Dissertations / Theses on the topic 'Crop species'
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1
Wilson, Susan Ann. "Response to SO2 exposure of crop species and important eucalyptus species in Australia." Thesis, Wilson, Susan Ann (1993) Response to SO2 exposure of crop species and important eucalyptus species in Australia. PhD thesis, Murdoch University, 1993. https://researchrepository.murdoch.edu.au/id/eprint/52515/.
Abstract:
The primary objective of this research was to investigate the impact of long-term exposure to SO2 on the growth and yield of major agricultural plant species and commercially important forest Eucalyptus species grown under Mediterranean climatic conditions in Australia; thereby providing the scientific criteria necessary for the development of air quality standards for sulphur dioxide (SO2) in Australia. There has been very little research on the response to SO2 of plants which grow in dry or Mediterranean climates; to date Australia has largely relied on overseas data to predict the impact of air pollutants on its agricultural and forestry industries. The vast majority of these data have been derived from studies on the effects of plants grown in cooler, moister climates. Vegetation grown in a Mediterranean climate, however, possesses certain biological features that enable success in such a climate; evidence suggests that the vegetations' response to SO2 may be different from that of other vegetation types. More particularly, as a most distinctive feature common to plants grown in Mediterranean climates is their drought stress resistance, it is possible that common mechanisms underlie the resistance of both drought stress and SO2 stress; this is explored at a theoretical level. As a consequence of biological differences, extrapolation from studies on plant species successful in cool, moist climates may be inappropriate in predicting the response to SO2 of Mediterranean climate vegetation.
The research was divided into two main areas. Firstly, the effects of long-term SO2 exposure on growth, yield and/or quality of the most important cereals, nitrogen-fixing pasture species and Eucalyptus tree species grown under Mediterranean climatic conditions in open-top chambers were studied. This resulted in a comprehensive documentation of the effects of SO2 on the most commercially important plants in Australia and the development of exposure-response models. Secondly, construction and analysis of a data base for all data derived in Australia was undertaken resulting in the establishment of generalised exposureresponse models to define the response to long-term SO2 exposure of agricultural species grown in a Mediterranean climate and the genus Eucalyptus. The data were derived from many experiments but represent a unique uniformity of sampling and exposure techniques. In all cases the most appropriate model to describe plant response to SO2 exposure was a regression between SO2 concentration and percentage yield change or the logarithm of percentage yield change; the models had the capacity to explain up to 75% of the variability in the data and were not improved by a number of transformations of either variable. The model limitations, conditions for application and areas highlighted by the study requiring further research are discussed.
The study provided several results which did not support the hypothesis that the genetic material, and therefore biological features, associated with the type of plants grown in Mediterranean regions of Australia would result in a response different to that of plants grown in other climatic regions. The findings suggested that as a group, agricultural plants adapted to water-limited conditions vary widely in their response to SO2 exposure and do not appear to differ in response from plants adapted to other climatic conditions. Therefore air quality standards developed overseas may be appropriate at a general level to protect agricultural plants. Eucalypts, however, appear to be amongst some of the most sensitive species to SO2 tested to date, world-wide and the transportation of overseas air quality standards would not be valid for their protection. It is postulated that this is, at least in part, attributable to their adaptation to low nutrient soils and to the fact that many species have the capacity, due to their root systems, to continue to transpire even under conditions of stress.
The research outlined derived empirical models to describe the response to a range of SO2 concentrations of agricultural species grown in a Mediterranean climate and Eucalyptus species. The next step in research should be aimed at defining exposure-response with a mechanistic basis for yield response thereby defining its qualitative and quantitative physiological basis. This would facilitate the achievement of a more complete description of plant response and provide a basis for extending the existing data to describe and predict potential plant responses to SO2 under a broader range of conditions.
2
Fletcher, Penny Hazel. "The pollination of four wild plants species in crop fields." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533764.
3
Badakshi, Farah. "Genomes in the evolution of polyploid crop species and hybrids." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/29061.
Abstract:
Many of the world’s crop species are recent polyploids. The various genomes from the diploid ancestors (known or, often, unknown) interact, with variable effects on genome packaging and nuclear organization (together the nuclear architecture), chromosome stability and gene expression. This project used a comparative approach to understand the genome composition in polyploids, focusing on millets in the Panicum group, saffron Crocus, Brassica and Nicotiana. In situ hybridization using DNA probes was used to identify the chromosomes and antibodies to synaptonemal complex, DNA repair and chromatin structure proteins including histones, which allow the understanding of the modulation of chromosome behaviour depending on the ancestral origin of the chromosomes, were used. The ancestors of proso millet, P. miliaceum (2n=4x=36), were identified as P. capillare and being the same as one genome in the 4x P. repens by in situ hybridization and ITS sequencing. A cell fusion hybrid of Nicotiana x sanderae + N. debneyi was confirmed, with demonstration of chromosome loss, by IRAP markers and in situ hybridization. Saffron Crocus, Crocus sativus 2n=3x=24, was shown to not be an autopolyploid, but to include three genomes with somewhat different chromosomal and sequence characteristics. The alien lines of Brassica and Raphanus with the fertility restorer genes were identified with B. rapa carrying the two chromosomes of Raphanus carrying the fertility restorer genes. Furthermore, the meiotic pairing basis of the alien lines of Brassica and Orychophragmus was also observed which gives an insight into the meiotic pairing between two different species. The water stress resistant genes could be identified from Panicum and thus be utilized in better water usage of plants. It would be possible in future to develop a synthetic C. sativus and thus rescue its declining production around the world, thus improving its economic potential. The fertility restorer gene can now be introduced into the B. rapa species using various mutagens.
4
Konkle, Samantha N. "Status of Amaranthus Species in Ohio Crop Production." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437400544.
5
Sayyari, Zahan Mohammad Hassan. "Manganese efficiency and manganese uptake kinetics of different crop species." Göttingen Cuvillier, 2008. http://d-nb.info/991005724/04.
6
Grindlay, Douglas J. C. "Principles governing the ability of cover crop species to trap nitrate." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294723.
7
Sigdel, Sailesh. "Seeding Time and Interseeded Cover Crop Species Influence Sugarbeet Yield and Quality." Thesis, North Dakota State University, 2020. https://hdl.handle.net/10365/31884.
Abstract:
Field experiments were conducted to evaluate cover crop interseeding time and species effect on sugarbeet production during 2018 and 2019 growing seasons. Cover crops were first interseeded in June and second interseeding was done in late June or early July. Four cover crops species, Austrian pea (Pisum sativum L.), winter rye (Secale cereale L.), winter camelina [Camelina sativa (L.) Crantz], and brown mustard (Brassica juncea L.), were examined. First interseeding resulted in significantly higher cover crop biomass than second interseeding. In 2018, the highest recoverable sugar yield was observed with pea (13.9 Mg ha-1) and camelina (6.6 Mg ha-1) first-interseeded, at Ada and Downer, MN, respectively. In 2019, camelina (11.2 Mg ha-1) at Ada, MN, and pea (12.4 Mg ha-1) at Prosper, ND both second-interseeded, had the highest recoverable sugar yield. Cover crops had no negative impacts on sugarbeet, but the selection of species and planting time are critical.
8
Wesheu, Irene Catherine. "Species richness - standing crop relationships on an infertile shoreline in Nova Scotia." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5200.
9
Persson, Helena. "Estimating genetic variability in horticultural crop species at different stages of domestication /." Alnarp : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-5838-2.pdf.
10
D'Utra, Vaz Fernando Berlinck. "Somatic and sexual hybridization in tropical fruit crop species passionfruit and tomato." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334766.
11
Chai, Hui Hui. "Developing new approaches for transcriptomics and genomics : using major resources developed in model species for research in crop species." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14246/.
Abstract:
With the estimated increase in global demand for food and over-reliance on staple food crops, the exploitation of agricultural biodiversity is important to address food security challenges. The aim of this study is to develop approaches to transfer major informational and physical resources developed in model plant and major crop species to resources poor crop species, using oil palm and Bambara groundnut as two exemplar crops. XSpecies (cross-species) approach, the core approach of the study, is described as the approach which uses microarrays developed for a given species to analyse another related species. The use of the XSpecies approach (here the cross-hybridisation of DNA from oil palm onto heterologous Affymetrix microarrays for Arabidopsis and rice), is the first experiment reported in oil palm and focused on a bulked segregant analysis of different shell-thicknesses for oil palm fruit. Primers design involved screening candidate probe-pairs filtered using PIGEONS software against oil palm transcriptome sequences generated using 454 sequencing technology. The results provided an insight into the effects of sequence divergence between oil palm and the reference species (Arabidopsis and rice) onto the power of detecting single feature polymorphism (SFPs) in oil palm, implying the importance of close association between studied and model plant/crop in XSpecies approach. The XSpecies approach coupled with genetical genomics was also tested within legumes, with Bambara groundnut as the query species compared to soybean as the resource rich species (20 Mya). A mild drought experiment, conducted in a controlled environment glasshouse, used an F5 segregating population derived from a controlled cross between DipC and Tiga Nicuru in Bambara groundnut. The cross-hybridisation of Bambara groundnut leaf RNA to the soybean GeneChip individual oligonucleotide probes resulted in a total of 1,531 of good quality gene expression markers (GEMs) on the basis of the differences in the hybridisation signal strength. The first ‘expression-based’ genetic map (GEM map) was constructed using 165 GEMs spanning 920.3 cM of Bambara groundnut genome. The first high density DNA-marker genetic map of 1,341.3 cM combining dominant DArT and co-dominant SNPs, developed using the DArT Seq approach, with additional pre-existing microarray-based DArT and SSR markers, was also developed in the F3 segregating population. Both maps were combined to form the first integrated map of 1,250.7 cM with 212 markers. Morphological differences and the rapid reduction in stomatal conductance observed within the F5 segregating population in the drought experiment provided trait data for a QTL analysis. The comprehensive QTL analysis in Bambara groundnut detected significant QTLs for morphological traits using GEM map, including internode length, peduncle length, pod number per plant, pod weight per plant, seed number per plant, seed weight per plant, 100-seed weight, shoot dry weight and harvest index across four linkage groups: LG1, LG2B, LG8B and LG11A. The loci controlling internode length and peduncle length were also consistently mapped to single marker on LG1 in DArTseq map using F3 segregating population, suggesting that these two traits are probably controlled by single gene or two closely linked genes. Despite significant genotypes effects on stomatal conductance tested in ANOVA analysis, no major QTLs were detected, suggesting the contributions of a number of small genetic effects to stomatal conductance. A preliminary homology search using the LG1 linkage group markers and associated gene models showed the ability to develop a framework for identification of candidate genes in Bambara groundnut relative to soybean. The present study also developed the resources for an eQTL analysis in a cross-species context. Translation from major and model plant species to underutilised and resource poor crops is critical to be able to develop many crop species with potential for future agriculture. This study examines some of the approaches which might be adopted and replicated in various underutilised crop species.
12
Fedkenheuer, Michael Gerald. "Understanding Plant Pathosystems in Wild Relatives of Cultivated Crop Plants." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81976.
