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1
Omar, Ibrahim. « Biological control of crown and root rot of tomato ». Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310952.
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Chowdhury, Prabir Roy. « Exploitation of Rhizosphere microorganisms of tea for protection against root rot pathogens ». Thesis, University of North Bengal, 2008. http://hdl.handle.net/123456789/1063.
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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.
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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.
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Kalonji, Kabengele Muzela J. B. « Evaluation of three fungicides for control of soilborne diseases of lettuce seedlings ». Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/29549.
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Lettuce (Lactuca sativa L.) seedlings diseases caused by soilborne pathogens are characterised by root rot, stem rot and damping-off of the seedlings that can occur at any time during growth. Fusarium solani, Pythium ultimum and Rhizoctonia solani are known to be the important destructive pathogens of lettuce, causing severe yield losses in South Africa. The aim of this research was to evaluate the effects of three selected fungicides to control these pathogens on lettuce seedlings. In this study the fungicides metalaxyl (Apron®), fludioxonil (Celest®) and mefenoxam (Subdue®) were applied at two concentrations as single and double doses on lettuce seedlings to determine their efficacy to control the pathogens Fusarium solani, Pythium ultimum and Rhizoctonia solani after significant reduction of mycelia growth was observed in vitro. Cultures of P. ultimum (UPGH024), R. solani (UPGH122) and F. solani (UPGH122) were obtained from the culture collection of the Department of Microbiology and Plant Pathology, University of Pretoria and cultivated on PDA for 2 days at 25ºC. Pasteurised soil was artificially inoculated with these pathogens. For the first experiment lettuce seeds were planted in polystyrene seedling trays at a depth of 1.0 cm. There were four replications of 50 seeds per treatment. In Experiment 2 pots (12 cm x 7 cm) were filled with pasteurised growing medium and 3-week old seedlings were transplanted. There were three replications of six pots containing three plants each. Seedling trays and pots were drenched with fungicides and placed in a randomised block design in a controlled environment room at 20- 26°C with a 12h-light/dark regime. The seedling trays and pots were rotated daily in the room. Seedling trays and pots were watered daily to maintain field capacity. The seedlings were able to grow larger in the pots than in seedling trays. It was confirmed that the treatment with fludioxonil (Celest®) at double and single dose inhibited the growth of the three fungi F. solani, P. ultimum and R. solani on lettuce seedlings without causing phytotoxicity. All three fungicides significantly reduced the diseases caused by the three pathogens. These findings are consistent with previous reports that fludioxonil, metalaxyl and mefenoxam can control oomycete fungi. There are few registered fungicides for the control of Fusarium solani, Pythium ultimum and Rhizoctonia solani on lettuce, therefore further work will aim to confirm these results in the field.Dissertation (MInstAgrar)--University of Pretoria, 2008.
Microbiology and Plant Pathology
unrestricted
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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.
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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.
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Samils, Nicklas. « Monitoring the control methods of Heterobasidion annosum s.l. root rot / ». Uppsala : Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200847.pdf.
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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.
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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.
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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.
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Moya, Ernesto Antonio. « Distribution and interaction of Fusarium crown rot and common root rot pathogens of wheat in Montana and development of an integrated management program for Fusarium crown rot ». Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/moya/MoyaE0810.pdf.
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This thesis had three objectives: i) Determining distribution of FCR and common root rot (CRR) of wheat in Montana; ii) Determining population dynamics between F. pseudograminearum and Bipolaris sorokiniana at different wheat development stages, and iii) Development of an integrated disease management program for Fusarium crown rot (FCR) using biological and fungicide seed treatments, cultivar resistance, and induced systemic resistance (SAR). Surveys of 91 fields over two years using qPCR identified FCR in 57% and CRR in 93% of the fields surveyed. Bipolaris sorokiniana, F. culmorum and F. pseudograminearum were isolated from 15, 13 and 8% of tillers respectively. FCR distribution was highly clustered while CRR was uniformly distributed with soil type, elevation and growing degree days influencing distribution. Data from intensively sampled fields estimated yield losses caused by FCR and CRR at 3.2 to 34.9% with losses influenced by pathogen population. This study is the first time qPCR was used to survey the distribution of FCR and CRR and to study the interaction of the respective pathogens. The effect of F. pseudograminearum and B. sorokiniana inoculum applied singly or in combination at three rates showed high and low rates of F. pseudograminearum inoculum reduced Bipolaris populations, while B. sorokiniana inoculations did not affect Fusarium populations in stems. Populations of both pathogens increased from heading until harvest with Fusarium colonizing stems earlier than Bipolaris. Mixed inoculations increased incidence of infection and co-infection relative to that observed in production fields. Both fungi alone or combined reduced the seedling counts. Grain yield was inversely correlated with Fusarium populations. Difenoconazole-mefenoxam seed treatment reduced FCR severity between 29.3-50% and fungal and bacterial seed treatments were ineffective. The cv. Volt was identified as partially resistant and had the highest levels of chitinase and beta-1, 3-glucanase activity of cultivars evaluated. Induction of SAR by Bacillus mycoides isolate BmJ or acibenzolar Smethyl significantly reduced the severity of FCR compared to water controls. Integration of cultivar resistance plus fungicide seed treatment or SAR induction provided equal control in greenhouse and irrigated trials. In a dryland field trial, integration of all management tools reduced FCR more than individual tools.
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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.
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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.
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Xia-Hong, He. « Bio-control of root rot disease in vanilla ». Thesis, University of Wolverhampton, 2007. http://hdl.handle.net/2436/15398.
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Fusarium oxysporum Schl. var. vanillae (Tucker) Gondon is known to cause root rot in Vanilla planifolia Andrews in most regions where it is grown, including the major plantations in Xishuangbanna, Yunnan Province of China. This is of serious economic concern to the Province since the vanilla flavouring extractable from the beans of the plant is a valuable food product and an important export commodity. There are no fungicides registered for the control of Fusarium root rot and the only available chemical control methods are ineffective and cause serious contamination of the soil. Breeding for resistance is difficult when no dominant gene is known or where little information is available on fungal pathogenicity. Biocontrol is the main alternative for disease control in this crop, an attractive approach because of increasing concerns for environmental protection. The investigation considers two biocontrol strategies: first the introduction of virulent, antagonistic, non-pathogenic strains, closely-related to the pathogen, to overcome pathogenic populations in infected soils; second the use of essential oils with antimicrobial properties when applied to infected soils. Pathogenicity tests have been done on 81 out of 87 F. oxysporum isolates collected in Yunnan Province. Among these, 32 isolates were non-pathogenic and 49 were pathogenic. The pathogenicity results showed the complexity of F. oxysporum in Yunnan. Seventeen isolates were recovered from the Daluo plantation, of which 14 were pathogenic isolates and 3 non-pathogenic isolates; 26 from the Menglun plantation, in which 12 were pathogenic and 14 were non-pathogenic; 18 isolates from the Manjingdai plantation, in which 12 isolates were pathogenic, whilst the other 6 were non-pathogenic and 20 were obtained from the plantation in Hekou i County, of which 11 were pathogenic isolates and 9 were non-pathogenic. Genetic diversity within this population of F. oxysporum has been investigated with respect to vegetative compatibility and to determine the relationship between VCGs and virulence. The VCG results showed that the 87 strains of Fusarium oxysporum f.sp vanillae isolated from Yunnan Province were complex. They could be distributed into 12 different VCGs and that a direct relationship between VCGs group and virulence could not be drawn. Two non-pathogenic strains, ML-5-2 and HK-5b-4-1, have been screened from 87 strains as candidate biocontrol agents by pathogenicity and VCG, which are self-incompatible and closely related to the pathogens. These two strains were effective in vanilla root rot control in controlled environments, but their effects in field experiments were less conclusive. Seven essential oils, which have long been regarded as having inhibitory effects on pathogens in nature, have also been investigated as biocontrol agents. Three oils, cinnamon oil, thyme oil and clove oil, were effective in inhibiting the growth of pathogen in vitro. These oils may develop into useful components of different management strategies with non-pathogenic strains. For the future, consideration will need to be given to the mechanism(s) of the interaction of the antagonistic components with the soil microbe population and host plant and also to appropriate formulation, to take account of soil type, crop status, cultural practices, environmental and economic factors. Biocontrol methods have considerable potential but must be acceptable to farmers as part of an overall crop management programme.
