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1
Odom, Jennifer Lorraine. « Evaluation of Field Pea Varieties for Resistance to Fusarium Root Rot Pathogens ». Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28500.
Texte intégralRésumé :
Fusarium root rot is one of the most important diseases of pulse crops, with numerous Fusarium spp. comprising the disease complex. Fusarium solani and F. avenaceum have been reported to be major pathogens in the pea root rot complex, and all commonly grown varieties are susceptible. Greenhouse methods to evaluate peas for resistance to Fusarium root rot resulted in inconsistent disease severity across varieties. In 2015, F. avenaceum infested field plots were more heavily damaged based on emergence and yield than F. solani infested plots, and opposite trends were observed in 2016. Differences in root rot severity between years could be due to F. solani infestation causing more damage under warmer temperatures, while plots infested with F. avenaceum caused more damage under cooler temperatures. These results highlight the difficulties observed when screening for soil-borne pathogens, and the increased difficulties when a pathogen complex and changing environmental conditions are involved.
2
Matheron, Michael E., Kevin M. Crosby et Martin Porchas. « Interaction of Pepper Experimental Lines with Phytophthora Crown and Root Rot in 2000 ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/214919.
Texte intégralRésumé :
This study was conducted in the greenhouse at the Yuma Agricultural Center. Thirty-nine experimental lines of pepper from the Texas A&M pepper breeding collection were seeded and grown in the greenhouse in 8 fl. oz. plastic pots. When plants were 2 months old (Aug 8), the potting mix in each pot was infested with Phytophthora capsici. Plants were placed in 2-in. deep containers filled with water for 48 hr every 2 weeks, which maintained the potting mix in a saturated condition and encouraged disease development. The mean temperature of the potting mix from the time it was infested with Phytophthora capsici to the termination date of the study was 81 °F. Disease progress and the relative susceptibility of each test plant to Phytophthora crown and root rot was assessed by recording the date when each plant displayed necrosis around the lower stem and was permanently wilted. The environmental conditions during this study were very favorable for disease development. The mean duration of plant survival for pepper selections ranged from 9 to 51 days. If no plants had died due to Phytophthora crown and root rot, the duration of plant survival would have been 74 days. Most plant selections were readily attacked and killed by Phytophthora capsici. The experimental lines with the highest survival rating may be somewhat tolerant to disease; however, additional testing in further greenhouse and field trials is required to substantiate these preliminary results.
3
Matheron, Michael E., et Martin Porchas. « Activity of Actigard® on Development of Phytophthora Root and Crown Rot on Pepper Plants ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214945.
Texte intégralRésumé :
Phytophthora blight of peppers (Capsicum annuum), caused by the oomycete pathogen Phytophthora capsici, occurs in most regions where this crop is grown. The root and crown rot phase of the disease develops on plants in areas of the field where soil remains saturated with water after an irrigation or rainfall. Subsequent periods of soil saturation encourage further disease development. Actigard (acibenzolar-S-methyl), is a chemical activator of plant disease resistance, has no known direct antifungal effects and is thought to mimic salicylic acid in the signal transduction pathway that leads to systemic acquired resistance (SAR). Foliar applications of Actigard were evaluated for suppression of root and crown rot on pepper plants growing in the greenhouse in pots and inoculated with Phytophthora capsici or grown in soil naturally infested with the pathogen. Inhibition of stem cankers on pepper cultivars Bell Tower and AZ9 after two to four treatments with Actigard was significantly greater than on plants receiving a single treatment of the chemical. Inhibition of stem canker elongation on Bell Tower or AZ9 peppers ranged from 93.2 to 97.2% and 87.4 to 92.4% when plants were inoculated with P. capsici at 1 or 5 weeks, respectively, after the fourth application of Actigard. Survival of chile pepper plants in field soil naturally infested with P. capsici was significantly increased by three foliar applications of Actigard compared to nontreated plants in all three trials when pots were watered daily and in two of three trials when pots were flooded for 48 hr every 2 weeks. When soil was flooded every 2 weeks, establishing conditions highly favorable for disease development, plants treated once with Ridomil Gold survived significantly longer than those treated with Actigard. On the other hand, when water was provided daily without periodic flooding, establishing conditions less favorable for disease development, there was no significant difference in plant survival between the two chemicals in two of three trials. Growth of shoots on chile pepper plants treated with Actigard, watered daily and grown in soil containing P. capsici generally was greater than nontreated plants. Pepper plants subjected to periodic saturated soil conditions and receiving three foliar applications of Actigard plus a soil treatment of Ridomil Gold survived significantly longer and produced a greater amount of shoot growth than plants treated with either chemical alone. This work suggests that Actigard could be an important management tool for Phytophthora root and crown rot on pepper plants.
4
Nischwitz, C., Mary Olsen et S. Rasmussen. « Influence of Salinity and Root-knot Nematode as Stress Factors in Charcoal Rot of Melon ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214946.
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Incidence of Charcoal rot, caused by the soil borne fungus Macrophomina phaseolina, may be increased in some crops by the addition of stress on the host caused by high salinity of soil or irrigation water and infection by plant pathogenic nematodes. Since both of these factors may be problematic in melon production in Arizona, studies were initiated to determine if higher salt concentrations of irrigation water and infection by Root-knot nematode (Meloidogyne incognita) may be involved in recent increased incidences of Charcoal rot of melon. In greenhouse trials, higher concentrations of salts in irrigation water significantly increased the percentage of plants that died due to Charcoal rot. However, no significant difference was found in the percentage of dead plants inoculated with both root-knot nematode and M. phaseolina compared to plants inoculated with M. phaseolina alone. Results of these trials indicate that salinity may be a factor in the increased incidence of Charcoal rot of melon, but that root-knot nematode infection may not play a role.
5
Levenfors, Jens. « Soil-borne pathogens in intensive legume cropping - Aphanomyces spp. and root rots / ». Uppsala : Dept. of Plant Pathology and Biocontrol Unit, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a393.pdf.
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6
Olsen, M., M. McClure et S. Husman. « Effect of Preplant Fumigation on Yield of Chile Pepper Infected with Root-Knot Nematode ». College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/220003.
Texte intégralRésumé :
A field test was established in 1999 to determine the effect of preplant soil fumigation on yield of chile pepper in southeastern Arizona in order to give growers data on which to base management decisions. Replicated plots within a nematode-infested field planted with New Mex 6-4 chile in March 1999 were either treated with Telone II fumigant at 7 gal/A two weeks before planting or not treated. In a mid-season assay in July 1999, the effects of fumigation were evident in plant canopy growth although numbers of J2/cc soil were not significant between treatments (p=0.058). Differences in yields between fumigated plots and untreated plots were significant (p=0.014). The average yield in fumigated plots was 12.4% higher than that in untreated plots.
7
Matheron, Michael E., et Martin Porchas. « Comparative Effect of Five Fungicides on the Development of Root and Stem Rot and Survival of Chile Pepper Plants Grown in Field Soil Naturally Infested with Phytophthora capsici ». College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/220000.
Texte intégralRésumé :
Five different fungicides, including azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and mefenozem (metalaxyl), were evaluated for their ability to inhibit the development of root and crown rot and increase the survival of chile pepper plants grown in soil naturally infested with Phytophthora capsici. For chile pepper plants grown in field soil naturally infested with P. capsici and subjected to a 48 h flood period every 2 weeks, growth and survival of plants receiving one treatment of dimethomorph at 100 μg/ml or fluazinam at 1,000 μg/ml were significantly greater than that for plants treated once with azoxystrobin at 1,000 μg/ml or fosetyl-Al at 3,000 μg/ml. For each tested fungicide, values for duration of plant survival and shoot and root fresh weight usually were numerically larger but not significantly different for chile peppers receiving water as needed compared to those flooded for 48 h every 2 weeks. The potential and relative value of azoxystrobin, dimethomorph, fosetyl-Al, and fluazinam as chemical management tools for Phytophthora root and stem rot on chile pepper, in addition to mefenozem (metalaxyl), has been demonstrated.
8
Sanabria, Andres SANABRIA. « EFFECTS OF ANAEROBIC SOIL DISINFESTATION COMBINED WITH BIOLOGICAL CONTROL ON ROOT-KNOT NEMATODE AND LETTUCE DROP ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534496965018979.
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9
Martin, Dana. « Investigation of the Biocontrol Activity in vitro and in planta of Different Pseudomonas Species Against Important Crown, Stem, Foliar and Root Pathogens of Ornamental Crops ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503063395390704.
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10
AZEVEDO, Thamara de Medeiros. « Expressão quantitativa de genes de Phytophthora parasitica e de citros durante a interação ». Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1151.
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CNPq
A gomose, provocada principalmente pelo oomiceto Phytophthora parasitica, é uma das mais graves doenças que acometem culturas de citros no âmbito mundial. Durante a interação, plantas induzem cascatas de sinalização a fim de induzir respostas de defesa. Contudo, P. parasitica secreta proteínas efetoras capazes de modular estas respostas por parte do hospedeiro, a fim de promover a infecção. No gênero Citrus, espécies comercialmente importantes são suscetíveis a infecção por este patógeno e a resistência a gomose é encontrada na espécie de citros Poncirus trifoliata. Considerando a escassez de informações acerca do patossistema citros-P. parasitica, o presente trabalho objetivou analisar, por meio de RT-qPCR, a expressão quantitativa de genes efetores apoplásticos e citoplasmáticos de P. parasitica e da cascata de defesa em citros, durante interações com espécies suscetíveis e resistentes, Citrus sunki e P. trifoliata, respectivamente. Dos 17 genes efetores estudados, 10 apresentaram expressão quantitativa relativa diferencial ao nível de significância induzida em P. parasitica após inoculação em raízes de P. trifoliata, sendo 06 apoplásticos e 04 citosólicos. Os perfis de expressão dos 17 genes efetores de P. parasitica apresentaram dois picos máximos de expressão, indicativos da síntese de novo desses genes ao longo dos pontos temporais de interação, sendo o acúmulo dos transcritos mais precoce sobre P. trifoliata (as 6 h.a.i.) e mais tardio sobre C. sunki (as 96 h.a.i.). Os elevados níveis de expressão de genes efetores em P. parasitica induzidos por C. sunki as 96 h.a.i. devem corresponder a fase necrotrófica de vida do oomiceto, consequentemente devido ao sucesso na penetração das células vegetais suscetíveis e acúmulo de biomassa do patógeno. A presença de hifas intracelulares no córtex de raízes de C. sunki foi abundantemente visualizada em micrografias as 96 h.a.i., a qual deve ocorrer como consequência da suscetibilidade da planta ao patógeno. Seis grupos hierárquicos de genes co-regulados foram formados a partir dos perfis de expressão dos 17 genes efetores em P. parasitica, os quais são reagrupados de modo diferente de acordo com a interação com C. sunki ou com P. trifoliata, indicando que o patógeno foi capaz de reconhecer entre hospedeiros suscetível ou resistente e sintetizar seletivamente quais efetores e em que intensidade devem ser segregados. As raízes de C. sunki expressaram 10 componentes de cascatas de resistência mediada pelo SA em resposta não bem-sucedida a infecção por P. parasitica. A supressão por P. parasitica da expressão de 05 genes de cascatas de resistência mediada pelo SA foi observada em raízes de P. trifoliata e deve indicar tentativas do patógeno de burlar com a imunidade da planta. Entretanto, a resistência de P. trifoliata a P. parasitica não deve utilizar genes envolvidos na cascata de resistência mediada pelo SA, mas sim genes PR-5 e calose sintase, envolvendo barreiras bioquímicas e estruturais. Portanto, o presente trabalho fornece uma nova visão para o entendimento acerca do processo de modulação de efetores de P. parasitica em interações suscetíveis e resistentes e, a maneira como estes hospedeiros respondem mediante interação
The gummosis, mainly caused by the oomycete Phytophthora parasitica, is one of the most serious diseases affecting citrus crops worldwide. During the interaction, plants induce signaling cascades in order to induce defense responses. However, P. parasitica secrets effector proteins capable of modulating these host responses in order to promote the infection. In Citrus genus, commercially important species are susceptible to infection by this pathogen and the gummosis resistance is achieved in Poncirus trifoliata citrus species. Considering the lack of information on citrus-P. parasitica pathosystem, this study aimed to analyze, through RT-qPCR, the quantitative expression of P. parasitica effector and citrus defense genes during citrus-P. parasitica susceptible and resistant interactions, with Citrus sunki and P. trifoliata, respectively. As results, P. parasitica was able to recognize among susceptible or resistant host and selectively synthesize which effectors and in that intensity should be expressed. Of the 17 studied effector genes, 10 showed quantitative relative differential expression at significance level induced in P. parasitica after inoculation in trifoliate orange roots, being 06 apoplastics and 04 cytosolics. The expression profiles for the 17 effector genes in P. parasitica had two maximum peaks of expression, that are indicative of de novo synthesis of these genes along the time points of interaction, showing transcript accumulation earlier on P. trifoliata (at 6 h.a.i.) and later on C. sunki (at 96 h.a.i.). High levels of the effector gene expression in P. parasitica induced by C. sunki at 96 h.a.i. must match the necrotrophic phase of life of this oomycete, consequently due to their successful penetration into the susceptible plant cells and pathogen biomass accumulation. The presence of intracellular hyphae in cortex of C. sunki roots was abundantly visualized in the micrographs at 96 h.a.i., which may occur as a result of the plant susceptibility to the pathogen. Six hierarchical groups of co-regulated genes were formed from the expression profiles of the 17 effector genes in P. parasitica, which are grouped differently according to interact with C. sunki or P. trifoliata, indicating that the pathogen was able to recognize between susceptible or resistant host and selectively synthesize which effectors and in that intensity should be segregated. The roots of C. sunki expressed 10 components of the cascade resistance mediated by SA in response not successful to P. parasitica infection. The suppression by P. parasitica of the expression of 05 genes of the cascade resistance mediated by SA was found in P. trifoliata roots, and must indicate pathogen attempts to circumvent with the immunity of the plant. However, P. trifoliata resistance to P. parasitica should not use genes involved in the resistance cascade mediated by SA, but instead PR-5 and callose synthase genes, involving biochemical and estructural barriers. In conclusion, this study provides a new insight into the understanding of the effectors of modulation process of P. parasitica in susceptible and resistant interactions and how these hosts respond through interaction.
