
quantitative RT-PCR with SYBR Green I assay facilitated the quantification of the
expression level of some of these genes.
21
Cerqueira, Andreia Filipa Lages. "Effects of phosphite in Pinus radiata-Fusarium circinatum interaction". Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17015.
Testo completoAbstract (sommario):
Mestrado em Biologia Molecular e CelularO cancro resinoso, provocado pelo fungo Fusarium circinatum, é uma doença que afeta Pinus spp. e Pseudotsuga menziesii em todo o mundo e está sujeita a medidas de quarentena. Caracteriza-se pela formação de grandes cancros resinosos que rodeiam rebentos, ramos e troncos e levam à morte do hospedeiro. Até à data não existem meios para o controlo da doença e, com a crescente necessidade de reduzir o uso de fungicidas, outras abordagens devem ser estudadas. Um método para o controlo de doenças fitopatogénicas passa pela indução da resistência do hospedeiro, através do pré-tratamento de plantas com compostos químicos ou de origem biológica que estimulam as defesas. O fosfito (Phi) é um sal inorgânico que apresenta a capacidade de indução da resistência e uma potencial estratégia mais amiga do ambiente. Neste estudo, a utilização do fosfito de potássio (KPhi) na redução do desenvolvimento dos sintomas da doença do cancro resinoso, assim como os seus efeitos no crescimento do fungo, foram estudados em diferentes concentrações. Numa primeira fase, colónias de F. circinatum foram crescidas em PDA suplementado com Phi (0%, 1% e 4%) para avaliação do seu efeito no crescimento radial. Posteriormente foram estudados os efeitos da aplicação foliar de Phi (0%, 1% e 4%) em plântulas de Pinus radiata, inoculadas e não inoculadas. A taxa de sobrevivência e a performance fisiológica (potencial hídrico, trocas gasosas e performance fotoquímica, pigmentos, peroxidação lipídica, libertação de eletrólitos, prolina e carbohidratos) foram avaliados. Os resultados mostram que aplicação de Phi atrasa o desenvolvimento dos sintomas de doença numa forma dependente da concentração de Phi, em semelhança ao observado relativamente à inibição do crescimento do micélio in vitro. Alterações fisiológicas ao nível da prolina e carbohidratos, peroxidação lipídica e trocas gasosas foram observadas. A aplicação de Phi apresenta-se como uma potencial alternativa viável na gestão da doença do cancro resinoso.
The pitch canker, caused by the fungus Fusarium circinatum, is a disease under quarantine measures affecting Pinus spp. and Pseudotsuga menziesii worldwide. Characterized by the formation of large resinous cankers that girdle shoots, branches, and trunks, leads to the death of the host. To date, there are no means for the control of the pitch canker and, with the growing need to reduce the use of fungicides, another approaches must be studied. A method for the control of phytopathogenic diseases is the enhancement of host resistance, through pre-treatment of seedlings with chemicals or biologically derived compounds that stimulate defense responses. Phosphite (Phi) is an inorganic salt with the capability of inducing host resistance and presents an approach more environmentally friendly. In this study, the ability of potassium phosphite (KPhi) in delaying the pitch canker symptom development, as well as its effects in fungal growth, were studied at different concentrations. In a first phase, F. circinatum colonies were grown in PDA medium supplemented with Phi (0%, 1% and 4%) to evaluation in the radial growth of the fungus. Posteriorly, were studied the effects of foliar application of Phi (0%, 1% and 4%) in Pinus radiata seedlings, inoculated and non-inoculated. Survival and physiological performance (water potential, gas exchange and photochemical performance, pigments, lipid peroxidation, electrolyte leakage, proline and carbohydrates) were assessed. Results showed that Phi application delayed disease symptoms in a dose dependent manner similarly to what was observed in mycelial growth inhibition during in vitro assays. Physiological alterations in proline, carbohydrates, lipid peroxidation and gas exchange parameters were observed. Thus, Phi application presents a potential viable alternative to the management of the pitch canker disease.
22
Wong, Mee-Hua. "Phosphite induces morphological and molecular changes in Phytophthora species". Thesis, Wong, Mee-Hua (2006) Phosphite induces morphological and molecular changes in Phytophthora species. Masters by Research thesis, Murdoch University, 2006. https://researchrepository.murdoch.edu.au/id/eprint/413/.
Testo completoAbstract (sommario):
The influence of the chemical phosphite on Phytophthora species was investigated by studying the morphological and molecular changes induced by phosphite.
In vitro experiments were conducted to study the effects of phosphite on five isolates of each of five species of Phytophthora grown in low phosphate defined medium. Sensitivity to phosphite varied greatly among the five isolates of each species and resulted in a significant interaction between isolate and phosphite effect. The EC50 values ranged from less than 5 to 10 mcg/ml for P. cinnamomi, to 13 mcg/ml for P. nicotianae, to 27 mcg/ml for P. citricola, to 24 mcg/ml for P. palmivora and to 49 mcg/ml for P. capsici.
Phosphite concentrations from 5 to 100 mcg/ml caused different degrees of morphological changes. Mycelial growth of all species was significantly suppressed by phosphite at 5 mcg/ml while at 100 mcg/ml there was hyphal lysis. Swelling of hyphae with stunted sidebranches and shrinking of cytoplasm from hyphal tips and hyphal walls were characteristic changes observed. Phosphite also retarded the development and caused distortion and lysis of chlamydospores, sporangia and zoospores. Zoosporogenesis was also adversely affected.
Differential display reverse transcription-PCR was used to study changes in gene expression in P. cinnamomi induced in response to phosphite stress. The differential conditions were simulated by growth on a defined medium with and without phosphite amendment. This technique resulted in the isolation of 34 putative differentially expressed cDNA fragments which were cloned and sequenced. Nucleotide sequences of 26 of these cDNA clones were generated. BLASTX analysis of these nucleotide sequences against the NCBI database revealed that 18 exhibited homology to gene sequences encoding known proteins involved in various biological processes. The remaining eight showed homology to either hypothetical or unknown or unnamed proteins.
The expression level of four of these cDNA clones were further analysed by real-time quantitative RT-PCR using SYBR Green 1 assay. Three candidate endogenous reference genes namely, tubulin, cyclophilin and actin were evaluated to determine their expression level under the influence of phosphite. None of these genes were significantly regulated by phosphite. As tubulin had the highest expression among the three, it was chosen as the endogenous reference gene. Amplification efficiencies between the reference gene and each of the target genes were validated and found to be approximately equal or within 5% of each other. The relative gene expression between the phosphite-treated and untreated samples can thus be determined using the comparative CT ([Delta][Delta]CT) method. One of the cDNA clones, CP6 which showed differential expression of three-fold was up-regulated. The remaining three were constitutively expressed. CP6 which encodes 1564 nucleotides showed sequence homology, at the amino acid level with proteophosphoglycans from Leishmania major.
This study demonstrated the growth inhibition and morphological deformities caused by phosphite in Phytophthora species. It also illustrated the use of a modified DDRT-PCR method to study genes expressed in phosphite stress regulation. The application of real-time quantitative RT-PCR with SYBR Green I assay facilitated the quantification of the expression level of some of these genes.
23
Wong, Mee-Hua. "Phosphite induces morphological and molecular changes in Phytophthora species". Wong, Mee-Hua (2006) Phosphite induces morphological and molecular changes in Phytophthora species. Masters by Research thesis, Murdoch University, 2006. http://researchrepository.murdoch.edu.au/413/.
Testo completoAbstract (sommario):
The influence of the chemical phosphite on Phytophthora species was investigated by studying the morphological and molecular changes induced by phosphite.
In vitro experiments were conducted to study the effects of phosphite on five isolates of each of five species of Phytophthora grown in low phosphate defined medium. Sensitivity to phosphite varied greatly among the five isolates of each species and resulted in a significant interaction between isolate and phosphite effect. The EC50 values ranged from less than 5 to 10 mcg/ml for P. cinnamomi, to 13 mcg/ml for P. nicotianae, to 27 mcg/ml for P. citricola, to 24 mcg/ml for P. palmivora and to 49 mcg/ml for P. capsici.
Phosphite concentrations from 5 to 100 mcg/ml caused different degrees of morphological changes. Mycelial growth of all species was significantly suppressed by phosphite at 5 mcg/ml while at 100 mcg/ml there was hyphal lysis. Swelling of hyphae with stunted sidebranches and shrinking of cytoplasm from hyphal tips and hyphal walls were characteristic changes observed. Phosphite also retarded the development and caused distortion and lysis of chlamydospores, sporangia and zoospores. Zoosporogenesis was also adversely affected.
Differential display reverse transcription-PCR was used to study changes in gene expression in P. cinnamomi induced in response to phosphite stress. The differential conditions were simulated by growth on a defined medium with and without phosphite amendment. This technique resulted in the isolation of 34 putative differentially expressed cDNA fragments which were cloned and sequenced. Nucleotide sequences of 26 of these cDNA clones were generated. BLASTX analysis of these nucleotide sequences against the NCBI database revealed that 18 exhibited homology to gene sequences encoding known proteins involved in various biological processes. The remaining eight showed homology to either hypothetical or unknown or unnamed proteins.
The expression level of four of these cDNA clones were further analysed by real-time quantitative RT-PCR using SYBR Green 1 assay. Three candidate endogenous reference genes namely, tubulin, cyclophilin and actin were evaluated to determine their expression level under the influence of phosphite. None of these genes were significantly regulated by phosphite. As tubulin had the highest expression among the three, it was chosen as the endogenous reference gene. Amplification efficiencies between the reference gene and each of the target genes were validated and found to be approximately equal or within 5% of each other. The relative gene expression between the phosphite-treated and untreated samples can thus be determined using the comparative CT ([Delta][Delta]CT) method. One of the cDNA clones, CP6 which showed differential expression of three-fold was up-regulated. The remaining three were constitutively expressed. CP6 which encodes 1564 nucleotides showed sequence homology, at the amino acid level with proteophosphoglycans from Leishmania major.