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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.
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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.
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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.
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Saiki, Shintarou. « The variations of drought tolerance along soil depth gradient and the physiological mechanisms of drought-induced and pathogenic tree die-offs in the Bonin Islands ». Kyoto University, 2017. http://hdl.handle.net/2433/228226.
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Ghosh, Anasooya. « Studies on soil –inhabiting siderophore producing bacteria and their role in suppression of plant root pathogens ». Thesis, University of North Bengal, 2012. http://hdl.handle.net/123456789/1541.
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Bright, Angela. « Organic amendment of soil to combat root pathogens / ». [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16752.pdf.
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Lees, Alison Kathryn. « Diagnosis and control of foot rot pathogens of wheat ». Thesis, Open University, 1995. http://oro.open.ac.uk/57549/.
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Foot rot disease of wheat is caused by the pathogens Fusarium cuImorum, F.avenaceum and Microdochium nivale. Symptoms of foot rot are a general browning of the stem base and leaf sheath. There is a discrepancy between the ability of fungicides to control these pathogens in vivo and in vitro, and no relationship between disease symptom severity and yield loss has been established in wheat. The identification of the causal agents of foot rot disease is not possible from examination of disease symptoms alone. This work showed that the azole fungicides flusilazole and prochloraz inhibited the germination of conidia and mycelial growth of F. culmonon, F. avenaceum and M. nivale in vitro to a varying extent. However, no consistent control of these pathogens in wheat was observed in the field using the same fungicides. Further studies employing a semicontrolled outdoor experiment showed a relationship between density and timing of inoculum application, disease symptom severity and yield loss in wheat artificially inoculated with F. culmorum and M. nivale. Molecular marker systems were used to address the problem of pathogen detection and identification. A Random Amplified Polymorphic DNA (RAPD) assay was developed to differentiate F.culmorum, F.avenaceum and two types of M.nivale (M.nivale var.nivale and M. nivale var .majus) in vitro. Selected RAPD products were cloned and sequenced and species specific primers constructed from this sequence infonnation. These primers were used in the polymerase chain reaction (peR) and were shown to detect the pathogens in host tissue. This technique was adapted by addition of a competitor fragment to the peR reaction resulting in a quantifiable competitive peR assay. Using this method the fungal biomass of each pathogen present in the host tissue could be estimated. The development of these techniques for the identification, detection and quantification of F. cuimorum, F.avenaceum, M.nivale var.nivale and M.nivale var.majus in plant tissue will allow more extensive studies of the epidemiology of these species, the competition between species and the effect of fungicides on these pathogens can be carried out.
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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.
Texte intégralRésumé :
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.
19
Lewis, Karen Jane. « Biological control mechanisms of the mycoparasite Pythium oligandrum Drechsler ». Thesis, University of Sheffield, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243848.
Texte intégral
20
Baimey, Hugues Kossi. « Scutellonema bradys as a pathogen of yam in Benin ». Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-10252006-164955.
Texte intégral
21
Bodles, William J. A. « Damping-off Oomycetes in natural regeneration of Scots Pine ». Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311160.
Texte intégralRésumé :
Phytophthora cinnamomi var. cinnamomi, Pythium ultimum var. ultimum and Pythium undulatum were successfully isolated from naturally regenerating Pinus sylvestris forests across north Scotland. Molecular and morphological characterisation enabled accurate identification of these Oomycetes to the variety level. In vitro and glasshouse pathogenicity trials demonstrated that under artificial temperature, light and water regimes the Oomycetes had the potential to reduce plant growth and cause chlorosis of the P. sylvestris foliage after two months. Soil pH was also determined as having a significant effect on P. sylvestris growth in terms of foliage colour and dry mass. Biological control in vitro experiments with Bacillus subtilis and Pseudomonas fluorescens produced significant inhibition of Oomycete growth but on transfer to the glasshouse trials, antagonism was not observed. This study was undertaken to establish the presence of fine root pathogens, namely those belonging to the Oomycetes, within regenerating Pinus sylvestris forests in northern Scotland. The identify of the pathogens was determined using morphological and molecular biology techniques. The virulence of the fine root pathogens on Pinus sylvestris seedlings (1 + 0) was then determined by a series of in vitro and glasshouse trials. Interactions between soil pH and bacterial biological control agents were also tested against each of the pathogens. Pathogen trials were undertaken to show the potential effect of the Oomycetes on Pinus sylvestris seedlings. The glass house trial was scored on foliage colour and dry weight of seedlings 18 months of age, grown in pH amended Irish moss peat. In comparison to the control, inoculation with P. cinnamomi caused a significantly greater frequency of chlorotic/dead seedlings. In contrast, inoculation with P. undulatum (syn. P. dimorphum) resulted in a greater number of healthy seedlings than the control. No significant difference in the proportion of healthy and chlorotic/dead seedlings was found between the bio-control bacteria groups. pH was found to have a significant effect on seedling growth. At pH 7, compared to pH 3, there was a significant greater likelihood of the seedlings being chlorotic/dead.
22
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.
Texte intégral
23
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.
Texte intégralRésumé :
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.
24
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.
Texte intégral
25
Day, Jennifer P. « In vitro studies into host-pathogen interactions of sunflower and Macrophomina phaseolina ». Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319785.
Texte intégral
26
Malligan, Cassandra D. « Crown rot (fusarium pseudograminearum) symptom development and pathogen spread in wheat genotypes with varying disease resistance ». University of Southern Queensland, Faculty of Sciences, 2009. http://eprints.usq.edu.au/archive/00006225/.