Abstract:
As the global population rises, the demand for food increases which underscores a
need for improvement in food security. Disease pressures are a major concern
surrounding sustainable agriculture. Static crop populations, containing little to no
genetic diversity, are vulnerable to diverse pathogen populations. Wild relatives of crop
plants are a reservoir for new disease resistance traits that can be introgressed into
cultivated crops. The identification of novel disease resistance is of paramount
importance because pathogen co-evolution is not only defeating current resistance genes
(R genes) but chemical controls as well. Phytophthora sojae (P. sojae), the causal agent
of Phytophthora root and stem rot disease, reduces soybean harvests worldwide. We
developed an approach to screen for new R genes that recognize core effectors from P.
sojae. We expect R genes identified by these screens to be durable because P. sojae
requires core effectors for virulence. We utilized effector-based screening to probe
Glycine soja germplasm with core RXLR effectors from P. sojae to search for novel R
genes. We developed segregating populations from crosses of P. sojae resistant G. soja
germplasm with susceptible G. max cultivar Williams to determine inheritance of
potential R genes in germplasm that responded to core effectors. We are using marker
assisted breeding to map disease resistance traits in recombinant inbred (RI) lines. To
better understand pathosystems, we examined host resistance and susceptibility using
bioinformatics. We analyzed the interaction between Arabidopsis thaliana ecotype Col-0
and Hyaloperonospora arabidopsidis isolate Emwa1 using a publicly available RNA
time-course experiment. We describe a new algorithm to sort genes into time-point
specific clusters using activation and repression parameters. Gene ontology annotations
were used to identify defense genes with unique expression profiles, and A. thaliana null
mutants for these genes were significantly more susceptible to Emwa1 than wild-type.
We plan to use these tools to rapidly identify and guide introgression of durable disease
resistance into crop species.Ph. D.
13
Barteri, Fabio. "Impact of transposition on the generation of genetic variability in Prunus crop species." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669550.
Abstract:
ls Elements transposables (ETs) són unitats genètiques mòbils aptes a canviar la seva posició en el genoma i difondre autònomament. En els eucariotes, els ETs constitueixen una part considerable del DNA genòmic. Diversos estudis relacionen la seva difusió al creixement de la mesura i de la variabilitat genètica dels genomes eucariotes. No obstant això, el abast de l’impacte d’aquests elements sobre l’estructura i funció del genoma deixa moltes preguntes sense resposta. Malgrat el gran desenvolupament de camps com la genòmica i l’anàlisi computacional de dades massius, encara cal un esforç en el desenvolupament i l’avaluació de software i protocols computacionals dedicat a l’estudi genòmic de ETs. En aquest sentit, la tesi de doctorat dipositada mitjançant aquesta sol·licitud es divideix entre l’esforç de mesurar l’impacte de ETs en la generació de variabilitat genètica en les espècies de cultius préssec (Prunus persica) i ametlla(Prunus dulcis), i l’avaluació tècnica de software dedicat a la detecció i caracterització de ETs a partir de dades NGS. La tesi es desenvolupa en tres capítols. El primer capítol presenta els resultats d’un benchmarking de diferents programes designats per detectar polimorfismes estructurals deguts a transposició. El segon capítol discuteix els resultats de l’anotació de ETs en ametller i presseguer. Després d’una anotació global del contingut de ETs en els dos genomes seqüenciats, hem refinat l’anotació dels retrotransposons LTR (RT-LTR), una subclasse de ETs habitualment molt actius en planta. Cadascun dels RT-LTR han estat associats a dues variables: el temps d’inserció i la seva conservació en una població de 16 varietats de presseguer i 19 varietats d’ametller, el genoma quedava disponible en forma de mostres Whole Genome Sequencing (WGS). La combinació d’aquestes dues variables indica que el precursor del presseguer va patir una reducció de la mida de població abans que la seva separació des ametller. Aquesta separació va ser seguida per un increment dramàtic del nombre d’insercions RT-LTR en presseguer. Per això, reconeixem la dinàmica de transposició de RT-LTR com distincta en les dues espècies i com a font potencial de diferenciació genètica entre elles. En el tercer capítol, aquest resultat es detalla des del punt de vista de l’expressió dels RT-LTR. A partir de dades públiques de RNA-seq, hem provat el Software TE-transcripts. Els resultats indiquen l’activitat transcripcional de 11 famílies de RT-LTR. En el seu conjunt, aquest treball de tesi representa un esforç tant en la direcció de la millora tècnica dels protocols computacional per a l’estudi de la transposició a nivell genòmic, com en l’avaluació biològica de l’impacte dels ETs en la diferenciació genètica de dos importants espècies de cultiu.Los Elementos Transponibles (ETs) son unidades genéticas móviles aptas a cambiar su posición en el genoma y difundirse autónomamente. En los eucariotas, los ETs constituyen una parte considerable del DNA genómico. Diversos estudios relacionan su difusión al crecimiento del tamaño del genoma y al incrementar de la variabilidad genética. Sin embargo, la medida del impacto de estos elementos sobre la estructura y función del genoma deja muchas preguntas sin respuesta. No obstante el gran desarrollo de campos como la genómica y el análisis computacional de datos masivos, se necesita todavía un esfuerzo en el desarrollo y la evaluación de software dedicado al estudio genómico de ETs. En este sentido, la tesis de doctorado depositada mediante esta solicitud se divide entre el esfuerzo de medir el impacto de ETs en la generación de variabilidad genética en las especies de cultivos melocotón (Prunus persica) y almendra (Prunus dulcis), y la evaluación técnica de software dedicado a la detección y caracterización de ETs a partir de datos NGS. La tesis se desarrolla en tres capítulos. El primer capítulo presenta los resultados de un benchmarking de distintos programas designados para detectar polimorfismos estructurales debidos a transposición. El segundo capítulo discute los resultados de la anotación de ETs en almendro y melocotonero. Tras una anotación global del contenido de ETs en los dos genomas secuenciados, hemos refinado la anotación de los retrotransposones LTR (RT-LTR), una subclase de ETs habitualmente muy activos en planta. Cada uno de los RT-LTR han sido asociados a dos variables: el tiempo de inserción y su conservación en una población de 16 variedades de melocotonero y 19 variedades de almendro, cuyo genoma quedaba disponible en forma de muestras Whole Genome Sequencing (WGS). La combinación de estas dos variables indica que el precursor del melocotonero sufrió una reducción del tamaño de población antes que su separación desde almendro. Dicha separación fue seguida por un incremento dramático del número de inserciones RT-LTR en melocotonero. Por esto, reconocemos la dinámica de transposición de RT-LTR como distincta en las dos especies y como fuente potencial de diferenciación genética entre ellas. En el tercer capítulo, este resultado se detalla desde el punto de vista de la expresión de los RT-LTR. A partir de datos públicos de RNA-seq, hemos probado el software TE-transcripts. Los resultados indican la actividad transcripcional de 11 familias de RT-LTR. En su conjunto, este trabajo de tesis representa un esfuerzo tanto en la dirección de la mejora técnica de los protocolos computacional para el estudio de la transposición a nivel genómico, cuanto en la evaluación biológica del impacto de los ETs en la diferenciación genética de dos importantes especies de cultivo.
Transposable Elements (TEs) are mobile genetic units that are capable to change their position in the genome and to spread autonomously. In eukaryotes, TEs make up a considerable part of the genomic DNA and their spread has been linked to the growth of the genome size and the increase of genetic variability during evolution. However, the extent of their impact on genome structure, function and disease remains a matter of open investigation. Despite the rise of genomics and large-scale bioinformatics allowed to unravel several aspects of these mobile elements, the increasing amount of complex genomics data calls for efforts in developing and testing more efficient software implementations. In this optics, the PhD thesis submitted through this application unfolds on a double track. On one side, the dissertation discusses the impact of TEs in the generation of genetic variability in the major crops peach (Prunus persica) and almond (Prunus dulcis). On the other side, a technical assessment of the performance of software dedicated to the detection and characterisation of TEs from NGS data. The dissertation is divided into three chapters. The first chapter discusses the results of the benchmarking of several software packages designed to detect structural polymorphisms from DNA-seq data. The second chapter reports the results from the annotation of TEs in peach and almond. After a global annotation of the TEs content in both genomes, we have refined the annotation of the LTR- retrotransposons (LTR-RTs), a subclass of retrotransposons that are usually active in plant genomes. Each of the resulting elements, identified on the reference genomes, has been then associated with two variables: their inferred insertion time, and their conservation within a population of 16 peach and 19 almond cultivated varieties, made available as Whole-Genome re-Sequencing (WGS) samples. The combination of these two variables indicates that peach precursor underwent a serious population shrinkage before its separation from sister species almond and that a burst of new insertions affected the peach genome after the separation of these two species. The LTR-RTs dynamics is hereby different in Universitat Autònoma de Barcelona Doctorat en Biologia i Biotecnologia Vegetal peach and almond, represents a major genetic difference between two very close species and it is a potential source of genetic differentiation between these two species. This result is further investigated in Chapter 3, where we perform a transcriptional quantitation of LTR-RTs elements in Peach. Starting from publicly available RNA-seq data of a Xanthomonas arboricola infection time-course experiment in two peach varieties (JH Hale and Redkist), we have tried the package TEtranscripts, that is specifically dedicated to the assessment of the transcriptional level of TEs. Results confirm the high transcriptional activity of 11 LTR-RTs families. Also, the potential impact of transposition on gene regulation is indicated by the proximity to a LTR-RTs insertion of a considerable proportion of the genes that are differentially expressed during the course of the infection. Globally, this thesis work represents both an effort in the technical improvement of the computational protocols to study transposition and a biological assessment of the impact of TEs in the genetic differentiation of two important crop species.
14
Alkadri, Dima <1979>. "Fusarium species responsible for mycotoxin production in wheat crop: involvement in food safety." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4884/.
Abstract:
Fusarium Head Blight (FHB) is a worldwide cereal disease responsible of significant yield reduction, inferior grain quality, and mycotoxin accumulation. Fusarium graminearum and F. culmorum are the prevalent causal agents. FHB has been endemic in Italy since 1995, while there are no records about its presence in Syria. Forty-eight and forty-six wheat kernel samples were collected from different localities and analyzed for fungal presence and mycotoxin contamination. Fusarium strains were identified morphologically but the molecular confirmation was performed only for some species. Further differentiation of the chemotypes for trichothecene synthesis by F. graminearum and F. culmorum strains was conducted by PCR assays. Fusarium spp. were present in 62.5% of Syrian samples. 3Acetyl-Deoxynivalenol and nivalenol chemotypes were found in F. culmorum whilst all F. graminearum strains belonged to NIV chemotype. Italian samples were infected with Fusarium spp for 67.4%. 15Ac-DON was the prevalent chemotype in F. graminearum, while 3Ac-DON chemotype was detected in F. culmorum. The 60 Syrian Fusarium strains tested for mycotoxin production by HPLC-MS/MS have shown the prevalence of zearalenone while the emerging mycotoxins were almost absent. The analysis of the different Syrian and Italian samples of wheat kernels for their mycotoxin content showed that Syrian kernels were mainly contaminated with storage mycotoxins, aflatoxins and ochratoxin whilst Italian grains with mainly Fusarium mycotoxins. The aggressiveness of several Syrian F. culmorum isolates was estimated using three different assays: floret inoculation in growth chamber, ear inoculation in the field and a validated new Petri-dish test. The study of the behaviour of different Syrian wheat cultivars, grown under different conditions, has revealed that Jory is a FHB Syrian tolerant cultivar. This is the first study in Syria on Fusarium spp. associated to FHB, Fusarium mycotoxin producers and grain quality.
15
Gathumbi, Stanley Mwangi. "Nitrogen sourcing by fast-growing legumes in pure and mixed species fallows in western Kenya." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322531.
16
Jacobs, Addison Denae. "Influence of Cover Crop Species on Soil Physical Properties in a Corn-soybean Rotation." Thesis, Arkansas State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10831039.
Abstract:
As crop land decreases and population increases, soil quality is becoming a concern. Utilizing cover crops in cropping systems could improve soil quality. This study examined 16 treatments of single-species cover crops, cover crop mixes, and two control treatments on a silt-loam soil, in a corn ( Zea mays L.) - soybean (Glycine max L. Merr.) crop rotation under no-tillage, to determine their effect on soil physical properties. Cover crop biomass differed (p<0.10) among treatments and produced a maximum of 15.6 Mg ha-1 of biomass in the crimson clover treatment. Water infiltration rates increased as much as 282% in the complete-mix treatment compared to the fallow control. Differences in infiltration rates due to cover crop species were shown in two-years. However, these results suggest that it may take more time for cover crops to affect change in bulk density and aggregate stability.
