Littérature scientifique sur le sujet « Soilborn pathogen »
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Articles de revues sur le sujet "Soilborn pathogen"
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You, Ming Pei, Jay Ram Lamichhane, Jean-Noël Aubertot et Martin J. Barbetti. « Understanding Why Effective Fungicides Against Individual Soilborne Pathogens Are Ineffective with Soilborne Pathogen Complexes ». Plant Disease 104, no 3 (mars 2020) : 904–20. http://dx.doi.org/10.1094/pdis-06-19-1252-re.
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Annual forage legumes across southern Australia continue to be devastated by soilborne diseases. Nine fungicide seed treatments (thiram, metalaxyl, iprodione, phosphonic acid, propamocarb, fluquinconazole, difenoconazole + metalaxyl, ipconazole + metalaxyl, sedaxane + difenoconazole + metalaxyl) and four foliar fungicide treatments (phosphonic acid, metalaxyl, propamocarb, iprodione) were tested on four subterranean clover cultivars against individual oomycete soilborne pathogens Pythium irregulare, Aphanomyces trifolii, and Phytophthora clandestina and the fungal pathogen Rhizoctonia solani. Best treatments were then further tested across southern Australia in 2 years of field experiments. Under controlled conditions, seed treatment with thiram was best against damping-off caused by P. irregulare across the four cultivars (Woogenellup, Riverina, Seaton Park, Meteora), while metalaxyl was the most effective for maximizing root and shoot weights. Against A. trifolii, metalaxyl, iprodione, difenoconazole + metalaxyl, ipconazole + metalaxyl, and sedaxane + difenoconazole + metalaxyl, all reduced damping-off; sedaxane + difenoconazole + metalaxyl, fluquinconazole, and ipconazole + metalaxyl all reduced lateral root disease across two or more cultivars; while iprodione, thiram, and sedaxane + difenoconazole + metalaxyl increased shoot dry weight. Against P. clandestina, metalaxyl was the most effective in reducing tap and lateral root rot followed by ipconazole + metalaxyl or phosphonic acid for tap and lateral rot, respectively. Against R. solani, there were no effects of fungicides. For P. irregulare and P. clandestina, there were strong seed fungicide × cultivar interactions (P < 0.001). Under controlled conditions for foliar fungicide spray treatments, phosphonic acid was best at preventing productivity losses from A. trifolii, but was ineffective against P. clandestina, P. irregulare, or R. solani. Overall, controlled environment studies highlighted strong potential for utilizing seed treatments against individual pathogens to ensure seedling emergence and early survival, with seed and foliar sprays enhancing productivity by reducing seedling damping-off and root disease from individual pathogens. However, in field experiments over 2 years across southern Australia against naturally occurring soilborne pathogen complexes involving these same pathogens, only rarely did fungicide seed treatments or foliar sprays tested show any benefit. It is evident that currently available fungicide seed and/or foliar spray treatment options do not offer effective field mitigation of damping-off and root disease on annual forage legumes that underpin livestock production across southern Australia. The main reason for this failure relates to the unpredictable and ever-changing soilborne pathogen complexes involved, highlighting a need to now refocus away from fungicide options, particularly toward developing and deploying new host tolerances, but also in deploying appropriate cultural control options.
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Dawadi, Sujan, Fulya Baysal-Gurel, Karla M. Addesso, Prabha Liyanapathiranage et Terri Simmons. « Fire Ant Venom Alkaloids : Possible Control Measure for Soilborne and Foliar Plant Pathogens ». Pathogens 10, no 6 (27 mai 2021) : 659. http://dx.doi.org/10.3390/pathogens10060659.
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The purpose of this study was to evaluate fire ant venom alkaloids and an alarm pheromone analog against several plant pathogens, including Botrytis cinerea, Fusarium oxysporum, Phytophthora nicotianae, P. cryptogea, Pseudomonas syringae, Phytopythium citrinum, Rhizoctonia solani, Sclerotonia rolfsii, Xanthomonas axonopodis, and X. campestris. All pathogens were tested against red imported fire ant venom alkaloid extract and alarm pheromone compound for growth inhibition in in vitro assay. The venom alkaloid extract inhibited fungal and oomycete pathogens. Neither of the treatments were effective against bacterial pathogens. Three soilborne pathogens, P. nicotianae, R. solani, F. oxysporum, and one foliar pathogen, B. cinerea were selected for further in-vivo assays on impatiens (Impatiens walleriana ‘Super Elfin XP violet’). Total plant and root weight were higher in venom alkaloid treated plants compared to an inoculated control. The venom alkaloid treatment reduced damping-off, root rot severity, and pathogen recovery in soilborne pathogen inoculated plants. Similarly, venom alkaloid reduced Botrytis blight. However, higher venom rates caused foliar phytotoxicity on plants. Therefore, additional work is needed to evaluate rates of venom alkaloids or formulations to eliminate negative impacts on plants. Overall, these results suggest that red imported fire ant venom alkaloids may provide a basis for new products to control soilborne and foliar plant pathogens.
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Dawadi, Sujan, Fulya Baysal-Gurel, Karla M. Addesso, Jason B. Oliver et Terri Simmons. « Impact of Cover Crop Usage on Soilborne Diseases in Field Nursery Production ». Agronomy 9, no 11 (14 novembre 2019) : 753. http://dx.doi.org/10.3390/agronomy9110753.