11
Sheridan, Grainne E. C. « Molecular studies of watercress phylogeny and the crook-root pathogen ». Thesis, University of Bath, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338381.
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12
Matheron, Michael E., et Martin Porchas. « Efficacy of New Fungicides as Potential Management Tools for Phytophthora Crown and Root Rot on Pepper Plants ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008. http://hdl.handle.net/10150/215006.
Texte intégralRésumé :
Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation or rainfall event. Disease severity can increase dramatically due to summer rains during July and August in the southeastern Arizona production area. Fungicides are an important component of a Phytophthora disease management system, when used in combination with other management practices such as crop rotation, raised beds, and water management. The efficacy of the systemic fungicide mefenoxam (Ridomil Gold) for control of Phytophthora blight on pepper has been documented; however, in many pepper production regions, populations of the pathogen insensitive to this fungicide have developed. Other chemistries, including dimethomorph (Acrobat) as well as some new fungicides in development, have activity on some species of Phytophthora and associated diseases on crops other than pepper. The objective of the following study was to evaluate these additional chemistries for efficacy in suppressing development of root and crown rot on pepper plants grown in soil naturally infested with Phytophthora capsici in a greenhouse environment. The mean duration of survival for Aristotle bell pepper plants in untreated soil infested with P. capsici was 29 days. On the other hand, a significant increase in pepper plant survival was achieved when soil was treated with Reason (fenamidone) + Previcur Flex (propamocarb), SA-110201, Ranman (cyazofamid), Omega (fluazinam), Ridomil Gold (mefenoxam), V-10161(fluopicolide), Forum (dimethomorph), NOA-446510 (mandipropamid), IR-6141 (kiralaxyl), and Maestro (captan). The data from this study suggest that several fungicides currently not registered for use on peppers may be effective components of a management program for Phytophthora crown and root rot. The data is promising; however, additional studies in field soil naturally infested with P. capsici are needed to confirm these preliminary findings as well as to determine the optimal application rate and timing for each new chemistry.
13
Grimme, Eva. « Mycofumigation with Muscodor albus effects on Verticillium wilt and black dot root rot of potato, effects on Glomus intraradices and ectomycorrhizal fungi, and M. albus proliferation in soil / ». Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/grimme/GrimmeE1208.pdf.
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Muscodor albus Worapong, Strobel & Hess, isolate CZ-620 (MA) is an endophytic fungus that produces volatile organic compounds (VOCs) and non-volatile antimicrobial compounds. The use of these VOCs to inhibit or kill a wide range of microorganisms is termed mycofumigation. This dissertation focuses on parameters of MA mycofumigation including: production and bioactivity of previously un-described water-soluble antimicrobial compounds produced by MA; distribution of antimicrobial compounds from a MA point source in three soil types as measured by effects on Verticillium dahliae and Colletotrichum coccodes; control of V. dahliae and C. coccodes on potato; the ability of MA to colonize soil; and the effects of mycofumigation on ectomycorrhizal fungi (EMF) in vitro and on the colonization of onion roots by the arbuscular mycorrhizal (AM) fungus Glomus intraradices. The bioactivity of water-soluble compounds produced in potato dextrose broth was significantly increased as measured in growth reduction of C. coccodes, V. dahliae, and Rhizoctonia solani. No reduction was observed for Aphanomyces cochlioides and Pythium ultimum. Antimicrobial compounds from a MA colonized barley point source reduced V. dahliae and C. coccodes populations in soils by 60-100% at distances up to 9 cm from the inoculation source depending on soil type. Mortality rate ranging from 70-100% was observed within a 3 cm radius from the inoculation source. In both field and greenhouse trials, MA colonized barley formulation reduced Verticillium wilt and black dot root rot severity and reduced populations of both pathogens in potato tissue as measured by real-time quantitative PCR and serial dilution. Planting directly into mycofumigated soil previously infested with V. dahliae or C. coccodes resulted in equal control of the pathogens when compared to a one-week mycofumigation period prior to planting. After six weeks of incubation MA did not colonize sterile soil further than 0.5 cm away from a MA inoculation point. In vitro experiments showed that most of the tested EMF were inhibited in the presence of MA VOCs, but were able to resume growth when removed from VOCs. Incorporating MA into soil had no negative but supportive effect on onion root colonization by the AM fungus G. intraradices.
14
Turnbull, Gillian Anne. « The role of motility in Pseudomonas fluorescens and Pseudomonas putida in soil-plant-microbe interactions ». Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367105.
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Sjöberg, Johanna. « Arbuscular mycorrhizal fungi : occurrence in Sweden and interaction with a plant pathogenic fungus in barley / ». Uppsala : Dept. of Crop Production Ecology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200533.pdf.
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Yang, Zhenbiao. « Gene regulation in a pathogen-plant interaction : soft rot erwinias versus potato tubers ». Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39693.
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Erwinia soft rot is a widespread disease destructive to numerous
important crop plants. Damage to plants is primarily due to celldegrading
enzymes (CDEs) secreted by the bacteria. I am interested in
potato (Solanum tuberosum) soft rot because it is of agricultural importance
and it represents an ideal model system for understanding molecular
events in plant-pathogen interactions. Much has been learned in
vitro about the molecular genetics of CDEs in the past decade; however,
little is known about their expression in plantae To study expression
of genes for these enzymes during pathogenesis and plant responses to
erwinias or their enzymes, I developed a membrane-separated system for
simultaneous studies of potato and bacterial gene expression. This system
facilitates the isolation of plant tissue-free bacterial cells and
bacteria-free plant tissue for subsequent analysis of gene expression by
RNA blot hybridization. Using this system, I demonstrated that in compatible
interactions, rnRNAs for three Erwinia carotovora subsp. carotovora
(Ecc) CDE genes were induced to high levels and were induced sequentially: exo-pectate lyase (PL), endo-PL, and then endopolygalacturonase
(PG) with maximal mRNA accumulations at 6, 9, and 12
hr, respectively. Induction of these mRNAs was well correlated with
tissue maceration. In the incompatible interaction, however, induction
of all three Ecc genes was reduced several-fold compared to the compatible
interaction. The kinetics of mRNA accumulation during pathogenesis
were distinct from those of in vitro accumulation induced by polygalacturonic
acid. My results confirm that in planta expression of
these genes was induced by exo-PL reaction products as suggested by
other researchers. In studies of plant genes correlated with plant
responses to pathogens and environmental stresses [plant defenseresponse
(PDR) genes], I also showed Ecc triggered active responses distinct
from wound responses. I used gene probes for phenylalanine ammonia-
lyase (PAL) and 3-hydroxy-3-methylglutaryl coenzyme A reductase
(HMGR), key genes in the biosynthesis of phenylpropanoid- and terpenoidderived
compounds believed to be important in plant defenses. Ecc
inoculation caused much more rapid and greater increases in PAL mRNA and
enzyme activity levels in potato tuber than wounding alone. Escherichia
coli, a non-plant pathogen, carrying a plasmid which encodes Ecc
endo-PL, also induced PAL mRNA accumulation. Ecc induced a specific
HMGR isogene (HMGR1) not activated by wounding. My results support the
existence of an HMGR mul-ci-gene family. Wounding resulted in a rapid
and transient accumulation of HMGR2 mRNA followed by a slower accumulation
of HMGR3 mRNA. These isogenes are distinct from the Ecc-induced
HMGRI gene.Ph. D.
17
Taheri, Abdolhossein. « Interaction between root lesion nematode, Pratylenchus neglectus, and root-rotting fungi of wheat ». Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09pht128.pdf.
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Bibliography: leaves 307-329. This study concludes that in soils in South Australia where root-rotting fungi and P. neglectus exist together, root disease of wheat is caused by their combined effect. Evidence suggests that P. neglectus not only contributes to this interaction through mechanical wounding of roots, but also causes biochemical and physiological changes in plants, making them more prone to fungal infection.
18
Ghazala, Al-Sadek Mohammed Salem. « Proteomic responses of uninfected tissues of pea plants infected by root-knot nematode, Fusarium and downy mildew pathogens ». Thesis, University of the West of England, Bristol, 2012. http://eprints.uwe.ac.uk/18313/.
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Peas suffer from several diseases, and there is a need for accurate, rapid in-field diagnosis. This study used proteomics to investigate the response of pea plants to infection by the root knot nematode Meloidogyne hapla, the root rot fungus Fusarium solani and the downy mildew oomycete Peronospora viciae, and to identify potential biomarkers for diagnostic kits. A key step was to develop suitable protein extraction methods. For roots, the Amey method (Chuisseu Wandji et al., 2007), was chosen as the best method. The protein content of roots from plants with shoot infections by P. viciae was less than from non-infected plants. Specific proteins that had decreased in abundance were (1->3)-beta-glucanase, alcohol dehydrogenase 1, isoflavone reductase, malate dehydrogenase, mitochondrial ATP synthase subunit alpha, eukaryotic translation inhibition factor, and superoxide dismutase. No proteins increased in abundance in the roots of infected plants. For extraction of proteins from leaves, the Giavalisco method (Giavalisco et al., 2003) was best. The amount of protein in pea leaves decreased by age, and also following root infection by F. solani and M. hapla at six weeks post-inoculation. F. solani caused a decrease in abundance of isocitrate dehydrogenase, glycerate dehydrogenase, carbonic anhydrase, oxygen evolving enhancer protein 2 (OEE2), phosphoglycerate kinase, chloroplastic and one unknown protein. Some leaf proteins increased in abundance, and included heat shock-related proteins (HSP70) and two unknown proteins. Proteins that decreased in leaves following root infection by M. hapla six week post-inoculation were RuBisCo large subunit, fructose bisphosphate aldolase 2, carbonic anhydrase, OEE1, OEE2, OEE3, RuBisCo small subunit and a 28KDa ribonucleoprotein. Some proteins increased in abundance, such as HSP70, fructose bisphosphate aldolase 1 and trypsin. In contrast to the decrease in protein observed at six weeks post-inoculation, the amount of protein increased in leaves three weeks after inoculation of roots with M. hapla. Root infection by both M. hapla and F. solani caused a reduction in leaf area, and also a reduction in fresh and dry weight of the shoot and root systems. The use of digital imaging and visible and infra-red light to study the changes in leaves was explored in this study. A clear difference was visible between leaves from healthy plants and between those from M. hapla and F. solani infected plants when imaged using a normal digital camera. In contrast, no clear differences were noticed between leaves of healthy, M. hapla and F. solani infected plants when using an infra-red camera with 850 nm wavelength light. This study indicates that specific proteins are altered in abundance in leaves following root infection, and provides the basis for future studies to develop rapid diagnostic tests.
19
Hutchins, John David. « Antagonism of the stem rot pathogen (Sclerotina sclerotiorum) by microorganisms from oilseed rape flowers : prospects for biological control ». Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281747.
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Matheron, Michael E., et Martin Porchas. « Evaluation of Fungicides as Potential Management Tools for Phytophthora Crown Rot on Pepper Plants ». College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/215030.
Texte intégralRésumé :
Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation or rainfall event. Disease severity can increase dramatically due to summer rains during July and August in the southeastern Arizona production area. The efficacy of the systemic fungicide mefenoxam (Ridomil Gold)) for control of Phytophthora blight on pepper has been documented; however, in many pepper production regions, populations of the pathogen insensitive to this fungicide have developed. Other chemistries, including dimethomorph (Acrobat) as well as some new fungicides in development, have activity on some species of Phytophthora and associated diseases on crops other than pepper. The objective of the following study was to evaluate additional chemistries for efficacy in suppressing development of root and crown rot on pepper plants grown in soil naturally infested with Phytophthora capsici. In the first trial, nontreated pepper plants were all dead after an average elapsed time of 5 days in soil infested with P. capsici. In the same trial, no plants died after 66 days when the soil was treated with Ranman (cyazofamid), V-10161 (fluopicolide), and Reason (fenamidone) + Previcur Flex (propamocarb). Additionally, only one out of five pepper plants died when treated with Omega (fluazinam), NOA-446510 (mandipropamid) and AgriFos (mono- and di-potassium salts of phosphorous acid). For all of these treatments, the duration of plant survival and fresh weight of plant shoots and roots did not differ significantly from plants grown in sterilized soil. Similar results were obtained in the second trial. The results from these trials suggest that several fungicides currently not registered for use on peppers may be effective components of a management program for Phytophthora root and crown rot. The data is promising; however, additional studies in field soil naturally infested with P. capsici are needed to confirm the preliminary findings of these initial experiments.
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Wicks, T. J. « Phytophthora crown rot of almond and cherry trees : pathogens, rootstock and scion susceptib[i]lity and control / ». Title page, table of contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09PH/09phw637.pdf.