Texte intégralRésumé :
[Abstract]Crown rot, caused by Fusarium pseudograminearum (Fpg), is an important soilborne disease of wheat and barley. The degree of crop damage depends on seasonal conditions. Typically, high moisture conditions early in the season encourage seedling infection from stubble residues. Moisture stress later in the season leads to the production of unfilled “whiteheads”. Current control relies on cultural practices and sowing of partially resistant varieties. In order to understand the nature of partial resistance, I have examined the patterns of disease symptom development and pathogen spread in susceptible and partially resistant tissues of both pot-grown wheat, barley and oat seedlings and field-grown inoculated wheat trials. Further research was conducted to determine whether differences in pathogenicity occur amongst a small subset of Australian Fpg isolates. Seedling experiments confirmed that differences in disease ratings between susceptible and partially resistant genotypes are detected in younger leaf sheaths of older seedlings. At later harvest times differences between these genotypes are not significant in older leaf sheaths. Re-isolation of Fpg from inoculated seedlings has shown that each tissue was infected later in partially resistant genotypes compared to susceptible ones with a significantly lower number of isolations recorded at each harvest time in 42 day old seedlings. Barley cultivars were rapidly infected by the pathogen and exhibited high levels of disease symptoms. By comparison levels of infection in oats were low compared to all other genotypes. No significant differences between genotypes were observed in coleoptile tissues, either in fungal colonisation or development of disease symptoms. Disease development in the subcrown internode varied between lines/cultivars but was not representative of the relative susceptibility of each genotype. The pathogen did not appear to invade plant tissue via the vascular system but rather spread directly across the stem from leaf sheath to leaf sheath. Field trials were designed to study disease symptom development and localisation of Fpg hyphae in all expanded tissues (excluding head and roots) in wheat genotypes of known susceptibility to crown rot. Plants were harvested at approximately fortnightly intervals throughout the growing season. The main effects and interactions of harvest, genotype and tiller on each plant part were examined with a detailed statistical analysis of differences seen in these factors between susceptible and partially resistant wheat genotypes, in two inoculated field trials. While differences between genotypes were mostly not significant at each harvest when disease rating or isolations from leaf sheath tissues were examined, important differences between susceptible and resistant genotypes were seen in disease developments and Fpg infections of stem tissue in field trials. Restriction of pathogen growth and symptom development was more pronounced in the tissues of 2-49 (possesses seedling resistance) than in the field resistant Sunco. At present, the mechanisms that lead to these resistance responses are unknown. The pathogenicity study aimed to determine whether 7 Fpg isolates and a mixed inoculum differed in ability to cause crown rot in 9 wheat genotypes ranging in susceptibility to this disease. Although a genotype*inoculum interaction was significant, there is no evidence of stable pathogenic races in the isolates examined in these experiments. The growth of all isolates was partially inhibited in a consistent manner on resistant genotypes when compared to very susceptible genotypes. These results confirm significant differences in the aggressiveness of Fpg isolates on wheat, evidenced by variation in mean disease severity between isolates growing on a range of host genotypes.
27
Vermeulen, Meagan. « A host-pathogen study of Fusarium Verticillioides in resistant and susceptible maize inbred lines ». Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96915.
Texte intégralRésumé :
Thesis (MSc)--Stellenbosch University, 2015ENGLISH ABSTRACT: Maize (Zea mays L.) is an important crop worldwide and forms the staple diet of many African countries including South Africa. Fusarium ear rot (FER) of maize is caused by a fungus, Fusarium verticillioides, which also produces the fumonisin mycotoxin group. The consumption of fumonisin contaminated maize grain has been associated with serious human and animal health complications. Several South African maize inbred lines exhibiting resistance to FER and fumonisin contamination have been identified. These locally adapted inbred lines could be used to generate mapping populations to identify QTLs associated with resistance to FER and fumonisin contamination. The corresponding markers could be utilised in breeding programmes through marker-assisted selection to ensure the development of commercial cultivars with resistance to FER and fumonisin contamination. In this study, resistant and susceptible maize inbred lines were utilised to commence the development of recombinant inbred line (RIL) populations for the mapping and validation of QTLs associated with FER and fumonisin resistance. One F2 population was phenotypically and genotypically analysed to produce a linkage map for the preliminary identification of QTLs associated with resistance to F. verticillioides infection and fumonisin deposition. A potential QTL for resistance to FER was detected and should be validated across several locations and years in the subsequent RIL population. Additionally, potential resistance barriers of maize to infection by F. verticillioides were investigated by histological studies. The importance of a closed stylar canal in determining resistance to FER was established for nine South African maize inbred lines by means of scanning electron microscopy (SEM). No significant association was observed between a closed stylar canal and the resistance/susceptible status of maize inbred lines before pollination, while the canals appeared closed in all inbred lines following pollination. The results suggest that the stylar canal architecture is not an essential factor determining resistance to F. verticillioides ingress in the maize inbred lines selected for this study. Furthermore, the possibility of resistance to FER and fumonisin contamination being initiated during the seedlings phase of a resistant and susceptible maize inbred line was investigated by means of confocal laser scanning microscopy (CLSM). Fusarium verticillioides growth originating from soil-borne or seed-borne contamination was monitored in various above and below soil plant tissues but no significant difference in the colonisation could be determined between resistant and susceptible maize seedlings. No fumonisin was produced regardless of the inoculation method or resistance status of the plant. These results suggests that the resistant and susceptible maize seedlings used in this study may not be resistant to systemic fungal ingress but may resist the deposition of fumonisins. The resistance associated with the resistant inbred line is not mediated during the seedling phase but potentially through structural and biochemical defence mechanisms during later plant developmental stages.
AFRIKAANSE OPSOMMING: Mielies (Zea mays L.) is ‘n belangrike graangewas wat wêreldwyd geproduseer word en dien as stapelvoedsel in talle Afrika-lande, insluitend Suid-Afrika. Fusarium kopvrot (FKV) in mielies word veroorsaak deur die swam, Fusarium verticillioides, wat ook die fumonisien mikotoksien groepe produseer. Die inname van fumonisien-geïnfekteerde mielies gaan gepaard met ernstige gesondheidsprobleme in mense en diere. Verskeie Suid-Afrikaanse ingeteelde mielielyne, wat weerstandbiedend is teen FKV en fumonisien kontaminasie, is voorheen identifiseer. Hierdie plaaslik-aangepaste teellyne kan gebruik word om kartering populasies te genereer om kwantitatiewe eienskap loci (KEL) te identifiseer wat verband hou met weerstandbiedenheid teen FKV en fumonisien kontaminasie. Die ooreenstemmende merkers kan gebruik word in teelprogramme deur gebruik te maak van merker-geassisteerde seleksie om kommersieële kultivars, wat weerstandbiedend is teenoor FKV en fumonisien kontaminasie, te ontwikkel. In hierdie studie is weerstandbiedende en vatbare mielie inteellyne gebruik om rekombinante inteellyn (RIL) populasies te begin ontwikkel vir die kartering en validasie van KEL’e geassosieer met FKV en fumonisien weerstandbiedenheid. Een F2 populasie was fenotipies en genotipies geanaliseer om ‘n koppeling-kaart te verwek vir die voorlopige identifikasie van KEL’e geassosieer met weerstandigheid tot F. verticillioides infeksie en fumonisein afsetting. ‘n Potensiële KEL vir weerstandbiedenheid is geïdentifiseer, wat verdere bevestiging in die daaropvolgende RIL populasie in verskeie geografiese areas en oor addisionele seisoene, benodig. Potensiële fisiese versperrings teen F. verticillioides tydens mieliesaad infeksie is ook ondersoek met behulp van histologiese studies. Die belangrikheid van ‘n geslote styl-kanaal vir weerstandbiedendheid teenoor FKV is bevestig in nege Suid-Afrikaanse inteellyne deur middel van skandeer elektron mikroskopie (SEM). Geen beduidende verwandskap tussen ‘n geslote styl-kanaal en die weerstandbiedenheid/vatbaarheid van die inteellyne voor bestuiwing is gevind nie, terwyl die kanaal in alle inteellyne gesluit was na bestuiwing. Die resultate dui daarop dat die styl-kanaal argitektuur nie ‘n noodsaaklike faktor is in die bepaling van weestand tot F. verticillioides besmetting in die suiwer mielielyne wat geselekteer was in hierdie studie nie. Verder is die moontlikheid dat weestand tot FKV en fumonisien kontaminasie geïnisieer kan word gedurende die saailing-fase ondersoek in beide ‘n weerstandbiedende en vatbare mielie inteellyn met behulp van konfokale laser skandering mikroskopie (CLSM). Die groei van F. verticillioides afkomstig vanuit die grond of saad is gemonitor in verskeie bo- en ondergrondse plantweefsels, maar geen beduidende verskille in kolonisasie kon opgespoor word tussen weerstandbiedende en vatbare mielie saailinge nie. Geen fumonisien produksie is waargeneem nie, ongeag die innokulasie metode of weerstand-status van die plant. Hierdie resultate dui daarop dat die weerstandbiedende en vatbare mielie saailinge wat in hierdie studie gebruik is moontlik nie weerstandbiedend is teen sistemiese swaminfeksie nie, maar wel weerstand kan bied tot afsetting van fumonisiene. Die weerstand geassosieër met die weerstandbiedende inteellyn word nie bemiddel gedurende die saailingfase nie maar waarskynlik deur strukturele en biochemiese verdedigingsmeganismes tydens latere plant ontwikkelings-stadia.