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Soilborne pathogens are a significant economic problem for nursery production in the Southeastern United States. The goal of this study was to determine the impact of cover crops on soilborne disease suppressiveness in such systems. Soils from red maple (Acer rubrum L.) plantation fields grown with and without cover crops were sampled, either while the cover crops were growing (pre-disked) or post-season, following cover crop incorporation into the soil (post-disked). Greenhouse bioassays were conducted using red maple seeds on inoculated (with Rhizoctonia solani (J.G. Kühn) or Phytophthora nicotianae (Breda de Haan)) and non-inoculated field soils. The damping-off, root rot disease severity, percent recovery of Rhizoctonia and Phytophthora, and pseudomonad population were examined during the two years of the experiment. Results showed that cover crop incorporation was beneficial for inducing disease supressiveness characteristics of soil. Cover crop incorporation into the soil significantly or numerically reduced disease severity and pathogen recovery in infested soil compared to the bare soil treatment. Cover crop incorporation was found to be partially associated with the reduction of seedling damping-off. The pseudomonad microbial population was greater when cover crop was present, and is thought to be antagonist to soilborne pathogens. Therefore, cover crops can be integrated in field nursery production systems to suppress soilborne pathogens.
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Hilbig, Bridget E., et Edith B. Allen. « Fungal pathogens and arbuscular mycorrhizal fungi of abandoned agricultural fields : potential limits to restoration ». Invasive Plant Science and Management 12, no 03 (9 août 2019) : 186–93. http://dx.doi.org/10.1017/inp.2019.19.
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AbstractLittle is known about impacts of soilborne pathogen legacies on reestablishment of native plant species in abandoned agricultural fields. We tested whether pathogens found in abandoned citrus orchards affect growth of native and invasive plant species in a controlled greenhouse experiment. In previous research, we identified several species of ascomycete (Fusarium spp.) and oomycete (Pythium spp.) pathogens from field roots and soils. The invasive annual grass, ripgut brome [Bromus diandrus (Roth.)], and native forbs, common fiddleneck [Amsinckia intermedia Fisch. & C.A. Mey.], coastal tidytips [Layia platyglossa (Fisch. & C.A. Mey.) A. Gray], and California goldfields [Lasthenia californica (DC. ex Lindl.)], were grown together in four different field soil treatments. Using pesticides on soils collected from abandoned citrus fields, we created four soil treatments that excluded different groups of potential pathogens: (1) untreated control (2) metalaxyl (oomyceticide) (3) fludioxonil (fungicide), and (4) steam-sterilized. Fludioxonil increased aboveground biomass of L. platyglossa (P = 0.005) and L. californica (P= 0.02) compared with sterile and metalaxyl-treated soils. Lasthenia californica had decreased arbuscular mycorrhizal colonization with metalaxyl, suggesting metalaxyl has non-target effects on mycorrhizae. Fludioxonil decreased potential pathogens in L. californica roots while having no effect on mycorrhizal colonization. Bromus diandrus had higher biomass in sterile and fludioxonil-treated soils than untreated soils (P = 0.0001), suggesting a release from soilborne pathogens. The release from soilborne pathogens with the use of fludioxonil in both native forbs and B. diandrus, combined with overall higher biomass across treatments in B. diandrus, suggests that pathogen impacts in a field setting are insufficient to reduce success of this invasive grass, and use of a fungicide would not benefit native species in mixed stands with B. diandrus.
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Li, Mei, Thomas Pommier, Yue Yin, Jianing Wang, Shaohua Gu, Alexandre Jousset, Joost Keuskamp et al. « Indirect reduction of Ralstonia solanacearum via pathogen helper inhibition ». ISME Journal 16, no 3 (20 octobre 2021) : 868–75. http://dx.doi.org/10.1038/s41396-021-01126-2.
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AbstractThe rhizosphere microbiome forms a first line of defense against soilborne pathogens. To date, most microbiome enhancement strategies have relied on bioaugmentation with antagonistic microorganisms that directly inhibit pathogens. Previous studies have shown that some root-associated bacteria are able to facilitate pathogen growth. We therefore hypothesized that inhibiting such pathogen helpers may help reduce pathogen densities. We examined tripartite interactions between a model pathogen, Ralstonia solanacearum, two model helper strains and a collection of 46 bacterial isolates recovered from the tomato rhizosphere. This system allowed us to examine the importance of direct (effects of rhizobacteria on pathogen growth) and indirect (effects of rhizobacteria on helper growth) pathways affecting pathogen growth. We found that the interaction between rhizosphere isolates and the helper strains was the major determinant of pathogen suppression both in vitro and in vivo. We therefore propose that controlling microbiome composition to prevent the growth of pathogen helpers may become part of sustainable strategies for pathogen control.
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Okubara, Patricia A., Amy B. Peetz et Richard M. Sharpe. « Cereal Root Interactions with Soilborne Pathogens—From Trait to Gene and Back ». Agronomy 9, no 4 (13 avril 2019) : 188. http://dx.doi.org/10.3390/agronomy9040188.
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Realizing the yield potential of crop plants in the presence of shifting pathogen populations, soil quality, rainfall, and other agro-environmental variables remains a challenge for growers and breeders worldwide. In this review, we discuss current approaches for combatting the soilborne phytopathogenic nematodes, Pratylenchus and Heterodera of wheat and barley, and Meloidogyne graminicola Golden and Birchfield, 1965 of rice. The necrotrophic fungal pathogens, Rhizoctonia solani Kühn 1858 AG-8 and Fusarium spp. of wheat and barley, also are discussed. These pathogens constitute major causes of yield loss in small-grain cereals of the Pacific Northwest, USA and throughout the world. Current topics include new sources of genetic resistance, molecular leads from whole genome sequencing and genome-wide patterns of hosts, nematode or fungal gene expression during root-pathogen interactions, host-induced gene silencing, and building a molecular toolbox of genes and regulatory sequences for deployment of resistance genes. In conclusion, improvement of wheat, barley, and rice will require multiple approaches.