This study demonstrated the growth inhibition and morphological deformities caused by phosphite in Phytophthora species. It also illustrated the use of a modified DDRT-PCR method to study genes expressed in phosphite stress regulation. The application of real-time quantitative RT-PCR with SYBR Green I assay facilitated the quantification of the expression level of some of these genes.
24
Howard, Kay. "The effect of the fungicide phosphite on ectomycorrhizal fungi". Thesis, Howard, Kay ORCID: 0000-0003-3977-1243 (2001) The effect of the fungicide phosphite on ectomycorrhizal fungi. PhD thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/3215/.
Testo completoAbstract (sommario):
In Western Australia, the fungicide phosphite is being applied to selected native plant communities in order to reduce the impact of the root and collar rot pathogen, Phytophthora cinnamomi. The effect of this fungicide on the growth and function of ectomycorrhizal (ECM) fungi and their mycorrhizas was unknown. Taking the hypothesis that phosphite has a deleterious effect on mycorrhizal fungi, this study explored potential detrimental effects of phosphite on early colonising ectomycorrhizal fungi.
Ten isolates of Scleroderma and Pisolithus from Western Australia, isolated from a range of host plants. These isolates were partnered with Agonis flexuosa, Melaleuca scabra, Eucalyptus globulus, E. sieberi and four clonal lines of E. marginata (jarrah) in vitro. The isolates that formed a mantle, Hartig net and epidermal cell elongation characteristic of a successful symbiosis, were chosen for further studies on two contrasting E. marginata clonal lines, that were resistant or susceptible to P. cinnamomi. Foliar drenching with phosphite induced different responses in the two clonal lines when they were non-mycorrhizal. Phosphite decreased root production in the resistant clone, and increased the number of plantlets that produced roots in the susceptible clonal line. Generally, 3 g phosphite/L reduced the host response to mycorrhizal infection, and mycorrhizas reduced root responses to phosphite compared to those seen in non-mycorrhizal plants.
To determine if phosphite could have a direct inhibitory effect on the hyphae of ECM fungi, three isolates of Laccaria, Scleroderma and Pisolithus were grown in pure culture, on media containing a range of phosphite and phosphate concentrations. The biomass of Laccaria generally decreased as phosphite concentration increased at low phosphate concentrations. As phosphate concentration increased, the biomass of each Laccaria isolate generally increased irrespective of phosphite concentration. In hyphae of the three isolates of Laccaria, the increasing concentrations of phosphate in the media resulted in significant accumulation of phosphate. In two isolates, external phosphite supply had no effect on phosphate uptake. Scleroderma and Pisolithus tolerated the same concentration of phosphite as phosphate, while Laccaria was more sensitive to phosphite. There was a significant difference in growth between Laccaria isolates, while there was less variation between isolates of Scleroderma and Pisolithus. Scleroderma was most sensitive with two isolates being killed by 40 mM and the third being killed by 100 mM phosphite, while 120 – 140 mM phosphite was fungicidal to Laccaria and Pisolithus isolates.
In the glasshouse, non-mycorrhizal seedlings of E. marginata, E. globulus and A. flexuosa were sprayed to run-off with 0 to 10 g phosphite/L, and then planted into soil naturally infested with early colonising mycorrhizal species. Phosphite had no effect on the percentage of roots infected with mycorrhizal fungi. In another experiment, E. globulus seedlings ectomycorrhizal with Scleroderma, Pisolithus and Descolea were treated with 0 to 10 g phosphite/L and infection of new roots by ectomycorrhizal fungi was assessed. At the recommended rate (5 g phosphite/L), phosphite had no effect on ectomycorrhizal formation, while at 10 g/L phosphite decreased infection by Descolea by 15%.
An in vitro study was undertaken on a clonal line of E. marginata to determine if the foliar application of 3 g phosphite/L had any effect on the ability of Scleroderma and Pisolithus spores to germinate and infect roots. There was no significant difference in the percentage of infected primary and lateral root tips in phosphite and control plants inoculated with Scleroderma or Pisolithus spores.
To determine if the soluble and cell wall bound peroxidases and phenolics involved in host defence responses are affected by phosphite treatment of the host, a series of interactions with E. marginata, ECM fungi and P. cinnamomi were examined. Phosphite significantly reduced P. cinnamomi lesion length in all mycorrhizal and non-mycorrhizal treatments and altered static peroxidase activity and phenolic concentrations in the roots of all non-mycorrhizal plants.
Phosphite did not induce changes in peroxidase activity or phenolic concentration in roots of the susceptible clone when in indirect contact with Pisolithus. However, there was a general increase in peroxidase activity and phenolic concentration in roots of the resistant clone in the presence of Pisolithus and P. cinnamomi. In contrast, phosphite decreased peroxidase activity in the susceptible clone in the presence of Scleroderma and had no effect on soluble or cell wall bound phenolics. Phosphite did not alter peroxidase activity or phenolic concentration in roots of the resistant clone challenged by P. cinnamomi in the presence of either Scleroderma or Pisolithus. In contrast, phosphite significantly increased peroxidase activity, and decreased soluble phenolic concentration in the roots of the susceptible clone in the presence of Pisolithus.
A glasshouse trial examined the effect of foliar applied phosphite (3 g/L) on P. cinnamomi infection of roots of mycorrhizal E. marginata plants. Laccaria, Scleroderma and Pisolithus mycorrhiza were established with seedlings and a P. cinnamomi susceptible clonal line of E. marginata prior to phosphite treatment. P. cinnamomi zoospores were inoculated to the root zone 10 days after phosphite application. P. cinnamomi was recovered from 84% and 52% of the untreated seedlings and clonal plants respectively, whether they were ectomycorrhizal or not. By contrast, in phosphite treated plants, P. cinnamomi was recovered in 10% of seedlings and 6% of clonal plants. There was no difference in P. cinnamomi recovery between mycorrhizal types in seedlings and clonal plants. More P. cinnamomi was recovered from mycorrhizal than non-mycorrhizal clonal plants. There was no correlation between the extent of mycorrhizal fungal colonisation and the percentage of P. cinnamomi infected roots in clonal plants or seedlings.
Overall conclusions
Although only a few ECM fungi and host species were examined in this study, it appears that phosphite, when used at the recommended rate (5 g/L), may not have a detrimental effect on ECM formation. The concentration of phosphite that is fungicidal to ECM fungi in vitro is generally in excess of levels that would be found in treated plant tissues. However, when the recommended rate was exceeded it was shown that phosphite significantly decreased infection by Descolea.
This study has shown that there is variation between genera of ECM fungi, host plants, type of plant (clonal material or seedlings) in response to phosphite. However, this study did not take into account differing phosphate concentrations and its effect on phosphite and mycorrhizal interactions, which would further increase these variations. This demonstrates that generalisations cannot be made on the effect of phosphite on ECM fungi and ECM plants.
25
Bendle, Martin. "Phosphoranimines : investigations of their phosphite-initiated polymerisation and novel reactivity". Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556980.
Testo completoAbstract (sommario):
This thesis describes investigations into the phosphite-initiated polymerisation of the phosphoranimines, their reactivity with phosphine oxides and dehalogenation reactions. Chapter 1 introduces a number of inorganic polymers, and then focuses on the synthetic routes to the poly(phosphazene)s and the broad range of properties and applications of these materials. This chapter also provides a general introduction to the chemistry of compounds containing phosphorus-nitrogen bonds, particularly the phosphazenes. The phosphoranimines are then discussed, and their synthesis, properties and reactions described in detail. In Chapter 2, the reactions between phosphine oxides, R3P=O (R = Me, tBU, Et, iPr and Ph) and bromophosphoranimines, BrPR'R"P=NSiMe3 (R' = R" = Me; R' = Me, R" = Ph; R' = R" = OCH2CF3) are described. These reactions were shown to initially give the phosphine oxide-donor stabilised phosphoranimine cations, [R3P=O•PR"R'=NSiMe3t. However, it was also demonstrated that these cations rearranged to generate species of the form [R3P=N=PR'R"O-SiMe3t. The reactions between the phosphine oxides and phosphoranimines were also monitored by 31p{ IH} NMR to gain insight into the mechanism of the rearrangement process. Chapter 3 discusses studies into the polymerisation of the bromophosphoranimine BrMePhP=NSiMe3 initiated by the phosphite (MeO)3P, and provides evidence that the phosphite is not the active initiator. It was subsequently found that the initiation requires the presence of impurities in samples of either the phosphoranimine or phosphite. An investigation into these impurities and related compounds led to the identification of a new, highly-active combination of co- initiators, as well as giving insight into the mechanism of the initiation process. Chapter 4 initially describes the reductive dehalogenation of the phosphoranimine ChP=NSiPh3 and identifies the product of this reaction to be the cyclodiphosphazane (CIPNSiPh3)2. The thermal decompositions of this and another compound, (CIPNSiMe3h are then discussed, along with the reaction of (CIPNSiPh3h with the halide-abstracting reagent, GaCh. Chapter 5 provides supplementary information to Chapter 2.