17
Al-shallash, Khalid S. "Studies on the biology and control of weedy species of Lolium (annual rye-grasses)." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261517.
18
Guretzki, Sebastian [Verfasser]. "Development of plant species and ecotypes tolerant to drought stress as crop plants / Sebastian Guretzki." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1053414587/34.
19
Davis, Cathryn Joyce. "Cover crops for soil health and forage." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/34537.
Abstract:
Master of ScienceDepartment of Agronomy
DeAnn R. Presley
Cover crops have numerous benefits and while cover crops have been used for centuries, currently there are few producers in Kansas growing them and so there is a need for additional research on how cover crops affect soil properties, and on the potential for utilizing cover crops as forage. Two studies are presented in this thesis. The first study evaluated the use of cover crops in a vegetable production system as compared to a fully tilled control. This study evaluated soil physical properties in the form of wet aggregate stability and infiltration, and microbial properties by soil microbial biomass carbon (MBC). Over the three year study, the most pronounced differences observed were in the wet aggregate stability between the cover crop and control treatments where the cover crop treatments had better soil aggregation compared to the control. At the conclusion of the study, there was not a difference between fall and spring planted cover crop treatments. The second study evaluates species composition and forage quality of various combinations of multi-species cover crop mixtures. This study evaluated sixteen treatments, each consisting of a three-way mixture of a brassica (turnip or radish), grass (rye, wheat, barley, oat), and a legume (berseem clover or Austrian winter pea). Species composition analysis found that the brassica species dominated the mixtures (60-80% by mass on a dry weight basis) in 2014 while the grass species were dominant (62 – 67%) in 2015. Overall all treatments produced prime quality forage (as compared to hay values), however some treatments cost significantly more to plant than others. Therefore an economic analysis compared the treatments and found that the treatments containing turnips and oats generally provided the best return on investment given that both of these species were among the cheapest to plant and produced moderate to high biomass compared to the other treatments. The results of these projects point to the potential benefits that cover crops can have for producers interested in improving soil or utilizing cover crops for forage.
20
Cantamutto, Sanchez Miguel Angel. "Agronomic study of two annual helianthus species naturalized in Argentina as potential sunflower crop genetic resource." Doctoral thesis, Universitat de Lleida, 2008. http://hdl.handle.net/10803/8341.
Abstract:
El gènere Helianthus (Asteraceae), nadiu d'Amèrica del Nord, compren no només elgirasol conreuat H. annuus var. Macrocarpus L., sinó també d'altres espècies que són
invasores. El gira-sol silvestre H. annuus ssp. Annuus L. i H. petiloaris Nutt. Són dues
espècies anuals naturalitzades en la part central d'Argentina. Ambdues resulten
d'interès com a recurs fitogenètic.
L'H. annuus silvestre fou probablement introduït per a ús farratger mentre que sembla
que l'H. petiolaris ingressà com a contaminant de llavors. S'estudiaren les condicions
ambientals i ecològiques dels hàbitats ocupats per les poblacions mitjançant anàlisi
multivariant. Es suggereix l'existència d'un procés de difusió des del punt d'ingrés de
cada espècie, seguint la infraestructura de les comunicacions terrestres. La invasió va
ocórrer en una banda de territori en el límit entre Mollisoles i Entisoles, els mateixos
ordres de sòls que existeixen en el centre d'origen. Dins d'aquesta banda, cada
espècie s'ubicà en diferents microhàbitats transformats per activitat antròpica, com ara
tancats de filferro, tallafocs, bancals, canals. Helianthus annuus mostrà preferència
pels sòls pesants mentres que H. petiolaris preferí sòls arenosos, a l'igual que allò
constatat per a Amèrica del Nord.
La hipòtesi de flux gènic entre els dos taxa silvestres i el conreu s'explorà mitjançant
l'estudi de la morfologia de la progènie de plantes de diferent tipus y poblacions pures
que havien florit en proximitat de l'altre taxa, trobades amb condicions naturals. Es
trobà entre 0,5 a 18% d'hibridació. Considerant les dimensions de les poblacions
trobades en contacte, aquestes freqüències poden significar milers a milions d'híbrids
de primera generació cada any.
Nou poblacions argentines d'H. annuus mostraren suficient biodiversitat com per
diferenciar-se entre elles. La biodiversitat continguda en aquest nou germoplasma fou
al voltant de dos terços d'aquella observada en una mostra de gira-sols silvestres de
17 estats d'EUA. Les accessions d'Argentina mostraren diferents combinacions dels
mateixos caràcters, però una d'elles presentà un cicle de més llarga durada. El
contingut de matèria grassa i el perfil d'àcids grassos no presentaren valors d'interès
per a la millora de l'oli de gira-sol. Actualment s'investiguen d'altres trets d'interès
agronòmic, com ara la resistència al SuCMoV o la presència d'androesterilitat.
Les empreses de llavors perderen l'interès pel gira-sol transgènic després de les
investigacions que revelaren l'existència de poblacions silvestres en moltes regions del
món, intens fluxe gènic entre el conreu i els parents silvestres i el possible increment
de la capacitat reproductiva per adquisició de transgens. Els esdeveniments en
avaluació de gira-sol genèticament modificat (GM) podrien millorar el comportament
del conreu però enfronten restriccions de mercat. El futur del gira-sol GM depèn de la
possibilitat de mitigar l'efecte dels transgens sobre els parents silvestres i malesa i a
canvis en l'acceptació del mercat. Aquesta podria augmentar si el gira-sol GM
impliqués una millor qualitat per al consumidor.
El género Helianthus (Asteraceae), que es nativo de América del Norte comprende no
solo el girasol cultivado H. annuus var. macrocarpus L. sino también otras especies
que son invasoras. El girasol silvestre H. annuus ssp. annuus L. y H. petiolaris Nutt.
son dos especies anuales naturalizadas en la parte central de Argentina. Ambas
resultan de interés como recurso fitogenético.
El H. annuus silvestre fue probablemente introducido para uso forrajero mientras que
pareciera que H. petiolaris ingresó como contaminante de semillas. Se estudiaron las
condiciones ambientales y ecológicas de los habitats ocupados por las poblaciones
mediante análisis multivariante. Se sugiere la existencia de un proceso de difusión
desde el punto de ingreso de cada especie, siguiendo la infraestructura de las
comunicaciones terrestres. La invasión ocurrió en una banda de territorio en el límite
entre Mollisoles y Entisoles, los mismos órdenes de suelos que existen en el centro de
origen. Dentro de esa banda, cada especie se ubicó en diferentes microhábitats
transformados por actividad antrópica, como alambrados, contrafuegos, banquinas,
canales. Helianthus annuus mostró preferencia por suelos pesados mientras que H.
petiolaris prefirió suelos arenosos, en modo análogo a lo informado para América del
Norte.
La hipótesis de flujo génico entre los dos taxa silvestres y el cultivo se exploró
mediante el estudio de la morfología de la progenie de plantas fuera de tipo y
poblaciones puras que habían florecido en proximidad del otro taxa, halladas bajo
condiciones naturales. Se encontró entre 0.5 a 18% de hibridización. Considerando las
dimensiones de las poblaciones halladas en contacto estas frecuencias pueden
significar miles a millones de híbridos de primera generación cada año.
Nueve poblaciones Argentinas de H. annuus mostraron suficiente biodiversidad como
para diferenciarse entre ellas. La biodiversidad contenida en este nuevo germoplasma
fue alrededor de dos tercios de la observada en una muestra de girasoles silvestres
de 17 estados de USA. Las accesiones de Argentina mostraron diferentes
combinaciones de los mismos caracteres, pero una de ellas presentó un ciclo de
mayor duración. El contenido de materia grasa y el perfil de ácidos grasos no
presentaron valores que puedan ser de interés para la mejora del aceite de girasol. Se
están investigando actualmente otros rasgos de interés agronómico, como la
resistencia al SuCMoV o la presencia de androesterilidad.
Las empresas de semillas perdieron interés en el girasol transgénico luego que las
investigaciones revelaran la existencia de poblaciones silvestres en muchas regiones
del mundo, intenso flujo génico entre el cultivo y los parientes silvestres y el posible
incremento de la capacidad reproductiva por adquisición de transgenes. Los eventos
bajo evaluación en girasol genéticamente modificado (GM) podrían mejorar el
comportamiento del cultivo pero enfrentan restricciones de mercado. El futuro del
girasol GM depende de la posibilidad de mitigar el efecto de los transgenes sobre los
parientes silvestres y malezas y a cambios en la aceptación del mercado. Esta podría
aumentar si el girasol GM implicara mejor calidad para el consumidor.
The genus Helianthus (Asteraceae), native from North America comprises not only the
cultivated sunflower H. annuus var. macrocarpus L., but also some invasive species.
The wild H. annuus ssp. annuus (common sunflower) and H. petiolaris Nutt. (prairie
sunflower) are two annual species of the genus naturalized in central Argentina. Both
species merit interest as genetic resources.
Wild H. annuus was probably introduced for forage purposes, but H. petiolaris seems
to have entered as a seed contaminant. Using multivariate tools, the environment and
ecological conditions of the habitats were analysed. A diffusive process from each
entry point is suggested, following the terrestrial infrastructure. Invasion took place in a
strip of land bordering between the Mollisols and Entisols, the same soil orders as in
the centre of origin. Within that strip, each species thrived in different microhabitats
transformed by human activity such as fences, fire lines, roadsides, ditches. Helianthus
annuus showed preference for microhabitats with heavy soils, while H. petiolaris
preferred sandy soils, as has been reported in North America.
The hypothesis of gene flow between both wild taxa and the crop was tested by the
morphological study of the progeny of off type plants and pure populations that
flowered in proximity to the other taxa found under natural conditions. Between 0.5 to
18% of hybridization was found. Taking into account the dimensions of the populations
found at the points of contact, these frequencies may mean thousands to millions of
first generation hybrids each year.
Nine argentine populations of wild H. annuus showed enough biodiversity to
differentiate among them. The biodiversity contained in this new germplasm was about
two thirds of that observed in a sample of wild sunflower from seventeen USA states.
The accessions from Argentina showed different combinations of the same traits and a
longer life cycle in one accession. The oil content and fatty acid profile did not show
values that could merit attention as a source of sunflower oil improvement. Other
agronomic traits of interest, such as resistance to SuCMoV or the presence of malesterility
are currently under evaluation.
Seed companies probably lost interest in transgenic sunflower after research
demonstrated the existence of wild populations in several regions of the world, the
intense gene flow between crop and wild relatives and the probable increase of
reproductive capacity due to the acquisition of transgenes. The traits under
experimentation in genetically modified (GM) sunflower could improve the performance
of the crop but face some market restrictions. The future of GM sunflower depends on
the possibility to mitigate the effect of transgenes on the wild and weedy relatives and a
change in market place acceptance, which could increase if GM means better quality
for the consumer.
21
Gilroy, Eleanor Marjorie. "Utilising model systems and crop species to discover and characterise novel genes in plant disease resistance." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/13910.
Abstract:
This project was a collaboration between groups within the Arabidopsis research community and the crop-based research community through which the best resources of both could be utilised to study aspects of resistance to biotrophic pathogens. An objective was to work towards transferring information between models and crop plant. Activation tagged Arabidopsis lines were screened for disease susceptibility to Pseudomonas syringae pv tomato (DC3000). Two mutant lines, named activated disease susceptibility (ads), were confirmed to be susceptible and candidate gene(s) affected by the activation tag were identified. On the other hand, functional analysis of genes in crop species, which currently lack sequenced genomes, relies on post-transcriptional gene silencing (PTGS) approaches that require sequence information prior to experimentation. Suppression subtractive hybridisation isolated a cathepsin B ESTs from P. infestans challenged potato undergoing resistance gene-mediated hypersensitive response (HR). N. benthamiana is mode for studying the HR, is a close relative of potato and therefore an established virus-induced gene silencing system was utilised to investigate the role of cathepsin B. Silencing of cathepsin B resulted in suppression of the Erwinia amylovora-induced HR which was confirmed using mammalian cathepsin B inhibitors. A final aim was the development of a PTGS system in Solanum tuberosum to allow functional investigation for current and future defence-related genes identified from models and crop plant species. A PVX-based VIGS system was successfully developed for cultivated, tetraploid potato cultivars and for wild diploid Solanum species.