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King, Stephen R., Angela R. Davis, Wenge Liu et Amnon Levi. « Grafting for Disease Resistance ». HortScience 43, no 6 (octobre 2008) : 1673–76. http://dx.doi.org/10.21273/hortsci.43.6.1673.
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The primary purpose of grafting vegetables worldwide has been to provide resistance to soilborne diseases. The potential loss of methyl bromide as a soil fumigant combined with pathogen resistance to commonly used pesticides will make resistance to soilborne pathogens even more important in the future. The major disease problems addressed by grafting include fusarium wilt, bacterial wilt, verticillium wilt, monosporascus root rot, and nematodes. Grafting has also been shown in some instances to increase tolerance to foliar fungal diseases, viruses, and insects. If the area devoted to grafting increases in the future, there will likely be a shift in the soil microbial environment that could lead to the development of new diseases or changes in the pathogen population of current diseases. This shift in pathogen populations could lead to the development of new diseases or the re-emergence of previously controlled diseases. Although grafting has been demonstrated to control many common diseases, the ultimate success will likely depend on how well we monitor for changes in pathogen populations and other unexpected consequences.
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Biernacki, M., et B. D. Bruton. « Quantitative Response of Cucumis melo Inoculated with Root Rot Pathogens ». Plant Disease 85, no 1 (janvier 2001) : 65–70. http://dx.doi.org/10.1094/pdis.2001.85.1.65.
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This experiment quantified the effects of three root rot pathogens on muskmelon (Cucumis melo L., var. cantalupensis) growth traits using computerized image analysis. Plants were grown from seed in sand infested with the soilborne pathogen Monosporascus cannonballus, Acremonium cucurbitacearum, or Rhizopycnis vagum. After 28 days in the growth chamber, images of plants were analyzed to quantify their response. Compared to noninoculated muskmelons, inoculated plants had significantly increased mean root diameter (45%), decreased root length (26%, primarily in roots of <0.5 mm diameter), decreased number of root tips (27%), decreased rhizosphere volume (40%), and decreased cumulative and mean surface area of leaves (24%). Effects of M. cannonballus on muskmelon growth were significantly different compared to A. cucurbitacearum and R. vagum. Isolate effects manifested a greater magnitude of difference on muskmelon traits than those observed at the species level. Multivariate analyses of plant responses were more powerful than univariate analyses to differentiate among effects of pathogen species and pathogen isolates. Discriminant analysis were useful to identify groups of plant traits modified by each fungal species or isolate at low disease levels. Digital image analyses proved to be a useful technique in quantitative assessment of plant damage caused by soilborne root rot pathogens.
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Molinero-Ruiz, Leire. « Recent advances on the characterization and control of sunflower soilborne pathogens under climate change conditions ». OCL 26 (31 août 2018) : 2. http://dx.doi.org/10.1051/ocl/2018046.
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The control of soilborne crop pathogens is conditioned by the limited management options due to difficult access to active infection courts and to restrictions in the use of synthetic pesticides in Europe. For most soilborne sunflower pathogens, an effective management relies on genetic resistance which is, however, hindered by new pathogen populations (new races). Special emphasis is thus put on updated monitoring and characterization of pathogens and on the enlargement of the set of tools for disease management. Concerning characterization, advances on the population structure of Verticillium dahliae affecting sunflower by means of genetic, molecular and pathogenic approaches are presented. Also in relation to increases of sunflower wilt diseases recently observed, the fungus Cadophora malorum has been identified in Russia and reported as a new pathogen of this crop. Third, new races of Plasmopara halstedii (sunflower downy mildew), have been identified in Spain and Portugal. Most of them have a high virulence, since they overcome several genes for resistance. With regard to alternatives for disease control, entomopathogenic fungi (EF) constitute a novel tool. Used for years in Integrated Pest Management strategies due to their efficacy in controlling insect pests affecting crops, new ecological roles of these fungi have recently been reported. The EF species Beauveria bassiana and Metarhizium brunneum have been assessed by their in vitro effect against V. dahliae and C. malorum by our research group. Our results suggest that antibiosis and/or competition for ecological niche are operating in some EF-pathogen interactions. In summary, pathogen characterization is essential for genetic resistance for worldwide environments of sunflower production. Moreover, the security of sunflower yield and profitability is dependent not only on effective genetic resistance, but also on additional new control options that can be included in successful strategies of sunflower disease management.
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Handelsman, Jo, et Eric V. Stabb. « Biocontrol of Soilborne Plant Pathogens ». Plant Cell 8, no 10 (octobre 1996) : 1855. http://dx.doi.org/10.2307/3870235.
Texte intégralThèses sur le sujet "Soilborn pathogen"
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Al-Gharabally, Dunia Hashim. « Biological control of soilborne plant pathogens by greenwaste compost ». Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393320.
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Fichtner, Elizabeth Jeanne. « Abiotic pathogen suppression physiology and biology of aluminum toxicity to soilborne fungi / ». NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-10222003-020101/.