National Research Foundation (NRF)
28
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.
29
Fang, Xingxiao. « Chemical Composition of Soybean Root Epidermal Cell Walls ». Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1281.
Texte intégralRésumé :
The root epidermis, being the outermost cell layer of the organ, is in contact with the soil environment. The position of the epidermis determines its important roles, such as taking up water and ions from the surrounding soil, and defending against harmful microorganisms. What is the chemical composition of the walls in this layer? The chemical nature of the soybean epidermal wall modifying substance was investigated in this study with the use of histochemical tests coupled with electron microscopy, and chemical depolymerizations in combination with chromatography. Soybean (Glycine max) was used as a test species in the present studay. Results of histochemical and electron microscopical studies indicated that the epidermal walls are modified with suberin. The suberized epidermal walls were permeable to apoplastic tracers, differing from those of cells with suberized Casparian bands, possibly due to the spatial distribution or chemical components of the suberin. Suberin may occur in a diffuse form linked with other wall components in the epidermis. What is the chemical nature of this modification, and does it play a role in pathogen resistance? The root epidermal wall compositions of two soybean cultivars were compared; one (cv. Conrad) is resistant to Phytophthora sojae and the other (cv. OX 760-6) is susceptible to this root-rot oomycete. Their epidermal walls were isolated enzymatically and subjected to two different degradation methods, i. e. BF3-MeOH transesterification and nitrobenzene oxidation. The compositions of depolymerisates of the cell walls determined by GC-MS indicated four dominant suberin monomers varying in chain length from C16 to C24. In all epidermal cell walls, ω-hydroxycarboxylic acids were more abundant than diacids, carboxylic acids and alcohols. Two of the monomers detected (hydroxycarboxylic acid and a,ω-dicarboxylic acid) are known to be characteristic suberin markers. The quantitative chemical compositions significantly differed in the epidermal cell walls of the two soybean varieties. Walls of the resistant cultivar (Conrad) had a greater quantity of both the aliphatic and aromatic components of the polymer than the susceptible cultivar (OX760-6), providing evidence to support the hypothesis that preformed suberin plays a role in plant defense.
30
Moročko, Inga. « Characterization of the strawberry pathogen Gnomonia fragariae, and biocontrol possibilities / ». Uppsala : Dept. of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200671.pdf.
Texte intégral
31
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.
Texte intégralRésumé :
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.
32
Das, Lopamudra. « Studies on tea seed mycoflora and resistance of young tea plants against Rhizoctonia solani, a soil born root pathogen of germinating tea seedlings ». Thesis, University of North Bengal, 2013. http://hdl.handle.net/123456789/1539.
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Frercks, Birutė. « Genetic variation of brown rot blossom blight pathogens and their hosts sweet and sour cherry ». Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20141008_132136-79491.
Texte intégralRésumé :
The aim of the research. To evaluate the genetic diversity in sweet and sour cher-ry populations, to characterize the injuries to blossoms and fruits caused by blossom blight brown rot, to identify the species composition of Monilinia patho-gens and to analyse the DNA polymorphism within and among pathogens popula-tions. Main tasks: 1. To analyse the genetic diversity of sweet and sour cherry cultivars and wild cherry population, growing in west Lithuania, using molecular marker methods (AFLP and SSR). 2. To determine factors affecting injuries caused by blossom blight. 3. To investigate characteristics of brown rot agent M. fructigena development in sweet and sour cherry cultivars differing in resistance to brown rot. 4. To identify species composition of Monilinia spp. in IH LRCAF stone fruit collection based on PCR methood and to evaluate inter- and intraspecific DNA polymorphism of Monilinia spp. based on AFLP method.Tyrimų tikslas. Įvertinti trešnės ir paprastosios vyšnios populiacijų ge-netinę įvairovę, ištirti trešnės ir paprastosios vyšnios žiedų bei vaisių užsikrėtimo kaulavaisinių monilioze mechanizmus, nustatyti šios ligos sukėlėjų Monilinia rūšinę sudėtį bei išanalizuoti jų tarprūšinį ir vidurūšinį DNR polimorfizmą. Tyrimų uždaviniai: 1. Išanalizuoti skirtingų pagal atsparumą moniliozinei degligei LAMMC SDI kaulavaisinių kolekcijoje augančių trešnės ir vyšnios veislių ir Vakarų Lietuvo-je augančios laukinės trešnės populiacijos genetinę įvairovę, naudojant molekuli-nius metodus (SSR ir PFIP) bei palyginti PFIP pradmenų kombinacijų informaty-vumo rodiklius. 2. Nustatyti žiedų pažeidimo moniliozine deglige (M. laxa) veiksnius: ištirti žiedo da¬lių atsparumą moniliozinei degligei, nustatyti kuriame žiedo raidos tarpsnyje jie yra jautriausi, įvertinti, ar kuokelių mechaninis pašalinimas (kastravimas) turi įtakos užsikrėtimui moniliozine deglige ir nustatyti ar žiedų ap-dulkinimas gali aktyvuoti augalo imunines reakci¬jas ir užkirsti kelią patogenui patekti į žiedo vidų. 3. Ištirti rudojo puvinio sukėlėjo M. fructigena vystymosi ypatumus kontrastinėse pa¬gal atsparumą rudajam puviniui trešnės ir vyšnios veislėse. Nusta-tyti, ar vaisiai jautresni patogenui yra nokimo pradžioje ar techninės brandos (skynimo) metu, įvertinti vaisių mechani¬nio pažeidimo poveikį užsikrėtimui ruduo-ju puviniu. 4. Identifikuoti Monilinia spp. LAMMC SDI kaulavaisinių kolekcijos augyne rūšinę sudėtį PGR... [toliau žr. visą tekstą]
34
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.
35
Ray, Pushpanjali. « Search for novel actinomycetes from soil as potential biocontrol agent against fungal root pathogens of phaseolus vulgaris (L.) vigna radiata(L.) ». Thesis, University of North Bengal, 2017. http://ir.nbu.ac.in/hdl.handle.net/123456789/2575.
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36
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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Li, Liang [Verfasser]. « Study of genes modifying morphology, pathogen interactions and MEP-derived metabolites during barley root colonization by Piriformospora indica via stable root transformation system / Liang Li ». Gießen : Universitätsbibliothek, 2012. http://d-nb.info/1064024890/34.
Texte intégral
38
Menkis, Audrius. « Root associated fungi of conifer seedlings and their role in afforestation of agricultural land / ». Uppsala : Dept. of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005106.pdf.
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39
Douglas, Lisa Iris. « Physiology and ecology of Idriella bolleyi, a biological control agent of cereal root and stem base pathogens ». Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/13702.