26
Waechtler, Thomas, Yingzhong Shen, Alexander Jakob, Ramona Ecke, Stefan E. Schulz, Lars Wittenbecher, Hans-Josef Sterzel et al. "Evaluation of Phosphite and Phosphane Stabilized Copper(I) Trifluoroacetates as Precursors for the Metal-Organic Chemical Vapor Deposition of Copper". Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600315.
Testo completoAbstract (sommario):
Copper has become the material of choice
for metallization of high-performance
ultra-large scale integrated circuits.
As the feature size is
continuously decreasing, metal-organic
chemical vapor deposition (MOCVD) appears
promising for depositing the Cu seed
layer required for electroplating, as well
as for filling entire interconnect structures.
In this work, four novel organophosphane
and organophosphite Cu(I) trifluoroacetates
were
studied as precursors for Cu MOCVD. Details
are reported on CVD results obtained with
Tris(tri-n-butylphosphane)copper(I)trifluoroacetate,
(nBu3P)3CuO2CCF3.
Solutions of this
precursor with acetonitrile and isopropanol
were used for deposition experiments
on 100 mm Si wafers sputter-coated with Cu,
Cu/TiN, and Al(2 % Si)/W. Experiments
were carried out in a cold-wall reactor at
a pressure of 0.7 mbar, using a
liquid delivery approach for precursor dosage.
On Cu seed layers, continuous films were
obtained at low deposition rates (0.5 to
1 nm/min). At temperatures above 320°C,
hole formation in the Cu films was observed.
Deposition on TiN led to the formation of
single copper particles and etching of the
TiN, whereas isolating aluminum oxyfluoride
was formed after deposition on Al(Si)/W. It
is concluded that the formation of CF3
radicals during decarboxylation has a
negative effect on the deposition results.
Furthermore, the precursor chemistry needs
to be improved for a higher volatility of
the complex.
27
Dempsey, J. J. "Suppression of Microdochium nivale by phosphite in cool-season amenity turfgrasses". Thesis, University of the West of England, Bristol, 2015. http://eprints.uwe.ac.uk/24798/.
Testo completoAbstract (sommario):
The ascomycete fungus Microdochium nivale (Fr.) Samuels and Hallett (teleomorph Monographella nivalis (Schafnitt) is one of the most ubiquitous and damaging pathogens of cool-season amenity turfgrasses. Current control measures rely on inputs of chemical fungicides, making alternative means of disease reduction desirable. Phosphite (PO33-), which is derived from the alkali metal salts of phosphorous acid (H3PO3-),has proven efficacy in reducing susceptibility to oomycete pathogens. The aims of this research were to determine if PO33- treatments to amenity turfgrasses can suppress the incidence and severity caused by M. nivale, to determine the processes involved in such suppression and to assess the effect PO33- treatment had on turfgrass growth and quality. The research produced significant and novel data. In vitro inhibition of M. nivale mycelial growth was determined by amending PDA with PO33- and phosphate (PO43-), with concentrations from 0.5 to 1000 μg/ml-1. It was determined that PO33- concentrations of 100 μg/ml-1 and above, fully inhibited mycelial growth, with EC50 values from 38 to 45 μg/ml-1. PO43- caused no inhibition. Microscopic analysis of hyphal morphology showed distinct irregularities in M. nivale growing on PO33- amended PDA, while on PO43- amended PDA, mycelial growth was normal. Further in vitro studies determined PO33- was fungistatic rather than fungicidal, and that the presence of PO33- in growth media significantly inhibited conidial germination. Field trials determined significantly lower percentages of M. nivale incidence on PO33- treated plots of turfgrass, when compared with untreated controls, with the addition of PO33- significantly enhancing fungicide efficacy. Turfgrass quality on all PO33- treated plots was significantly better than either control or PO43- treated plots. Analysis of PO33- treated turfgrass tissues using High Performance Ion Chromatography, determined rapid in planta accumulation, symplastic mobility and no conversion to PO43- The data also indicate that PO33-, applied sequentially at four week intervals, would maintain leaf tissue amounts of approximately 2000 ppm, but would lead to cumulative accumulations in meristematic tissues. Furthermore, PO33- applications applied sequentially in excess of a six month period, can lead to increases in soil P levels. In phosphorus (P) deficient rootzones foliar applied PO33- does not supply a usable form of P and can repress plant P deficiency responses. In P sufficient rootzones foliar-applied PO33- increases plant biomass, with a reduction in root to shoot ratios. Assessment of turfgrass infection incidences determined M. nivale hyphae are the main source of inoculum and that infection was by means of stomatal penetration. Conidia produced via sporodochia following infection, are the means of propagation and dispersal. Analyses of infected turfgrass confirmed that increased synthesis of phenolic compounds and H2O2 are a component of initial defence responses and that PO33- pre-treatment, enhanced these responses. In conclusion, this work has shown that phosphite, when applied sequentially as a component of a balanced nutrient program, will suppress M. nivale incidence, increase the efficacy of turfgrass fungicides and lead to an enhancement of turfgrass quality. The results of this research will lead to changes in golf green management procedures, resulting in reduced requirements for chemical plant protectants, with added benefits of cost savings and a reduced environmental impact.
28
Stasikowski, Patricia. "Biochemical effects of phosphite on the phytopathogenicity of Phytophthora cinnamomi Rands". Thesis, Stasikowski, Patricia (2012) Biochemical effects of phosphite on the phytopathogenicity of Phytophthora cinnamomi Rands. PhD thesis, Murdoch University, 2012. https://researchrepository.murdoch.edu.au/id/eprint/14887/.
Testo completoAbstract (sommario):
Phosphite, a chemical analogue of orthophosphate, controls disease symptoms and spread of Oomycete plant pathogens, particularly those caused by Phythophthora spp. Phosphite can be applied to horticultural and native plant species as a foliar spray or trunk injection and results in in planta phosphite concentrations of between 25 - 425 μg g-1 dry weight (equivalent to 0.3 – 6.0 mM). However, despite its extensive use it is not known why phosphite is biostatic towards oomycetes, although several mechanisms have been proposed.
This thesis aims to devise and test a biochemical model of phosphite action that could account for the observed effects of phosphite on the interaction between Phytophthora cinnamomi and a susceptible plant host. However, prior to this it was necessary to devise a test to assess the concentration of phosphite in planta and to establish that phosphite needs to be present at the plant /pathogen interface in order to have an effect. A silver nitrate staining method was developed and its ability to detect phosphite was assessed in a variety of native Australian and horticultural plants. The method demonstrated that phosphite concentrations of between 1 and 3 mM were present in the tips of the roots of lupins that had been foliar sprayed with 0.5 % phosphite (equivalent to 62 mM) and that in most instances, these concentrations were sufficient to completely control the development of disease symptoms.
As phosphite is chemically similar to orthophosphate its presence in a cell is likely to interfere with many aspects phosphate metabolism in both plant and pathogen. In order to discern the mechanism of action of phosphite it was important to separate the antipathogenic effects from the general/ pleotropic effects. A bioassay was devised whereby the roots of lupin seedlings were inoculated with filter paper discs that had been colonised with P. cinnamomi isolate MP94-48 and then treated with phosphite or other chemicals that would be expected to reduce its pathogenicity. The extent of lesion development and the root growth below the point of inoculation were the two parameters by which the effect of the chemicals on pathogenicity was assessed.
Increasing either the concentration of orthophosphate (0 – 100 mM) or phosphite (0 – 10 mM) in the growth medium of P. cinnamomi colonised discs reduced lesion development on inoculated lupin seedling roots. Orthophosphate concentrations of between 3 – 10 mM, in combination with 1 mM phosphite did not reduce the extent of lesion development. In contrast, plants inoculated with discs treated with concentrations of orthophosphate above 10 mM together with 3 and 10 mM phosphite, lesions were reduced when compared to plants inoculated with discs treated with phosphite alone.
The inhibition of phosphatase activity in P. cinnamomi is often proposed to be a primary effect of phosphite. Treatment of P. cinnamomi colonized discs with the phosphatase inhibitors okadaic acid, sodium fluoride, and a mixture of inhibitors containing sodium vanadate, sodium molybdate, sodium tartrate and imidazole, neither decreased nor increased the development of lesions, and no change in the degree of phosphorylation of cytosolic proteins could be detected by Pro-Q Diamond phosphoproteins staining. The addition of the kinase inhibitor staurosporine (0.1 - 1 mM) reduced lesion development on lupins and this effect was augmented slightly, but significantly, by the addition of phosphite (3 mM). It was not possible to draw any conclusions from the results of experiments testing the effect of addition of exogenous cAMP or the phosphatase inhibitor phenyl arsine oxide to colonised discs on the ability of P. cinnamomi to produce lesions in lupins. These results suggest that phosphorylation reactions and cascades may not be the primary control mechanism in either initiation or inhibition of phytopathogenesis. However, the addition of glucose (30 mM) increased pathogenicity and the development of lesions.
As evidence exists that abscisic acid (ABA) increases the susceptibility of plants to infection by Phytophthora spp. and that ABA signaling involves phospholipase D (PLD) the effect of inhibitors on this signaling pathway were tested on the ability of P. cinnamomi to produce lesions. Primary, 2o and 3o butyl alcohol, as well as the guanine nucleotide exchange factor (GEF) inhibitor brefeldin A, and ABA itself were added to cultures of P. cinnamomi. The application of either 1o, 2o or 3o butyl alcohol to P. cinnamomi colonised discs had no effect on lesion development, which would be expected were the generation of phosphatidic acid per se was vital to pathogenicity. However, Brefeldrin A (10 - 250 μM) had a highly significant and concentration dependent effect on the development of lesion on lupins. These results suggested that a member of the Ras-superfamily (such as an ADP ribosylation factor) is likely to be involved in the development of lesions and that the exchange of GDP for GTP on this protein is required for pathogenesis. The results from the bioassays of addition of exogenous ABA to P. cinnamomi colonised discs were ambiguous and additional experimentation is needed to elucidate the role of ABA in the phytopathogenesis of P. cinnamomi.