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An interdisciplinary approach was utilized to study the toxicity of aluminum (Al) to soilborne plant pathogens with the goal of developing a pathogen-suppressive potting medium containing non-phytotoxic, Al-organic matter complexes. Toxicological studies addressed the toxicity of monomeric Al species to Thielaviopsis basicola and Phytophthora parasitica and documented the sensitivity of these organisms to the metal. Until recently, research on Al-toxicity to fungi has only focused on the trivalent Al cation (Al3+) which is also considered the most phytotoxic Al ion. The toxicity of Al-hydrolysis species to fungi were tested by modeling in vitro test solution equilibria using GEOCHEM-PC and correlating the predicted values of Al-species activities with reduction in spore production of the two pathogens. Chlamydospore production of T. basicola was negatively correlated with Al3+ activity, whereas inhibition of sporangia production of P. parasitica was related to the activity of multiple monomeric Al species. Toxicity of Al to T. basicola was observed in solutions containing ≥ 20 micromolar Al. Sensitivity of P. parasitica to Al was observed at < 1.0 micromolar Al, suggesting that P. parasitica is more sensitive to Al than T. basicola. Using fluorescence microscopy, the localized accumulation of Al in pathogen tissues was detected using lumogallion, an Al-specific, fluorescent stain. Accumulation of Al was observed under various chemical conditions, ranging from salt solutions to more complex systems containing Al-peat complexes. An ecological approach was applied to study the dynamic interactions of soil chemical and physical properties with soil microflora for the suppression of P. parasitica in a medium amended with Al2(SO4)3 and composted swine waste (CSW). Abiotic and biological mechanisms of pathogen suppression were incorporated into the CSW-amended medium. Al-mediated suppression resulted in reduction of sporangia production in medium exhibiting K-exchangeable Al levels > 2 micromolar Al. Biological suppression also resulted in reduction of sporangia production and this suppression was maintained after Al levels dropped below the threshold necessary for abiotic suppression. The incorporation of abiotic and biological control mechanisms into a potting media may facilitate suppression of a wide range of soilborne pathogens and enhance applicability of disease-suppressive media in a disease management strategy.
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Tilston, Emma Louise. « Phytoprotective properties of composted recycled organic matter against soilborne plant pathogens ». Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323987.
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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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Kapsalis, Apostolos V. « Biological control of soilborne pathogens causing damping-off symptoms in cotton plants ». Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430919.
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Fang, Lynn. « Biological Indicators Of Compost-Mediated Disease Suppression Against The Soilborne Plant Pathogen Rhizoctonia Solani ». ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/456.
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Compost can suppress soilborne plant pathogens that cause significant damage on globally important food crops. However, reports of plant pathogen suppression are inconsistent likely because there are no established standards for feedstock material, application rate, and maturity age upon application. Excellent results can be achieved in greenhouse trials, but field applications are much less reliable. Disease suppression occurs through the activity of biocontrol organisms (direct antagonism), and general microbial competition. Biocontrol species are hypothesized to colonize the pile during the curing phase, but single species may not be as important as microbial consortia. Substrate composition during maturation may give rise to a suppressive microbial community. More research is needed to understand the relationships between feedstock, maturity, and production process on compost microbial ecology. The thesis had two main objectives: 1) identify biological indicators in compost that could (a) characterize maturity, process, and feedstock, and (b) predict disease suppression against R. solani, and 2) identify bacterial and fungal community composition and/or structure that is associated with suppression of soilborne disease.
Rhizoctonia solani is a facultative saprophytic fungus and soilborne plant pathogen that attacks many globally important food crops and turfgrass. Prior research suggests that managing carbon quality and compost maturity will alter relative competition between biological control microbes and the R. solani pathogen. The pathogen is responsible for economic losses to organic vegetable production in Vermont and there are no available methods to manage the disease that meet organic certification. R. solani on radish was chosen as a model system given its global importance, competitiveness affected by carbon quality, and lack of disease management options for organic production.
Compost samples were most abundant in the bacterial phyla Proteobacteria and Bacteroidetes, and known biocontrol species were not detected in abundance. Compost samples did not differ significantly in fungal community composition, suggesting a dominance effect from the native soil fungal community.
Overall, anaerobic digestate and vermicompost were most suppressive against R. solani. Thermophilic composts were not very suppressive overall, though a specially made hardwood bark compost was comparable to the suppressiveness of vermicompost application. Ecoenzyme analysis was able to integrate information on environmental substrate composition, microbial nutrient acquisition, and microbial community metabolism, offering the best view of current ecological conditions in compost. Ecoenzyme analysis showed that the most suppressive composts, anaerobic digestate and vermicompost, were most nutrient limited. All compost samples were severely nitrogen (N) limited, and anaerobic digestate and vermicompost were severely limited in both N and phosphorus (P). The additional P limitation may support non-pathogenic species to outcompete R. solani. The key to disease suppression may lie in matching up the ecology of the plant pathogen with the ecology of biocontrol, which may be engineered in compost.
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Filgueira, Pimentel Mirian. « EVALUATION AND FUNCTIONAL CHARACTERIZATION OF BIOCONTROL AGENTS TARGETING SELECT SOILBORNE PATHOGENS OF SOYBEAN ». OpenSIUC, 2021. https://opensiuc.lib.siu.edu/dissertations/1886.