22
Peterson, Kendra Leigh. "Effects of humic acids and soil symbionts on growth, physiology, and productivity of two crop species." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501187076919492.
23
Vargas, Rojas Bladimir. "Agronomical evaluation of six species of forage grass tolerant to salinity in the Tamborada region." BYU ScholarsArchive, 2005. https://scholarsarchive.byu.edu/etd/5448.
Abstract:
Six forage grass species from the United States were evaluated for salinity tolerance and growth performance. A randomized block design was used with six repetitions of five furrows each to maintain experimental consistency. The study was conducted in the Tamborada region of Cochabamba, Bolivia from December 2003 through June 2004. Results indicated that significant differences exist between species (Pr<0.01). The species Elymus cinereus and Agropyron elongatum demonstrated the best performance regarding plant height, achieving heights of 35.4 cm and 32.7 cm respectively. Festuca arundinacea and Agropyron elongatum obtained larger percent coverage than the other species with 79.59% and 76.53% respectively. These species also exceed the others in production of green forage (1500.00 kg/ha and 13985.80 kg/ha) as well as in production of dry matter (5000.70 kg/ha and 4862.85 kg/ha). They are recommended for production in the region of Tamborada, Cochabamba, Bolivia.
24
Kuykendall, Matti Beth. "Biomass production and changes in soil water with cover crop species and mixtures following no-till winter wheat." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19080.
Abstract:
Master of ScienceDepartment of Agronomy
P. V. Vara Prasad,
Kraig L. Roozeboom
Replacing fallow with cover crops can provide many benefits, including improved soil quality and reduced nitrogen fertilizer requirements. The addition of cover crops into no-till systems has become popular in recent years as a means of increasing cropping system intensity and diversity. A primary concern of producers in the Great Plains is the possibility that cover crops may reduce the amount of soil water stored in the profile for the next grain crop, potentially reducing yields. Multi-species cover crop mixtures that enhance the ecological stability and resilience of cover crop communities may produce greater and more consistent biomass than single species. Field experiments were established in 2013 and 2014 near Belleville and Manhattan, KS following winter wheat (Triticum aestivum L.) harvest to evaluate the effect of cover crop species and species complexity on changes in soil profile water content and water use efficiency. Along with a chemical fallow control, ten cover crop treatments were tested: six single species, two-three component mixes, a mix of six species, and a mix of nine species. Volumetric water content was measured using a neutron probe and a Field Scout TDR 300. Similar data were collected in 2014 from an experiment established in 2007 comparing fallow, double-cropped soybean, and four cover crop types (summer and winter legumes and non-legumes) in a no-till winter wheat-grain sorghum-soybean cropping system near Manhattan, KS. Results from both studies showed that grasses produced the most dry matter with the highest water use efficiency (up to 618 kg cm-1). Fallow lost up to 7.9 cm less water than all cover crop treatments throughout cover crop growth and in the fall, but captured up to 3.4 cm less moisture in the spring than the cover crops that added residue to the soil surface. Brassica species extracted water from deeper in the soil profile than the other cover crop species. Species complexity affected water use only relative to the proportions and productivity of their individual components, with no advantage in water use efficiency for the more complex mixtures.
25
Lee, David Jackson. "Population Dynamics of Rhizoctonia Species in Tall Fescue and Creeping Bentgrass in Response to Disease Management Programs." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-07122004-140248/.
Abstract:
Rhizoctonia species are important pathogens of all turfgrasses, yet little is known about the structure of populations of these pathogens or the effect of disease control programs on population dynamics. Isolates of Rhizoctonia were obtained from a single creeping bentgrass putting green in 2002 and 2003 and from multiple tall fescue landscapes in 2003. Creeping bentgrass isolates were obtained by placing 5 mm soil cores on alkaline water agar, incubated at ~24 C for 1 to 2 days and the actively growing hyphae were transferred to potato dextrose agar (PDA). Tall fescue isolates were obtained from foliar lesions using the same procedures. Isolates were characterized using morphological characteristics, anastomosis reactions, nuclear staining, and ribosomal DNA (rDNA) sequences. From creeping bentgrass, 21 distinct clones of R. solani AG 2-2 IIIB were present in the sample population in 2002. Seven of these clones were also recovered on multiple sampling dates. Fifteen of the 21 clones from 2002 were recovered in 2003. All seven clones that were isolated in multiple sampling dates in 2002 were also recovered in 2003. There were 29 and 21 isolates of R. zeae collected from the sample population in 2002 and 2003, respectively. All 21 clones exhibited similar EC50 values to mancozeb, chlorothanlonil and azoxystrobin. Of 224 isolates collected from tall fescue during 2003, 88 were R. solani AG 1, 105 were binucleate Rhizoctonia CAG 1, 14 were R. zeae, two were R. cerealis, and 15 were not identified to species or AG. One hundred and seventy four of the isolates were assayed for sensitivity to the fungicides flutalonil, iprodione, tebuconazole, and trifloxystrobin. Mean EC50 values varied across fungicides and species, but generally were below 3.3 mg L-1. The diversity of Rhizoctonia populations associated with tall fescue, and the range in fungicide sensitivities among species indicates that response to management programs may vary with location and environment. The effects of phosphorous acid on fungal growth, disease incidence and turfgrass quality was evaluated in vitro and in vivo. Mean EC50 values of azoxystrobin (+SHAM) for R. solani 2-2 IIIB, and AG 1, P. aphanidermatum, and R. zeae were 1.27, 0.04, 0.012, and 0.145 mg L-1, respectively. Applications of phosphorous acid to creeping bentgrass and tall fescue did not significantly reduce brown patch incidence or increase turfgrass quality in field or greenhouse experiments. The benefit of phosphorous acid as a fungicide or plant nutrient is questionable.
26
Ma, Li. "Ecophysiology of the effect of red to far-red light ratio on selected weed and crop species." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63174.
Abstract:
Plants growing in canopies are exposed to reduced light intensity as well as low red/far-red light ratios, a signal of impending competition. In order to advance our understanding of the eco-physiological role of red/far-red ratio in agroecosystems, growth chamber and greenhouse studies were conducted to investigate 1. the growth and morphological responses of common lamb’s-quarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.) and tomato (Solanum lycopersicum L.) to different red/far-red ratios, 2. how leaf optical properties at red (660 nm) and far-red (730 nm) wavelengths change with leaf position and plant development, and 3. if red/far-red ratio influences response of corn (Zea mays L.), lettuce (Lactuca sativa L.), and pigweed plants to UV-B radiation. Three red/far-red ratios were achieved by using supplemental far-red lamps in growth chambers, while maintaining the photosynthetically active radiation. Results showed that red/far-red ratio treatment influenced several growth and allometric parameters and tomato, lamb’s-quarters, and pigweed differed in this regard. This differential response among species suggests that fluctuations in the red/far-red ratio in canopies could impact inter-plant interactions among these species. Red/far-red ratio in a plant canopy is affected by leaf optical properties. A study of leaf optical properties of lamb’s-quarters, pigweed and tomato using a CI-710 Miniature Leaf Spectrometer showed that leaf optical properties changed with leaf position and plant development, which could modify the light environment in canopies comprising populations of these species. Interestingly, these species differed in this regard, suggesting differences in their ability to signal potential competition. Leaf optical properties, as well as leaf position and plant development effects, therefore, should be taken into consideration in assessing the eco-physiological functions of a vegetation cover. Effect of pre-exposure to low red/far-red ratio on plant susceptibility to UV-B radiation could impact plant interaction. However, my research showed that red/far-red ratio pre-treatment and the associated change in anthocyanin concentration did not alter the response of corn, lettuce and pigweed seedlings to enhanced UV-B radiation. This improves our understanding of the eco-physiological role of these environmental stressors in agro-ecosystems, where both red/far-red ratio and UV-B levels fluctuate.Land and Food Systems, Faculty of
Graduate
27
Šišić, Adnan [Verfasser]. "Evaluation of Pathological Risks Associated with Use of Leguminous Cover crop and Living mulch species / Adnan Šišić." Kassel : Universitätsbibliothek Kassel, 2017. http://d-nb.info/1174700572/34.
28
Sherriff, C. "Physiologic specialization of the downy mildew fungus, Peronospora parasitica (Pers. Ex. Fr.)Fr., on Brassica crop species." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373340.
29
Knight, Patricia Heather Radcliffe. "Factors affecting the uptake and activity of foliage-applied diflufenican in a selected crop and weed species." Thesis, University of Strathclyde, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291992.
30
Whitacre, Marina K. "Cattle as Grazing Management and Seed Dispersal Tools for Increasing Native Species Diversity on Great Basin Rangelands." DigitalCommons@USU, 2004. https://digitalcommons.usu.edu/etd/6604.
Abstract:
A series of experiments evaluated: 1) the influence of seed intake and gut
retention time on seed passage , recovery , and germinability; 2) fecal seeding and
broadcast /trampling as techniques to incorporate seeds into a well-established
Agropyron desertorum (Fisch.) Schult. stand in Skull Valley , Utah; 3) intensive
grazing as a means to reduce Agropyron biomass and increase establishment and
survival of seeded species; and 4) the recovery and germinability of seed extracted
from dung collected from the field. Two shrubs (Artemisia tridentata Nutt. ssp.
wyomingensis Beetle & Young and Atriplex confertifolia Torr. & Frem.), a grass
(Elymus elymoides (Raf.) Swezey) , and a forb (Sphaeralcea grossulariaefolia (H. &
A.) Rydb.) were selected as representative native species. Holstein heifers were fed
15,000 , 30 ,000 , and 60,000 seeds of Artemisia , Sphaeralcea, and Elymus. Elymus
recovery was negatively correlated to seed intake. Sphaeralcea had the highest
percentage of recovered, undamaged seed, followed by Elymus and Artemisia.
Sphaeralcea and Artemisia seed passage was highest on Day 1 then dropped sharply.
Elymus passage and recovery were more consistent through time. Post-passage
germjnability was highest for Elymus and Sphaeralcea on Day 1. Artemisia
germjnation was neghgible.
In the fall seeding, Sphaeralcea emerged in 6% of the subplots (half were
volunteers). Overall seedling mortality was 93%. Elymus emerged in 63% of the
dung pats, with 86% mortality. No Artemisia emerged. Drought and Anabrus
simplex herbivory contributed to low seedling emergence and survival. In April
2003, similar treatments were applied, except Atriplex seed was substituted for
Artemisia, and a third treatment was added (broadcast seeding/raking). No
emergence was observed. Sphaeralcea had the highest seed recovery from dung
collected in the field trials, followed by Elymus, Atriplex, and Artemisia.
Sphaeralcea germinability was similar for seeds collected from both trials (11 %) and
Elymus germination was highest in the fall seeding (13%).
These studies indicate that: 1) physical seed properties (size, shape, density,
seed coat) influence seed passage , recovery, and germination; 2) intensive grazing
can reduce Agropyron biomass by 50% for 2 years; 3) broadcast/trampling may be
effective for Sphaeralcea; and 4) an average-sized dung pat (714 g) may have ample
germinable Sphaeralcea and Elymus seeds for plant establishment.
31
Leeks, C. R. F. "Determining seed vigour in selected Brassica species." Lincoln University, 2006. http://hdl.handle.net/10182/1274.