Calcium ion signatures and cytosolic gradients are known to be important components of many signal transduction pathways and increased soil calcium can limit the development of Phytophthora disease. The effect of external calcium ion concentration and the calcium channel blockers ruthenium red (RR), lanthanum chloride (La3+) and the calcium ion chelator EGTA on the development of lesions was investigated. The results of the bioassays indicated that external calcium ion concentration, RR and La3+ (100 μM) reduced lesion development significantly as did EGTA (1 mM) and that this reduction was further enhanced in the presence of phosphite.
The combined role of phosphite and external calcium ion concentration was further investigated in a glasshouse pathogenicity trial using P. cinnamomi and the Australian plant Banksia leptophilia in a factorial nested pot design with foliar phosphite and soil calcium sulphate concentration as independent variables. The results one year post-inoculation confirmed that when foliar phosphite (0.1% - 0.3%) was used in conjunction with soil supplementation with calcium sulphate (3 – 30 mM) disease symptoms and lesion development were significantly reduced and general plant health was improved.
The combined results of these experiments suggested not only a role for calcium ion concentration and signaling in pathogenicity but, together with the 35-fold increase in PPi concentration, imply that inhibition of the calcium dependent ATPase responsible for regulating cytosolic Ca 2+ concentration may be the cause of the antipathogenic effect of phosphite in P. cinnamomi. Calcium dependent ATPases are known to be involved in the gravitropic response of roots as well as the polar growth of pollen tubes (i.e. presence of the Ca2+ channel blocker La3+ results in inhibition of the gravitropic and polar response). Preliminary results of the effect of phosphite on the gravitropism of lupin seedling roots indicate that phosphite does inhibit the gravitropic response, suggesting that there is a causal link between the mechanism of action of phosphite and calcium-dependent ATPases.
29
Roth, Nina. "Kupfer- und Ruthenium-Precursoren: Synthese, Charakterisierung und deren Verwendung zur Abscheidung metallischer Schichten nach dem CVD-Verfahren". Doctoral thesis, Universitätsbibliothek Chemnitz, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200901579.
Testo completoAbstract (sommario):
Die vorliegende Arbeit befasst sich mit neuartigen Kupfer(I)- und Ruthenium(II)-komplexen und deren Verwendung als CVD-/ALD-Precursoren. Die Synthese Lewis-Basen-stabilisierter Kupfer(I)-β-Diketonat- bzw. -Carboxylat-Komplexe des Typs [LnMX] (M = Cu(I), X = Acetylacetonat, Iminopentenolat, Carboxylat; L = Phosphan PR3, Phos-phit P(OR)3; R = einbindiger, organischer Rest) standen hierbei im Vordergrund. Verbin-dungen des Typs [(PR3)MX] dienten als Ausgangsverbindungen zur Darstellung einkerni-ger Komplexe mit σ Donorliganden. Durch die Wahl der Lewis-Base sowie des β-Diketonato- bzw. Carboxylato-Fragmentes war es möglich, Einfluss auf die Eigenschaften der erhaltenen Komplexe zu nehmen. Somit waren auch die Untersuchung der thermischen Eigenschaften sowie das Abscheideverhalten der Komplexe während der MOCVD zu ana-lysieren. Thermogravimetrische Untersuchungen bzw. MOCVD-Versuche liessen Rück-schlüsse auf die Eignung der Komplexe des Typs [(PR3)MX] zur Abscheidung elementa-ren Kupfers zu. Des Weiteren wurde die Eignung von Ruthenium-Komplexen des Typs RuX2 (X = substituierte Cyclopentadienyle, 2,4-Dimethylpentadienyl, 4-Methylpent-3-en-2-on-yl) zur Erzeugung von elementaren bzw. oxidierten Rutheniums während MOCVD-Versuchen untersucht. Vorhergehende thermische Untersuchungen an den synthetisierten Komplexen liessen erste Rückschlüsse auf deren Eigenschaften zu. Da der Dampfdruck der für CVD-Zwecke eingesetzten Precursoren besonders interessant ist, wurden diese für die verwendeten Ruthenium-Komplexe bestimmt und sowohl untereinander als auch mit Lite-raturwerten verglichen. Ausgewählte Ruthenium-Komplexe wurden zur Erzeugung metal-lischer oder oxidischer Schichten während MOCVD-Versuchen eingesetzt.
30
Fairbanks, Meredith Margaret. "The effect of the fungicide phosphite on some aspects of plant reproduction". Thesis, Fairbanks, Meredith Margaret (2001) The effect of the fungicide phosphite on some aspects of plant reproduction. PhD thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/51677/.
Testo completoAbstract (sommario):
Phytophthora cinnamomi Rands is a plant pathogen capable of infecting about 20% of native plant species in the south-west of Western Australia. The fungicide phosphite (phosphonate) provides an inexpensive and effective control of the pathogen. Phosphite can be applied by injection, soil drench, spray to run-off and misting. In the Mediterranean climate of the south-west of Western Australia operational sprays to native plant communities are applied in autumn or spring.
The up-take of phosphite was compared using spraying foliage to run-off with 0, 2.5, 5 and 10 gL-1 and misting with 100, 200 and 400 gL-1 phosphite. High Performance Ion Chromatography showed that the phosphite concentration in shoot apices of Corymbia {Eucalyptus) calophylla (marri) sprayed to run-off with 5 gL-1 phosphite, was comparable to the concentration in shoot apices of plants misted with 100 gL phosphite. In plants sprayed with 10 gL-1 phosphite the concentration in shoots was comparable to that in plants misted with 200 or 400 gL-1 phosphite. In root apices, spray to run-off at 5 and 10 gL-1 phosphite gave comparable concentrations to a 100 and 200 gL-1 phosphite mist treatment. Operational treatments of native vegetation are carried out at 5 gL-1 phosphite for spray and 400 gL-1 phosphite for mist. The results on marri suggest that these treatments are not comparable in terms of phosphite uptake. Analysis of additional species is required to determine whether the concentrations used should be reviewed to obtain comparable results from spraying and misting.
Phosphite has in general, low phytotoxicity to vegetative plant parts, but its effect on sexual reproduction had not previously been evaluated. The effect on pollen fertility was studied in detail and it was shown that in some species pollen fertility was significantly reduced for many months after spraying. Phosphite had a varying effect on sexual reproduction of some annuals in the Eucalyptus marginata (jarrah) forest. It reduced pollen fertility of the annual Pterocheata paniculata when plants were sprayed in the vegetative stage and of Pt. paniculata, Podotheca gnaphalioides and Hyalosperma cotula when sprayed at anthesis. Seed germination was reduced by phosphite, in Pt. paniculata and H. cotula when plants were sprayed in the vegetative stage, and in H. cotula when sprayed at anthesis. Phosphite at concentrations of 5 and 10 gL-1 killed a proportion of plants from all 3 species with up to 90% of Po. gnaphalioides plants dying.
Phosphite also affected sexual reproduction of some perennial species of the jarrah forest. In Dryandra sessilis, which flowers from autumn to early spring, pollen fertility was reduced by phosphite for up to 35 and 60 weeks after spraying in spring and autumn, respectively. Seed germination was not affected by phosphite. Pollen fertility of Trymalium ledifolium, a winter to early spring flowering species, was reduced by phosphite for up to 38 and 61 weeks after spraying in spring and autumn, respectively. Seed germination was reduced by phosphite 11 weeks after a spring spray. Phosphite was still detected in T. ledifolium shoots 62 weeks after spraying. In Lasiopetalum floribundum a species that flowers in spring, pollen fertility was reduced for 3 weeks when sprayed in spring. There was no effect on seed germination. Phosphite was also found to reduce pollen fertility of perennial species from the northern sandplains of Western Australia for up to 8 months after spraying.
The deleterious effect of phosphite was shown to be partly a result of its effect on cell division. Model plants Vicia faba. Petunia hybrida and Tradescantia virginiana, which are used for cytological research and are readily available and fast growing, were used to study this interaction. Phosphite significantly increased the number of chromosome laggards and bridges/stickiness in mitotic cells in the root tips of V. faba and P. hybrida sprayed with phosphite. Phosphite also increased the number of univalents and micronuclei in T. virginiana pollen microspore cells. The levels of abnormality. although significant, were not large enough to account for the level of pollen sterility observed.
Another mechanism for the effect of phosphite was the disruption of the normal timing of tapetum breakdown. Phosphite at 20 gL-1 brought about the premature breakdown of the tapetum in P. hybrida, and a small alteration in protein synthesis in the tapetum of treated plants, 7 days after spraying.
Phosphite has mutagenic properties. The Ames in vitro spot test showed that 400 gL-1 phosphite increased the number of DH5a Escherichia coli mutants by 60%. Tests of 24 hour cultures of this E. coli strain in solutions of 0.4, 4, and 40 gL-1 phosphite resulted in an increase in mutation rate by a factor of 10 to 100. Phosphite reduced E. coli growth after 24 hours exposure at concentrations as low as 0.4 gL-1.