Texte intégral
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Huh, Jung-Hyun. « Biochemical, Molecular and Functional Analysis of Volatile Terpene Formation in Arabidopsis Roots ». Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77151.
Texte intégralRésumé :
Plants produce secondary (or specialized) metabolites to respond to a variety of environmental changes and threats. Especially, volatile compounds released by plants facilitate short and long distance interaction with both beneficial and harmful organisms. Comparatively little is known about the organization and role of specialized metabolism in root tissues. In this study, we have investigated the root-specific formation and function of volatile terpenes in the model plant Arabidopsis.
As one objective, we have characterized the two root-specific terpene synthases, TPS22 and TPS25. Both enzymes catalyze the formation of several volatile sesquiterpenes with (E)-β-farnesene as the major product. TPS22 and TPS25 are expressed in the root in distinct different cell type-specific patterns and both genes are induced by jasmonic acid. Unexpectedly, both TPS proteins are localized to mitochondria, demonstrating a subcellular localization of terpene specialized metabolism in compartments other than the cytosol and plastids. (E)-β-Farnesene is produced at low concentrations suggesting posttranslational modifications of the TPS proteins and/or limited substrate availability in mitochondria. We hypothesize that the mitochondrial localization of TPS22 and TPS25 reflects evolutionary plasticity in subcellular compartmentation of TPS proteins with emerging or declining activity. Since (E)-β-farnesene inhibits Arabidopsis root growth in vitro, mitochondrial targeting of both proteins may fine tune (E)-β-farnesene concentrations to prevent possible autotoxic or inhibitory effects of this terpene in vivo.
We further investigated the role of volatile terpenes in Arabidopsis roots in interaction with the soil-borne oomycete, Pythium irregulare. Infection of roots with P. irregulare causes emission of the C11-homoterpene (or better called C4-norterpene) 4,8-dimethylnona-1,3,7-triene (DMNT), which is a common volatile induced by biotic stress in aerial parts of plants but was not previously known to be produced in plant roots. We demonstrate that DMNT is synthesized by a novel, root-specific pathway via oxidative degradation of the C30-triterpene, arabidiol. DMNT exhibits inhibitory effects on P. irregulare mycelium growth and oospore germination in vitro. Moreover, arabidiol and DMNT biosynthetic mutants were found to be more susceptible to P. irregulare infection and showed higher rates of Pythium colonization in comparison to wild type plants. Together, our studies demonstrate differences and plasticity in the metabolic organization and function of terpenes in roots in comparison to aboveground plant tissues.Ph. D.
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Southwood, Michael J. « Evolution and detection of Fusarium oxysporum f. sp. cepae in onion in South Africa ». Thesis, Stellenbosch : Stellenbosch University, 2010. http://hdl.handle.net/10019.1/4499.
Texte intégralRésumé :
Thesis (PhDAgric (Plant Pathology))--Stellenbosch University, 2010.ENGLISH ABSTRACT: In the Western Cape onion industry in South Africa, Fusarium oxysporum Schlechtend.:Fr. f.sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans. (Focep) has been identified as the leading cause of harvest and storage losses. This pathogen is of world-wide importance and causes Fusarium basal rot of onions (Allium cepa), affecting all onion growth stages. No information is available on the evolution, genetic diversity, molecular detection and inoculum sources of the South African Focep population. Similar to what is the case for South Africa, limited information is available on Focep in other regions of the world. World-wide, four vegetative compatibility groups (VCGs) and two single-member VCGs (SMVs) have been identified among two Japanese and 19 Colorado (USA) isolates. This polyphyletic origin of Focep suggested by VCG analyses was confirmed through molecular analyses of isolates from a few countries. Only the mating type (MAT)1-1 idiomorph has been reported for Focep isolates from Welsh onion (Allium fistulosum). The development of sustainable management strategies of Focep is dependent on knowledge of (i) the genetic diversity and evolution of Focep, (ii) whether high throughput molecular methods can be developed for identifying the most virulent and widespread Focep genotypes and (iii) the role of seedlings and seeds as primary inoculum sources, and the Focep genotypes associated with these growth stages. Therefore, the three main aims of the current study were to investigate the aforementioned three aspects. In the first aim of the study, the genetic diversity and evolution of Focep was investigated using a collection of 79 F. oxysporum isolates from South Africa (27 Focep and 33 non-pathogenic isolates) and Colorado (19 Focep isolates). VCG analyses revealed the presence of six VCGs, four among the Colorado Focep isolates (VCGs 0421, 0422, 0423 and 0424) and two among the South African bulb-associated isolates (VCGs 0425 and 0426). VCG 0421 and VCG 0425 were the two main VCGs in Colorado and South Africa, respectively. Four SMVs and one heterokaryon selfincompatible (HSI) isolate were also identified. The polyphyletic nature of Focep in South Africa and Colorado was shown through a combined translation elongation factor 1α (EF-1α) and mitochondrial small-subunit (mtSSU) phylogeny. The phylogeny divided the Focep isolates into two main clades, of which one contained the two main VCGs (0421 and 0425), SMVs and non-pathogenic isolates. The second, ancestral clade contained the HSI isolate, VCGs 0422, 0423 and 0424, and non-pathogenic isolates. Unlike the clade containing the two main VCGs, which were highly virulent toward onion bulbs, the ancestral clade contained isolates that were mostly moderately virulent. The incongruence of the EF-1α and mtSSU datasets with an intergenic spacer (IGS) region data set, and the presence of both MAT idiomorphs within the same isolate for some isolates, suggested possible exchange of genetic material between isolates. The second aim of the study was to develop molecular methods for identifying the two main Focep VCGs (0425 and 0421), using DNA fingerprinting methods and sequence-characterized amplified region (SCAR) markers. These techniques were first developed using the F. oxysporum isolates from the first aim, and were then used to investigate the prevalence of VCG 0425 among 88 uncharacterized F. oxysporum isolates from onion bulbs in South Africa. Two random amplified polymorphic DNA primers provided two diagnostic amplicons for VCG 0425, but attempts to develop SCAR markers from these amplicons were unsuccessful. In contrast, an interretrotransposon amplified polymorphism (IRAP) fingerprinting method enabled the developed of a multiplex IR-SCAR polymerase chain reaction method that detected the VCG 0421, 0425 and SMV 4 isolates as a group. Fingerprinting and SCAR marker testing of the 88 uncharacterized F. oxysporum isolates from South Africa (65 Focep and 23 non-pathogenic) confirmed that VCG 0425 is the main VCG in South Africa associated with mature onion bulbs, since 63 of the Focep isolates had the molecular characteristics of VCG 0425. The third aim of the study was to determine whether seed and seedling transplants are inoculum sources of Focep, and whether the same genotype (VCG 0425) that dominated on mature bulbs could be detected from these sources. Focep isolates were obtained from seven of the 13 investigated onion seed lots, as well as from onion seedling transplants that were collected from all five onion nurseries in the Western Cape. Focep seedling infection more than doubled from the 6-week growth stage to the 14-week growth stage. Seed infections by Focep were low, but the seedborne nature of Focep was confirmed by showing that a green fluorescent protein labelled Focep transformant could be transmitted from infected soil to onion seed via the onion bulbs and seedstalks. It is thus clear that commercial seed and seedlings are inoculum sources of Focep. However, the Focep genotypes on seed and seedlings are different from those in mature bulbs and were not dominated by VCG 0425. Furthermore, most (≤ 60%) of the seed and seedling isolates were moderately virulent, as compared to the mostly highly virulent isolates from mature bulbs.
AFRIKAANSE OPSOMMING: In die Wes-Kaapse uiebedryf in Suid-Afrika is Fusarium oxysporum Schlechtend.:Fr. f.sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans. (Focep) geïdentifiseer as die vernaamste oorsaak van oes- en opbergingsverliese. Hierdie patogeen is van wêreldwye belang; dit veroorsaak Fusarium-bolvrot van uie (Allium cepa) en affekteer alle plantgroeistadia. In Suid-Afrika is daar geen inligting beskikbaar oor die evolusie, genetiese diversiteit, molekulêre opsporing en inokulumbronne van die Focep-populasie nie. Soortgelyk aan wat die geval in Suid-Afrika is, is daar beperkte inligting beskikbaar oor Focep in ander wêrelddele. Wêreldwyd is daar vier vegetatiewe versoenbaarheidsgroepe (VVGe) en twee enkellid VVGe (ELVe) geïdentifiseer onder twee Japannese en 19 Colorado (VSA) isolate. Hierdie veelvuldige oorsprong van Focep wat deur VVG-analise voorgestel was, is deur die molekulêre analises van isolate uit ’n paar ander lande bevestig. Slegs die paringstipe (PT)1-1 idiomorf is vir Focep-isolate uit Walliese-tipe uie (ook bekend as ‘lenteuie’ in Suid Africa) (Allium fistulosum) berig. Die ontwikkeling van volhoubare bestuurstrategieë vir Focep steun op kennis van (i) die genetiese diversiteit en evolusie van Focep, (ii) of hoë-deurset molekulêre metodes ontwikkel kan word vir die identifisering van die mees virulente en wydverspreide Focep-genotipes en (iii) die rol van saailinge en saad as primêre inokulumbronne, en die Focep-genotipes wat met hierdie groeistadia geassosieer word. Daarom was die hoof doelstellings van hierdie studie om die bogenoemde drie aspekte te bestudeer. Om die eerste doel van die studie te bereik is die genetiese diversiteit en evolusie van Focep bestudeer deur gebruik te maak van ‘n versameling van 79 F. oxysporum-isolate uit Suid-Afrika (27 Focep en 33 nie-patogeniese isolate) en uit Colorado (19 Focep-isolate). VVG-analises het die teenwoordigheid van ses VVGe aangetoon – vier onder die Colorado Focep-isolate (VVGe 0421, 0422, 0423 en 0424) en twee onder die Suid-Afrikaanse bol-geassosieerde isolate (VVGe 0425 en 0426). VVG 0421 en VVG 0425 was die twee hoof VVGe in onderskeidelik Colorado en Suid-Afrika. Vier ELVe en een meerkernige self-onversoenbare (MSO) isolaat is ook geïdentifiseer. Die veelvuldige oorsprong van Focep in Suid-Afrika en Colorado is ook aangetoon deur ‘n gekombineerde translasie verlengings faktor 1α (VF-1α) en mitokondriale klein-subeenheid (mtKSE) filogenie. Dié filogenie het die Focepisolate in twee groepe verdeel, waarvan die een groep die twee hoof VVGe (0421 en 0425), ELVe en nie-patogeniese isolate bevat het. Die tweede, basal groepering het die MSO-isolaat, VVGe 0422, 0423 en 0424, en nie-patogeniese isolate bevat. In teenstelling met die eersgenoemde groepering wat hoogs virulente isolate van uiebolle bevat het, het die basale groepering isolate bevat wat meestal matig virulent was. Die inkongruensie van die VF-1α en mtKSE-datastelle met ‘n intergeen-gespasieerde (IGS) area datastel – asook die teenwoordigheid van beide PT-idiomorwe binne dieselfde isolaat by sommige isolate – het op ’n moontlike uitruiling van genetiese materiaal tussen isolate gedui. Die tweede doel van die studie was om molekulêre metodes te ontwikkel vir die identifisering van die twee hoof Focep VVGe (0425 en 0421) deur gebruik te maak van DNA-vingerafdrukke en nukleotied-gekarakteriseerde geamplifiseerde area (NKAA) merkers. Hierdie tegnieke is ontwikkel deur van die F. oxysporum-isolate van die eerste doelstelling gebruik te maak en is daarna gebruik om die frekwensie van VVG 0425 onder 88 ongekarakteriseerde F. oxysporum-isolate van uiebolle in Suid-Afrika te ondersoek. Twee gerandomiseerde geamplifiseerde polimorfiese DNS (RAPD) merkers het twee diagnostiese nukleotiedbasis-areas vir VVG 0425 gelewer, maar pogings om NKAA-merkers uit hierdie geamplifiseerde nukleotiedbasis-areas te onwikkel was onsuksesvol. In teenstelling hiermee het ‘n inter-retrotransposon geamplifiseerde polimorfisme (IRAP) vingerafdrukmetode die ontwikkeling van ‘n multipleks IR-NKAA polimerase kettingreaksiemetode moontlik gemaak wat die VVG 0421-, VVG 0425- en ELV 4-isolate as ’n groep aangedui het. Vingerafdruktoetsing en NKAA-merkertoetsing van die 88 ongekaraktariseerde F. oxysporum isolate van Suid-Afrika (65 Focep en 23 nie-patogenies) het bevestig dat VVG 0425 die hoof VVG in Suid-Afrika is wat met volwasse bolle geassosieer word, aangesien 63 van die Focep-isolate die molekulêre eienskappe van VVG 0425 gehad het. Die derde doel van die studie was om vas te stel of saad en saailinge inokulumbronne van Focep is, en of dieselfde genotipe (VVG 0425) wat op volwasse bolle dominant is, waargeneem kon word op hierdie bronne. Focep-isolate is verkry van sewe van die 13 uiesaadlotte asook van uiesaailinge wat in al vyf uiesaailingkwekerye in die Wes-Kaap versamel is. Focep-saailinginfeksie was meer as dubbel in die 14-week groeistadium as wat dit in die 6-week stadium was. Saadinfeksies deur Focep was laag, maar die saadgedraagde aard van Focep is bevestig deur aan te toon dat ’n Focep-transformant wat met ‘n groen fluoreserende proteïen geëtiketeer is, van geïnfekteerde grond na uiesaad oorgedra kon word via die uiebolle en -saadstele. Dit is dus duidelik dat kommersiële saad en saailinge as inokulumbronne van Focep dien. Die Focep-genotipes op saad en saailinge verskil egter van dié in volwasse bolle en is nie deur VVG 0425 gedomineer nie. Verder was die meeste (≤ 60%) saad- en saailingisolate matig virulent, in teenstelling met die meestal hoogs virulente isolate uit volwasse bolle.