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Soybean crops are vulnerable to a wide range of pathogens that reduce yield and cause extensive losses worldwide. In the United States, the soilborne pathogens Pythium spp., causing soybean damping-off, and Fusarium virguliforme, causing sudden death syndrome (SDS) of soybean, have been among the top diseases that most reduced soybean yields. This study demonstrated that biological control using native fungal antagonists could be a powerful tool to integrate with current management strategies for more efficient control of Pythium damping-off and SDS in soybean. Trichoderma spp. and Clonostachys rosea demonstrated the ability to mycoparasitize and antagonize the pathogens using different mechanisms and exhibited a protective effect on soybean in field conditions. The development of an efficient biological control program for disease management relies on a deep understanding of the BCA-pathogen interaction’s biology. This research also uncovered the molecular mechanisms involved in the F. virguliforme-T. afroharzianum interaction by using a dual RNAseq approach. Significant changes in both fungal organisms’ transcriptomes were discovered at different stages in their interaction. The results provided here can contribute to the future implementation of effective biological control programs for soybean. The benefits may also extend to other crops.
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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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au, nolad@iprimus com, et Nola Kim D'Souza. « Pathosystem development, characterisation and genetic dissection of the soil pathogen Phytophthora medicaginis and the model legume Medicago truncatula : a view to application of disease resistance in susceptible legume species ». Murdoch University, 2009. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090423.105414.
Texte intégralRésumé :
Phytophthora medicaginis is an important soil-borne oomycete pathogen of lucerne (Medicago sativa) and chickpea (Cicer arietinum) within Australia and overseas. To understand the host/pathogen interaction, a pathosystem was developed using the model legume Medicago truncatula. Using the resources developed for genetics and molecular characterisation in this model plant, the aim of this research was to understand the interaction between M. truncatula and P. medicaginis, with a view to improving resistance to this important pathogen in related legumes.
To observe and characterise the interaction between M. truncatula and P. medicaginis, a pathosystem was developed by first screening a germplasm collection of 99 M. truncatula accessions. This revealed a continuous distribution in disease phenotypes with variable extremes in natural resistance to P. medicaginis culture UQ5750, isolated originally from M. sativa. P. medicaginis zoospore inoculation of 1-2 week-old seedlings in glasshouse experiments proved to be a robust and repeatable method to consistently confirm the responses observed for six key M. truncatula accessions; SA8618 and SA8623 exhibit high natural resistance to this pathogen, accession A17 is moderately resistant, A20 is moderately susceptible and accessions Borung and SA30199 are susceptible.
To characterise the genetic basis of resistance to P. medicaginis, two reciprocal F2 populations from cross pollinations between A17 and Borung and SA8618 and SA30199 were produced and then phenotyped for disease symptoms. Genetic segregation patterns indicated the involvement of a gene with a major effect in both reciprocal populations. In particular, a 3:1 segregation ratio for resistance in the F2 populations from cross pollinations between A17 and Borung indicated the possibility of a single dominant gene for moderate resistance. Further phenotyping of F3 families is required to verify this.
A M. truncatula linkage map was constructed using 50 F2 individuals of the A17 X Borung population and 49 F2 individuals from the Borung X A17 population. The map, covering 519.3 cM, is comprised of 84 SSR markers with an average distance between markers of 8.7 cM. These are evenly spaced over 7 linkage groups, including a super linkage group conferred by a translocation event between LG4 and LG8 of accession A17.
Quantitative trait locus (QTL) analysis confirmed there was a QTL with a major effect in the A17/Borung reciprocal populations. A significant QTL was determined by quantifying two symptoms of P. medicaginis infection - proportion of dead/chlorotic leaves and root fresh weight. The trait loci for both symptoms were located on the same linkage group within the same region, supporting the putative position of the QTL and the authenticity of its involvement in resistance to P. medicaginis. This QTL was located on LG6 and accounted for 69.5% of the observed variation in proportion of dead/chlorotic leaves or 38.1% of the variation in root fresh weight within the inoculated populations. The effect of this QTL on resistance to P. medicaginis translated into 27.5% less dead/chlorotic leaves or 0.86 g more root fresh weight. Other QTLs with minor effects that are potentially involved in the interaction are located elsewhere on LG6 and LG2. However, the marker density of the linkage map and the population size need to be increased to verify this.
In parallel to this, an F7 recombinant inbred line (RIL) population of chickpea (BG212 X Jimbour), developed by breeders at the New South Wales Department of Primary Industries (NSW DPI), was also assessed for the genetic basis of resistance to P. medicaginis. Variance component analysis of phenotype scores for this intraspecific RIL population indicated that 57.15% of the differences in between-family and withinfamily variance could be attributed to a genetic component. However, gene-based markers developed in M. truncatula and established simple sequence repeat (SSR) markers of chickpea were not sufficiently polymorphic in size to produce a linkage map for further QTL analysis.
An interspecific cross between C. arietinum and C. echinospermum (Howzat X ILWC246) was also performed by breeders at the NSW DPI to develop RILs. In the duration of this research these interspecific RILs were bred to generation F3 and phenotyping assessment had not been performed. However, marker screening of the parents revealed 122 size polymorphic chickpea SSR markers. A sufficient linkage map could be produced for QTL analysis once field assessment of this population is performed. Initial screening of the M. truncatula gene-based markers on the parents of this interspecific cross also revealed that 50% show a sequence-identified base pair difference. A chickpea linkage map incorporating these markers could be comparatively mapped with M. truncatula.
Molecular investigations of the M. truncatula/P. medicaginis pathosystem were performed to elucidate the possible underlying defence mechanisms involved in the observed resistance. To determine the function of ethylene in the resistant response, the characterisation of defence associated mutants of M. truncatula and Agrobacterium rhizogenes-mediated hairy root transformations were employed. Comparison of response to inoculation of an ethylene insensitive mutant of M. truncatula (sickle) with the moderately resistant background genotype A17 showed that sickle was hypersensitive to P. medicaginis. This indicated that ethylene insensitivity was not the source of resistance to this pathogen and importantly that ethylene is a key defence signalling molecule in the moderate resistance of A17 to P. medicaginis.