From the findings of this thesis, it is recommended that the current management and application of phosphite be reviewed. The concentrations of phosphite that are currently applied as spray to run-off or mist are not comparable and measures should be taken to ensure that the application methods are comparable if equivalent effects are expected. Phosphite was found to have deleterious effects on plant sexual reproduction of both annual and perennial native Australian species. When species are in flower at the time of phosphite application, their pollen fertility is significantly reduced. It would be beneficial therefore to spray when plants are not in flower. However, due to the limited period of ideal climatic conditions for aerial application, in autumn and spring, it is not feasible to apply phosphite at other times. However, when the treatment is being applied in order to protect rare species, it would be advisable to spot spray when the species is not flowering.
31
Wright, Glenn C., e Marco Peña. "Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange trees". College of Agriculture, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/198099.
Testo completoAbstract (sommario):
This experiment was established in January 2000 in a block of ‘Washington’ navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield, and only slight effect upon fruit size, grade and quality. For 2001-02, there was a slight effect of treatment upon yield as LB urea led to improved yield, while potassium phosphite led to reduced yield. Normal grower practice was intermediate between these two extremes. For 2002-03, we noted a large increase in yield, however the yield data was lost when the block was inadvertently harvested.
32
Wright, Glenn C., e Marco Peña. "Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange trees". College of Agriculture, University of Arizona (Tucson, AZ), 2004. http://hdl.handle.net/10150/197989.
Testo completoAbstract (sommario):
This experiment was established in January 2000 in a block of ‘Washington’ navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield, and only slight effect upon fruit size, grade and quality. For 2001-02, there was a slight effect of treatment upon yield as LB urea led to improved yield, while potassium phosphite led to reduced yield. Normal grower practice was intermediate between these two extremes. For 2002-03, we noted a large increase in yield, however the yield data was lost when the block was inadvertently harvested. For 2005, there was no effect of treatments upon total yield.
33
Wright, Glenn C., e Marco Peña. "Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange trees". College of Agriculture, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/223652.
Testo completoAbstract (sommario):
This experiment was established in January 2000 in a block of 'Washington' navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield, and only slight effect upon fruit size, grade and quality. For 2001-02, there was a slight effect of treatment upon yield as LB urea led to improved yield, while potassium phosphite led to reduced yield. Normal grower practice was intermediate between these two extremes.
34
Wright, Glenn, e James Walworth. "Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange Trees". College of Agriculture, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/226094.
Testo completoAbstract (sommario):
This experiment was established in January 2000 in a block of 'Washington' navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield. There was a slight effect upon fruit size and grade. Trees subject to summer LB urea application had significantly more fruit of size 56, compared to trees subject to winter LB urea, and untreated, and untreated trees had significantly more fruit of size 88 than did treated trees. Also, treated trees had slightly more fruit in the fancy grade than did untreated trees.
35
Harrison, Karl Nicholas. "The synthesis and characterisation of Tris(2-methoxyphenyl)phosphite nickel palladium and platinum complexes". Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303757.
Testo completo
36
Ortuoste, Nerea. "Inhibition of phosphite antioxidant hydrolysis via synergistic blends for the thermal processing of polyolefins". Thesis, Manchester Metropolitan University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402660.
Testo completo
37
Eshraghi, Leila. "Genetic analysis of host and phosphite mediated resistance to Phytophthora cinnamomi in Arabidopsis thaliana". Thesis, Eshraghi, Leila (2012) Genetic analysis of host and phosphite mediated resistance to Phytophthora cinnamomi in Arabidopsis thaliana. PhD thesis, Murdoch University, 2012. https://researchrepository.murdoch.edu.au/id/eprint/12737/.
Testo completoAbstract (sommario):
Phosphite (Phi), an analogue of phosphate (Pi) is highly effective for the control of Phytophthora cinnamomi, a devastating necrotrophic pathogen worldwide. This study describes the effect of phosphite (Phi) on the induction of defence responses in Phytophthora cinnamomi-infected Arabidopsis thaliana accessions Ler and Col-0, and mutants defective in salicylic acid (SA), jasmonic acid (JA), ethylene (ET), abscisic acid (ABA), phosphate starvation response (PSR) and auxin response signalling pathways. The inoculation of the resistant Col-0 with P. cinnamomi induced a rapid increase in callose deposition (by 6 h after inoculation) and hydrogen peroxide (H2O2) production (by 24 h after inoculation) whereas inoculation of susceptible Ler showed a delayed and reduced response. Treatment of Ler with Phi produced a response to P. cinnamomi inoculation similar to that observed in Col-0 in terms of timing and magnitude suggesting Phi primes the plant for a rapid and intense response to infection involving heightened activation of a range of defence responses.
A reliable method for measuring disease progression is important when evaluating susceptibility in host–pathogen interactions. A sensitive quantitative polymerase chain reaction (QPCR) assay was developed for the quantitative measurement of P. cinnamomi DNA (biomass) in planta that avoids problems caused by variation in DNA extraction efficiency and degradation of host DNA during host tissue necrosis. Purified plasmid DNA, containing the pScFvB1 mouse gene, was added during DNA extraction and the pathogen’s biomass was normalized based on plasmid DNA rather than host DNA or sample fresh weight. It was demonstrated that normalization of pathogen DNA to sample fresh weight or host DNA in samples with varying degrees of necrosis led to an overestimation of the pathogen’s biomass.
Inoculation of mutants in the SA, JA, and ET defence signalling pathways did not affect the resistance of Col-0 suggesting alternative pathways are involved. A high level susceptibility was observed in the aba2-4 mutant suggesting a role for ABA signalling in the induction of resistance to P. cinnamomi. Phi treatment of aba2-4 increased resistance but not to the wild type levels indicating a possible role for ABA-dependent and ABA independent signalling in Phi mediated resistance. Application of Phi to non-inoculated A. thaliana seedlings elevated transcription of defence genes in the SA (PR1 and PR5) and JA/ET (THI2.1 and PDF1.2) pathways. Furthermore, analysis of gene expression in Col-0 revealed that either Phi or P. cinnamomi caused the down-regulation of the transcriptional level of AtMYC2 (a positive regulator of ABA signalling which also negatively regulates JA-related genes) and increased the transcriptional abundance of PDF1.2. Together these results suggest that the resistance response of Col-0 and Phi treatment both act partially through an ABA dependent mechanism which is independent of the antagonism between ABA and elements of the JA/ET pathway such as PDF1.2.
Phosphite has been suggested to interfere with various plant processes including Pi homeostasis therefore the potential involvement of the Pi and auxin signalling pathways in resistance to P. cinnamomi was investigated using several PSR and auxin response pathway mutants. The mutants tir1-1, an auxin response mutant deficient in the auxin-stimulated SCF (Skp1−Cullin−F-Box) ubiquitination pathway and phr1-1, a mutant defective in response to Pi starvation were highly susceptible to P. cinnamomi compared to their parental background Col-0. Complementation restored resistance to the level observed in Col-0. Moreover, inhibition of auxin transporters by TIBA (2,3,5-triiodobenzoic acid) led to a significant increase in susceptibility of Lupinus angustifolius seedlings to P. cinnamomi supporting the importance of the auxin signalling pathway in P. cinnamomi resistance. The 26S proteasome subunits mutants; rpn10-1 (Defective in ubiquitin/26S proteasome-mediated proteolysis) and pbe1-1 (proteasome subunit beta type-5-A) were also susceptible to P. cinnamomi. The rpn10-1 mutant has also been associated with the auxin signalling pathway and the susceptibility of rpn10-1 and pbe1-1 indicates that the 26S proteasome and auxin signalling could play a role in resistance to P. cinnamomi. Given the apparent involvement of auxin and PSR signalling in the resistance to P. cinnamomi, the possible involvement of these pathways in Phi mediated resistance was also investigated. Application of Phi at both low and high concentrations attenuated some of the Pi starvation inducible genes such as At4, AtACP5 and AtPT2. However, in phosphate sufficient plants, Phi treatment mimicked Pi starvation responses in terms of enhanced expression of PHR1, AUX1, AXR1, AXR2 and SGT1B; suppression of primary root elongation, and increased root hair formation. Together, these results suggest that the auxin response pathway, particularly auxin sensitivity and transport, plays a role in the plant’s resistance to P. cinnamomi and suggest that phosphite-mediated resistance may in some part be through its effect on stimulation of the auxin response pathway.
38
Naeemi, Qaseem [Verfasser]. "Studies in Enantioselective Transition Metal Catalysis Using Modular Phosphine-Phosphite Ligands Copper-catalyzed 1,4-Addition of Grignard Reagents to alpha,beta-Unsaturated Carbonyl Compounds / Qaseem Naeemi". München : Verlag Dr. Hut, 2012. http://d-nb.info/1020299428/34.
Testo completo
39
Aberton, Michael J., e lswan@deakin edu au. "The use of phosphite as a control for Phytophthora cinnamomi in southeastern Victorian vegetation communities". Deakin University. School of Biological and Chemical Sciences, 2005. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20060921.150649.
Testo completoAbstract (sommario):
One of the major aims of the research presented in this thesis was to assist managers of native vegetation communities in southeastern Australia in understanding the dynamics of P. cinnamomi with an important ecological species, Xanthorrhoea australis. It trialed the use of phosphite in large-scale field applications to establish the usefulness of this management option for the first time on Victorian flora.
This thesis describes the process of disease development within mature X. Australia plants. For the first time it was shown that within X. australis plants, secondary disease symptoms are related to the percentage of stem that has been infested by the disease. It was evident that after initial invasion the pathogen moves via root xylem and throughout the plant within vascular to the stem, especially within the desmium. The research shows that the pathogen could not be isolated consistently even though it was considered to be responsible for disease symptoms.