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Van, Coller Gerhardus J. (Gerhardus Johannes). « An investigation of soilborne fungi associated with roots and crowns of nursery grapevines ». Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49844.
Texte intégralRésumé :
Thesis (MScAgric)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: Soilborne diseases of grapevines represent a complex problem with limited information available, both locally and internationally. Previous research in South Africa indicated that Phytophthora and Pythium spp. were the most widespread and devastating pathogens in grapevine nurseries and vineyards in the Western Cape province. The local grapevine industry is currently expanding; new cultivars, methods and agricultural chemicals are being used which can affect soilborne pathogens. It has therefore become necessary to reassess the status of soilborne pathogens in nurseries, since information in this regard is crucial for the development of disease management practices for the expanding local grapevine industry. Soilborne fungal genera associated with roots and crowns of declining nursery grapevines were assessed in surveys conducted at three different grapevine nurseries in the Western Cape province. Cylindrocarpon, Fusarium, Pythium, and Rhizoctonia spp. were consistently isolated from roots and crowns of declining nursery grapevines. Cylindrocladiella spp. and Phytophthora cinnamomi were infrequently isolated from diseased roots, crowns and soil whereas Pythium spp. were abundant in most of the soils. Results suggest that the status of soilborne fungal pathogens in grapevine nurseries in the Western Cape province has changed over the last 30 years. The DNA phylogeny and pathogenicity of the isolates of Cylindrocladiella were determined. Four species of Cylindrocladiella occur on grapevines in South Africa, namely C. lageniformis, C. parva, C. peruviana, as well as a new species, described in this study as C. viticola, which forms part of the C. infestans species complex. Pathogenicity trials were inconclusive. Ten Fusarium spp. were isolated from roots and crowns of declining nursery grapevines, namely F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum and F. solani. The dominant species was F. oxysporum, followed by F. proliferatum and F. solani. In pathogenicity trials F. oxysporum and F. solani significantly reduced root volume, root dry mass, length of new shoots, stem diameter and number of leaves, but increased the percentage of chlorotic leaves and root rot severity. Fusarium proliferatum also caused a significant reduction in new shoot growth, number of leaves and increased root rot severity compared to the controls. Fusarium so/ani seems to be more virulent than F. oxysporum, followed by F. pro/iferatum. This is the first report of F. oxysporum, F. pro/iferatum and F. so/ani as pathogens of grapevines in South Africa, and the first report of F. proliferatum as a pathogen of grapevines in the world. Phytophthora cinnamomi was isolated at low frequencies from declined grapevines, although present in the rhizosphere soil. It is possible that the extensive use of downy mildew chemicals in grapevine nurseries may protect grapevines from infection by P. cinnamomi. The effect of chemicals used to combat downy mildew on Phytophthora root rot of nursery grapevines was evaluated in a glasshouse. There was very little discernable effect of the chemicals tested relative to the control plants for the parameters measured and it was concluded that the inoculation technique needed refinement. However, plants treated with phosphorous acid tended to be taller and have more leaves, greater stem diameter and root volume than controls or plants treated with the other chemicals. The data obtained in this study are not conclusive, but indicated certain trends that more glasshouse trials and field trials would resolve. Results presented in this thesis indicate that a major shift has occurred in the status of soilborne fungi associated with roots and crowns of grapevines in nurseries in the Western Cape since the 1970s when Phytophthora and Pythium were predominant. The prevalence and role of soilborne fungi need to be determined so that new appropriate disease management strategies can be developed to limit losses in grapevine nurseries and ensure the sustainable production of healthy plants for the grapevine industry.
AFRIKAANSE OPSOMMING: 'N ONDERSOEK NA GRONDGEDRAAGDE SWAMME GEASSOSIEER MET WORTELS EN KRONE VAN WINGERD IN KWEKERYE Grondgedraagde siektes van wingerd is 'n komplekse probleem waaroor min inligting, beide plaaslik en internasionaal, beskikbaar is. Vorige navorsing in Suid-Afrika het aangedui dat swamme van die genera Phytophthora en Pythium die mees algemene en vernietigende grondgedraagde patogene in kwekerye en wingerde in die Wes-Kaap provinsie is. Die plaaslike wingerdbedryf brei huidiglik uit; nuwe kultivars, metodes en landbouchemikalieë word gebruik wat 'n invloed kan hê op grondgedraagde patogene. Gevolglik het dit noodsaaklik geword om die status van grondgedraagde patogene in wingerdkwekerye weer te bepaal, aangesien inligting in hierdie verband noodsaaklik is vir die ontwikkeling van siekte bestuurspraktyke vir die ontwikkelende plaaslike wingerdbedryf. Grondgedraagde swamgenera geassosieer met wortels en krone van terugsterwende wingerd in kwekerye is bepaal in opnames wat by drie verskillende wingerdkwekerye in die Wes-Kaap provinsie uitgevoer is. Cylindrocarpon, Fusarium, Pythium, en Rhizoctonia spp. is konstant vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, Cylindrocladiella spp. en Phytophthora cinnamomi is ongereeld vanuit siek wortels, krone en grond geïsoleer, terwyl Pythium spp. algemeen in meeste gronde voorgekom het. Resultate dui daarop dat die status van grondgedraagde swampatogene in wingerdkwekerye in die Wes- Kaap provinsie oor die laaste 30 jaar verander het. Die DNA filogenie en patogenisiteit van die isolate van Cylindrocladiella is bepaal. Vier spesies van Cylindrocladiella kom voor op wingerd in Suid-Afrika, naamlik C. lageniformis, C. parva, C. peruviana, sowel as 'n nuwe spesie, wat in hierdie studie as C. viticola aangedui is en wat deel is van die C. infestans spesie kompleks. Patogenisiteits proewe was onvoldoende om die patogeniese status van die swam me te bepaal. Tien Fusarium spp. is vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, naamlik F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum en F. solani. Die dominante spesies was F. oxysporum, gevolg deur F. proliferatum en F. solani. In pathogenisteitsproewe het F. oxysporum en F. solani gelei tot 'n betekenisvolle laer wortelvolume, droë massa van wortels, lengte en droë massa van nuwe groei en aantal blare, maar het die persentasie chlorotiese blare en graad van wortelvrot verhoog. Fusarium proliferatum het ook gelei tot 'n betekenisvolle afname in lengte en massa van nuwe groei, aantal blare en 'n verhoogde graad van wortelvrot in vergelyking met die kontrole behandelings. Dit wil voorkom asof Fusarium solani meer virulent is as F. oxysporum, gevolg deur F. proliferatum. Hierdie is die eerste aanmelding van F. oxysporum, F. proliferatum en F. solani as patogene van wingerd in Suid-Afrika, en die eerste aanmelding van F. proliferatum as 'n patogeen van wingerd in die wêreld. Phytophthora cinnamomi is konstant teen lae frekwensies vanuit terugsterwende wingerd in kwekerye geïsoleer, alhoewel dit in risosfeer gronde teenwoordig was. Dit is moontlik dat die ekstensiewe gebruik van chemikalieë teen donsskimmel in wingerdkwekerye die wingerdplante kan beskerm teen infeksie deur P. cinnamomi. Die effek van chemikalieë wat gebruik word teen donsskimmel op Phytophthora wortelverrotting van wingerd in kwekerye, is 'n glashuis geëvalueer. Die chemikalieë wat gestoets is, het vir die gemete parameters, tot baie min onderskeibare effek gelei relatief tot die kontrole plante, en daar is afgelei dat die inokulasie tegniek verbetering benodig. Plante wat met fosforiensuur behandel is, het egter geneig om langer te wees met meer blare, 'n groter stamdeursnee en wortelvolume as kontrole plante of plante behandel met ander chemikalieë. Data verkry vanuit die hierdie studie was onvoldoende, maar sekere neigings is aangedui wat deur verdere glashuis- en veldproewe verklaar sal word. Resultate wat in hierdie tesis weergegee is, het aangedui dat 'n algehele verskuiwing in die status van grondgedraagde swamme geassosieer met wortels en krone van wingerd in kwekerye vanaf die 1970s, toe Phytophthora en Pythium die dominante genera was, plaasgevind het. Die voorkoms en rol van grondgedraagde swamme moet bepaal word, sodat nuwe voldoende siektebestuurspraktyke ontwikkel kan word om verliese in wingerdkwekerye te beperk en sodoende die volhoubare produksie van gesonde plante vir die wingerdbedryf te verseker.
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Björkman, Maria. « Effects of intercropping on the life cycle of the turnip root fly (Delia floralis) : behaviour, natural enemies and host plant quality / ». Uppsala : Dept. of Crop Production Ecology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/2007125.pdf.
Texte intégral
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Jung, M. C. Victoria. « The role of selected plant and microbial metabolites in the nutrient solution of closed growing systems in greenhouses / ». Alnarp : Swedish University of Agricultural Sciences, 2003. http://diss-epsilon.slu.se/archive/00000343/.
Texte intégralRésumé :
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003.Appendix consists of reprints and manuscripts of five papers co-authored with others. Includes bibliographical references. Also partially available online in PDF format; online version lacks appendix.
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Andrade, Linares Diana Rocío. « Characterization of tomato root-endophytic fungi and analysis of their effects on plant development, on fruit yield and quality and on interaction with the pathogen Verticillium dahliae ». Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5137/.
Texte intégralRésumé :
Non-mycorrhizal fungal endophytes are able to colonize internally roots without causing visible disease symptoms establishing neutral or mutualistic associations with plants. These fungi known as non-clavicipitaceous endophytes have a broad host range of monocot and eudicot plants and are highly diverse. Some of them promote plant growth and confer increased abiotic-stress tolerance and disease resistance. According to such possible effects on host plants, it was aimed to isolate and to characterize native fungal root endophytes from tomato (Lycopersicon esculentum Mill.) and to analyze their effects on plant development, plant resistance and fruit yield and quality together with the model endophyte Piriformospora indica.
Fifty one new fungal strains were isolated from desinfected tomato roots of four different crop sites in Colombia. These isolates were roughly characterized and fourteen potential endophytes were further analyzed concerning their taxonomy, their root colonization capacity and their impact on plant growth. Sequencing of the ITS region from the ribosomal RNA gene cluster and in-depth morphological characterisation revealed that they correspond to different phylogenetic groups among the phylum Ascomycota. Nine different morphotypes were described including six dark septate endophytes (DSE) that did not correspond to the Phialocephala group. Detailed confocal microscopy analysis showed various colonization patterns of the endophytes inside the roots ranging from epidermal penetration to hyphal growth through the cortex. Tomato pot experiments under glass house conditions showed that they differentially affect plant growth depending on colonization time and inoculum concentration.
Three new isolates (two unknown fungal endophyte DSE48, DSE49 and one identified as Leptodontidium orchidicola) with neutral or positiv effects were selected and tested in several experiments for their influence on vegetative growth, fruit yield and quality and their ability to diminish the impact of the pathogen Verticillium dahliae on tomato plants. Although plant growth promotion by all three fungi was observed in young plants, vegetative growth parameters were not affected after 22 weeks of cultivation except a reproducible increase of root diameter by the endophyte DSE49. Additionally, L. orchidicola increased biomass and glucose content of tomato fruits, but only at an early date of harvest and at a certain level of root colonization. Concerning bioprotective effects, the endophytes DSE49 and L. orchidicola decreased significantly disease symptoms caused by the pathogen V. dahliae, but only at a low dosis of the pathogen.
In order to analyze, if the model root endophytic fungus Piriformospora indica could be suitable for application in production systems, its impact on tomato was evaluated. Similarly to the new fungal isolates, significant differences for vegetative growth parameters were only observable in young plants and, but protection against V. dahliae could be seen in one experiment also at high dosage of the pathogen. As the DSE L. orchidicola, P. indica increased the number and biomass of marketable tomatoes only at the beginning of fruit setting, but this did not lead to a significant higher total yield. If the effects on growth are due to a better nutrition of the plant with mineral element was analyzed in barley in comparison to the arbuscular mycorrhizal fungus Glomus mosseae. While the mycorrhizal fungus increased nitrogen and phosphate uptake of the plant, no such effect was observed for P. indica.