Agrobacterium-mediated hairy root transformations of M. truncatula with 4GCC::Luc constructs, revealed that the production of ethylene and consequently ethylene response factors (ERFs) after inoculation by P. medicaginis was a general defence reaction by all accessions. The two susceptible M. truncatula accessions exhibited a much stronger and earlier response to inoculation than the highly resistant and moderately resistant accessions. This indicated that the resistant response may be directed by a transcriptional component governed by the host genotype, downstream of ethylene production. The M. truncatula/P. medicaginis hairy root transformation assay has scope to be a powerful functional genomics tool for this pathogen interaction.
Reverse transcriptase quantitative polymerase chain reaction (RTqPCR) was employed to determine the general patterns of gene expression and function underlying the response to P. medicaginis infection. Relative changes in gene expression of key enzymes in each of the salicylic acid, jasmonic acid, ethylene and isoflavonoid defence pathways and in genes encoding downstream target proteins revealed potential genes involved in the resistance to P. medicaginis. There was a distinct molecular difference in the response between the high and moderately resistant M. truncatula phenotypes to this pathogen. Moderate resistance to P. medicaginis in M. truncatula is possibly
mediated by ethylene and involves the considerable induction of pathogenesis related protein 5 (PR5), which was not the same defence response that conferred the high resistance to P. medicaginis. Early and consistent expression of genes encoding key enzymes of the isoflavonoid pathway by the highly resistant accession indicated that phytoalexin response could be associated with the high resistance. Confirmation of the involvement of isoflavonoid phytoalexins in the high resistance response to P. medicaginis merits further investigation.
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Jensen, Alexa Lunt. « Evaluating Nitrogen and Carbon Differences in Standing Litter from Normal and Prematurely Senesced Bromus tectorum Plants ». BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8265.
Texte intégralRésumé :
Bromus tectorum, an invasive winter annual, has displaced native vegetation throughout the western United States. Bromus tectorum litter influences nutrient cycling near the soil surface as well as plant establishment. Failed seed production of B. tectorum occasionally occurs in the field, with plants exhibiting weak flowering culms that turn straw-colored in spring when normal plants are green or purple in color. Because annual grasses transport most soluble carbon (C) and nitrogen (N) to reproductive organs, seed production failure results in significantly different fates for these nutrients compared with normal plants. As part of larger efforts to understand events leading to large-scale seedling emergence failure (termed die-offs), occasionally observed in near mono-cultures of B. tectorum, we here test the hypothesis that prematurely senesced litter associated with seed production failure has higher soluble C and N than normal litter. C and N concentrations of aboveground biomass were compared for normal and prematurely senesced B. tectorum plants. Two methods were used to cause premature senescence: fungal pathogen infection with Clarireedia capillus-albis and glyphosate herbicide application. In a related experiment, field sampling of normal and prematurely senesced plants under natural conditions was conducted to compare C and N levels in-situ. Herbicide-induced senescence resulted in 1.5 to 2 times greater soluble C concentrations, but fungal infection had no effect on soluble C under experiment conditions. Prematurely senesced litter had increased total N concentrations, resulting in lower C:N ratios. The C:N ratio for prematurely senesced plants (averaged across all studies) was 68:1, whereas mature normal plants averaged 243:1. These findings illustrate failed seed production associated with premature senescence results in B. tectorum litter with significantly higher N concentrations and can result in increased soluble C concentrations. Altered nutrient status may contribute to changes in soil microbial activity, including activity of soilborne pathogens found in die-offs.
Livres sur le sujet "Soilborn pathogen"
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Soilborne plant pathogens. New York : Macmillan Pub. Co., 1987.
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K, Sarbhoy A., Gangawane L. V et Agarwal D. K, dir. Compendium of soil borne plant pathogens. New Delhi : Malhotra Pub. House, 1987.
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Melbourne), International Congress of Plant Pathology (4th 1983 University of. Ecology and management of soilborne plant pathogens. St. Paul, Minn., U.S.A : American Phytopathological Society, 1985.
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Robert, Hall, et International Congress of Plant Pathology (6th : 1993 : Montréal, Québec), dir. Principles and practice of managing soilborne plant pathogens. St. Paul, Minn : APS Press, 1996.
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Watanabe, Tsuneo. Pictorial Atlas of Soilborne Fungal Plant Pathogens and Diseases. Boca Raton, FL : CRC Press, Taylor & Francis Group, 2018. | Series : Mycology series ; [33] : CRC Press, 2018. http://dx.doi.org/10.1201/b22340.
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European Foundation for Plant Pathology. Conference. Biotic interactionsand soil-borne diseases. Amsterdam : Elsevier, 1991.
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F, Schmitthenner A., et Water Engineering Research Laboratory, dir. Effects of composted municipal sludge on soilborne plant pathogens : Project summary. Cincinnati, OH : U.S. Environmental Protection Agency, Water Engineering Research Laboratory, 1988.
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L, Singleton Larry, Mihail Jeanne D et Rush Charles M. 1951-, dir. Methods for research on soilborne phytopathogenic fungi. St. Paul, Minn : APS Press, 1992.
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D, Hornby, et Cook R. James 1937-, dir. Biological control of soil-borne plant pathogens. Wallingford [England] : CAB International, 1990.