Trials of a control fungicide (Foli-R-fos 200) shows that protection occurs in many susceptible plants when 2 and 6g a.i./L phosphite is applied. Phytotoxicity occurred in native plants at Anglesea and within controlled environment trials when using ≥ 6g a.i./L. It will be shown that 2g a.i./L phosphite controls disease in sprayed plots within heathlands at Anglesea and a recently burnt coastal woodland community at Wilsons Promontory. The proportion of healthy X. australis plants treated with phosphite was significantly higher than the proportion in control plots without phosphite. The research shows that phosphite was recovered from leaves of three species treated with Foli-R-fos 200 in the field. For the first time it has been shown that seed germination was reduced in two species when high concentrations of phosphite were applied. The first documentation of the effect that phosphite has on soil properties showed that nitrogen and oxidised organic carbon were the only parameters to alter significantly.
This thesis provides answers to some important questions, answers that can now be used by managers in formulating better policies and actions at an operational level. There has been a dire need in Victoria to address many issues regarding P. cinnamomi and this thesis provides relevant and informative approaches to disease control, and a better understanding of the disease progress.
40
Darakis, Georges. "Phosétyl-al et phosphite, leurs activités directe et indirecte sur la pathogénie des Phytophthora spp". Paris 6, 1987. http://www.theses.fr/1987PA066047.
Testo completoAbstract (sommario):
Le présent travail porte sur le mode d'action du phoséthyl-al (Tris-0-éthylphosponate d'aluminium), composé systémique et son métabolite actif l'ion phosphite vis-à-vis des Oomycètes. Une méthode de dosage de ces molécules dans les tissus végétaux, combinant la chromatographie en phase gazeuse à été mise au point. Elle nous a permis, sur la base de la comparaison des concentrations en fongicide in vitro et in vivo, d'examiner les deux possibilités qui existent en ce qui concerne son mode d'action directe et indirecte.
41
Darakis, Georges. "Phoséthyl-Al et phosphite, leurs activités directe et indirecte sur la pathogénie des Phytophthora spp". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37604293q.
Testo completo
42
Barrett, Sarah. "Phytotoxic effects of phosphite in native plant communities on the south coast of Western Australia". Thesis, Barrett, Sarah (2001) Phytotoxic effects of phosphite in native plant communities on the south coast of Western Australia. PhD thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/32427/.
Testo completo
43
Wilkinson, Carla. "The ability of Phytophthora cinnamomi to sporulate from colonised host plant tissue treated with phosphite". Thesis, Wilkinson, Carla (1997) The ability of Phytophthora cinnamomi to sporulate from colonised host plant tissue treated with phosphite. Honours thesis, Murdoch University, 1997. https://researchrepository.murdoch.edu.au/id/eprint/32811/.
Testo completo
44
Mambingo, Doumbe Samuel. "Simulation de la phase gazeuse des réactions tribochimiques des additifs phosphorés et soufrés". Thesis, Ecully, Ecole centrale de Lyon, 2012. http://www.theses.fr/2012ECDL0063.
Testo completoAbstract (sommario):
La maîtrise de l’additivation est l’un des enjeux majeurs de la formulation des lubrifiants, notamment pour l’industrie automobile. La formulation d’une huile est toutefois très complexe en raison du nombre important d’additifs et des nombreuses interactions possibles entre additifs, notamment entre les additifs de surface. Les phosphites organiques et les polysulfures organiques ont déjà montré leur efficacité en tant qu’additifs de surface. Toutefois malgré leur usage répandu dans les formulations des lubrifiants automobiles, peu d’études traitent des interactions pouvant avoir lieu entre ces deux types de composés. Ce travail de thèse a pour objectif la compréhension des mécanismes d’interaction (antagonisme/synergie) pouvant exister entre les phosphites organiques et les polysulfures organiques. Pour cela, une approche originale sur la lubrification par la phase gazeuse s’est avérée très pertinente. Le couplage du Tribomètre à Environnement Contrôlé (TEC) avec les systèmes d’analyses de surface XPS/Auger a permis d’analyser les tribofilms générés in situ et d’éviter ainsi toute contamination et/ou oxydation du tribofilm avant analyse. Les molécules choisies sont les additifs de lubrification industriels (polysulfures tertaires) à faibles poids moléculaires ou alors des molécules à faible poids moléculaires ayant les mêmes fonctions chimiques que les additifs usuels : trimethyl phosphite (TMPi), dimethyl phosphite (DMPi). L’étude des réactions des tribochimiques des molécules phosphorés a permis de mettre en évidence le rôle ambivalent du DMPi qui se comporte à la fois comme un phosphite pour former un phosphure de fer et comme un phosphate. Le mécanisme formation du phosphure de fer a peu être étayé par la réalisation de calculs ab initio sur l’adsorption dissociative du TMPi sur une surface de fer. Les TPS étudiés génèrent quant à eux des tribofilms à base disulfure de fer. Les mélanges binaires réalisés en phase gazeuse ont permis de mettre en évidence l’importance des rapports de concentrations des vapeurs introduites et du mode d’introduction des molécules dans le tribomètre. Les résultats obtenus en tribologie en phase gazeuse ont été corroborés par des essais complémentaires en phase liquideMastering the addivation is one of the biggest issues for the lubricants formulation, especially in the automobile industry. However automotive lubricants are very complex systems due to the numerous additives mixed with base oils. Many interactions can occur between additives, especially between surface additives. Organic phosphites and organic polysulphides have already demonstrated their effectiveness as surface additives. However, despite their widespread use in the formulations of automotive lubricants, few studies deal with the interactions taking place between these two types of compounds. The aim of this study is to understand the interactions, antagonistic or synergetic effect between these kinds of additives using Gas Phase Lubrication (GPL) approach. A Environmental Controlled Tribometer (TEC) was used as a tool to simulate the interaction between organophosphate additives and polysulfurous additives. In situ surface analysis was performed in the tribofilm formed during friction using of X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy(AES) in order to avoid any oxidation or air contamination. The molecules selected for the study can be same as the additive like the TPS molecules which are widely used as lubricant additives. Howeverto simulate the phosphite chemical function of phosphite additives, we need to select smaller molecule having the same chemical function. These molecules are dimethyl phosphite (DMPi), trimethylphosphate (TMPi) for simulating the phosphite chemical function and organic polysulphides (TPS44and TPS32). The study of the tribochemical reactions of organic phopshites allowed to clearly characterise the ambivalence of DMPi, which can react like a phosphite and induce iron phosphide formation or react like a phosphate. Ab initio numerical simulation on TMPi dissociative adsorption was carried out to identify the reactions pathways leading to iron phosphide formation. The tribochemical reaction of TPS44 on metallic iron surface leads to the formation of iron disulphidebased tribofilm. The binary vapours mixtures studied by GPL allowed to clearly identify the importance of the vapour concentration ratio between phosphite and polysulphide. Liquid phase experiments were also carried out to confirm the trend observed in GPL approach
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Gomes, Giovanna Larissa Gimenes Cotrick [UNESP]. "Alterações metabólicas de plantas de milho submetidas à aplicação de glyphosate e fosfito". Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/97185.
Testo completoAbstract (sommario):
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O glyphosate é um herbicida de largo espectro de controle, não seletivo, e seu sítio de ação é a inibição da enzima 5-enolpiruvilchiquimato 3-fosfato sintase (EPSPs). Com a inibição da enzima, e o bloqueio da rota do ácido chiquímico pelo glyphosate, ocorre o acúmulo de alguns compostos como os ácidos chiquímico e quínico, além de outras alterações metabólicas e fisiológicas nas plantas. O objetivo deste trabalho foi avaliar as alterações metabólicas e fisiológicas de plantas de milho submetidas à aplicação de glyphosate isolado e em associação com fosfito. O experimento foi conduzido em casa-de-vegetação, no Núcleo de Pesquisas Avançadas em Matologia (NUPAM), pertencente à Faculdade de Ciências Agronômicas – FCA/UNESP. Foi utilizado o híbrido de milho Pioneer 30F53, em vasos contendo 5 litros de substrato e os tratamentos foram compostos da aplicação de: glyphosate (72 g e.a. ha-1); glyphosate (720 g e.a. ha-1); glyphosate (72 g e.a. ha-1) + fosfito (3 L p.c. ha-1); glyphosate (720 g e.a. ha-1) + fosfito (3 L p.c. ha-1); fosfito (3 L p.c. ha-1); e uma testemunha sem aplicação. Foram realizados dois experimentos, com os mesmos tratamentos, mas com avaliações distintas. No primeiro, foram realizadas cinco coletas de todas as folhas das plantas aos 2, 4, 6, 10 e 15 dias após a aplicação (DAA) dos tratamentos. No segundo experimento, foi realizada a medição do fluxo de transporte de elétrons (ETR) nas folhas jovens e maduras, avaliações visuais de intoxicação, medição da altura e quantificação da matéria seca ao final do experimento. As folhas coletadas foram secas e moídas e utilizadas para quantificação dos seguintes compostos: ácido chiquímico, ácido quínico, ácido desidrochiquímico, ácido aminometilfosfônico (AMPA), glyphosate, fenilalanina, tirosina e triptofano. Foram também realizados testes de extração dos compostos...