In summary this work shows that many different fungal endophytes can be also isolated from roots of crops and, that these isolates can have positive effects on early plant development. This does, however, not lead to an increase in total yield or in improvement of fruit quality of tomatoes under greenhouse conditions.Endophyten, die nicht zu den Mykorrhizapilzen gehören, können das Innere von Wurzeln ohne sichtbare Krankheitssymptome besiedeln und bilden so mit der Pflanze neutrale oder mutualistische Wechselwirkungen. Diese Pilze, auch als nicht-clavicipetale Endophyten bekannt, haben ein breites Wirtsspektrum von mono- und dikotyledonen Pflanzen und weisen eine hohe Diversität auf. Einige von ihnen fördern Pflanzenwachstum und erhöhen Resistenz und Toleranz gegenüber biotischem und abiotischem Stress. Ausgehenden von diesen möglichen Effekten auf ihre Wirtspflanzen war das Ziel der vorliegenden Arbeit die Isolierung und Charakterisierung neuer pilzlicher Wurzelendophyten der Tomate (Lycopersicon esculentum Mill.) und die Analyse ihres Einflusses auf Pflanzenentwicklung und Pflanzenresistenz, sowie auf Ertrag und Fruchtqualität unter Einbeziehung des Modellendophyten Piriformospora indica. Aus vier verschiedenen Anbaugebieten in Kolumbien konnten 51 neue Pilzstämme von oberflächensterilisierten Tomatenwurzeln isoliert werden. Diese Isolate wurden vorcharakterisiert und 14 potentielle Endophyten bezüglich ihrer Taxonomie, ihrer Besiedlungsmuster und ihres Einfluss auf das Pflanzenwachstum näher untersucht. Sequenzierung der ITS Region des ribosomalen RNA Genclusters und genaue morphologische Charakterisierung zeigten, dass sie zu verschiedenen phylogenetischen Gruppen innerhalb der Ascomycota gehören. Neun Morphotypen ließen sich beschreiben, wobei sechs zu den ‚Dark Septate Endophytes’ (DSEs) gehören, aber nicht mit der bekannten Phialocephala Gruppe verwandt waren. Ausführliche konfokale mikroskopische Untersuchungen ergaben sehr verschiedene Besiedelungsmuster der Wurzelendophyten vom Endringen in die Epidermis bis zum Hyphenwachstum durch den Kortex. Topfexperimente unter Gewächshausbedingungen zeigten dass die Isolate in Abhängigkeit von der Inokulumkonzentration und der Zeit der Besiedlung das Wachstum der Tomaten sehr unterschiedlich beeinflussten. Drei neue Isolate (die beiden unbekannte pilzlichen Endophyten DSE48 und DSE49 und eines identifiziert als Leptodontidium orchidicola) mit neutralen oder positiven Effekten wurden für weitere Versuche ausgewählt. In mehreren Experimenten sollte ihr Einfluss auf das vegetative Wachstum, auf Ertrag und auf Fruchtqualität untersucht werden, sowie ihre Fähigkeit die Auswirkungen des Pathogens Verticillium dahliae auf Tomatenpflanzen zu vermindern. Obwohl wachstumsfördernde Effekte durch alle drei Pilze in jungen Pflanzen beobachtet wurden, waren vegetative Wachstumsparameter nach 22 Wochen der Besiedlung nicht mehr beeinflusst bis auf ein signifikante Erhöhung des Wurzeldurchmessers durch den Endophyten DSE49. L. orchidicola dagegen erhöhte die Biomasse und den Glukosegehalt der Früchte, aber nur zu frühen Ernteterminen und bei einer bestimmten Intensität der Wurzelbesiedelung. Hinsichtlich eines schützenden Effekts, konnten die Endophyten DSE49 und L. orchidicola die Krankheitssymptome, die durch V. dahliae verursacht wurden, vermindern, aber nur bei einem geringen Pathogendruck. Um zu überprüfen, ob der Modellendophyt P. indica in Produktionssytemen eingesetzt werden kann, wurde seine Auswirkungen auf Tomaten untersucht. Ähnlich wie die neuen pilzlichen Isolate, zeigte aber auch er seinen fördernden Einfluss nur auf das frühe vegetative Wachstum. Schützende Effekte gegen V. dahliae konnten ebenfalls nur bei niedrigem Pathogendruck konstant beobachtet werden. Wie L. orchidicola erhöhte P. indica die Biomasse an marktfähigen Tomaten am Anfang des Fruchtansatzes, was nicht zu einem insgesamt höheren Ertrag führte. Ob die beobachteten Effekte auf ein verbesserte Nährstoffversorgung der Pflanze zurückzuführen seien, wurde in Gerste im Vergleich mit dem arbuskulären Mykorrhizapilz Glomus mosseae untersucht. Während der Mykorrhizapilz sowohl Phosphat wie Stickstoffaufnehme der Pflanze erhöhte, konnte dies für P. indica nicht festgestellt werden. Zusammenfassend zeigt diese Arbeit, dass auch aus Wurzeln von Kulturpflanzen viele verschiedene pilzliche Endophyten isoliert werden können, und dass einige von diesen durchaus einen positiven Effekt auf die frühe Pflanzenentwicklung aufweisen. Zumindest für Tomate unter Gewächshausbedingungen führen diese Effekte aber nicht zu einer Erhöhung des Gesamtertrags oder einer nachhaltigen Verbesserung der Fruchtqualität.
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Musungu, Bryan Manyasi. « THE HOST-PATHOGEN INTERACTOME AND REGULATORY NETWORKS OF ASPERGILLUS FLAVUS PATHOGENESSIS OF ZEA MAYS : RESISTANCE IN MAIZE TO ASPERGILLUS EAR ROT AND TO AFLATOXIN ACCUMULATION ». OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1212.
Texte intégralRésumé :
The relationship between a pathogen and its host is a complex series of events that occurs at the molecular level and is controlled by transcriptional and protein interactions. To facilitate the understanding of these mechanisms in Aspergillus flavus and Zea mays, three approaches were taken: 1) the development of a predicted interactome for Z. mays (PiZeaM), 2) the development of co-expression networks for Z. mays and A. flavus from RNA-seq data, and 3) the development of causal inference networks depicting interactions between the host and the pathogen. PiZeaM is the genome-wide roadmap of protein-protein interactions that occur within Z. mays. PiZeaM helps create a novel map of the interactions in Z. mays in response to biotic and abiotic stresses. To further support the predicted interactions, an analysis of microarray-based gene expression was used to produce a gene co-expression network. PiZeaM was able to capture conserved resistance pathways involved involved in the response to pathogens, abiotic stress and development. Gene Co-expression networks were developed by the simultaneous use of correlations to develop networks for differentially expressed genes, resistance marker genes, pathogenicity genes, and genes involved is secondary metabolism in Z. mays and A. flavus. From these networks, correlation and anti-correlation of host and pathogen gene expression was detected, revealing genes that potentially interact at different stages of pathogenesis. Finally, causal gene regulatory relationships were inferred using partial correlation analysis of Z. mays infected with A. flavus over a 3 day period. The gene regulatory network (GRN) sheds light on the specifics of the mechanisms of pathogenesis and resistance that govern the Z. mays-A. flavus interaction. The direct product of this research is the understanding of key transcription factors and signaling genes involved in resistance. This body of research highlights how PPIs and GRNs can be utilized to identify biomarkers and gene functions in both Z. mays and A. flavus.
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Winslow, Jonathan W. « Evaluation of Host Resistance and the Utilization of Organic Amendments to Manage Macrophomina Crown Rot of Strawberry in California ». DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2075.
Texte intégralRésumé :
The production of strawberries can be severely limited by soilborne plant pathogens, insects and weeds. Macrophomina phaseolina is a problematic soilborne fungal pathogen in California strawberry production inciting the disease Macrophomina crown rot. When established, the pathogen can cause extensive plant decline and mortality. Host resistance will be a critical tool for managing this disease and guiding breeding programs in the post methyl bromide era. Evaluation of host resistance in strawberry germplasm to M. phaseolina was evaluated through phenotypic assessments of disease incidence. A total of 90 strawberry cultivars and elite selections were included in a replicated field trial conducted in artificially inoculated soils to assess host resistance. Significant differences in levels of resistance and susceptibility were observed among genotypes tested in this trial. The five most resistant strawberry genotypes from highest to lowest in percent plant mortality were: UC-R, UC-G, UC-V, Manresa, and Osceola. The five most susceptible strawberry genotypes with the highest percent mortality in ranking order from highest to lowest were: UC-J, Ruby June, Festival, UC-Y, and UC-A. Of the genotypes tested in this trial UC-V, Manresa and Osceola could be characterized as highly resistant, but no complete resistance was observed.
An additional study was conducted to correlate host symptom expression with the extent of pathogen colonization in different strawberry tissues, and to determine if resistant germplasm can contribute to secondary inoculum production in the field. An established qPCR method was utilized to quantify M. phaseolina colonization of strawberry tissues. There were significant effects for cultivar (P < 0.0001) as well as a significant two-way interaction of cultivar x sample time (P= 0.0083) on the concentration of M. phaseolina DNA detected in strawberry tissues. Expression of the resistant phenotype in strawberry cultivars was associated with limited plant colonization by M. phaseolina. The extent of colonization of a specific cultivar by M. phaseolina was dependent on the sample time after inoculation with the pathogen. In addition, the roots and crowns of a specific strawberry cultivar were equally colonized on a per plant tissue weight basis, but this provides only speculation into the mechanisms conferring host resistance.
A third study was conducted to integrate host resistance of strawberry genotypes with the use of organic amendments in effort to mutually enhance the efficacy of each factor for the control of Macrophomina crown rot. Artificially inoculated potting substrate was amended with Brassica juncea mustard seed meal at a rate of 4.94 tons ha-1(MSM), and anaerobic soil disinfestation utilizing rice bran at a rate of 22.24 tons ha-1 (ASD) were compared to a non-amended (UTC) and steam controls. The soil assay indicated that the ASD and steam treatments were able to reduce the CFU g-1 potting substrate of M. phaseolina by 99.7-100%. In addition, there were significant effects of soil treatment on the fresh biomass of weed seedlings recovered from the potting substrate. However, disease severity and host colonization of multiple strawberry cultivars by M. phaseolina was not reduced when grown in the treated potting substrate. The effect of strawberry cultivar on the extent of pathogen colonization was highly significant (P < 0.0001), in which cultivars characterized as resistant from phenotypic screenings possessed lower concentrations of M. phaseolina DNA. The suppression of M. phaseolina in response to organic amendments was limited but this study supports findings from previous experiments that genotype specific host resistance minimizes host colonization and reduces the production of secondary inoculum.
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Muppa, Saritha. « Molecular detection of pathogenic Fusarium species in roots and stalks of maize plants with or without transgenic resistance to corn rootworm ». [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1473237.
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Nauth, Brittany J. « Soybean QTL Mapping and Candidate Gene Identification for Pythium irregulare and Phytophthora sojae Partial Resistance ; and Root-Knot Nematode Induced Suppression of Gene Silencing ». The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406151869.
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Ramirez-Suero, Montserrat. « Etude de l'interaction de Medicago truncatula avec Fusarium oxysporum et du rôle de l'acide salicylique dans les interactions de la plante avec différents agents pathogènes et symbiotiques ». Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT015A/document.
Texte intégralRésumé :
Des études de l'interaction de la plante modèle des légumineuses Medicago truncatula avec des microorganismes pathogènes et symbiotiques ont été réalisées. Tout d'abord un pathosystème fongique a été caractérisé: M. truncatula en interaction avec Fusarium oxysporum spp., champignon responsable des fusarioses, soit du flétrissement vasculaire ou de la pourriture racinaire chez de nombreuses plantes cultivées. Deux lignées de M. truncatula: A17 et F83005.5 ont été identifiées comme sensible et tolérante respectivement à F. oxysporum f.sp. medicaginis, la forma specialis attribuée à la luzerne. De plus 9 souches de F. oxysporum isolées de différentes plantes hôtes et une souche non pathogène du sol ont été testées dans des expériences d'inoculation avec ces deux lignées. Elles ont toutes été capables d'induire les symptômes de la maladie chez M. truncatula. A l'aide d'une souche de F. oxysporum f.sp. medicaginis exprimant le gène rapporteur GFP, les étapes de colonisation de la racine par le champignon ont été caractérisées. Les observations en microscopie à fluorescence et microscopie confocale des racines d'A17 et F83005.5 ont indiqué un patron de colonisation inhabituel et ont montré que la tolérance de F83005.5 n'était pas corrélée à un mécanisme d'exclusion du cylindre central. Cependant, des différences dans l'expression de gènes de défense ont été détectées entre les deux lignées. Dans la deuxième partie, le rôle de l'acide salicylique a été étudié. Les résultats d'expériences avec l'acide salicylique exogène ont indiqué que le prétraitement de racines avec ce composé pouvait conférer une protection aux plantes vis-à-vis de F. oxysporum f.sp. medicaginis et la bactérie phytopathogène Ralstonia solanacearum. Avec l'objectif d'étudier le rôle de l'acide salicylique endogène dans les interactions avec les microorganismes, la transformation génétique de M. truncatula avec le gène NahG codant le salicylate hydroxylase a été entreprise. Cette enzyme dégrade l'acide salicylique en catechol. Seulement la lignée 2HA a pu être transformée et régénérée en plantes transgéniques. Ces plantes 2HA-NahG ont été inoculées avec des microorganismes pathogènes (R. solanacearum, Verticillium albo-atrum, F. oxysporum f. sp. medicaginis Colletotrichum trifolii et C. higginsianum) ainsi qu'avec le champignon endomycorhizien Glomus intraradices. Les limitations expérimentales n'ont pas permis de conclure définitivement, mais indiquent qu'il est possible que la signalisation par l'acide salicylique ne soit pas impliquée dans les défenses de M. truncatula face à ces microorganismes pathogènes et symbiotiquesA study on the interactions of the plant model legume Medicago truncatula (M.t.) with pathogens and symbiotic microorganisms was undertaken. First, a fungal pathosystem was characterized: M. truncatula in interaction with Fusarium oxysporum spp., the causal agent of Fusariosis, of Fusarium wilt and of root rot in many crop plants. Two M. truncatula lines, A17 and F83005.5, were identified as susceptible and tolerant respectively to F. oxysporum f.sp. medicaginis, the forma specialis related to alfalfa. Besides, 9 strains of F. oxysporum isolated from different host plants and a non-pathogenic soil-borne strain were tested in inoculation experiments with both lines. All the strains were able to trigger disease symptoms in M. truncatula. Using the F. oxysporum f.sp. medicaginis strain transformed with the GFP reporter gene, the stages of the root colonization by the fungi were characterized. Fluorescence and confocal microscopy observations on A17 and F83005.5 roots showed an unusual pattern of colonization and showed that the F83005.5 tolerance was not related to an exclusion mechanism in the central cylinder. However, differences on defence gene expression were detected in both lines. In the second part, the role of salicylic acid was studied. Results of experiments with exogenous salicylic acid indicated that prior treatment of roots with this compound may confer a protection towards F. oxysporum f. sp. medicaginis and the phytopathogenic bacterium Ralstonia solanacearum. With the goal to study the role of endogenous salicylic acid, the genetic transformation of M. truncatula with the NahG gene was initiated. This gene codes for a salicylate hydroxylase which degrades salicylic acid to catechol. Only the highly embryogenic 2HA line could be transformed and regenerated into transgenic plants. These 2HA plants were inoculated with pathogenic microorganisms (Ralstonia solanacearum, Verticillium albo-atrum, Fusarium oxysporum f.sp. medicaginis Colletotrichum trifolii and C. higginsianum) as well as the mycorrhiza fungus Glomus intraradices. Experimental limitations did not allow us to conclude definitely, but it seems possible that the salicylic acid signaling way may not be implicated in the defence of M. truncatula against these pathogenic and symbiotic microorganisms
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Golanowska, Malgorzata. « Characterization of Dickeya solani strains and identification of bacterial and plant signals involved in induction of virulence ». Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0087/document.