Texte intégralRésumé :
Idriella bolleyi strains, T560, J10 and AB1, differed considerably in their tolerance to water-stress - this was apparent in both osmotic and matric potentials and in all aspects of their growth cycle. The level of tolerance for one strain, T560, was comparable to the take-all pathogen Gaeumannomyces graminis var. tritici, which is associated with low water-stress tolerance, and another strain, AB1, was comparable to the foot-rot pathogen Fusarium culmorum, known to be highly tolerant of drought conditions. Variation in response to osmotic potential was also observed in root and stem base field isolates of I. bolleyi. The field isolates differed in the level of mycelial growth and sporulation at potentials of -1.5 MPa (control) and -5.0 MPa. Isolates from the same plant were found to have different levels of sporulation - this may have been related to the degree of microcycle conidiation they exhibited. Idriella bolleyi isolates, T560 and AR1, were able to colonise straw in soil at different matrix potentials down to -7.0 MPa. Straw colonisation was found to increase from 2 to 8 weeks, indicating that both strains were actively growing at all water potentials during this period. A number of other fungal species were isolated from the straw along with I. bolleyi, suggesting that a high degree of competition was associated with colonisation. Water potential appeared to be the most influencing factor with regard to the activity of each species. Idriella bolleyi could increase its population on unsterilised wheat seeds buried in soil. Idriella bolleyi was inoculated onto the seeds as either an alginate or water suspension. For both seed treatments the detectable level of conidia increased exponentially on the seeds over five days, this increase coinciding with the production of young wheat roots. As the seed aged the detectable level of conidia decreased.
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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.
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Le, Thanh Toan, Trong Ky Vo et Huy Hoang Nguyen. « Evaluation of two eco-friendly botanical extracts on fruit rot pathogens of orange (Citrus sinesis (L.) Osbeck) ». Technische Universität Dresden, 2018. https://tud.qucosa.de/id/qucosa%3A33345.
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Fruit rot caused by Aspergillus niger and Colletotrichum sp. could cause rapid and severe damage on orange fruits. Current control method of orange fruits is mainly applied by usage of harmful pesticides, leading to chemical residues on fruits, environmental pollution and human poisoning. One of alternative methods of reducing pesticides is to use botanical extracts. This study was conducted to evaluate the in vivo antifungal efficacy of aqueous extracts from the leaves of neem and basket plants against A. niger and Colletotrichum sp. Orange fruits artificially inoculated by fruit rot pathogens were immersed into leaf extracts of 6% (w/v) neem or basket plants for 30 s, and kept for 11 days to record lesion length at room temperature. Orange fruits immersed into sterile distilled water were used as the control treatment. The results showed that at 11 days after inoculation, extracts of neem and basket plants significantly reduced the Aspergillus rot lesions by 109.08 and 124.00 mm, respectively. In addition, anthracnose lesions on orange fruits were statistically inhibited by treatments of neem and basket plants, with the average lesion diameters approximately 160.00 and 154.75 mm, respectively, at day 11 of the conducting experiment. The results of this study showed that leaf extracts of neem and basket plant at the concentration of 6% could be used as a natural alternative to control the in vivo growth of rot pathogens of orange fruits. These extracts have a bright future in modern plant protection to replace conventional synthetic pesticides in agro-ecosystem.Thối trái bởi Aspergillus niger và Colletotrichum sp. gây ra các thiệt hại nghiêm trọng trên cam. Biện pháp phòng trừ bệnh trên trái cam hiện nay chủ yếu dựa vào thuốc hóa học, dẫn đến tồn dư thuốc trên trái cây, ô nhiễm môi trường và gây độc cho con người. Một trong các phương pháp thay thế giúp giảm sử dụng thuốc hóa học là sử dụng dịch trích thực vật. Nghiên cứu này đã được thưc hiện để đánh giá hiệu quả in vivo của dịch trích ở nồng độ 6% của neem hoặc lược vàng đối với A. niger và Colletotrichum sp. Các trái cam đã lây nhiễm nhân tạo tác nhân gây thối trái thì được nhúng vào dịch trích ở nồng độ 6% của neem hoặc lược vàng trong 30 giây, và giữ đến 11 ngày để ghi nhận chiều dài vết bệnh ở nhiệt độ phòng. Cái trái cam được nhúng vào nước cất thì dùng như nghiệm thức đối chứng. Kết quả cho thấy ở 11 ngày sau khi chủng bệnh, dịch trích neem và lược vàng làm giảm đáng kể vết thối Aspergillus lần lượt là 109,08 và 124,00 mm. Bên cạnh đó, vết bệnh thán thư trên trái cam đã bị ức chế có ý nghĩa thống kê bởi các dịch trích neem và lược vàng, với đường kính trung bình các vết bệnh lần lượt là 160,00 và 154,75 mm, ở ngày 11 của thí nghiệm. Kết quả của nghiên cứu này đã chỉ ra rằng dịch trích neem và lược vàng ở nồng độ 6% có thể sử dụng như một biện pháp thay thế tự nhiên trong việc phòng trừ sự phát triển của tác nhân gây thối trái cam. Các loại dịch trích này có tương lai trong bảo vệ thực vật hiện đại, thay thế các loại thuốc hóa học tổng hợp truyền thống trong hệ sinh thái nông nghiệp.
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au, A. Jayasekera@murdoch edu, et Arunodini Uthpalawanna Jayasekera. « Interactions between Phytophthora cinnamomiand Acacia pulchella : consequences on ecology and epidemiology of the pathogen ». Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061129.134500.
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Phytophthora cinnamomi is an important pathogen of many plant species in natural ecosystems and horticulture industries around the world. In Western Australia, a high proportion of native plant species are susceptible to P. cinnamomi attack. Acacia pulchella, a resistant legume species native to Western Australia has been considered as a potential biological control tool against P. cinnamomi. To develop effective control methods, it is important to understand the interactions between the control agent and the different life forms of the pathogen. In this thesis the interactions are investigated between P. cinnamomi and varieties of A. pulchella which occur in jarrah (Eucalyptus marginata) forest and sand plain ecosystems.
The soil inoculum of P. cinnamomi was compared under the potted plants of the three common varieties of A. pulchella, var. pulchella, var. glaberrima and var. goadbyi. These were grown in infected jarrah forest soil in the glasshouse and in vitro in a sterilised soil-less mix aseptically. Acacia urophylla (a species non suppressive towards P. cinnamomi) was also included as a control. An isolate of the most commonly found clonal lineage of P. cinnamomi in the jarrah forest, A2 type 1 was selected for use in experiments after testing showed it reliably produced zoospores and chlamydospores both axenically and in non-sterile conditions, in comparison to several other isolates. The lowest survival of P. cinnamomi inoculum was found under A. pulchella var. goadbyi plants grown both in non sterile soil and in aseptic soil-less mix.
All the life forms of P. cinnamomi were affected by A. pulchella (Chapters 2, 3, 4 and 5). The soil leachates from potted plants of A. pulchella var. goadbyi reduced sporangial production (Chapter 2) and caused cytoplasm collapse of chlamydospores (Chapter 3). The confirmation was obtained that soil under A. pulchella was inhibitory to sporangial stage of P. cinnamomi and new evidence was obtained on chlamydospore inactivation. Cytoplasm collapse in the chlamydospores was observed both for chlamydospores on mycelial discs on Mira cloth exposed to the soil leachate and within infected roots buried in soils under the three varieties of A. pulchella plants. The effect was strongest under the plants of A. pulchella var. goadbyi and indicated that the chlamydospores of P. cinnamomi are unlikely to act as persistent structures under A. pulchella var. goadbyi plants.