The glyphosate is a broad spectrum herbicide, non-selective, and the site of action is the inhibition of the enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPs). The inhibition of the enzyme results in a reduction in the synthesis of aromatic amino acids (phenylalanine, tyrosine and tryptophan), and secondary compounds. The glyphosate block of the shikimic acid pathway and causes the accumulation of some compounds like shikimic acid and quinic acid, and other metabolic and physiological effects in plants. The objective of this study was to evaluate the metabolic and physiological effects in corn plants after application of glyphosate and phosphite. The experiment was carried out in greenhouse in the Faculty of Agronomic Sciences at São Paulo State University. It was used the corn Pioneer 30F53, planted in vases containing 5 liters of substrate. The treatments were: glyphosate (72 g a.e. ha 1), glyphosate (720 g a.e. ha-1), glyphosate (72 g a.e. ha-1) + phosphite (3 L ha-1), glyphosate (720 g a.e. ha-1) + phosphite (3 L ha-1), phosphite (3 L ha -1) and an untreated control. Two experiments were carried out with the same treatments but with different evaluations. At first, it were realized five samples of all corn plant leaves at 2, 4, 6, 10 and 15 days after application (DAA). The second experiment was performed the evaluation of the electron transport rate (ETR) in young and mature leaves, visual evaluations of intoxication, height and weight of the plants. The leaves collected were dried, grated and used to quantify the compounds: shikimic acid, quinic acid, 3-dehydroshikimic acid, aminomethylphosphonic acid (AMPA), glyphosate, phenylalanine, tyrosine and tryptophan. Extraction tests of compounds were conducted to choose the most appropriate and were development of analytical methods in LC-MS/MS. The extraction of the compounds that proved most appropriate was using the dry mass... (Complete abstract click electronic access below)
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Pilbeam, Ros. "Effects of phosphite on disease development and histological responses in Eucalyptus marginata infected with Phytophthora cinnamomi". Thesis, Pilbeam, Ros (2003) Effects of phosphite on disease development and histological responses in Eucalyptus marginata infected with Phytophthora cinnamomi. PhD thesis, Murdoch University, 2003. https://researchrepository.murdoch.edu.au/id/eprint/260/.
Testo completoAbstract (sommario):
Phosphite is currently used for the management of Phytophthora cinnamomi in native plant communities. A greater understanding of how phosphite affects the host-pathogen interaction is required in order to determine the most effective treatment. This thesis aimed to investigate the effects of applied phosphite concentration on phytotoxicity, in planta concentration of phosphite, disease development and anatomical responses of Eucalyptus marginata.
Spraying the foliage to run-off with 7.5 and 10 g phosphite/L led to the development of severe leaf necrosis within 7 days, with greater than 60% of the leaf area damaged. Moderate phytotoxicity was observed after treatment with 5 g phosphite/L. In planta concentration of phosphite in stems, lignotubers and roots did not differ significantly between applied concentrations of phosphite.
Stem tissue contained the largest concentration of phosphite at one week after spraying, with approximately 210 and 420 g phosphite/g dry weight detected after treatment with 5 and 10 g phosphite/L, respectively. In a subsequent field trial, the applied concentration of phosphite was found to affect the duration of effectiveness of phosphite in protecting E. marginata seedlings from stem colonisation by P. cinnamomi. Plants were wound-inoculated with P. cinnamomi at 6-monthly intervals after spraying with phosphite. The 2.5 and 5 g phosphite/L treatments were effective against colonisation by P. cinnamomi when inoculated 0 and 6 months after spraying, but only the 5 g phosphite/L treatment inhibited P. cinnamomi within 12 months of spraying. Phosphite had no effect on colonisation by P. cinnamomi when plants were inoculated at 17 months after spraying. The in planta concentration of phosphite detected in the leaves, stems and roots of plants treated with 5 g phosphite/L did not differ significantly between the time of harvest or tissue type at 0.2 and 6 months after spraying. P. cinnamomi remained viable in plants treated with phosphite.Treatment with 2.5 and 5 g phosphite/L when P. cinnamomi was well established in the stems was ineffective at preventing the death of E. marginata.
Between 45 and 89% of plants were girdled on the day of spraying. Spraying plants with 2.5 and 5 g phosphite/L when conditions were less favourable for the pathogen reduced the mortality of E. marginata for up to 10 months.
E. marginata seedlings responded to damage by P. cinnamomi with the production of kino veins and woundwood. Bark lesions were in the process of being sloughed off by 7 months after inoculation in plants that remained alive. In plants of a resistant (RR) clonal line and susceptible (SS) clonal line, phosphite treatment inhibited lesion extension in stems, but lesions did not indicate the amount of stem colonised by P. cinnamomi. The pathogen was isolated from up to 17 cm beyond the lesion front in the RR clonal line. Treatments that reduced the mortality of E. marginata were 5 g phosphite/L in the RR clonal line (RR/5) and 10 g phosphite/L in the SS clonal line (SS/10).
Uninoculated plants were wounded with liquid nitrogen to determine the microscopic responses to injury in the absence of the pathogen. Wound closure was achieved within 21 days of wounding, with callus formation and vascular cambium regeneration. A wound periderm separated wounded tissue from healthy tissue, adjacent to a lignified boundary zone. Two types of phellem were observed - thin-walled phellem (TnP) and thick-walled phellem (TkP). The first-formed TnP layers contained variable-shaped cells, while subsequent layers were more cubical in shape. Multiple TnP layers developed up to 42 days after wounding, with TkP cells sandwiched between the TnP layers. Genotype and phosphite treatment did not affect the wound responses.
Inoculated plants with a restricted lesion extension also formed a wound periderm to separate damaged tissue from healthy tissue. Phosphite treatment stimulated the responses to P. cinnamomi in both clonal lines. Early development of the wound periderm was visible by 6 days after phosphite treatment. It waspreceded by the formation of a ligno-suberised boundary zone in the cambial zone and in phloem parenchyma cells existing prior to injury. Suberin was not detected in the SS/0 treatment. TnP layers completely surrounded lesioned tissue in plants still alive by 24 days after phosphite treatment. Extensive callus production was evident in the SS/10, RR/5 and RR/10 treatments.
Temperature affected the post-inoculation efficacy of phosphite and anatomical responses of E. marginata. At 20 degrees C lesion extension was restricted in both clonal lines of E. marginata, irrespective of phosphite treatment. Greater than 70% of inoculated plants in all treatments produced a ligno-suberised boundary zone at 20 degrees C and between 30 and 70% formed a wound periderm. At 28 degrees C, lesion extension was reduced in phosphite-treated plants at 7 days after treatment. However, lesions continued to extend up to 5 mm per day in the SS clonal line and very few SS plants formed a wound periderm at the lesion front. This contrasted with the strong responses to abiotic wounding observed in uninoculated SS plants at 28 degrees C. The most extensive responses to P. cinnamomi were detected in the RR/5 treatment at 28 degrees C, with a ligno-suberised boundary zone and differentiated TnP of a wound periderm observed in greater than 70% of plants. This treatment resulted in significantly less girdled plants than all other treatments at 28 degrees C, including the RR/0 treatment. At 23 and 24 degrees C, there was no significant difference in acropetal lesion extension or circumferential lesion spread between clonal lines. The inoculation technique and environmental conditions may have resulted in too high a disease pressure for a full expression of resistance in the RR clonal line.
This thesis demonstrates that phosphite has the potential to enhance the resistance of young E. marginata and enable them to survive infection by P. cinnamomi. However, its effectiveness is dependent upon a number of factors, including host resistance, environmental conditions, the applied phosphite concentration and the timing of application.
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Pilbeam, Ros. "Effects of phosphite on disease development and histological responses in Eucalyptus marginata infected with Phytophthora cinnamomi". Murdoch University, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040820.140206.
Testo completoAbstract (sommario):
Phosphite is currently used for the management of Phytophthora cinnamomi in native plant communities. A greater understanding of how phosphite affects the host-pathogen interaction is required in order to determine the most effective treatment. This thesis aimed to investigate the effects of applied phosphite concentration on phytotoxicity, in planta concentration of phosphite, disease development and anatomical responses of Eucalyptus marginata.
Spraying the foliage to run-off with 7.5 and 10 g phosphite/L led to the development of severe leaf necrosis within 7 days, with greater than 60% of the leaf area damaged. Moderate phytotoxicity was observed after treatment with 5 g phosphite/L. In planta concentration of phosphite in stems, lignotubers and roots did not differ significantly between applied concentrations of phosphite.
Stem tissue contained the largest concentration of phosphite at one week after spraying, with approximately 210 and 420 µg phosphite/g dry weight detected after treatment with 5 and 10 g phosphite/L, respectively. In a subsequent field trial, the applied concentration of phosphite was found to affect the duration of effectiveness of phosphite in protecting E. marginata seedlings from stem colonisation by P. cinnamomi. Plants were wound-inoculated with P. cinnamomi at 6-monthly intervals after spraying with phosphite. The 2.5 and 5 g phosphite/L treatments were effective against colonisation by P. cinnamomi when inoculated 0 and 6 months after spraying, but only the 5 g phosphite/L treatment inhibited P. cinnamomi within 12 months of spraying. Phosphite had no effect on colonisation by P. cinnamomi when plants were inoculated at 17 months after spraying. The in planta concentration of phosphite detected in the leaves, stems and roots of plants treated with 5 g phosphite/L did not differ significantly between the time of harvest or tissue type at 0.2 and 6 months after spraying. P. cinnamomi remained viable in plants treated with phosphite.Treatment with 2.5 and 5 g phosphite/L when P. cinnamomi was well established in the stems was ineffective at preventing the death of E. marginata.
Between 45 and 89% of plants were girdled on the day of spraying. Spraying plants with 2.5 and 5 g phosphite/L when conditions were less favourable for the pathogen reduced the mortality of E. marginata for up to 10 months.