Texte intégralRésumé :
Les bactéries pectinolytiques des genres Pectobacterium (ancien nom Erwinia carotovora) et Dickeya (ancien nom Erwinia chrysanthemi) sont les agents des maladies de la jambe noire et de la pourriture molle. Ils provoquent des dommages aux cultures et des pertes économiques élevées. Les pertes causées par les bactéries pectinolytiques sont évaluées à environ 2 à 10% du rendement de pommes de terre, en fonction de l'année. En 2009, les pertes en pommes de terre en Europe ont été estimées à 250 millions d'euros. Au cours des dernières années, des souches de Dickeya ont été de plus en plus souvent isolées de plantes malades en Pologne, en France et d'autres pays européens. Le genre Dickeya est un groupe très diversifié, qui, selon la nomenclature actuelle contient sept espèces: D. aquatica, D. chrysanthemi, D. dadantii, D. dianthicola, D. paradisiaca, D. solani et D. zeae. Les résultats récents, obtenus dans différents pays européens, indiquent qu'un nouveau groupe de souches de Dickeya peut infecter efficacement les plantes de pomme de terre et causer des symptômes de la maladie en climat tempéré. Les souches de D. solani sont considérés comme plus agressives que les autres bactéries causant la jambe noire. Une analyse préliminaire a suggéré qu’elles ont besoin de plus faibles températures optimales pour le développement de la maladie ainsi que de niveaux d'inoculum inférieurs pour la propagation de l'infection. Elles semblent avoir une plus forte capacité à coloniser les racines de plantes de pomme de terre et à se propager à travers le système vasculaire de la plante. Les souches de D. solani produisent une large gamme d’enzymes dégradant de la paroi cellulaire végétale, qui sont les principaux facteurs de virulence. Les objectifs de l'étude étaient les suivants: 1) la caractérisation phénotypique et génotypique des souches de D. solani isolées dans des pays ayant des conditions climatiques différentes: Pologne, Finlande et Israël, 2) l'étude de l’influence d'extraits de pomme de terre sur l'expression de quelques gènes sélectionnés de D. solani: pelD, pelL, tssk, lfaA, 3) la génomique comparative de dix souches de D. solani, basée sur 4 génomes séquencés pour cette étude et 6 séquences génomiques disponibles dans la base de données GenBank. En conclusion, toutes les études génomiques ont montré que les souches de D. solani forment un groupe très homogène. Cependant, leur analyse phénotypique révèle une certaine variabilité entre les souches provenant de différentes conditions climatiques. La raison des variations observées dans les traits phénotypiques peut être liée à la régulation de l'expression des gènes codant les facteurs de virulence qui peuvent être influencés par la température, le pH, la carence en fer ou en oxygène et la disponibilité en azote, ainsi que par la présence de composés spécifiques des tissus végétauxDickeya solani is a species consisting of newly emerged plant pathogenic bacteria that cause blackleg and soft rot diseases. They are responsible for great damages to potato plantations in most of European countries. D. solani strains produce a wide range of plant cell-wall degrading enzymes which are the main virulence factors. The aims of the study were: 1) phenotypic and genotypic characterizations of the D. solani strains isolated in countries with different climatic conditions: Poland, Finland and Israel, 2) study of the potato tuber extract influence on the expression of a few selected D. solani genes : pelD, pelL, tssK, lfaA,3) comparative genomics of ten D. solani strains, performed on 4 genomes sequenced for this study and 6 genome sequences available in the GenBank databases. The results showed that the strains from different climatic conditions have identical profiles in rep-PCR (with three different primers) and in Restriction Fragments Lenght Polymorphism-Pulse Field Gel Electrophoresis. However, they do differ phenotypically, especially in the activity of plant cell-wall degrading enzymes. Polish strains have higher activities of pectinolytic, cellulolytic and proteolytic enzymes than Finnish and Israeli strains. D. solani mutants in the pelD, pelL, tssK, lfaA genes were constructed by site-specific mutagenesis. The highest induction by plant extracts was observed for the lfaA gene. The expression of pelL is also induced by plant derived signal(s), but not that of pelD and tssK. Comparative genomics helped to elucidate the D. solani pangenome. The 10 D. solani strains genomes are coding for a total of 41 947 proteins which were grouped into 5 045 Orthologous Groups, 3 809 belonging to the core genome, 413 to the accessory genome and 823 to the unique genome. Some pathogenicity-related genes as well as their regulators were selected on the basis of the knowledge available for D. dadantii 3937, the most studied Dickeya strain, which belongs to a closely related species. Analysis of their protein sequence showed no difference in the sequence of those genes within the 10 genomes. All the genetic studies proved that D. solani strains form a very homogenous group. On the other hand, the phenotypic analysis showed some variability among strains from different climatic conditions. The observed variations in the phenotypic traits can results from a different regulation of the expression of the genes encoding virulence factors which are influenced by temperature, pH, iron deprivation, oxygen and nitrogen availability, as well as by the presence of plant compounds
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Dore, Dalin Shelley. « Grapevine rhizosphere bacteria : influence of diversity and function on two root diseases : a thesis submitted in fulfilment of the requirements for the degree of Master of Science at Lincoln University / ». Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1305.
Texte intégralRésumé :
The overall goal of this research was to determine what, if any, role grapevine rhizosphere bacteria play in the differing susceptibilities of New Zealand grown rootstocks to Cylindrocarpon black foot disease. The size and diversity of bacterial populations associated with the rhizospheres of grapevine rootstocks: 101-14, 5C, Schwarzmann and Riparia Gloire were evaluated. Dilution plating showed that total bacterial (P=0.012, P=0.005 for NA and KB, respectively) and fluorescent Pseudomonad (P=0.035) rhizosphere counts differed between rhizosphere and bulk soils but did not correlate with the differing susceptibilities of the rootstock varieties to black foot. No varietal differences were found for spore forming bacteria (P=0.201). SSCP banding patterns showed that species diversity was similar for most rootstocks, but that there were some differences in the composition of bacterial populations, probably attributable to vigour. Some functional characteristics of the bacteria isolated from the rhizospheres of the most and least susceptible rootstock varieties were assessed to investigate their potential to suppress the pathogen. In dual culture, bacteria from Riparia Gloire, 101-14 and the control soil all had little ability to antagonise Cylindrocarpon destructans. However, they differed in their degrees of activity for glucanase (P=0.000), protease (P=0.001) and siderophores (P=0.000). In all tests, bacterial isolates from the rhizosphere of 101-14 had the largest number of active isolates (P≤0.002); however, those from Riparia Gloire had the greatest degree of positive responses for the glucanase and siderophore assays. Bacterial isolates from the control soil produced few glucanases and no siderophores, but had the highest degree of protease activity. Bands excised and sequenced from SSCP gels frequently matched to other ‘uncultured bacteria’ in GenBank, as well as to other bacterial phyla, classes and genera commonly isolated from soil and sediment samples. These included members of the Firmicutes, Proteobacteria (α, δ, γ), Verrucomicrobia, Acidobacteria and Chromatiales. The pathogenicity of C. destructans and Fusarium oxysporum was investigated by inoculating soil containing wounded ungrafted rootstocks of 101-14, 5C, Schwarzmann and Riparia Gloire. Results indicated that F. oxysporum might be a more aggressive pathogen than C. destructans. Inoculation with F. oxysporum or C. destructans increased disease severity, P=0.018 and P=0.056, respectively at 0 cm. Rootstock variety influenced disease severity caused by C. destructans (P<0.001) and F. oxysporum (P=0.090), with rootstocks 101-14 and 5C being most susceptible to C. destructans, and Riparia Gloire and Schwarzmann most susceptible to F. oxysporum. There was also an indication that inoculation with one pathogen increased plant susceptibility to the other, with increased F. oxysporum infection in the C. destructans inoculated treatments of Riparia Gloire and Schwarzmann (P<0.05). The effect of carbohydrate stress (leaf trimming) and inoculation on C. destructans disease severity, incidence, and rootstock rhizosphere bacterial populations was evaluated by inoculating the soil containing one year old plants of Sauvignon Blanc scion wood grafted to rootstocks 101-14 and Schwarzmann. Disease severity and incidence was similar for both Schwarzmann (8.4% and 29.3%, respectively) and 101-14 (14.9% and 31.0%, respectively). When data for the moderate and no stress treatments were combined, because their effects were similar, the disease severity was significantly higher for the highly stressed plants(P=0.043). Stress did not influence disease incidence (P=0.551). Infection occurred in the non-inoculated plants, but disease severity was higher in the plants inoculated with C. destructans than those that were not. Root dry weight of highly stressed plants was lower than in both the moderately stressed (P=0.000) and unstressed plants (P=0.003). An interaction between inoculation and stress (P=0.031) showed that inoculated and highly stressed plants had the lowest root dry weight but there was no effect of rootstocks (P=0.062). There was no significant effect of carbohydrate stress (P=0.259) or inoculation (P=0.885) on shoot dry weight. SSCP banding patterns showed that bacterial diversity was generally similar between rootstocks, but stress and inoculation altered rhizosphere bacterial communities. This study has demonstrated that functionality of grapevine rhizosphere bacteria do differ between grapevine rootstock varieties that have different susceptibilities to black foot disease, but that this role needs to be further investigated if more accurate and practically relevant conclusions are to be drawn.
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Patil, Neeraj. « Detection of Sclerotinia sclerotiorum using qPCR assay and comparison between three qPCR systems to check sensitivity ». Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-20265.
Texte intégralRésumé :
Sclerotinia sclerotiorum is a pathogenic fungus that infects around 400 species of host plants. Stem rot disease caused by this fungus is economically disastrous for Brassica napus cultivators in Sweden. Due to the lack of disease resistant cultivars, disease management has been solely dependent on fungicide application. The current disease prediction models are not scientifically accurate and take into account factors such as weather, previous disease incidence, and conomic effects which often result in unnecessary and excessive use of fungicides by cultivators. Real-Time Polymerase Chain Reaction has proven to be the fastest, most accurate and reliable technique for detecting plant pathogens as it gives an idea about disease severity by measuring pathogen concentration in environmental samples. Reproducible and able qPCR assays have the potential of being the main principle on which more scientifically accurate plant disease prediction and management models an be developed. The aim of this study was to validate a previously established qPCR assay to detect S. sclerotiorum. An absolute quantification experiment was performed by using plasmid DNA cloned with a target gene as template. Further, three different qPCR machines were compared to make a plausible conclusion regarding their sensitivity and efficiency in detecting minuscule amounts of DNA from the environment. While a solid conclusion could not be reached regarding the sensitivity of each of these machines, this study pointed out some basic trends about each machine that may help researchers in selecting the most efficient qPCR system when working with detection of plant pathogens.
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Sobrinho, Candido Athayde. « Patossistema caupi X Macrophomina phaseolina : método de detecção em sementes, esporulação e controle do patógeno ». Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/11/11135/tde-29042005-161211/.