In Chapter 4, bioassays were conducted with axenically produced mycelia, chlamydospores and zoospores to test the inhibitory effect of the root exudates collected from aseptically grown A. pulchella var. goadbyi plants. The zoospores of the same isolate used in the soil leachate tests were immobilised (became sluggish and encysted) within one to two minutes. When incubated for 24 h, zoospores predominantly clumped and germ tubes were observed only from the clumped ones. Chlamydospores produced by four isolates of the common A2 type 1 strain and the only one A2 type 2 strain available at the time were tested. A higher percentage of chlamydospores collapsed and a very low percentage germinated after 24 h. Chlamydospores of all the A2 type 1 isolates were inhibited by the root exudates whilst the A2 type 2 isolate remained viable. The findings showed that the suppressive effect must be due at least in part to substances exuded by the A. pulchella plants. However, it appeared that the A2 type 1 isolates were more vulnerable to this effect than the single A2 type 2 isolate.
In Chapter 5, the effect of season on sporangial suppression of P. cinnamomi was shown using field soils collected from three jarrah forest soil vegetation types and a Banksia woodland on Bassendean sand, collected in winter and summer. The effect of age of A. pulchella plants was demonstrated using the soils collected from rehabilitated bauxite mine pits. In all the locations soils were collected under A. pulchella plants and 5 m away from the nearest A. pulchella. An effect of soil type was evident as whilst the soil leachates made from the three lateritic jarrah forest soil types where A. pulchella is common in the understorey were suppressive to the sporangial stage of P. cinnamomi, this effect was not evident in the Bassendean sand under A. pulchella. A. pulchella soils collected in winter were less suppressive towards sporangial production than soils collected in summer. An effect of plant age was demonstrated as soil leachates from four year-old A. pulchella stands in rehabilitated bauxite mine sites were more suppressive for sporangia than leachates from one year-old stands.
Further information on the behaviour of the pathogen in soil and in potting mix with and without A. pulchella was obtained by infecting lupin radicles with an isolate of each A2 type, 1 and 2 strains of P. cinnamomi and burying them in the soil under the three varieties of A. pulchella plants. After a week, the chlamydospores were mostly collapsed and hyphae deteriorated. Oospores were observed and in significant numbers under the potted plants of A. pulchella var. glaberrima.
Isolates of all three clonal lineages of P. cinnamomi found in Australian soil were tested for the ability to produce oospores. Two isolates of the A1 and A2 type 2 and three isolates of the common A2 type 1 were screened. The two isozyme types of the A2 clonal lineage isolated in Australia varied in ability to self and produce oospores in planta in several soils from the jarrah forest. The isozyme type 2 of the A2 clonal lineage of P. cinnamomi produced oospores under these experimental conditions. This stimulation was not effective for most of the tested isolates of the A2 type 1 and the A1 clonal lineage. The in planta oospores were viable but dormant and the oogonial-antheridial associations were amphigynous both in vitro and in vivo. For the first time it was established that, the stimulus for selfing and oospore formation in the A2 type 2 of P. cinnamomi is available in some jarrah forest soils, with and without A. pulchella and also in the potting mix used. This raises important questions for the management of the pathogen.
Several factors were identified as potential stimuli for selfing. Among them, soil nutrient levels and essentially enhanced sulphur presence were found important. Temperature also played a key role. Oospores were produced abundantly at 21 25 ºC but not over 28 ºC.
The biology of P. cinnamomi has been studied for several decades but some important aspects remain un-researched. This thesis pioneers research into the in planta selfing aspect of the pathogen in soil. It also improved the understanding of the interactions between P. cinnamomi and A. pulchella which to some extent supports use of A. pulchella as a biological control tool against P. cinnamomi. However, attention is drawn to the natural mechanisms of this complex pathogen to survive in planta by producing oospores, the most persistent form of its life cycle.
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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.
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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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Lee, Miin-Huey. « Microscopic, physiological and molecular studies of pathogenesis in Monilinia fructicola, the brown rot pathogen for stone fruits / ». For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Danial, Janathan. « Studies on the genetic diversity of the potato brown rot pathogen Ralstonia solanacearum race 3/biovar 2A ». Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2384.
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Ralstonia solanacearum is a genetically diverse and geographically widespread plant pathogen. It has a wide host range and is a significant pathogen of potato, causing brown rot. Brown rot is caused by a distinct, closely-related, intraspecific group: race 3, biovar 2A. In Europe, infection of potato crops with brown rot primarily occurs via irrigation with contaminated surface water. Brown rot has never been found in Scottish potatoes though the bacterium has been found previously in one Scottish river system, the River Tay, both in water samples and on its secondary host, bittersweet (Solanum dulcamara), growing on the river banks. A molecular strain-typing method principally used in clinical microbiology, multi-locus sequence typing (MLST), was used to study genetic variation within a collection of 106 R. solanacearum isolates, principally race 3 biovar 2A isolates from potato, S. dulcamara and contaminated water sources. Twenty-seven isolates from contaminated water and S. dulcamara from Scotland and other isolates from diverse geographic locations, from a variety of diseased plants and the environment, were resolved into 16 sequence types. A subsequent follow-up to the first experiment was carried out by looking at more variable genes within the race 3, biovar 2A genome and again similar or identical relationships were uncovered. All Scottish isolates were found to be identical and similar to most race 3 biovar 2A isolates tested. Analysis of Variable Number Tandem Repeats (VNTRs) confirmed this observation. After sequencing one of the tandem repeat regions, the results strongly suggest that contamination of the River Tay in Scotland occurred as a single or limited event, since the Scottish isolates had a unique tandem repeat pattern different from the patterns observed for the rest of the race 3 biovar 2A isolates and strains studied. This suggests that the Scottish isolates are clonal and the contamination is a single event and not a multiple contamination.
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Joy, Jennifer Ann. « Survival of Salmonella and Shigella on tomatoes in the presence of the soft rot pathogen, Erwinia carotovora ». [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012145.
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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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Hidayah, Baiq Nurul. « Sclerotinia stem rot disease on canola in Western Australia : Understanding of the pathogen and exploring biological control agents ». Thesis, Hidayah, Baiq Nurul (2017) Sclerotinia stem rot disease on canola in Western Australia : Understanding of the pathogen and exploring biological control agents. PhD thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40955/.
Texte intégralRésumé :
Sclerotinia sclerotiorum (Lib.) de Bary is fungal pathogen that attacks over 400 plant species worldwide, causing Sclerotinia stem rot (SSR), an important disease in canola (Brassica napus L.). In Australia, SSR disease is one of the major soil-borne diseases in the canola industry. Furthermore, SSR has emerged as a serious problem on canola production in Western Australia (WA) over the past few years where crop losses can be up to 40% in the worst affected crops. Current management of Sclerotinia disease mostly relies on cultural and chemical control options that often only provide partial and/or sporadic control and can be cost prohibitive. Biological control is one of the alternatives to control soil-borne fungal diseases on brassica and there is an increased interest in biological control encouraged by public awareness about issues related to the use of chemical pesticides and biological control will likely become more important in agricultural systems in the future.
The research in this thesis addresses major gaps in knowledge on S. sclerotiorum on canola in WA through examination of the biological characterization of WA isolates of S. sclerotiorum, their pathogenicity on canola, and the possibility of applying biological control in the field. The research involves plant and soil sampling to collect isolates of the pathogen and potential local Biological Control Agents (BCAs); laboratory, glasshouse and field experiments to identify biological characteristics and pathogenicity of S. sclerotiorum and to test the effectiveness of potential local BCAs.