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Akhtar, C. M. Biological control of some soil borne vegetable diseases : Final report. [Faisalabad], Pakistan : University of Agriculture, Faisalabad, 1989.
Trouver le texte intégralChapitres de livres sur le sujet "Soilborn pathogen"
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Moura, Andréa Bittencourt, David Backhouse, Ismail Teodoro de Souza Júnior et Cesar Bauer Gomes. « Soilborne Pathogens ». Dans Subsoil Constraints for Crop Production, 199–224. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-00317-2_9.
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Dan Jensen, Funck, et Robert D. Lumsden. « Biological Control of Soilborne Pathogens ». Dans Integrated Pest and Disease Management in Greenhouse Crops, 319–37. Dordrecht : Springer Netherlands, 1999. http://dx.doi.org/10.1007/0-306-47585-5_23.
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Hornby, David. « Diseases caused by soilborne pathogens ». Dans The Epidemiology of Plant Diseases, 308–22. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-3302-1_15.
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Paulitz, Timothy C., Patricia A. Okubara et Kurtis L. Schroeder. « Integrated Control of Soilborne Pathogens of Wheat ». Dans Recent Developments in Management of Plant Diseases, 229–45. Dordrecht : Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-8804-9_17.
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Thakur, Pratibha, et Ishwar Singh. « Biocontrol of Soilborne Root Pathogens : An Overview ». Dans Soil Biology, 181–220. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-75910-4_7.
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Reddy, P. Parvatha. « Grafted Vegetables for Management of Soilborne Pathogens ». Dans Sustainable Crop Protection under Protected Cultivation, 83–97. Singapore : Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-287-952-3_7.
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Fravel, D. R., et A. P. Keinath. « Biocontrol of soilborne plant pathogens with fungi ». Dans The Rhizosphere and Plant Growth, 237–43. Dordrecht : Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3336-4_50.
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Gilligan, C. A. « Mathematical Modeling and Analysis of Soilborne Pathogens ». Dans Epidemics of Plant Diseases, 96–142. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75398-5_4.
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Mawar, Ritu, et Satish Lodha. « Suppression of Soilborne Plant Pathogens by Cruciferous Residues ». Dans Soil Biology, 413–33. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-23075-7_20.
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Gilligan, C. A. « Analysis of the Spatial Pattern of Soilborne Pathogens ». Dans Experimental Techniques in Plant Disease Epidemiology, 85–98. Berlin, Heidelberg : Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-95534-1_7.
Texte intégralActes de conférences sur le sujet "Soilborn pathogen"
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Megan N. Marshall et Jean S. VanderGheynst. « Combining Compost Application and Soil Solarization for Control of Soilborne Plant Pathogens ». Dans 2003, Las Vegas, NV July 27-30, 2003. St. Joseph, MI : American Society of Agricultural and Biological Engineers, 2003. http://dx.doi.org/10.13031/2013.14969.
Texte intégralRapports d'organisations sur le sujet "Soilborn pathogen"
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Katan, Jaacov, et Michael E. Stanghellini. Clinical (Major) and Subclinical (Minor) Root-Infecting Pathogens in Plant Growth Substrates, and Integrated Strategies for their Control. United States Department of Agriculture, octobre 1993. http://dx.doi.org/10.32747/1993.7568089.bard.
Texte intégralRésumé :
In intensive agriculture, harmful soilborne biotic agents, cause severe damage. These include both typical soilborne (clinical) major pathogens which destroy plants (e.g. Fusarium and Phytophthora pathogens), and subclinical ("minor") pathogens (e.g. Olpidium and Pythium). The latter cause growth retardation and yield decline. The objectives of this study were: (1) To study the behavior of clinical (major) and subclinical (minor) pathogens in plant growth substrate, with emphasis on zoosporic fungi, such as Pythium, Olipidium and Polymyxa. (2) To study the interaction between subclinical pathogens and plants, and those aspects of Pythium biology which are relevant to these systems. (3) To adopt a holistic-integrated approach for control that includes both eradicative and protective measures, based on a knowledge of the pathogens' biology. Zoospores were demonstrated as the primary, if not the sole propagule, responsible for pathogen spread in a recirculating hydroponic cultural system, as verified with P. aphanidermatum and Phytophthora capsici. P. aphanidermatum, in contrast to Phytophthora capsici, can also spread by hyphae from plant-to-plant. Synthetic surfactants, when added to the recirculating nutrient solutions provided 100% control of root rot of peppers by these fungi without any detrimental effects on plant growth or yield. A bacterium which produced a biosurfactant was proved as efficacious as synthetic surfactants in the control of zoosporic plant pathogens in the recirculating hydroponic cultural system. The biosurfactant was identified as a rhamnolipid. Olpidium and Polymyxa are widespread and were determined as subclinical pathogens since they cause growth retardation but no plant mortality. Pythium can induce both phenomena and is an occasional subclinical pathogen. Physiological and ultrastructural studies of the interaction between Olpidium and melon plants showed that this pathogen is not destructive but affects root hairs, respiration and plant nutrition. The infected roots constitute an amplified sink competing with the shoots and eventually leading to growth retardation. Space solarization, by solar heating of the greenhouse, is effective in the sanitation of the greenhouse from residual inoculum and should be used as a component in disease management, along with other strategies.
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Freeman, Stanley, Russell Rodriguez, Adel Al-Abed, Roni Cohen, David Ezra et Regina Redman. Use of fungal endophytes to increase cucurbit plant performance by conferring abiotic and biotic stress tolerance. United States Department of Agriculture, janvier 2014. http://dx.doi.org/10.32747/2014.7613893.bard.