E. marginata seedlings responded to damage by P. cinnamomi with the production of kino veins and woundwood. Bark lesions were in the process of being sloughed off by 7 months after inoculation in plants that remained alive. In plants of a resistant (RR) clonal line and susceptible (SS) clonal line, phosphite treatment inhibited lesion extension in stems, but lesions did not indicate the amount of stem colonised by P. cinnamomi. The pathogen was isolated from up to 17 cm beyond the lesion front in the RR clonal line. Treatments that reduced the mortality of E. marginata were 5 g phosphite/L in the RR clonal line (RR/5) and 10 g phosphite/L in the SS clonal line (SS/10).
Uninoculated plants were wounded with liquid nitrogen to determine the microscopic responses to injury in the absence of the pathogen. Wound closure was achieved within 21 days of wounding, with callus formation and vascular cambium regeneration. A wound periderm separated wounded tissue from healthy tissue, adjacent to a lignified boundary zone. Two types of phellem were observed thin-walled phellem (TnP) and thick-walled phellem (TkP). The first-formed TnP layers contained variable-shaped cells, while subsequent layers were more cubical in shape. Multiple TnP layers developed up to 42 days after wounding, with TkP cells sandwiched between the TnP layers. Genotype and phosphite treatment did not affect the wound responses.
Inoculated plants with a restricted lesion extension also formed a wound periderm to separate damaged tissue from healthy tissue. Phosphite treatment stimulated the responses to P. cinnamomi in both clonal lines. Early development of the wound periderm was visible by 6 days after phosphite treatment. It waspreceded by the formation of a ligno-suberised boundary zone in the cambial zone and in phloem parenchyma cells existing prior to injury. Suberin was not detected in the SS/0 treatment. TnP layers completely surrounded lesioned tissue in plants still alive by 24 days after phosphite treatment. Extensive callus production was evident in the SS/10, RR/5 and RR/10 treatments.
Temperature affected the post-inoculation efficacy of phosphite and anatomical responses of E. marginata. At 20°C, lesion extension was restricted in both clonal lines of E. marginata, irrespective of phosphite treatment. Greater than 70% of inoculated plants in all treatments produced a ligno-suberised boundary zone at 20°C and between 30 and 70% formed a wound periderm. At 28°C, lesion extension was reduced in phosphite-treated plants at 7 days after treatment. However, lesions continued to extend up to 5 mm per day in the SS clonal line and very few SS plants formed a wound periderm at the lesion front. This contrasted with the strong responses to abiotic wounding observed in uninoculated SS plants at 28°C. The most extensive responses to P. cinnamomi were detected in the RR/5 treatment at 28°C, with a ligno-suberised boundary zone and differentiated TnP of a wound periderm observed in greater than 70% of plants. This treatment resulted in significantly less girdled plants than all other treatments at 28°C, including the RR/0 treatment. At 23 and 24°C, there was no significant difference in acropetal lesion extension or circumferential lesion spread between clonal lines. The inoculation technique and environmental conditions may have resulted in too high a disease pressure for a full expression of resistance in the RR clonal line.
This thesis demonstrates that phosphite has the potential to enhance the resistance of young E. marginata and enable them to survive infection by P. cinnamomi. However, its effectiveness is dependent upon a number of factors, including host resistance, environmental conditions, the applied phosphite concentration and the timing of application.
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Belhaj, Rajah. "New Phytophthora species in Western Australia: Pathogenicity and control by phosphite in vitro and in planta". Thesis, Belhaj, Rajah (2017) New Phytophthora species in Western Australia: Pathogenicity and control by phosphite in vitro and in planta. PhD thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/41174/.
Testo completoAbstract (sommario):
A number of new Phytophthora species to Western Australia, have been isolated from dying native species in southwest Western Australia (SWWA). However, little is known about their host range or whether the pathogenic species can be controlled by phosphite. The effect of phosphite on 23 Phytophthora species was investigated in vitro. On solid medium, EC50 values were 5 to >160 μg/ml phosphite, whilst in liquid medium buffered using 0.03 M MES (2-(N-morpholino) ethanesulfonic acid), EC50 values ranged from 30 to >900 μg/ml. Nineteen of 23 species displayed a much higher level of tolerance in buffered liquid medium to phosphite than in solid, or unbuffered liquid medium. Assessment of phosphite tolerance was more accurate using liquid, rather than solid medium. Casuarina obesa, Banksia littoralis, B. occidentalis, B. grandis, Lambetia inermis, Corymbia calophylla, and Eucalyptus marginata were screened in the glasshouse as possible susceptible hosts by inoculating soil with 22 Phytophthora species and assessing plant growth after 6 weeks. P. niederhauserii had a wide host range similar to P. cinnamomi. Other species that killed one or more hosts were P. elongata, P. boodjera, P. moyootj, P. constricta and P. rosacearum. No Phytophthora species tested killed C. calophylla. To test the effectiveness of phosphite as a control agent, Eucalyptus marginata, B. occidentalis, B. littoralis and L. inermis were sprayed with 0.5% phosphite seven days before soil inoculation with ten Phytophthora species. No phosphite-treated plants died, but in unprotected controls P. cinnamomi and P. neiderhauserii killed at least one host plant of all species, while plants of E. marginata were also killed by P.constricta, P. boodjera, P. elongata, and P. multivora. For P. constricta, P. boodjera, P. multivora, P. rosacearum and P. arenaria, for one or more host species, the reduction of shoot or root growth caused by the pathogen was not eliminated by spraying plants with phosphite. There was no relationship between phosphite tolerance in vitro (as determined by EC50) and the response to phosphite in planta: for example, P. gibbosa was highly tolerant in vitro but controlled by phosphite in planta. In L. inermis subsp. inermis all species of Phytophthora reduced root mass even in plants sprayed with phosphite. Phosphite prevented lesion development in E. marginata and B. occidentalis after underbark inoculation of with Phytophthora cinnamomi and P. niederhauserii.
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com, kathrynmccarren@hotmail, e Kathryn McCarren. "Saprophytic ability and the contribution of chlamydospores and oospores to the survival of Phytophthora cinnamomi". Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060807.92625.
Testo completoAbstract (sommario):
Phytophthora cinnamomi has been recognised as a key threatening process to Australias biodiversity by the Commonwealths Environment Protection and Biodiversity Conservation Act 1999. Despite over 80 years of extensive research, its exact mode of survival is still poorly understood. It is widely accepted that thin- and thick-walled chlamydospores are the main survival propagules while oospores are assumed to play no role in the survival of the pathogen in the Australian environment, yet evidence is limited. The saprophytic ability of the pathogen is still unresolved despite the important role this could play in the ability of the pathogen to survive in the absence of susceptible hosts. This thesis aimed to investigate chlamydospores, oospores and the saprophytic ability of P. cinnamomi to determine their contribution to survival.
Phytophthora cinnamomi did not show saprophytic ability in non-sterile soils. The production of thick-walled chlamydospores and selfed oospores of P. cinnamomi in vitro was documented. Thick-walled chlamydospores were sporadically formed under sterile and non-sterile conditions in vitro but exact conditions for stimulating their formation could not be determined. The formation of thick-walled chlamydospores emerging from mycelium of similar wall thickness was observed, challenging the current knowledge of chlamydospore formation.
Selfed oospores were abundant in vitro on modified Ribeiros minimal medium in one isolate. Three other isolates tested also produced oospores but not in large numbers. Although the selfed oospores did not germinate on a range of media, at least 16 % were found to be viable using Thiozolyl Blue Tetrazolium Bromide staining and staining of the nuclei with 4´, 6-diamidino-2-phenylindole.2HCl (DAPI). This indicated the potential of selfed oospores as survival structures and their ability to exist dormantly.
The ability of phosphite to kill chlamydospores and selfed oospores was studied in vitro. Results challenged the efficacy of this chemical and revealed the necessity for further study of its effect on survival propagules of P. cinnamomi in the natural environment. Phosphite was shown to induce dormancy in thin-walled chlamydospores if present during their formation in vitro. Interestingly, dormancy was only induced by phosphite in isolates previously reported as sensitive to phosphite and not those reported as tolerant.
Chlamydospores were produced uniformly across the radius of the colony on control modified Ribeiros minimal medium but on medium containing phosphite (40 or 100 µg ml-1), chlamydospore production was initially inhibited before being stimulated during the log phase of growth. This corresponded to a point in the colony morphology where mycelial density changed from tightly packed mycelium to sparse on medium containing phosphite. This change in morphology did not occur when the pathogen was grown on liquid media refreshed every four days, and chlamydospores were evenly distributed across the radius of these colonies. This trend was not observed in selfed oospores produced in the presence of phosphite. Selfed oospore production was found to be inhibited by phosphite at the same concentrations that stimulated chlamydospore production.
Isolates of P. cinnamomi were transformed using a protoplast/ polyethylene glycol method to contain the Green Fluorescent Protein and geneticin resistance genes to aid in future studies on survival properties of the organism. Although time constraints meant the stability of the transgene could not be determined, it was effective in differentiating propagules of the transformed P. cinnamomi from spores of other microrganisms in a non-sterile environment. Two different sized chlamydospores (approximately 30 µm diameter and < 20 µm diameter) were observed in preliminary trials of transformed P. cinnamomi inoculated lupin roots floated in non-sterile soil extracts and these were easily distinguished from microbial propagules of other species. The growth and pathogenicity was reduced in two putative transformants and their ability to fluoresce declined over ten subcultures but they still remained resistant to geneticin.
This study has improved our knowledge on the survival abilities of P. cinnamomi in vitro and has provided a useful tool for studying these abilities under more natural glasshouse conditions. Important implications of phosphite as a control have been raised.
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Enriquez, Sevilla Luis Javier. "Activity of phosphite antioxidants in synergistic blends in the thermal and photooxidation of high-density polyethylene (HDPE)". Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364483.
Testo completo