Abstract:
Variables for the accelerated ageing (AA) test, methods for reducing fungal contamination during the AA test, using the conductivity test as a vigour test, the effect of seed size on seed vigour and the relationship between laboratory test results and field perfonnance in selected Brassica spp were investigated. In the first experiment, three seed lots of turnip rape hybrid (B. rapa x campestris), turnip (B. campestris) and forage rape (B. napus); and seven seed lots of Asian rape (B. napus), six seed lots of Asian kale (B. oleraceae var. alboglabra L.) and five seed lots of choisum (B. rapa var. pekinensis) with germinations above 90% were aged at two different temperatures (41 and 42°C ± 0.3°C) and three ageing times (24, 48 and 72 ± 15 minutes). The second experiment was divided into three sections. In the first, the same seed lots and species were aged at one temperature (41°C) and time (72 h), but either 40 ml of saturated salts; KCl (83%RH), NaCl (76%RH), NaBr (55%RH); or distilled water (96%RH) were used as the ageing solutions. In the second, one turnip rape hyprid seed lot was aged at three temperatures (41, 42 and 45°C) and two times (72 and 96h), again using the three saturated salts and distilled water as ageing solutions. In the third, three turnip rape hybrid seed lots and three Asian kale seed lots were surface sterilised (1 % sodium hypochlorite) prior to ageing at one temperature (41°C) and time (72 h). In the third experiment, the same species and seed lots used in experiment one at their original seed moisture content (SMC) were tested for conductivity after soaking in deionised water for 4, 8, 12, 16, 20 and 24 h. They were then re-tested after the SMC had been adjusted to 8.5%. In the fourth experiment, three seed lots of forage rape and three seed lots of Asian kale were graded into three seed size categories; large (retained on a 2.0 mm screen), medium (retained on a 1.7 mm screen) and small (passed through a 1.7 mm screen). Graded seeds were then tested for standard germination, AA (41°C/48 h) and conductivity (measured at 16 and 24 h). In the final experiment, the relationships between laboratory tests for the six species (each consisting of three seed lots), field emergence from three sowings, and cold room emergence were evaluated. Both time and temperature influenced post-AA germination. Increasing the ageing period from 48 to 72 hours at 41°C, and 24 to 48 hours at 42°C resulted in decreased mean germination percentage for all species but not always clear separation of seed lots. While there were sometimes few differences between ageing at 41°C and 42°C, the former is preferred because it is already the temperature used for other species. For Asian rape, choisum and turnip, the previously recommended testing conditions of 41°C/72 h provided good seed lot separation, but for Asian kale and turnip rape hybrid, AA testing at 41°C/48 h provided better results. Seed moisture content after ageing ranged from 29-37% depending on species. Fungal growth on seeds during the ageing period appeared to reduce post-ageing germination in some seed lots . Substituting saturated salts for distilled water did not stress seed lots in the AA test, due to the lowered RH%, the exception being seed lots 1210 and 1296. For forage and Asian species, seed lot germination mostly remained above 90% when aged for 72 h at lowered RH%. Increasing the ageing duration from 72 to 96 hours resulted in some decreases in post-AA germination but no clear separation of seed lots. Surface sterilising the seeds prior to the AA test resulted in a lower incidence of contaminant fungi which was associated with a lower percentage of abnormal seedlings. The conductivity test was mostly able to identify vigour differences among forage and Asian vegetable brassica seed lots. Differences in conductivity readings were observed among seed lots in all species. Increasing the period of imbibition resulted in increased conductivity from most seed lots but radicle emergence occurred after 16-20 h of imbibition. Variation was observed in the time to reach 95% maximum of the imbibition curve for most species. Conductivity readings at 16 h would avoid possible influences of radicle emergence on results. Adjusting the SMC to 8.5% resulted in reduced variation in conductivity among replicates of seed lots, due to a reduction in imbibition damage. Seed size had a significant effect on both post-AA germination and conductivity results. In forage rape, large size seeds had higher post-AA germination cf. medium cf. small size seeds. In Asian kale, large size seeds had higher post-AA germination compared with small size seeds. For both forage rape and Asian kale, large size seeds had lower conductivity readings cf. small size seeds. The correlation analyses demonstrated significant relationships between AA testing and field emergence parameters (percentage emergence, emergence index and emergence rate). Significant relationships were also observed between conductivity testing and these field emergence parameters. Based on the correlation analysis, AA testing at 41°C/48 hand/or 42°C/48 h could be recommended to be used as an AA test for turnip and Asian rape; and 41°C/48 hand/or 41°C/72 h for Asian kale and choisum. Based on the correlation analysis, conductivity testing at 16 h can be used to predict the field emergence potential of forage and Asian vegetable seed lots. Vigour tests were consistently able to provide better indicators of field perfonnance than the standard germination test, although these relationships did vary with the different field sowings.
32
Bramley, Helen. "Water flow in the roots of three crop species : the influence of root structure, aquaporin activity and waterlogging." University of Western Australia. School of Plant Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0102.
Abstract:
[Truncated abstract] The hydraulic properties of the roots of three crop species important to Western Australia were examined: wheat (Triticum aestivum), narrow-leafed lupin (Lupinus angustifolius) and yellow lupin (L. luteus). Generally, the hydraulic conductivity (Lpr) of root systems differs between species and can change in response to adverse conditions. To determine the significance of root anatomy and aquaporin activity on the pathway of water flow through roots, water flow was measured across cell membranes, individual roots and whole root systems. The combination of measurements identified that wheat and lupin roots have contrasting hydraulic properties. Wheat roots absorb water preferentially in the apical region, whereas lupin roots appear to absorb water more evenly along the entire root length. Lupin roots have a greater axial hydraulic conductance than wheat, due to more abundant xylem vessels and axial conductance increases with root length, in conjunction with xylem vessel development. However, water flow through the radial pathway is the limiting factor in whole root hydraulic conductance, in all species. Modelling and the inhibition of aquaporin activity with mercuric chloride demonstrated that radial water flow in wheat roots occurs by a combination of the cell-to-cell and apoplastic pathways, but in lupins, water flow appears to be predominantly apoplastic. Despite the presence of aquaporins in root cell membranes of all species, their role in regulating bulk water flow across roots is not clear in lupins, because of the significance of the apoplastic pathway ... After draining the chambers, the root systems of yellow lupin resumed growth, but there was no subsequent recovery in narrow-leafed lupin root systems. The growth and survival strategies of wheat and lupin root systems are disparate. Wheat root systems are comprised of numerous fine, highly branched, individual roots that extract water near the root tips and have the ability to regulate flow. These attributes may be advantageous in non-uniform or variable environments. Moreover, the ability of wheat roots to regulate flow may not only support survival during waterlogging, but also enhance recovery. In comparison, lupin root systems are designed like conduits, for the rapid uptake and transport of water when conditions are favourable. However, their thick taproots and lack of regulation of water transport or anatomical changes make them unsuitable for very wet soils.
33
陳堅峰 and Kin-fung Chan. "Phylogenetic relationships and genetic diversity detected by rapd and isozyme analysis of crop and weedy species of amaranthus." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B29803846.
34
Chan, Kin-fung. "Phylogenetic relationships and genetic diversity detected by rapd and isozyme analysis of crop and weedy species of amaranthus /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17665450.
35
Kale, Manoj Ashokrao. "Bird Species in Urban and Agricultural Landscapes : Bird diversity patterns along an urbanisation gradient and crop damage caused by birds on the Deccan Plateau, India." Doctoral thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154421.
Abstract:
The major human activities that have transformed the Earth include agriculture and urbanization. The present study was conducted to contribute to a description of the effect on birds of urbanization and agriculture in an Indian region. Terrestrial bird assemblages were censused along a five-stage urbanisation gradient between January and April 2010-2013 near the city of Amravati, on the Deccan Plateau, Central India. Altogether, 89 species of birds were recorded, with the highest species richness in the rural areas (67 species) and lowest in the urban stage (29 species). The assemblages were significantly nested in all the five stages. Maximum cumulative species abundance (12 399 individuals over four years) was found in the urban stage, and was due to the constant presence of large groups of Rose-ringed Parakeets (Psittacula krameri). The lowest bird abundance was found in the industrial zone (4837 in total), where there was also a nearly two-fold decrease from 2010 to 2013. Thirty-six species demonstrated significant variation in their densities at least in one stage and between at least two months (p<0.05). Densities of 13.9% (n=5) of those species varied significantly in two stages, that of Copsychus saularis in three stages, and of Phoenicurus ochruros, in all five stages. Urban, suburban, periurban and forest stages were characterised by relatively stable species densities (significant changes observed only for 17.2% (n=5), 17.1% (n=6), 12.9% (n=7), and 17.8% (n=16) species, respectively). The additive diversity partitioning indicated that of the overall diversity (gamma-diversity), alpha diversity (within transects located within one stage) contributed 50.1% to the total diversity, and the controbution of within-stage variability was small (2.7%). Additionally, censuses on cultivated fields were taken. In two areas under mixed cropping systems, 53 bird species were identified in the two years period between June and December, 2011 and 2012. Out of the 53 detected species, only 14 were common (recorded at ≥50% of visits). Twenty-one species were recorded at Zadgaon in crops of tur (Cajanus cajan), cotton (Gossypium arboreum) and soybean (Glycine max). Nineteen species were recorded at Bhankhed in jawar (Sorghum bicolor), cotton and mung bean (Phaseolus aureus). At Zadgaon, territorial activity was observed in four species: the House Sparrow (Passer domesticus), Jungle Babbler (Turdoides striata), Yellow-eyed Babbler (Chrysomma sinense) and Red-wattled Lapwing (Vanellus indicus). The study indicated that four bird species were found under high risk, thirteen species at medium risk and eight species at low risk due to pesticide applications in croplands. The extent of crop damage in fields of groundnut, pearl millet, peas, sorghum, and sunflower was assessed by doing actual field censuses. The sustainable solution for reducing crop damage is a need for the farmers and such techniques will help to avoid direct or indirect effects of use of lethal bird control techniques on bird species diversity.QC 20141022
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Cooney, Jackson. "The Effect of Bat Predation on Crop Yield in Thailand and the Winter Garden Region of South-Central Texas." Scholarship @ Claremont, 2018. http://scholarship.claremont.edu/cmc_theses/1727.
Abstract:
The Wrinkle-lipped free-tailed bat (T. plicata) in Thailand and the Brazilian free-tailed bat (T. brasiliensis) in south-central Texas are integral in the control of agricultural pests. The effect on the production of rice and cotton is determined by the bats consumption of a particular pest species in that region. In Thailand, it is the White-Backed Planthopper (Sogatella furcifera), while in south-central Texas, it is the cotton bollworm (Helicoverpa zea). The ecological service these bat species provide is measured in millions of dollars saved by farmers each year. Finally, a conclusion was made about which species had a greater effect on the economy when compared to each other.
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Heineman, Arne M. "Species selection for alley cropping in Western Kenya : system management, nutrient use efficiency and tree-crop compatibility (1988-1995)." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318545.
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Benefer, Carly Marie. "The molecular and behavioural ecology of click beetles (Coleoptera: Elateridae) in agricultural land." Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/485.