Texte intégralRésumé :
Major threats to agricultural sustainability in the 21st century are drought, increasing temperatures, soil salinity and soilborne pathogens, all of which are being exacerbated by climate change and pesticide abolition and are burning issues related to agriculture in the Middle East. We have found that Class 2 fungal endophytes adapt native plants to environmental stresses (drought, heat and salt) in a habitat-specific manner, and that these endophytes can confer stress tolerance to genetically distant monocot and eudicot hosts. In the past, we generated a uv non-pathogenic endophytic mutant of Colletotrichum magna (path-1) that colonized cucurbits, induced drought tolerance and enhanced growth, and protected 85% - 100% against disease caused by certain pathogenic fungi. We propose: 1) utilizing path-1 and additional endophtyic microorganisms to be isolated from stress-tolerant local, wild cucurbit watermelon, Citrulluscolocynthis, growing in the Dead Sea and Arava desert areas, 2) generate abiotic and biotic tolerant melon crop plants, colonized by the isolated endophytes, to increase crop yields under extreme environmental conditions such as salinity, heat and drought stress, 3) manage soilborne fungal pathogens affecting curubit crop species growing in the desert areas. This is a unique and novel "systems" approach that has the potential to utilize natural plant adaptation for agricultural development. We envisage that endophyte-colonized melons will eventually be used to overcome damages caused by soilborne diseases and also for cultivation of this crop, under stress conditions, utilizing treated waste water, thus dealing with the limited resource of fresh water.
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Fravel, Deborah, Jaacov Katan et Chen Ginzburg. Basis for the Weakening of Propagules of Soilborne Plant Pathogens by Sublethal Heat and Chemical Disinfestation and its Implications for Disease Control. United States Department of Agriculture, avril 1994. http://dx.doi.org/10.32747/1994.7604312.bard.
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Thomashow, Linda, Leonid Chernin, Ilan Chet, David M. Weller et Dmitri Mavrodi. Genetically Engineered Microbial Agents for Biocontrol of Plant Fungal Diseases. United States Department of Agriculture, 2005. http://dx.doi.org/10.32747/2005.7696521.bard.
Texte intégralRésumé :
The objectives of the project were: a) to construct the site-specific integrative expression cassettes carrying: (i) the chiA gene for a 58-kDa endochitinase, (ii) the pyrrolnitrin biosynthesis operon, and (iii) the acdS gene encoding ACC deaminase; b) to employ these constructs to engineer stable recombinant strains with an expanded repertoire of beneficial activities; c) to evaluate the rhizosphere competence and antifungal activity of the WT and modified strains against pathogenic fungi under laboratory and greenhouse conditions; and d) to monitor the persistence and impact of the introduced strains on culturable and nonculturable rhizosphere microbial populations in the greenhouse and the field. The research generally support our concepts that combining strategically selected genes conferring diverse modes of action against plant pathogens into one organism can improve the efficacy of biological control agents. We hypothesized that biocontrol agents (BCAs) engineered to expand their repertoire of beneficial activities will more effectively control soilborne plant pathogens. In this work, we demonstrated that biocontrol activity of Pseudomonas fluorescens Q8r1-96 and Q2-87, both producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) effective against the plant pathogenic fungus Rhizoctonia solani, can be improved significantly by introducing and expressing either the 1.6-kb gene chiA, encoding the 58-kDa endochitinase ChiA from the rhizosphere strain SerratiaplymuthicaIC1270, or the 5.8-kb prnABCDoperon encoding the broad-range antibiotic pyrrolnitrin (Prn) from another rhizosphere strain, P. fluorescens Pf-5. The PₜₐcchiAandPₜₐcprnABCDcassettes were cloned into the integrative pBK-miniTn7-ΩGm plasmid, and inserted into the genomic DNA of the recipient bacteria. Recombinant derivatives of strains Q8r1-96 and Q2-87 expressing the PₜₐcchiA or PₜₐcprnABCD cassettes produced endochitinase ChiA, or Prn, respectively, in addition to 2,4-DAPG, and the recombinants gave significantly better biocontrol of R. solani on beans under greenhouse conditions. The disease reduction index increased in comparison to the parental strains Q8r1-96 and Q2-87 to 17.5 and 39.0% from 3.2 and 12.4%, respectively, in the case of derivatives carrying the PₜₐcchiAcassette and to 63.1 and 70% vs. 2.8 and 12,4%, respectively, in the case of derivatives carrying the PₜₐcprnABCDcassette. The genetically modified strains exhibited persistence and non-target effects comparable to those of the parental strains in greenhouse soil. Three integrative cassettes carrying the acdS gene encoding ACC deaminase cloned under the control of different promoters were constructed and tested for enhancement of plant growth promotion by biocontrol strains of P. fluorescens and S. plymuthica. The integrative cassettes constructed in this work are already being used as a simple and efficient tool to improve biocontrol activity of various PGPR bacteria against fungi containing chitin in the cell walls or highly sensitive to Prn. Some parts of the work (e. g., construction of integrative cassettes) was collaborative while other parts e.g., (enzyme and antibiotic activity analyses) were fully synergistic. The US partners isolated and provided to the Israeli collaborators the original biocontrol strains P. fluorescens strains Q8r1-96 and Q2-87 and their mutants deficient in 2,4-DAPG production, which were used to evaluate the relative importance of introduction of Prn, chitinase or ACC deaminase genes for improvement of the biocontrol activity of the parental strains. The recombinant strains obtained at HUJI were supplied to the US collaborators for further analysis.