One hundred and forty isolates of S. sclerotiorum were collected from WA canola growing areas between 2009 and 2014. Isolate growth on PDAA (Potato Dextrose Agar + Aureomycin) medium at 24 and 48-hours showed highly significant (P≤0.001) differences between isolates. The number of sclerotia produced by isolates over 14 days in-vitro varied from 0 to 50 sclerotia per colony with highly significant differences between isolates (P≤0.001). More than 25 isolates (17.9%) formed an average of 20 sclerotia while 15 isolates (10.7%) did not form sclerotia and only one isolate (0.7%) formed 50 sclerotia. The general colour of the mycelia of the WA isolates of S. sclerotiorum was white but variation was observed from white to grey.
Pathogenicity on 10 day-old canola seedlings varied among isolates, both after 48 hours incubation in a misting chamber and after another 48 hours in a growth room. Pathogenicity of fungal pathogens is one of the indi-cators used to determine variability among isolates. S. sclerotiorum has a wide host range and many studies have shown that it is differentiated in pathogenicity. Results of mycelial agar plug inoculations on 10-day old seed-lings indicated that there was variation in pathogenicity among the isolates of S. sclerotiorum from WA and these were categorized as having low, medium or high level of pathogenicity. There were highly significant differences (P≤0.001) in seedling mortality among isolates at 48 hours after incubation in a misting chamber. In addition, there were highly significant differences (P≤0.001) in seedling mortality at 48 hours after being placed into a growth room. At 48 hours after incubation in the misting chamber, only 5 isolates of S. sclerotiorum caused 100% seedling mortality, while 26 isolates caused 0% mortality. The highest frequency of seedling mortality was 10% caused by 44 isolates. Pathogenicity was further investigated after seedlings were returned to the growth room for another 48 hours. Here 33 isolates caused 100% seedling mortality.
Research on variability of fungal pathogens has been conducted for many species, including S. sclerotiorum, all over the world. One of the conventional methods used is Mycelial Compatibility Groups (MCGs). Mycelial compatibility is an indirect measure of genetic diversity in fungal populations, and can show the degree of relatedness between or within MCGs. A total of 31 WA isolates of S. sclerotiorum, representative of a range of pathogenicity levels, were chosen for MCG tests. The 31 isolates were classified into 9 my-celial compatibility groups.
Fifteen potential fungal biological control agents (F-BCAs) and three potential bacterial biological control agents (B-BCAs) were isolated from canola growing regions in WA. The potential F-BCAs were grown in Petri dishes on PDAA. Mycelial colour showed wide variation, from dark green to white. Radial mycelial growth at 24 and 48 hours differed (P≤0.001) be-tween isolates. At 24 and 48 hours after incubation, isolate F-BCA9 had the highest radial mycelial growth rate with a diameter of 3.2 and 8.5 cm, re-spectively. All potential F-BCA isolates showed some capacity to inhibit the radial mycelial growth of S. sclerotiorum as well as reduce the number of sclerotia formed by the pathogen in dual culture tests in Petri dishes. There were significant differences (P≤0.001) in the magnitude of inhibition of radial mycelial growth (40 – 60%) and sclerotial formation (65 - 100% inhibition).
Isolates F-BCA12 and F-BCA15 totally inhibited the formation of sclerotia by the pathogen. Colonization of sclerotia in soil indicated that sclerotia were colonized by the spores of each F-BCA and therefore all sclerotia in the presence of F-BCAs could not form any new sclerotia in Petri dishes.
The colony colour of the 3 potential B-BCAs ranged from yellow to whitish yellow. Isolate B-BCA3 had the fastest colony growth rate. There was no significant difference among the potential B-BCAs in their ability to inhibit radial mycelial growth (57 - 59%) of the pathogen (P=0.934>0.05) or for-mation of sclerotia (89 - 95%) (P=0.079>0.05).
Using Sanger Sequencing molecular tools (ITS regions), the F-BCAs were identified as Trichoderma atroviride (four isolates), T. gamsii (three iso-lates), T. koningiopsis (two isolates), T. longibrachiatum (two isolates), T. paraviridescens (two isolates), T. pseudokoningii (one isolate), and T. viri-descens (one isolate). Identification of B-BCAs through 16S rRNA sequencing revealed that B-BCA1 and B-BCA2 were Serratia proteamaculans while BCA3 was Ochrobactrum anthropi.
Three field experiments were undertaken with canola to evaluate effi-cacy of BCAs. Experiment 1, conducted in 2014 was established as a Randomized Complete Block Design. However, no SSR disease symptoms were observed and there were no significant (P=0.2744>0.05) yield differ-ences between treatments at harvest.
In field experiment 2 undertaken in 2015, a Randomized Complete Factorial Design (RCFD) was used consisting of 16 treatments with pseudo- replication inside the treatment due to limited space. Because of pseudo-replication, Restricted Maximum Likelihood (REML) analysis was used to evaluate treatments effects. There were differences (P<0.001) among the BCAs in controlling SSR disease and there was an interaction (P<0.001) be-tween BCAs and the flowering stage of pathogen application. Protein and oil contents of canola seed harvested were analysed and there was a significant effect on the protein content between treatments due to the application of BCAs during the green bud phase (P=0.022<0.05) and also on the applica-tion of the pathogen during different flowering times (P=0.019<0.05). In ad-dition, there were significant differences in oil content between the treat-ments from the application of BCAs (P=0.030<0.05), but there was no signif-icant difference in oil content between treatments on the application of path-ogen at different flowering stages (P=0.051>0.05). The protein content of the untreated control treatement was significantly higher compared to the BCA treatments, but for oil content it was significantly lower compared to the other treatments. The best BCA for grain oil content in experiment 2 was B-BCA1.
In the second experiment undertaken in 2015, the RCFD consisted of fifteen treatments with pseudo-replication inside the treatments. Clear symp-toms of SSR disease were apparent when the canola crop was sprayed with S. sclerotiorum. The REML analysis revealed significant effects among the BCAs (P<0.001), and time of application of the pathogen (P<0.001), but time of fungicide application was not significant (P=0.901>0.001). There were also differences between time of BCA application (P<0.001), but no significant difference (P=0.382>0.001) between interation of BCAs and time of spraying the pathogen. Moreover, protein and oil contents based on dif-ferent flowering stage of BCA application showed that seed protein content, when the application of BCAs was made at 50% flowering stage, was signifi-cantly higher compared to application of BCAs at 30% and 10% flowering stages. The seed oil content was lowest when the BCAs were applied at 50% flowering. There were no significant differences in seed protein content be-tween the treatments (P=0.854>0.05), spraying time (P=0.850>0.05), and flowering stage (P=0.828>0.05). Furthermore, there were no significant dif-ferences in oil content between treatments (P=0.855>0.05), timing of BCA application (P=0.624>0.05) and flowering time (P=0.694>0.05).
The flowering trial was undertaken to observe after how many days newly formed flowers drop their petals. Data for petal dynamics at first flow-ering, at first petal drop, and at end of flowering, in the field and glasshouse showed that first flower opening occurred in the glasshouse at 74 days after sowing (DAS), while in field plots the first flower opening occurred 2 days later. First petal drop in the glasshouse was at 78 DAS while in the field plots first petal drop was at 79 DAS. Furthermore, flowering finished in the glasshouse on 109 DAS, but in the field plots flowering finished 107 DAS. However, there was no significant difference in timing of petal dynamics be-tween glasshouse and field studies where the mean flowering period in the glasshouse was 35 days and in the field was 32 days.