Abstract:
The larvae (wireworms) of some click beetle genera inhabit the soil in agricultural land and are crop pests. In the UK, a pest complex of Agriotes species, A. obscurus, A. sputator and A. lineatus, has been identified as the cause of the majority of damage. However, studies on their ecology are lacking, despite knowledge of this being important for the development of sustainable risk assessment and pest management strategies, in part due to the morphologically cryptic nature of wireworms. The ecology of economically important click beetle species was investigated, focusing on UK Agriotes species. The relationship between sex pheromone trapped male Agriotes adults and wireworms, identified using a molecular tool (T‐RFLP), was influenced by sampling method, and some environmental variables significantly correlated with species distributions. Scale of sampling influenced the observed distribution of wireworms and other soil insect larvae. Other wireworm species were trapped together with Agriotes species, but mitochondrial 16S rRNA sequences could not be matched to those of other UK species. Sequences from Canadian wireworm samples revealed possible cryptic species. Differences in adult movement rates were found in laboratory tests (A. lineatus > A. obscurus > A. sputator). Molecular markers (AFLPs) were developed to assess dispersal in adult male Agriotes but further protocol optimisation is required. The results show the importance of identifying wireworms to species for assessing adult and wireworm distributions, since the Agriotes pest complex may not be present or as 3 widespread as previously assumed. Sex pheromone trapping of adults may not be appropriate for risk assessment as the relationship between aboveground adult and belowground wireworm species distribution is not straightforward. The differences observed in Agriotes species’ ecology have implications for the implementation of pest management strategies. The techniques used here can be applied in future studies to provide information on other economically important click beetle species worldwide.
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Czyzewicz, Nathan. "Functional characterisation of small signalling peptides and a receptor kinase involved in root architecture development in Arabidopsis and crop species." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41776/.
Abstract:
Post-embryonic root development is a plastic process by which plants are able to interface with the rhizosphere in order to provide anchorage, and increase surface area available for acquisition of nutrients and water. While root growth is governed primarily by auxin/cytokinin interactions, roots are able to sense the presence of surrounding nutrient deposits and changes to environmental conditions – directing growth accordingly – due to the action of signalling cascades. This thesis presents data pertaining to the characterisation of two signalling elements involved in governing root architecture; the small signalling peptide CLAVATA/EMBRYO SURROUNDING REGION 26 (CLE26), and the receptor kinase ARABIDOPSIS CRINKLY 4 (ACR4). Initially, the origins and evolutionary history of root architecture are explored, and an overview of signalling elements involved in root architectural development is provided, before discussing the potential benefits that manipulation of signalling events may allow in targeted crop improvement. To provide background on peptide signalling, the physiological and biochemical effects of small signalling peptides are discussed in view of the current literature, demonstrating the diverse range of developmental processes which are known to be regulated by these ligands and their known receptors. Following this, functional characterisation analyses indicate CLE26 as a novel, potent inhibitor of primary root growth and protophloem development in Arabidopsis, and is also shown to induce a similar effect upon exogenous application to several crop species. Furthermore, data is presented demonstrating the clear requirement for functional analysis during the development phase of creating antagonistic peptides, as a previously described antagonistic peptide technology was not applicable in all cases. Concluding the exploration of CLE26 signalling, a phosphoproteomics screen was conducted to probe further into CLE26 function, determining 23 putative effectors of CLE26 signalling, which are discussed in view of their potential to mediate CLE26 signalling, according to current literature. Next, the known roles of ACR4 and its orthologues are reviewed, demonstrating the importance of ACR4 signalling in many developmental processes, including regulation of asymmetric cell division during postembryonic root development. Although ACR4 activity is known to regulate asymmetric cell division in both columella stem cells and lateral root primordia, little is known about the downstream mediators of ACR4 signalling. In an attempt to fill this gap in knowledge, yeast 2-hybrid and co-immunoprecipitation approaches were employed. These two parallel proteomics screens together resulted in identification of 19 putative interactors of ACR4 signalling (PAIPs), which are discussed as potential mediators of ACR4 signalling in view of current literature. Of the identified PAIPs, three were further characterised by loss of function analysis, demonstrating that loss of PHOSPHOLIPASE Iγ2 and a PROTEIN OF UNKNOWN FUNCTION (At1g49840/UNK) was able to affect root architecture. Further in-silico characterisation of UNK reveals its similarity to soluble phospholipase receptors, which, alongside PLA-Iγ2, may potentially implicate ACR4 as a key player in a novel mechanism involved in regulation of bioactive lipid production.
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LAKIN, KENNETH RYAN. "SYSTEMATICS AND BIOLOGY OF THE CROP ASSOCIATED SPECIES OF POLYNEMA (HYMENOPTERA: MYMARIDAE) IN SOUTHERN ARIZONA (PARASITOIDS, PARASITE, ALFALFA HOPPERS, LEAFHOPPERS)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188052.
Abstract:
Egg parasitoid wasps of the genus Polynema (Hymenoptera: Mymaridae) were collected over a 4-year period from crop-associated areas in southern Arizona. Seven morphologically distinct species were collected with 3 species identified. Evidence was found for the existence of an additional sibling species. Taxonomic characters currently used for this genus were evaluated for stability when the parasitoids develop in alternate hosts and some were found to be unreliable. A key to the Polynema species from Arizona were composed utilizing new characters. Biological studies were carried out on 5 of these species to determine host species, longevity, developmental time, and potential fecundity. Three of these species exhibit the potential for sympatric parasitization of the eggs of the threecornered alfalfa hopper. A 2-year study of the seasonal distribution of these parasitoids in alfalfa fields in southern Arizona was carried out.
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Paye, Paye Freddy Óscar. "Agronomic evaluation and comparison of the yield of six multiannual forage species, under dry land conditions in the Ingavi province." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/5419.
Abstract:
The agronomical evaluation and the comparative work of six multiannual forage species was conducted in the facilities of the Benson Institute, in the community of Contorno de Letanias, Ingavi province, La Paz. The objectives were to evaluate the agronomic behavior, as well as to evaluate the dry matter (DM) yield of six multiannual forage species (grasses) under local conditions, and to determine the partial cost of production of the studied species. The annual mean temperature was 9.14°C, and 517.6 mm of precipitation. The test was conducted under the random block design test, with six different forage species, and three repetitions. The evaluated species were: Hybrid grass (Agropyrum crisantum x A. desertorum), Bromus grass(Bromus inermis), Phleum grass (Phleum pratense), Pubescent grass (Agropyron trichophorum), Orchard grass (Dactylis glomerata), and Weeping lovegrass (Eragrostis curvula). The evaluated response variables were: Plant density (%), plant height (cm), base area (m²), tip area (m²), leaf/stem relationship, dry matter yield (kg/ha), and plant vigor. The forage species (grass) that presented a better behavior in relationship to plant density were the weeping lovegrass, Phleum, Orchard, Bromus, and Pubescent grass with: 92.17, 84.44, 75.95, 70.77, and 68.6%. The hybrid grass presented the least density with a 55.50% respectively. According to plant height at two different cut times, the Orchard, Pubescent, Weeping lovegrass, Bromus, Phleum, and Hybrid grass species presented a mean height of 23.0, 26.24, 15.31, 12.27, and 15.5 cm respectively, a tip area of.037, 0.26,.032, 0.32, 0.28, and 0.25 m², and a base area of 0.14, 0.09, 0.10, 0.16, and 0.10 m². The dry matter yield (The total sum of two cuts) was of 3936.0 kg/ha for Pubescent grass, 3459.0 kg/ha of Bromus grass, 2780.7 kg/ha of Weeping lovegrass, 2358.0 kg/ha of Hybrid grass, and 2089.0 kg/ha of Pleum grass. The relationship leaf/stem relationship resented an average of 1.13, 3.38, 3.71, 2.84, 2.49, and 2.93 respectively. The species: Orchard and pubescent grass presented a variable cost of 1384.9 and 1604.9 Bs/Ha in relationship to the other studied species. Also, both grasses (bromus and pubescent) presented a marginal return of 138%; therefore, Orchard grass (Dactylis glomerata) is recommended as an alternative species.
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Musunda, Bothwell Zvidzai. "Evaluation of cover crop species for biomass production, weed suppression and maize yields under irrigation in the Eastern Cape Province, South Africa." Thesis, University of Fort Hare, 2010. http://hdl.handle.net/10353/347.
Abstract:
Achieving high biomass yields of cover crops has been a challenge to the success of Conservation Agriculture (CA) practices in the Eastern Cape (EC). A study was conducted to evaluate strategies for optimizing cover crop biomass production. Trials were carried out to screen summer and winter cover crops, as well as evaluate intercropping patterns and planting dates for biomass, weed suppression and subsequent maize yield under irrigation. Four summer legume cover crop species were evaluated under a Randomised Complete Block Design (RCBD) design. The cover crops were fertilized with 13.34 kg ha-1 of N, 20 kg ha-1 P and 26.66 kg ha-1 K. In the 2008/09 summer season a maize crop was superimposed on the 2007/08 screening trial under no-till. The crop was fertilized with 60 kg ha-1 of N. An intercropping trial was conducted over two seasons as a way of investigating the best way of incorporating cover crops into farmers cropping systems. This was done bearing in mind the limitation of resources such as land. The trial evaluated 3 factors laid as a 2 x 2 x 3 factorial arranged in a split-plot design. The main factor was cover crop planting date (planting at maize planting or 2 weeks after maize planting). The sub plot factor was intercropping pattern (strip intercropping and between row intercropping). A trial was also conducted to evaluate the effect of planting date (End of April and mid May) and four winter legume cover crop species on cover crop biomass, weed suppression and maize grain yield. The experiment was laid out as a Randomised Complete Block Design (RCBD) replicated 3 times. In the subsequent summer season a maize crop was superimposed on the winter trial to test the residual effects of the cover crop species. Another study was conducted to evaluate winter cereal cover crop species for biomass accumulation, weed suppression and subsequent maize grain yield. The cover crops as well as a weedy fallow control plot treatments were laid out as a Randomised Complete Block Design replicated 3 times. In the subsequent summer season a maize crop was superimposed on the site under no-till to evaluate the residual effect of the cover crops on maize. The results showed sunhemp, cowpea and lablab as the best cover crops with high biomass and weed suppression whilst mucuna was the least. Sunhemp consistently yielded higher cover biomass averaging 11200 kg ha-1 over the two seasons whilst mucuna had a consistently lowest average biomass yield of 4050 kg ha-1. These cover crops were above the critical 6 t ha-1 for effective weed suppression. There was a significant (p<0.01) relationship of cover crop dry weight and weed dry weight in both seasons. Subsequent maize grain yield was significantly higher in the sunhemp plots (64.2 %) than the weedy fallow plot. Mucuna, lablab and cowpea had maize grain yield increases of 16.6%, 33% and 43.2% respectively. Intercropping cover crops at maize planting yielded higher cover crop dry weights than a delay in intercropping cover crops. A delay in intercropping resulted in significantly higher average maize grain yield of 4700 kg ha-1 compared to intercropping at maize planting (3800 kg ha-1) and sole maize (4300 kg ha-1) over the two seasons. Strip intercropping also yielded higher (5000 kg ha- 1) average maize grain yield compared to row intercropping (3600 kg ha-1) and sole maize (4300 kg ha-1). There was a significant (p<0.05) relationship between cover crop dry weight in the 2007/08 season and maize grain yield in the 2008/09 season. Early planting grazing vetch gave the highest biomass yield of 8100 kg ha-1 whilst early planted red clover had the lowest biomass of 635 kg ha-1. Low weed dry weights were also obtained from the early planted grazing vetch as opposed to the other treatments. There was a significant (p<0.001) relationship of cover crop dry weight and weed dry weight. In the subsequent 2008/09 summer season early planted grazing vetch had the highest maize yield of 7500 kg ha-1 which was 56.3 % more than the weedy fallow plot had 4800 kg ha-1. The weedy fallow plot also had high weed infestation than the cover crop plots. There were significant (p<0.01) relationships between cover crop dry weight and maize grain yield, winter weed dry weight and maize grain yield and summer weed dry weight and maize grain yield. The results also showed triticale (13900 kg ha-1) as the best winter cover crop for biomass production. Italian ryegrass (6500 kg ha-1) produced the least amount of biomass. In The subsequent maize crop white oats gave highest maize grain yield (6369 kg ha-1) which was 33 % more than the weedy fallow plot (4784 kg ha- 1). There were also significant (p< 0.01) relationships of maize grain yield and winter weed dry weight, maize grain yield and summer growing weeds. The various studies demonstrated that there is opportunity for high biomass production under small scale farmers irrigated conditions using cover crops both in winter and summer. Best bet cover crops were sunhemp, cowpea and lablab for summer and triticale, white oats, barley, Italian ryegrass and grazing vetch for winter. Cover crops can also be incorporated into farmers cropping systems as sole crops or intercrops within the maize based cropping systems. Strip intercropping can be used by farmers as a way of introducing cover crops. Critical to achievement of high biomass is the time of planting cover crops with high biomass when planting is done early. A 2 week delay in strip intercropping cover crop into maize can be used as a way of incorporating cover crops into farmers cropping systems with minimal maize yield reduction.