Texte intégralRésumé :
Apesar da espécie Vigna unguiculata (L.) Walp. ser bastante rústica e estar adaptada às condições adversas de clima e solo brasileiros, seu rendimento é muito baixo. Diversas causas têm sido levantadas para explicar esse comportamento; entre elas destacam-se as doenças fúngicas, sobretudo aquelas cujos patógenos são transmitidos por sementes, em especial a podridão cinzenta do caule, causada por Macrophomina phaseolina (Tassi) Goid. A abordagem analítica desse patossistema revelou alguns problemas emergentes. Entre eles, destacam-se: a) desconhecimento da qualidade sanitária das sementes de caupi, utilizadas para semeadura; b) desunifomidade na metodologia usada para detectar os patógenos presentes nas semente; c) dificuldade na esporulação do patógeno, máxime de alguns isolados reticentes em esporular em meios artificiais de cultivo, cujo comportamento dificulta os trabalhos de seleção de genótipos resistentes; d) carência de medidas de controle do patógeno, que empreguem práticas naturais, como uso de sementes sadias, de indutores de resistência e de cultivares resistentes, de fácil uso e passível de adoção por parte dos produtores. Na estruturação da matriz lógica do presente estudo, referidos problemas foram transformados em objetivos. Os trabalhos foram conduzidos no Departamento de Entomologia, Fitopatologia e Zoologia Agrícola da ESALQ/USP, em Piracicaba-SP. Os resultados indicaram o teste de sanidade de sementes de caupi empregando o método do papel de filtro com restrição hídrica utilizando NaCl a 0,8Mpa, como o mais adequado para detecção dos fungos presentes nas sementes de caupi, especialmente M. phaseolina. A análise sanitária das amostras de sementes originadas de vários estados brasileiros revelou que, em 62% das amostras analisadas, o fungo M. phaseolina estava presente, sendo as amostras originadas do estado da Paraíba, Piauí, Pará e Bahia as que apresentaram maiores níveis de incidência do patógeno. Os melhores níveis de esporulação do patógeno foram conseguidos com a combinação de sobreposição de discos de folhas de trigo ao meio BDA, com temperatura de 25oC. Quanto à identificação de indutores de resistência, capazes de controlar M. phaseolina, os resultados revelaram que o acibenzolar-S-metil (ASM) foi o mais eficiente, quando comparado com quitosana e com um produto silicatado derivado de rocha micronizada (PSiM), apresentando um controle residual por mais de 40 dias após a semeadura. A maior eficiência verificada pelo ASM ocorreu devido a sua capacidade de ativar mecanismos bioquímicos de defesa, configurando-se em efetivo ativador da resistência induzida nas plantas de caupi, por atuar na cinética de importantes enzimas relacionadas à defesa, como a fenilalanina amônia-liase, peroxidase e quitinase. Quanto à reação de cultivares de caupi à doença, foi possível verificar razoável nível de resistência de algumas cultivares, tendo sido consideradas resistentes Mulato, Guariba e Maratauã.Notwithstanding the specie Vigna unguiculata (L.) Walp is sufficiently rustic and adapted to the adverse conditions of the Brazilian soil and climate, its improvement is very low. Many causes have been raised in order to explain such behavior; among them the fungal diseases stand out, over all those whose pathogens are transmitted by the seeds especially the charcoal rot disease caused by Macrophomina phaseolina (Tassi) Goid. The analytical approach of such pathosystem has revealed some emerging problems. Among them, it stands out: a) the ignorance of the sanitary quality of the cowpea seeds used for sowing; b) the non-uniformity in the used methodology in order to detect the pathogens, which are present in the seed; c) the difficult in pathogen sporulation, principally of some isolated reticent in forming spores in cultivation artificial environments whose behavior hampers the selection works of the resistant genotypes; d) lack of pathogen control measures, which utilize natural practices, such as the use of healthy seeds, resistance inducers and resistant cultivars of easy utilization and liable to adoption by the producers. In structuring the logical matrix of this study, such problems were transformed into objectives. The works were conducted at the Entomology, Phytopathology and Agricultural Zoology Departments of ESALQ/USP, in Piracicaba-SP. The results have pointed out the sanity test of the cowpea seeds through the method of filter paper with hydric restriction using NaCI 0,8Mpa, as the most suitable for detecting the current fungus in cowpea seeds, especially M. phaseolina. The sanitary analysis of the seeds samples originated from several Brazilian states has revealed that in 63% of the analyzed samples, the fungus M. phaseolina was present, and the samples originated from the states of Paraíba, Piauí, Pará and Bahia were those that have presented higher incident levels of pathogen. The best levels of sporulation were obtained with the combination of the superposition of wheat leaves disks in the middle of BDA in 25ºC. As to the identification of the resistance inducers, capable of controlling the M. phaseolina, the results have revealed that the acinbezolar-S-methyl (ASM) was more efficient when compared to chitosan and with a silicate product originated from micronized rock (PsiM), presenting a residual control for more than 40 days after the sowing. The greatest efficiency ascertained by ASM has occurred due to its capacity of activate the defense biochemistries mechanisms, forming itself in an activator effect of the induced resistance in cowpea plants because it acts in the kinetic of important enzymes related to the defense, such as the phenylalanine ammonia-lyase, peroxidase and chitinase. As to the cowpea cultivars reaction to the disease, it was possible to ascertain a reasonable resistance level of some cultivars, and BR 14 Mulato, Guariba e Maratauã were considered as resistant.
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Abraham, Abraha Okbasillasie. « Biological control of Phytophthora root rot of citrus seedlings and cuttings ». Thesis, 2005. http://hdl.handle.net/10413/3830.
Texte intégralRésumé :
With an increasing realization that many agrochemicals are hazardous to animals and humans, came the desire to replace these chemical agents with biological approaches that are more friendly to the environment and human health. Microorganisms play an important role in plant disease control, as naturally occurring antagonists. Microorganisms may also have beneficial
effects on plant development when applied to plant roots. Research efforts worldwide have recorded successes in biological control and growth stimulation on many crops, particularly when using members of the genera Bacillus and Trichoderma. Their use on citrus rootstock could be advantageous to nurserymen and growers in reducing the incidence of seedling mortality and increasing production. To achieve these objectives, laboratory and tunnel experiments were conducted to develop effective biocontrol agents for citrus seedlings and cuttings. Nineteen 0 ut 0 f 23 Trichoderma isolates tested in vitro against Phytophthora p arasitica sp
showed antagonistic activity by hyperparasitism and four out of eight Bacillus isolates resulted in antagonism by forming inhibition zones. The positive in vitro activity of Trichoderma and Bacillus isolates on Phytophthora provided motivation step for further trials in the greenhouse to evaluate their biological control activity on citrus seedlings and cuttings. A greenhouse trial was carried out to evaluate the biological control potential of 23 Trichoderma isolates (drenched at 5 x 105 spores / rnI) and two Bacillus isolates (drenched at 1 X 106 or 1 X 108 colony forming units (CFU) / rnI) to suppress Phytophthora parasitica sp. of rough lemon (Citrus jambhirini Lush.) seedlings. Five isolates ofTrichoderma (AA12, AA5, Trichoderma harzianum (AA16), SY3F and Eco-T~ were highly effective in suppressing Phytophthora root rot, with AA12 providing the best control. The Bacillus isolates also suppressed the pathogen but were not as effective as the Trichoderma isolates. This trial was used to test for growth stimulation activity by some of the biocontrol agents. To verify these results, a further trial was carried out to evaluate growth stimulation capabilities in the absence of any pathogen. Trichoderma Isolates AA13 and AA17 caused no 111 change in seedling growth, while other Trichoderma and Bacillus isolates had an inhibitory effect on the seedling growth. This trial indicated that the biocontrol activity was affected by
inoculum densities, and as a result in vitro sporulation capacity was evaluated. TrichodermaIsolate AA16 was the largest spore producer, followed by Eco-T®. Spore production was lowest from Trichoderma isolates AA4 and AA12. Growth stimulation responses of Trichoderma Isolates AA4, AA16, Eco-TID and SYN6 were further studied at four different doses (1 X 103, 1 X 104, 5 X 105 or 1 X 106 spores / ml) on rough lemon and trifoliate orange seedlings. Trifoliate oranges responded positively to 1 X 104 and 5 X 105 spores / ml of Eco-TID, but rough lemon responded negatively to all dosages of the Trichoderma isolates applied. This indicates that the inoculum density responses may be host specific. Higher population density of 1 X 106 spores / ml of all tested Trichoderma isolates had a stunting effect on seedling growth of both species. Based on t he positive results 0 f individual applications of some Trichoderma and Bacillus isolates, of the biological control agents on rough lemon seedlings against Phytophthora
parasitica in an earlier greenhouse trial, their combined effect in the control of the pathogen was performed. Before carrying out a greenhouse trial, activities of the isolates to be combined were evaluated in vitro. This trial showed that Trichoderma Isolates AA16 and Eco-T®were compatible. Trichoderma isolates AA16 and Eco-T®were also found to be compatible with
Bacillus Isolates B77, B81 and PHP. As a result, further in vivo trials were conducted. The tunnel trials were carried out as two separate experiments:
In the first experiment, a combination of two Trichoderma Isolates A A 16 and Eco-T®was conducted assayed at 5 X 105 or 1 X 106 spores / ml, on rough lemon seedling, and cuttings and trifoliate orange and sour orange seedlings. A combination of Trichoderma isolate AA16 and Eco-T®at 5 X 105 spore / ml increased significantly the new flush biomass of rough lemon cuttings compared to AA16 alone, but was not different from Eco-TID alone. The combination of AA16 and Eco-T® achieved no change of biomass of rough lemon and trifoliate orange seedlings. The combination of AA16 and Eco-TID did not increase the root biomass of sour orange compared to AA16 or Eco-r® alone. The combination of AA16 and Eco-r® at higher doses (1 x 106 spores / ml) showed significantly better suppression of Phytophthora root rot of rough lemon cuttings but did not show disease suppression in all seedling species verities tested. In a second experiment, individual and combined effects of Trichoderma isolates (drenched at 5 X 105 spores / ml) with Bacillus isolate (drenched at 1 X 106 colony forming units (CFU) / ml) for suppression of Phytophthora root rot on rough lemon and trifoliate orange seedlings was performed. The combination of Trichoderma Isolate AA16 and Bacillus Isolate B81 increased root biomass on rough lemon seedlings compared to the combination of Trichoderma AAI6 or Bacillus PHP but was not significantly different to Trichoderma AA16 alone. Bacillus PHP combined with Trichoderma AA16 or singly had no effect on rough lemon seedlings. Combining Trichoderma Eco--r® and with Bacillus B8I or PHP did not increase biomass of rough lemon seedlings compared to Trichoderma Isolate Eco--r® alone. There was no statistically significant differences in the effects of the combinations of the Trichoderma and Bacillus isolates compared to their individual applications on the biomass of trifoliate oranges. This study established the antagonistic potential of several South African isolates of
Trichoderma and Bacillus as a viable alternative to agrochemicals for controlling Phytophthora parasitica. The growth stimulation capabilities of Trichoderma isolates in terms of seedling development was also demonstrated.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
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Ramputla, Mogwale Janet. « Nutritional water productivity of hot chilli (capsicum annuum) under infection with meloidogyne javanica and meloidogyne incognitarace 2 ». Thesis, 2019. http://hdl.handle.net/10386/3168.
Texte intégralRésumé :
Thesis (M.Sc. Agriculture (Soil Science)) -- University of Limpopo, 2019Nutritional water productivity (NWP) is an assessment tool, which describes the amount of water that has been used to produce selected mineral malnutrition (MMN) elements and micronutrient malnutrition (MNMN) substances. Therefore, it links agricultural production to human nutrition. Deficiencies in MMN elements and/or MNMN substances in human nutrition referred to as malnutrition, had been linked with fatal diseases. Agricultural soils could be affected by soil-borne pathogens such as plant-parasitic nematodes, which could limit the availability of MMN elements and MNMN substances. In some communities, vegetable crops, including chilli are regarded as a major source of MMN elements and MNMN substances. Effects of root-knot (Meloidogyne species) nematodes on NWP of chilli (Capsicum annuum L.) have not been documented. The objective of the study was to determine the effects of increasing population densities of M. incognita race 2 and M. javanica on the NWP of hot chilli plants. A microplot trial was conducted at the Green Biotechnologies Research Centre of Excellence (GBRCE), University of Limpopo, South Africa. Pots were filled with 10-L steam-pasteurised (300oC) sandy clay loam soil sourced from GBRCE and Hygromix-T (Hygrotech, Pretoria North) growth medium in the ratio 3:1 (v/v). Thereafter, three-week-old hot chilli cv. 'Serrano' seedlings were transplanted into each pot, with inoculum prepared by extracting eggs and second-stage juveniles (J2) of M. incognita race 2 and M. javanica from roots of grown nematode susceptible tomato cv. 'Floradade' (Solanum lycopersicum L.) in a 1% NaOCl solution. Fourteen days after transplanting, treatments 0, 50, 125, 250, 625, 1250 and 2000 eggs and second-stage juveniles (J2) of M. incognita race 2 and M. javanica were separately inoculated using a 20 ml plastic syringe into 5-cm-deep holes in pots. At 56 days after the initiation of the treatments, Meloidogyne species xiv decreased soil pH and increased organic carbon, contributing 29 and 43% in total treatment variation (TTV) of the respective variables. Treatment effects caused the pH to decrease. NWP variables against increasing nematode numbers exhibited quadratic relations, with coefficients of determination ranging from 59 to 86% for M. incognita race 2 trial and 80 to 98% for M. javanica trial. Meloidogyne species population densities against plant variables did not show any significant relationship, except for root galling and chlorophyll content where treatments contributed 76, 98 and 47% TTV of the respective variables. Generally, root galling increased with increase in Meloidogyne species population densities, whereas chlorophyll content decreased with increasing inoculum levels. Nematode variables against their increasing population exhibited quadratic relationship with the model explained by 44 to 95% for M. incognita race 2 and 28 to 82%, association, respectively for M. javanica. In conclusion, Meloidogyne species interfered with NWP of mineral elements in chilli plant and therefore, nematode management practices should be done to reduce the nematode population densities that would confer quality to agricultural produce for human health benefits.