The results from these preliminary experiments indicate that local WA BCAs have some ability to control SSR disease in the field, however multiple trials in grower’s fields are needed in order to observe the stability of the BCAs and maintenance of their virulence against the pathogen. Further investigation is needed to determine other mechanisms of bio-control such as antibiosis and myco-parasitism as well as improving formulations and delivery systems. Untimately, biological control products should be as effec-tive as pesticides, economical, easy to use, non-toxic, environmentally safe and acceptable to regulatory agencies, growers and consumers.
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Porto, Maria Alice Formiga. « Associação de Fusarium solani, Macrophomina phaseolina e Rhizoctonia solani causando podridão radicular em meloeiro sob efeito de adubos verdes ». Universidade Federal Rural do Semi-Árido, 2015. http://bdtd.ufersa.edu.br:80/tede/handle/tede/105.
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Previous issue date: 2015-02-27Conselho Nacional de Desenvolvimento Científico e Tecnológico
The occurrence of root diseases is one of the main reasons of yield loss in melon crop, especially the pathogens that causes root and collar rot, as the fungi Fusarium solani (Mart.) Sacc., Macrophomina phaseolina (Tassi) Gold. and Rhizoctonia solani Kuhn, being observed in muskmelon either alone or associated. The use of crop residues and plant materil, besides the improvement in the physical properties of the soil, also favors microbial activity of the species presents in this environment and affects negatively onpathogens population. Therefore, the objective of this work was to evaluate the associations of F. solani, M. phaseolina and R. solani in the incidence and severity of root rot and fresh and dry weight of muskmelon and verify the effect of green manure in root rot caused by these pathogens alone or associated. The experiment was conducted in two stages, in a greenhouse. The first stage evaluated the association of F. solani, M. phaseolina and R. solani causing root rot in melon, using a randomized block design with 8 treatments (F. solani; M. phaseolina, R. solani, F. solani + M. phaseolina, F. solani + R. solani; M. phaseolina + R. solani, F. solani + M. phaseolina + R. solani; non-infested soil) and 8 repetitions with experimental unit of one pot (3.5 L) with 2 plants. The characteristics evaluated were the incidence of root rot in melon plants at the end of the cycle; disease severity based on a scale notes, and the fresh and dry weight of muskmelon. At the second stage, evaluated the effects of green manure in the association of these pathogens in muskmelon, which was conducted one experiment with Jack beans (Canavalia ensiformis L. DC) and another with Pearl millet (Pennisetum glaucum (L.) R. BR.). The experiments were performed simultaneously in a randomized block design with 8 x 4 factorial {8 types of fungi / association (M. phaseolina, R. solani, F. solani, M. phaseolina + R. solani; M. phaseolina + F. solani, R. solani + F. solani; M. phaseolina + R. solani + F. solani; non-infested soil), 4 forms of management [incorporated, in coverage, polyethylene film (mulching) and without managment]} and 4 repetitions. The characteristics evaluated were the incidence of root rot of melon plants at the end of the cycle, and the fresh and dry weight of muskmelon. The results of disease incidence were submitted to the non-parametric test of Kruskal-Wallis and the fresh and dry weight of muskmelon were analyzed by the Scott-Knott test, both with significance level of 5% of probability (α = 0.05%). At stage 1, the treatment with the three pathogens F. solani, M. phaseolina and R. solani associated resulted in lower incidence of plants with symptoms and was not statistically different from the control. The pathogen R. solani was the least prevalent in the associations. The lowest accumulation of fresh and dry matter happened when the soil was infested with Fusarium solani alone. At stage 2, Jack beans in coverage provided lower incidence of root rot in muskmelon with Fusarium solani alone and in triple association (F. solani +M. phaseolina and R. solani). The use of Pearl millet had no effect on root rot incidence in most treatments. In both experiments (Jack beans andPearl millet), Macrophomina phaseolina was the fungus that prevailed in almost all associations. Jack beans and millet did not increase the fresh and dry weight of muskmelon in most treatments
A ocorrência de doenças radiculares representa uma das principais causas de perda de rendimento na cultura do melão, com destaque para os patógenos causadores das podridões de raízes e colos, como os fungos Fusarium solani (Mart.) Sacc., Macrophomina phaseolina (Tassi) Gold. e Rhizoctonia solani Kuhn, sendo observados no meloeiro tanto de forma isolada quanto associada. A utilização de restos de cultura e material vegetal, além de melhorar as propriedades físicas do solo, favorece a atividade microbiana das espécies presentes neste ambiente e interfere negativamente sobre a população de patógenos. Portanto, objetiva-se com este trabalho avaliar as associações dos patógenos F. solani, M. phaseolina e R. solani na incidência e severidade de podridão radicular e na massa da matéria fresca e seca do meloeiro e verificar o efeito de materiais vegetais na podridão radicular causada por estes patógenos isolados ou associados. O experimento foi conduzido em duas etapas, em casa de vegetação, sendo que na primeira avaliou-se a associação de F. solani, M. phaseolina e R. solani causando podridão radicular em meloeiro, quando foi utilizado o delineamento em blocos casualizados com 8 tratamentos (F. solani; M. phaseolina; R. solani; F. solani + M. phaseolina; F. solani + R. solani; M. phaseolina + R. solani; F. solani + M. phaseolina + R. solani; solo não infestado) e 8 repetições, com unidade experimental de 1 vaso (3,5 L) com duas plantas. As características avaliadas foram: incidência de podridão radicular nas plantas de melão no fim do ciclo, severidade da doença com base em escala de notas, além da matéria fresca e seca das plantas de melão. Na segunda etapa, foi avaliado o efeito de materiais vegetais na associação desses patógenos, também em meloeiro, onde foi realizado um experimento com Feijão-de-porco (Canavalia ensiformis L. DC) e outro com Milheto (Pennisetum glaucum (L.) R. BR.). Os experimentos foram conduzidos simultaneamente, em delineamento experimental de blocos casualizados, com esquema fatorial 8 x 4, sendo 8 tipos de fungos/associação (M. phaseolina; R. solani; F. solani; M. phaseolina + R. solani; M. phaseolina + F. solani; R. solani + F. solani; M. phaseolina + R. solani + F. solani; solo sem inoculação), 4 formas de manejo (incorporado, cobertura, mulching e sem manejo) e 4 repetições. As características avaliadas foram: incidência de podridão radicular nas plantas de melão no fim do ciclo, a massa da matéria fresca e seca das plantas de melão. Os resultados de incidência de doença obtidos foram submetidos ao teste não paramétrico de Kruskal-Wallis e a massa damatéria fresca e seca foram analisados pelo teste de Scott-Knott, ambos com nível de significância a 5% de probabilidade (α = 0,05%). Na etapa 1, o tratamento no qual foram associados três patógenos F. solani, M. phaseolina e R. solani propiciou menor porcentagem de plantas com sintomas da doença e não diferiu estatisticamente da testemunha. O fitopatógeno R. solani foi o que menos prevaleceu nas associações. Quando o solo foi infestado com Fusarium solani, isoladamente, o melão obteve baixo acúmulo de matéria fresca e seca. Na etapa II, o feijão-de-porco em cobertura proporcionoiu menor incidência de podridão radicular do meloeiro quando o Fusarium solani estava sozinho e em associação tripla (F. solani +M. phaseolina e R. solani). A utilização do milheto não apresentou efeito na incidência de podridão radicular na maioria dos tratamentos. Tanto na utilização do feijão-de-porco quanto do milheto, M. phaseolina foi o fungo que prevaleceu na maioria das associações nas quais estava presente. O feijão-de-porco e o milheto não proporcionaram aumento na massa da matéria fresca e seca do meloeiro na maioria dos tratamentos