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Curran, Helen R. (Helen Rae). "Thecaphora anther-smut fungi : ecology and implications for CFR Oxalis species." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20293.
Abstract:
Thesis (MSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Only a limited number of systems involving anther-smut fungi have been studied, usually due to the economic significance of their crop plant hosts. A smut fungus of the genus Thecaphora has been discovered infecting Oxalis hosts in South Africa. This pathogenic fungus, Thecaphora capensis, produces dark-coloured spores in the anthers of host flowers, rendering it an anther-smut fungus. The host genus is the seventh largest plant genus in the Cape Floristic Region (CFR) and the largest geophytic genus of this region. Nine Oxalis species that host T. capensis have been identified across a wide distribution in the CFR of South Africa. A preliminary assessment of T. capensis infections of Oxalis was conducted in 2009, which provided a foundation for further research into the ecological and evolutionary consequences of hosting this fungus. In this study, a comprehensive host diversity assessment was conducted to determine the extent of infected Oxalis individuals within the CFR. Three new Oxalis host species for Thecaphora capensis were discovered. This brings the total number of known hosts to twelve. The morphological and reproductive effects of the fungus were assessed on two host species (O. incarnata and O. lanata) by comparing healthy and infected individuals of these species. Infection by Thecaphora capensis had a significantly negative effect on both of these factors. Host resources appear to be co-opted for fungal spore production, since floral morphological characters of infected individuals were reduced in size. Furthermore, infection by T. capensis ensured near-universal sterility in both hosts. Differences in floral characters and pollinator preferences for healthy Oxalis incarnata and O. lanata individuals from disease-free and diseased populations were compared to determine the evolutionary influence of Thecaphora capensis infections. It was shown that this pathogen can have a significant evolutionary influence on its hosts, showing its ability to shape flower size and pollinator activity in O. lanata, but not in O. incarnata. A need has therefore been identified to assess these evolutionary forces independently for each host and its pathogen before making erroneous assumptions for conservation practices. Plant pollinators play an integral role in plant fitness. Pollinator movements within a population are important when between-flower spore transfer by pollinators increases the likelihood of new infections. Pollinator movements may be influenced by host density and the frequency of diseased individuals, amongst other factors. Pollinators were found to mediate Thecaphora capensis spore transfers within diseased Oxalis populations. Host density and disease frequency affected the number of spores transferred under field and standardized conditions. More research is required to investigate confounding factors in these complex systems. This study highlighted the complexities of a fungal-plant-insect relationship, the evolutionary consequences of such fungal infections and the various factors influencing the likelihood of new infections. This research adds to the limited body of knowledge on multi-organismal interactions in the CFR and provides a base for more detailed future studies on this intriguing system.
AFRIKAANSE OPSOMMING: 'n Brandswam, wat deel is van die Thecaphora genus,is ontdek in 'n Oxalis blom waar dit die gasheer plant se blom gebruik om spore in te produseer. Die swam, Thecaphora capensis, produseer donker gekleurde spore in die helmknoppe van die blomme van gasheer plante, daarom word dit geklasifiseer as 'n brandswam van die helmknop. Die gasheer plante van die swam is deel van die genus Oxalis, die sewende grootste plant genus in die Kaapse Floristiese Streek (KFS) en die grootste geofitiese genus in die streek. Nege Oxalis species is al klaar identifiseer as gasheer plante van T. capensis. Hulle is versprei oor 'n groot area van die KFS van Suid Afrika. 'n Primêre ondersoek van T. capensis infeksies op Oxalis is in 2009 onderneem. Hierdie ondersoek het gelei tot meer vrae oor die sisteem en het 'n goeie fondasie geskep vir verdere navorsing rakende die ekologiese koste verbonde daaraan om as gasheer plant vir 'n swam op te tree. 'n Deeglike ondersoek is in die KFS aangepak om die Oxalis gasheer plante van die brand swam te identifiseer en om voort te bou op die basiskennis wat in die primêre ondersoek daargestel is. Drie nuwe Oxalis gasheer plante van Thecaphora capensis is ontdek. Die totale aantal gasheer plante staan nou op twaalf. Gesonde en geinfekteerde individuele gasheer plante is gebruik om die morfologiese en reproduktiewe effekte van die swam te toets in twee Oxalis spesies (O. incarnata en O. lanata). Die negatiewe gevolge om 'n gasheer plant van die brand swam te wees was duidelik toe gesonde en geinfekteerde individuele met mekaar vergelyk is. Dit kom voor asof gasheer plante se hulpbronne vir spoor produksie gebruik word, want hulle is morfologies kleiner en meestal steriel. Die evolusionêre effek van Thecaphora capensis op 'n populasie is getoets met gesonde individuele in populasies van twee Oxalis spesies. Blomkenmerke en insek bestuiwers van gesonde individue in gesonde en geinfekteerde populasies is ondersoek om die effekte van T. capensis op populasies te toets. Daar is suksesvol gedemonstreer dat swamme sterk evolusionêre kragte uitoefen, en die vermoë het om plantpopulasies te vorm en te verander, ofskoon nie in alle gevalle ewe sterk nie. Daarom is dit belangrik om die evolusionêre kragte vir elke gasheer plant en sy patogeen onafhanklik te assesseer, sonder om algemene aannames te maak in bewaringspraktyke. Plantbestuiwers speel 'n belangrike rol in die fiksheid van plante. Hulle kan hul fiksheid verbeter deur bestuiwers te lok met blomme en deur aspekte geassosieer met blomme. Die bewegingspatrone van plantbestuiwers is baie belangrik indien hulle helmknop-geproduseerde spore van brandswamme vervoer instede van stuifmeel, want dit vergroot die kanse vir nuwe infeksies. Die bewegingspatrone van plantbestuiwers word, onder andere, beinvloed deur die digtheid en frekwensie van geinfekteerde individue. Plantbestuiwers speel 'n belangrike rol in die vervoer van Thecaphora capensis spore in geinfekteerde Oxalis populasies. Die digtheid en frekwensie van geinfekteerde blomme het die vervoer van spore geaffekteer onder veld en gestandardiseerde kondisies, alhoewel baie veranderlikes so 'n komplekse natuurlike sisteem beinvloed. Hierdie studie beklemtoon die kompleksiteit van 'n fungus-plant-insek verhouding, die gevolge van so 'n interaksie en die verskeie faktore wat die waarskynlikheid van nuwe infeksies beinvloed. Tot dusver is daar 'n beperkte aantal sisteme soos hierdie bestudeer waarin 'n brandswam van die helmknop betrokke is, en die enkele beskikbare studies is onderneem meestal as gevolg van hulle ekonomiese effekte op landboukundig belangrike gasheer plante. Hierdie studie verteenwoordig 'n belangrike byvoeging tot die inter-organismiese studies in die KFS. 'n Holistiese ekologiese oorsig soos hierdie verskaf 'n belangrike basis vir toekomstige studies en bewarings- en bestuurspraktyke.
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Brown, Angela Philip. "Pollen, embryo and endosperm development following cross-pollination within and between the crop species Brassica campestris, Brassica oleracea, Brassica napus and Raphanus sativus." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/12858.
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Nambili, Julia Nghituvali. "The interference potential of nine selected South African spring wheat cultivars with selected weed species." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019.1/1631.
46
Hamilton, Kim Nicole. "Ex Situ Conservation of Australian Citrus Species: Investigations on Seed Biology, Cryopreservation and in Vitro Culture." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/365585.
Abstract:
Many potentially economically important taxa of Australia are threatened in situ and are vulnerable to erosion of genetic diversity and extinction. In this study, over one hundred rare and threatened Queensland edible plants and/or crop wild relatives were identified. Many of these species have subtropical to tropical distribution and may have non-orthodox seed storage behaviour, thus excluding standard seed banking approaches for long-term ex situ conservation. There is an urgent need to develop alternative ex situ conservation strategies to conserve this diversity. Establishment of ex-situ collections of this valuable germplasm in field collections would be prohibitive in cost and would be susceptible to environmental damage, including disease and pest attack. In vitro and cryopreservation techniques offer alternative strategies for medium and long-term storage of germplasm. However, there have been very few attempts to apply in vitro storage and cryopreservation techniques to any wild Australian tropical or subtropical species. Moreover, limitations exist for the development of alternative ex situ storage techniques due to a lack of basic research on plant ecology or biology, including seed physiology and morphology. Further restrictions to the development of ex situ conservation of these species occurs because of a lack of supporting techniques needed for cryostorage, such as in vitro culture, germination protocols, propagation and acclimation. The Australian wild species of the Citrus genus are a priority for investigation of ex situ conservation strategies because of their conservation priority, potential socioeconomic importance (e.g. novel genes and fruits), probable non-orthodox seed storage behaviour and lack of corresponding techniques for their long term ex situ conservation. This study reports on seed biology, cryopreservation and in vitro culture of three Australian wild Citrus species, C. australasica (finger lime), C. inodora (Russell River lime) and C. garrawayi (Mount White lime), to facilitate germplasm storage and as a regeneration system. Descriptors of mature seed morphology and anatomy are reported in C. australasica, C. inodora and C. garrawayi - vital to the development and application of effective seed storage protocols (i.e. seed lot quality). C. garrawayi seed shape and seed coat morphology was found to be different to C. australasica and C. inodora. In addition, seed topography, as viewed by scanning electron microscopy, was found to be a useful tool for taxa identification. In terms of both germination and seedling growth, temperatures of _20ºC were found to be sub-optimal for germination. Germination from seeds of all the three species was optimal at 30ºC and above 80%. Both C. australasica and C. inodora displayed ‘essentially’ orthodox seed storage behaviour, i.e. desiccation and cryopreservation tolerance, whilst C. garrawayi displayed more complex seed storage behaviour. Overall, it appears that seed banking of germplasm of these species could be by standard orthodox protocols (i.e. 5%MC at -20ºC). However, because of variation in seed responses and other storage constraints in these species, cryopreservation is recommended as the safest storage option to prevent seed deterioration (loss of viability). Cryobiology studies have allowed the determination of the unfrozen water content (WCu) of C .australasica (11%), C. inodora (est. 8%MC) and C. garrawayi (14%). Desiccation of seeds to well below the WCu resulted in high levels of germination (radicle emergence <1mm) after liquid nitrogen exposure, but negligible levels of germination were observed from seeds above the WCu. This data both supports other studies undertaken on cultivated citrus and provides evidence that seed of these species will tolerate cryostorage when below the WCu. In addition, this study demonstrated in vitro culture systems for the micropropagation and medium term storage of C. australasica, C. inodora and C. garrawayi, as well as shoot-tip cryopreservation in C. australasica using a vitrification- based method. In vitro embryogenic potential, using a range of culture media, was low to moderate in C inodora and low in C. australasica, whilst C. garrawayi was recalcitrant to in vitro embryogenesis. The addition of citric acid to the embryo induction medium resulted in the best quality and highest number of somatic embryos from callus proliferated through liquid culture in C. inodora. This is the first report of the promotive affect of citric acid on embryo formation in the Citrus genus. Cryopreservation of encapsulated C. inodora embryogenic callus gave high levels of recovery (69%). However, further optimisation of embryo formation and plantlet recovery is needed to improve efficiency to be suitable conservation purposes. Micropropagation provides a useful tool, for medium-term storage of rare and threatened germplasm and offers a valuable step in the implementation of horticultural and restoration programs. Establishment of an in vitro culture system for shoot-tips also provides a technique for producing virus free material for germplasm exchange or maintenance. The findings of this study facilitate the development of ex situ conservation of Australian wild Citrus, which is of significant interest to complement in situ conservation and secure sustainable access to this rich biodiversity.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Biomedical Sciences
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Leveau, Aymeric. "Caractérisation structurale de l'éliciteur du virus X de la pomme de terre (PVX) : recherche, chez les plantes cultivées, de gènes hôtes, impliqués dans la résistance liée à Rx." Thesis, Evry-Val d'Essonne, 2012. http://www.theses.fr/2012EVRY0036.