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« Association of chickpea with soil fungi : a comparison of cultivars ». Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-11-1848.
Texte intégralRésumé :
Certain crop plants are susceptible to pathogens or unable to develop efficient microbial symbioses. These crops adversely impact soil biological quality with consequences on plant health and productivity of cropping systems. Chickpea is a rotational pulse crop with two types: kabuli and desi, and several cultivars. Cultivation of chickpea has inconsistent effects on soil microbial communities and subsequent wheat crops. I conducted field studies and used high throughput molecular analyses to explore the variations among chickpeas to identify cultivars developing fungal communities that are conducive to plant health and productivity. I also carried out greenhouse studies and used biochemical analyses to investigate the response of chickpea cultivars to arbuscular mycorrhizal (AM) fungi and non-AM fungal endophytes and identify the influence of root and root metabolites on the endophytic and pathogenic fungi. Cultivars and types of chickpeas and environmental conditions promoted different fungal communities in the root endosphere. Funneliformis and Claroideoglomus were the dominant AM fungal genera and Fusarium and Alternaria were the dominant non-AM fungal genera in the roots of chickpea. The roots of cultivars CDC Corrine, CDC Cory and CDC Anna hosted the most diverse fungal communities in contrast to CDC Alma and CDC Xena roots which hosted the least diverse communities. Plant response to AM and non-AM fungal endophytes varied with genotype and type of chickpea. The root symbiosis effectively promoted plant growth in CDC Cory, CDC Anna and CDC Frontier and stimulated nitrogen fixation in CDC Corrine. Cultivars of chickpea responded differently to dual inoculation of the AM and non-AM fungal endophytes. Co-inoculation with AM and non-AM fungal endophytes had additive effects on CDC Corrine, CDC Anna and CDC Cory but non-AM fungal endophytes reduced the positive effect of AM fungi in Amit and CDC Vanguard. Desi chickpea appeared to form more efficient symbioses with soil fungal resources than kabuli chickpea. Protein(s) up-regulated in the mycorrhizal roots of the desi chickpea CDC Anna suppressed the growth of the fungal endophytes Trichoderma harzianum and Geomyces vinaceus and of the pathogens Fusarium oxysporum and Rhizoctonia sp. The formation of AM symbiosis decreased the production of root bioactive metabolites soluble in 25% methanol. Some of the root metabolites stimulated the growth of Trichoderma harzianum and Geomyces vinaceus, and a few inhibited Rhizoctonia sp. and Fusarium oxysporum. A few metabolites with contrasting effects on the different fungal species were detected. The non-protein phytochemicals had selective effects on the endophytes and pathogens whereas the antifungal proteins of mycorrhizal roots were non-selective. Overall the study reveals a "genotype effect" of chickpea on the soil microbiota suggesting the possibility to improve the performance of this crop through the selection of genotypes improving the communities of root associated fungi, by associating and responding to beneficial fungi and repressing the pathogens.
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(12298370), Alison S. Jensen. « Redefining pachymetra root rot management strategies and cultivar resistance in commercial sugarcane fields ». Thesis, 2020. https://figshare.com/articles/thesis/Redefining_pachymetra_root_rot_management_strategies_and_cultivar_resistance_in_commercial_sugarcane_fields/19426862.
Texte intégralRésumé :
Pachymetra chaunorhiza is an important soilborne pathogen of sugarcane and is found only in Australia. Pachymetra root rot is managed primarily by growing resistant cultivars, which are chosen for planting based on oospore levels in the soil. This management strategy does not account for differences in virulence among Pachymetra populations, despite previous research demonstrating that two genetically distinct groups of Pachymetra occur, which may differ in pathogenicity. Higher than expected yield losses have been associated with high oospore levels under some cultivars with intermediate resistance to the pathogen. Increased virulence of Pachymetra towards specific cultivars, following long-term exposure to that cultivar, could explain these reports of high yield losses in intermediate cultivars. This research project aimed to deliver knowledge of the genetic and pathogenic variation among Pachymetra populations in different growing regions and following long-term exposure to different cultivars.
The level of genetic and pathogenic variation among Pachymetra populations and the factors contributing to pachymetra root rot were investigated in a series of field trials, glasshouse experiments and laboratory molecular analyses. Results from field experiments generally support the current guidelines used for Pachymetra management. No evidence was found to support the hypothesis that planting the same intermediate cultivar over multiple crop cycles could lead to higher than expected yield losses due to pachymetra root rot. Yield losses of 17 percent were associated with continual cropping of Q208A in a field trial near Bundaberg, in the southern Queensland sugarcane-growing region. A range of putative Pachymetra genes were identified which could play a role in pathogenicity. Collectively, the findings from this research supported the conclusion that two genetically distinct groups of Pachymetra occur in growing regions a) north of Townsville and b) south of Townsville, as previously reported. Three potential native hosts of Pachymetra were also identified, including Themeda australis and this finding supports the theory that lighter soil types are conducive to pachymetra root rot.
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Mackey, Melora. « Resistance to Verticillium in Tomatoes : the Root-Stem Controversy ». Thesis, 2013. http://hdl.handle.net/10214/7749.
Texte intégralRésumé :
Verticillium is a soil-borne fungus that is one of the world's foremost plant pathogens. Commercial plant grafting suggests that resistance occurs in the root; this conflicts with decades of research indicating that resistance occurs in the stem. The goal of this thesis work was to use an alternative approach to determine the location of resistance by expressing the Ve1 gene using organ-specific promoters. Promoter sequences for the stem-specific gene, Ribulose 1,5-bisphosphate carboxylase oxygenase small chain 2A (Rbsc2A), and root-specific gene, Tobacco Mosaic Virus Induced (TMVi) were taken from the Sol Genomics Network (SGN) database, cloned into constructs with the Ve1 gene and susceptible tomato germplasm was transformed using Agrobacterium tumefaciens. Preliminary results suggest that resistance may not be localized and expression of the Ve1 gene in either the root or the stem is sufficient to develop whole plant resistance to the Verticillium pathogen.
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Hsiao, Yun-Hsuan, et 蕭韻軒. « Development of simple differential and disease diagnosis assays for plant soft rot pathogen, Pectobacterium chrysanthemi ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/81100298821863514878.
Texte intégralRésumé :
碩士輔仁大學
生命科學系碩士班
103
The first purpose of this study is to test the feasibility of the 3XPGMA strip paper and two differential media, NGM and NGCa, for the diagnosis of orchid soft rot diseases caused by Pectobacterium chrysanthemi (Pch) or Burkholderia gladioli (Bgla) and for the detection of Pch or Bgla on the leaf surface of orchids. In the disease diagnosis, the diseased tissues caused by Pch or Bgla were first wiped by a wet cotton swab, and the swab was then put into a plastic tube containing 3XPGMA strip paper. The swab wiped on soft rot tissues caused by Pch turned the paper blue, and that on Bgla-inducing disease tissues turned the paper yellow in 2-3 days. Pch or Bgla could be isolated from the blue or yellow-colored paper by using NGN or NGCa medium, respectively. In the pathogen detection, five kinds of orchid (Cattleya, Dendrobium, Paphiopedilum, Oncidium and Phalaenopsis) and totally 30 plants were detected. The orchid leaf surfaces were first wiped by a wet cotton swab, and the swab was put into a plastic tube containing 3XPGMA strip paper. One paper turned blue, and 10 papers became yellow in 2-3 days. The bacteria on colored papers were isolated by NGN or NGCa medium. It was found that the bacterium on the blue-colored paper was not Pch, that from one of the yellow papers was Bgla, and others were not Bgla. The results indicated that some saprophytic bacteria on orchid leaf surfaces could turn the paper blue or yellow, and color change on the paper could not correspond to the existence of Pch or Bgla. The saprophytic bacterium which turns the paper blue was identified as Pseudomonas aeruginosa, and the saprophytic bacteria on yellow colored papers were also identified and included Pseudomonas oryzihabitans, Pantoea stewartii and Chryseobacterium sp. The further experiments showed that the blue color caused by P. aeruginosa on the paper could become red by adding 1N HCl solution, but the blue color of Pch unchanged. The yellow color caused by Bgla or Chryseobacterium sp. on the paper would turn blue by adding 1% tetramethyl-p-phenylenediamine dihydrochloride (TPD) solution, and that caused by P. oryzihabitans and P. stewartii remained yellow. If the yellow-colored papers caused by Bgla or Chryseobacterium sp. were washed in sterile water by centrifugation, and the supernatant from paper only with Bgla became blue by adding 1% TPD solution. Therefore, color changes on the paper caused by Pch, Bgla, or the saprophytic bacteria could be differentiated by adding 1N HCl or 1% TPD solution. In addition to orchids, Pch can cause soft rot symptoms on many other plant hosts which could be infected by another soft rot pathogen, P. carotovora subsp. carotovora (Pcc). The soft rot symptoms caused by Pch and Pcc are not easily distinguished. In this study, it was found that both Pch and Pcc have abilities to hydrolyze X-gal. The ability of Pch was constitutively expressed and not inhibited by glucose, but that of Pcc was repressed by glucose. One differential medium, YTG-X was developed. Pch turned blue but Pcc remained white on the YTG-X medium after incubation for 1-2 day. Furthermore, one X-gal paper was also developed for rapid diagnosis of plant soft rot tissues. The diseased tissues of Pch on the X-gal paper became blue in 10-15 minutes, but those of Pcc took more than one hour to turn blue. The promoter region of lacZ gene (-galactosidase) of Pch contains only one operator (LacI-binding site) and no cap site, which may be one of the reasons why the X-gal hydrolysis ability was constitutively expressed and not inhibited by glucose in Pch.
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Wicks, T. J. (Trevor J. ). « Phytophthora crown rot of almond and cherry trees : pathogens, rootstock and scion susceptib[i]lity and control ». 1987. http://web4.library.adelaide.edu.au/theses/09PH/09phw637.pdf.
Texte intégral
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Wicks, T. J. (Trevor J. ). « Phytophthora crown rot of almond and cherry trees : pathogens, rootstock and scion susceptibility and control / T.J. Wicks ». 1987. http://hdl.handle.net/2440/21591.
Texte intégralRésumé :
Bibliography: leaves 169-185viii, 185 leaves, [1] leaf of plates : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1987
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Wanthaya, Somprathana, et 王姍姍. « Antifungal Activities of Medicinal Plants Extract for Controlling Crown Rot Pathogens on ‘Pei-Chiao’ Banana (Musa spp., Giant Cavendish, AAA Group) ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/26184126697885677872.
Texte intégralRésumé :
碩士國立中興大學
園藝學系所
103
Banana (Musa spp.) is a commercially important fruit crop of world. However, its short shelf life and suffers severe postharvest losses seriously limit the marketing of the fruits. Fungal disease, maning crown rot is a serious problem in banana. Fungicides are the primary means for controlling fungal diseases. However, many consumers prefer chemical free banana for their taste and pesticide free status. Medicinal plants are alternative methods that can control fungal disease, because a range of biological activities had been found in plant extracts including wound healing activity, anti-inflammatory, analgesic, antioxidant, and antimicrobial. In this study, the effect of different medicinal plants on mycelial growth of three pathogens causing crown rot disease, which include Collectotrichum musae, Fusarium spp., and Lasiodiplodia theobromae was studied in vitro and in vivo conditions. The first experiment, the assay was conducted with extract of In Plantago asiatica L. seed extract (PAS) concentrations that were extracted by blender of 1%, 2%, 5%, 10%, 15%, 50% and 90%. The hyphae of PAS concentration with 90% treatment had been normally grown, but these hyphae could not form mycelium. The second experiment is the effect of different medicinal plants which include cortex phellodendri extract, cinnamon oil, cinnamon extract and clove extract at 10% with autoclave and non-autoclave medium in vitro condition. With or without autoclaved were not effected on the efficiency of medicinal plant extract. All treatments delayed these three fungi, especially cinnamon oil and clove extract. The third experiment is the effect of different concentrations of cinnamon oil and clove extract in vitro condition, on peduncle discs and on banana fruits. 20% concentration of clove extract can inhibit a mycelium growth in vitro condition. In vivo condition, the crown treated with clove extract had less mycelium on the surface. The most efficient inhibition is cinnamon. Between essential oil and extract of Cinnamon'' bark, cinnamon oil is more efficiency than extract and the high oil property means the high inhibition. The last experiment is the effect of synthetic cinnamon oil on mycelial growth of three pathogens causing crown rot and anthracnose diseases in vitro condition and banana fruits. Synthetic cinnamon oil can completely inhibit at 0.025%-0.05% in all pathogens causing crown rot in vitro condition. Concentration at 0.1 is too high for treated on banana fruits because of a phytotoxic on the peel. These suggest that medicinal plants can delay and inhibit the growth of three fungi which are causing crown rot disease on banana fruits. Medicinal plants are an alternative method for controlling crown rot disease which is more safety than a synthetic fungicide, especially cinnamon and clove. However, we should use in appropriate dose because of a tolerance of fruits and an allergy in some people.
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Andrade, Linares Diana Rocío [Verfasser]. « Characterization of tomato root-endophytic fungi and analysis of their effects on plant development, on fruit yield and quality and on interaction with the pathogen Verticillium dahliae / von Diana Rocío Andrade Linares ». 2010. http://d-nb.info/1014227321/34.
Texte intégral