Abstract:
De nos jours, les agents pathogènes des plantes, engendrent encore des pertes agricoles importantes. A terme, la solution la plus adaptée semble être la création de variétés de plantes cultivées présentant une résistance génétique à large spectre et durable. Créer de telles plantes nécessite la compréhension des mécanismes de résistance mis en jeu dans des pathosystèmes modèles, tels que celui impliquant le gène de résistance Rx et le virus X de la pomme de terre. Dans ce système, la protéine Rx intervient dans la perception d’un facteur d'avirulence issu du virus: sa protéine de capside (Cp). Cependant, les mécanismes moléculaires déclenchant la résistance chez la plante exprimant Rx demeurent obscurs. Cette étude s’est focalisée sur l’étape de reconnaissance de l’éliciteur viral par Rx. Une première approche a permis la mise en évidence d’un éliciteur minimal de 90 acides amine. L’étude d’un fragment légèrement plus grand par des méthodes de biochimie structurale, tend à exclure un modèle selon lequel, la différence de structuration tertiaire entre Cp élicitrice et Cp non élicitrice déterminerait la reconnaissance par Rx. Une seconde approche, de biologie moléculaire, a mis en évidence deux protéines hôte interagissant avec ce petit fragment éliciteur. L'étude s’est focalisée sur un gène codant un facteur de transcription, nbERF5, et a révélé que cette protéine interagit aussi bien avec les Cp de souches de Potexvirus avirulentes que virulentes dans la résistance liée à Rx, mais également avec la protéine de résistance Rx et l’intéracteur direct: RanGAP2. La poursuite de la caractérisation de cet ERF, permettra de déterminer son importance dans la résistance liée à RxNowadays, phytopathogenic agents are still causing significant agricultural losses. The most suitable option appears to be the creation of crop species carrying a genetic durable and broad spectrum resistance. In order to create such varieties, we need to understand the mechanisms underlying resistance, involved in model Pathosystems, Such as the one composed of the resistance gene Rx and the potato virus X. In that system, the host gene encodes a protein assimilated to a receptor implicated in the perception of an avirulence factor produced by the virus: its capside protein (Cp). Nevertheless, the molecular mechanisms triggering the resistance remain largely unknown. This study has been focused on the elicitor recognition mediated by Rx. A first approach led to the identification of a minimal elicitor containing 90 amino acids has. The structural characterization of a slightly larger protein fragment using biochemical methods suggested that the difference in the tertiary structuration of both elicitor and non-elicitor Cp would not be the determinant of Rx mediated recognition. Second, a molecular approach led to the discovery of two host proteins interacting with the small elicitor fragment. The work was focused on a transcription factor, nbERF5 and showed that this protein interacts similarly with elicitor or non-elicitor Cps of Rx mediated resistance. Interestingly, this gene product is able to directly interact with the Rx protein, but also with the direct interactor of Rx: RanGAP2, protein required for the Rx mediated resistance efficiency. Further characterization of this ethylen response factor will help us to understand its role in Rx mediated resistance
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Rogers, Gordon Stephen, of Western Sydney Hawkesbury University, of Science Technology and Agriculture Faculty, and School of Horticulture. "Influence of N and P nutrition on the responses of wheat and cotton to elevated CO2." THESIS_FSTA_HOR_Rogers_G.xml, 1996. http://handle.uws.edu.au:8081/1959.7/227.
Abstract:
The atmospheric CO2 concentration is rising. These higher CO2 concentrations will certainly affect growth but may also affect nutrient responses of crop plants. The overall aim of this thesis was to investigate the effect of elevated CO2 on the nitrogen and phosphorus nutrition of two different crop species: wheat and cotton. Once establishing the new nutrient requirements of these crop species at elevated CO2 the study focussed on the interactive effects of elevated CO2 and N supply on growth and leaf N concentrations in cotton and wheat, carbohydrate metabolism, source:sink interactions and photosynthetic enzyme levels in the two species. Having established these effects, the role of N supply in controlling source:sink effects on Rubisco concentration were studied at the molecular level in wheat. Finally, some implications of the effect of elevated CO2 on wheat were examined, specifically on the quality of flour produced from wheat grain grown at elevated CO2. The foliar nitrogen concentrations, required to produce maximum shoot growth (critical concentrations) were lower at elevated CO2 while the critical phosphorus concentrations were higher.Doctor of Philosophy (PhD)
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Ganyani, Lloyd Munashe. "Evaluating summer cover crop species and management strategies for rainfed maize based cropping systems in the central region of the Eastern Cape Province of South Africa." Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/373.
Abstract:
The overall objective of the whole study was to assess whether conservation agriculture (CA) systems can work in the Eastern Cape Province (EC). The CA systems were engaged through cover cropping to address land degradation problems by emphasizing high biomass production in order to realize short term benefits such as moisture conservation, weed suppression and soil fertility benefits under rainfed conditions in the central region of the Eastern Cape province. Since rainfall is the most limiting factor to crop production in the EC, a within season rainfall distribution analysis was conducted to expose the quality of the season (onset, end and duration) and hence the feasibility of CA systems to guide agronomic decisions by farmers in EC. To assess season parameters, thirty four years of daily rainfall was collected from the University of Fort Hare Research station and used to conduct the rainy pentad (5 day rainfall totals) analysis and the daily rainfall analysis using INSTAT software programme. Based on the pentad analysis, results showed that Alice does not have a rainy season in 1 out of 2 years (50% probability) but has one in 1 out of 4 years (25% probability level). This criterion proved to be harsher and conservative when compared to the daily rainfall approach which is more precise in measuring trends on season parameters. The daily rainfall analysis indicated a 65% feasibility for the dry land cropping systems in the EC. The pentad analysis however was effective in illustrating seasonality and it showed that the wet season begins on the 1st of November, ending on the 22nd of March lasting for 140 days. Though the season duration appeared too long, the existence of dry spells during critical growth stages adversely affects the quality of the season. The daily rainfall analysis also managed to derive a signal which can guide planting decisions. For planting to be successful, this analysis determined that 20 mm of rain should be received in two consecutive days after the 1st of November. A screening trial for cover crop biomass production and weed suppression was conducted on-station Fort Hare Research Farm (32°46' S and 26° 50' E), and Msobombvu village (MSBV) (32°44' S, and 26° 55' E) over two seasons (2007/08 and 2008/09). Six summer cover crops i.e. cowpea (Vigna unguiculata), dolichos lablab (Dolichos argenteus), sunnhemp (Crotalaria juncea), buckwheat (Fagopyrum sagittatum), forage sorghum (Sorghum bicolor) and sunflower (Helianthus annus) were evaluated for biomass yield, and weed suppression. Decomposition rates, moisture conservation and residual effects of these cover crops on the succeeding main crop were also evaluated under dryland conditions. The screening trial was laid in randomized complete block design replicated three times. Forage sorghum (Sorghum bicolor) and sunflower (Helianthus annus) were identified as high biomass producers and their dry matter yields ranged from 8 -12 t ha-1. These cover crops can be useful in generating high biomass in rainfed cropping systems in the EC. Other cover crops produced 3 - 4 t ha-1 of biomass which fell short of the 6 t ha-1 expected benchmark. However, these biomass yields were important in weed management since all cover crop species showed a similar degree of weed suppression which surpassed the weed fallow treatment. As dead mulches, the cover crops failed to show residual moisture conservation and weed control benefits for the succeeding maize crop mainly because of poor residue persistence, and low harvestable fallow rainfall. Buckwheat (Fagopyrum esculentum), was selected for further investigations in a follow up trial on station in 2008/09 season because of its weed smothering qualities, suitability to short cycle rotations, and possible allelopathic properties. The trial aimed at finding weed and cost effective management options of buckwheat that are none detrimental to the succeeding maize crop. Results showed that cropping systems where buckwheat is followed by a main crop may not work as they are unprofitable with respect to R100 rand invested. Though perceived to have allelopathic properties, buckwheat failed to demonstrate the possibilities of allelopathic action against weeds. Intercropping trial was conducted on-station in 2007/8-2008/09 seasons to try and find better ways of fitting legume cover crops into maize based cropping systems without compromising production of staple cereals on limited landholdings. The trials evaluated three factors in factorial combination, cover crop planting date, intercropping strategy, and cover crop species. The trial was laid as 2 x 2 x 3 factorial arranged in a split-split plot design. The main plot factor was cover crop planting date, cover crops simultaneously planted with maize and cover crop planted two weeks after planting maize (DKC 61-25). The sub-plot factor was intercropping strategy, strip intercropping and betweenrow intercropping. The sub-sub-plot factor was cover crop species, Dolichos lablab (Dolichos argenteus (Highworth), and Cowpea Vigna ungiculata (Agrinawa) plus control plots of sole maize. Results showed that same time planting of leguminous cover crops with maize using the in-between row intercropping patterns can derive appreciable system biomass (maize/cover crop) yields, utilize land efficiently whilst getting favourable maize grain yield. Based on the rainfall analysis, results showed that the probability of success when relay seeding cover crops after two weeks into standing maize is low (15% chances of success). This suggests that relay intercropping strategies would not work due to the unavailability of a good quality season.
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Payne, Kathryn Marie. "ENHANCED EFFICIENCY NITROGEN FORMULATION EFFECT ON GRASS-LEGUME PASTURE PRODUCTIVITY." UKnowledge, 2019. https://uknowledge.uky.edu/pss_etds/113.
Abstract:
The use of nitrogen (N) fertilizer is generally restricted on mixed species forage systems due to its stimulatory effect on grasses which increases competition with legume species. Reduced legume growth from this competition can compromise forage nutritive value and prospective yields. The controlled-release nature of several enhanced efficiency fertilizer N products holds the potential to improve legume persistence in mixed species pastures while providing supplemental N required by the grass component. The studies contained in this dissertation evaluated the effect of different enhanced efficiency N formulations (ATU, ESN, methylene urea, SuperU, and a 75% ESN: 25% urea blend) and untreated urea on yield, nutritive value, and legume persistence in a ‘Wrangler’ bermudagrass and ‘Durana’ white clover mixture (2014-2016 growing seasons), ‘KY-31’tall fescue and ‘Kenland’ red clover mixture (2015-2016 growing seasons), and ‘KY-31’ stockpiled tall fescue (2015-2017). The three studies were conducted at the University of Kentucky Spindletop Research Farm in Lexington, KY in a randomized complete block design. In the bermudagrass-white clover study, all enhanced efficiency N sources maintained white clover populations similar to the unfertilized grass/clover control, but only ESN caused greater clover composition than standard urea. Total forage yields increased linearly with N rate in all years, but dry weather conditions in the second and third years resulted in lower total yield. Forage nutritive value followed general trends throughout each growing season, but ESN’s ability to maintain clover resulted in higher nutritive value. In the tall fescue-red clover, total forage yields curvilinearly increased with N rate in 2015 but did not vary in 2016. ESN and ESN+urea blend treatments retained clover composition similar to that of the unfertilized control. Stockpiled forage yield increased with higher N rates. Enhanced efficiency N fertilizers with the ability to control N release can enhance forage yield while maintaining clover in mixed species swards.