Academic literature on the topic 'Plant root pathogens'
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Journal articles on the topic "Plant root pathogens"
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Thomashow, Linda S. "Biological control of plant root pathogens." Current Opinion in Biotechnology 7, no. 3 (June 1996): 343–47. http://dx.doi.org/10.1016/s0958-1669(96)80042-5.
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Jousset, Alexandre, Laurène Rochat, Arnaud Lanoue, Michael Bonkowski, Christoph Keel, and Stefan Scheu. "Plants Respond to Pathogen Infection by Enhancing the Antifungal Gene Expression of Root-Associated Bacteria." Molecular Plant-Microbe Interactions® 24, no. 3 (March 2011): 352–58. http://dx.doi.org/10.1094/mpmi-09-10-0208.
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Plant health and fitness widely depend on interactions with soil microorganisms. Some bacteria such as pseudomonads can inhibit pathogens by producing antibiotics, and controlling these bacteria could help improve plant fitness. In the present study, we tested whether plants induce changes in the antifungal activity of root-associated bacteria as a response to root pathogens. We grew barley plants in a split-root system with one side of the root system challenged by the pathogen Pythium ultimum and the other side inoculated with the biocontrol strain Pseudomonas fluorescens CHA0. We used reporter genes to follow the expression of ribosomal RNA indicative of the metabolic state and of the gene phlA, required for production of 2,4-diacetylphloroglucinol, a key component of antifungal activity. Infection increased the expression of the antifungal gene phlA. No contact with the pathogen was required, indicating that barley influenced gene expression by the bacteria in a systemic way. This effect relied on increased exudation of diffusible molecules increasing phlA expression, suggesting that communication with rhizosphere bacteria is part of the pathogen response of plants. Tripartite interactions among plants, pathogens, and bacteria appear as a novel determinant of plant response to root pathogens.
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Delavaux, Camille S., Josh L. Schemanski, Geoffrey L. House, Alice G. Tipton, Benjamin Sikes, and James D. Bever. "Root pathogen diversity and composition varies with climate in undisturbed grasslands, but less so in anthropogenically disturbed grasslands." ISME Journal 15, no. 1 (September 21, 2020): 304–17. http://dx.doi.org/10.1038/s41396-020-00783-z.
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AbstractSoil-borne pathogens structure plant communities, shaping their diversity, and through these effects may mediate plant responses to climate change and disturbance. Little is known, however, about the environmental determinants of plant pathogen communities. Therefore, we explored the impact of climate gradients and anthropogenic disturbance on root-associated pathogens in grasslands. We examined the community structure of two pathogenic groups—fungal pathogens and oomycetes—in undisturbed and anthropogenically disturbed grasslands across a natural precipitation and temperature gradient in the Midwestern USA. In undisturbed grasslands, precipitation and temperature gradients were important predictors of pathogen community richness and composition. Oomycete richness increased with precipitation, while fungal pathogen richness depended on an interaction of precipitation and temperature, with precipitation increasing richness most with higher temperatures. Disturbance altered plant pathogen composition and precipitation and temperature had a reduced effect on pathogen richness and composition in disturbed grasslands. Because pathogens can mediate plant community diversity and structure, the sensitivity of pathogens to disturbance and climate suggests that degradation of the pathogen community may mediate loss, or limit restoration of, native plant diversity in disturbed grasslands, and may modify plant community response to climate change.
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Stephens, Cameron M., Travis W. Gannon, Marc A. Cubeta, Tim L. Sit, and James P. Kerns. "Characterization and Aggressiveness of Take-All Root Rot Pathogens Isolated from Symptomatic Bermudagrass Putting Greens." Phytopathology® 112, no. 4 (April 2022): 811–19. http://dx.doi.org/10.1094/phyto-05-21-0215-r.
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Take-all root rot is a disease of ultradwarf bermudagrass putting greens caused by Gaeumannomyces graminis (Gg), Gaeumannomyces sp. (Gx), Gaeumannomyces graminicola (Ggram), Candidacolonium cynodontis (Cc), and Magnaporthiopsis cynodontis (Mc). Many etiological and epidemiological components of this disease remain unknown. Improving pathogen identification and our understanding of the aggressiveness of these pathogens along with growth at different temperatures will advance our knowledge of disease development to optimize management strategies. Take-all root rot pathogens were isolated from symptomatic bermudagrass root and stolon pieces from 16 different golf courses. Isolates of Gg, Gx, Ggram, Cc, and Mc were used to inoculate ‘Champion’ bermudagrass in an in planta aggressiveness assay. Each pathogen was also evaluated at 10, 15, 20, 25, 30, and 35°C to determine growth temperature optima. Infected plant tissue was used to develop a real-time PCR high-resolution melt assay for pathogen detection. This assay was able to differentiate each pathogen directly from infected plant tissue using a single primer pair. In general, Ggram, Gg, and Gx were the most aggressive while Cc and Mc exhibited moderate aggressiveness. Pathogens were more aggressive when incubated at 30°C compared with 20°C. While they grew optimally between 24.4 and 27.8°C, pathogens exhibited limited growth at 35°C and no growth at 10°C. These data provide important information on this disease and its causal agents that may improve take-all root rot management.
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Dawadi, Sujan, Fulya Baysal-Gurel, Karla M. Addesso, Prabha Liyanapathiranage, and Terri Simmons. "Fire Ant Venom Alkaloids: Possible Control Measure for Soilborne and Foliar Plant Pathogens." Pathogens 10, no. 6 (May 27, 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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Biernacki, M., and B. D. Bruton. "Quantitative Response of Cucumis melo Inoculated with Root Rot Pathogens." Plant Disease 85, no. 1 (January 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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Lee, Jang Hoon, Anne J. Anderson, and Young Cheol Kim. "Root-Associated Bacteria Are Biocontrol Agents for Multiple Plant Pests." Microorganisms 10, no. 5 (May 19, 2022): 1053. http://dx.doi.org/10.3390/microorganisms10051053.
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Biological control is an important process for sustainable plant production, and this trait is found in many plant-associated microbes. This study reviews microbes that could be formulated into pesticides active against various microbial plant pathogens as well as damaging insects or nematodes. The focus is on the beneficial microbes that colonize the rhizosphere where, through various mechanisms, they promote healthy plant growth. Although these microbes have adapted to cohabit root tissues without causing disease, they are pathogenic to plant pathogens, including microbes, insects, and nematodes. The cocktail of metabolites released from the beneficial strains inhibits the growth of certain bacterial and fungal plant pathogens and participates in insect and nematode toxicity. There is a reinforcement of plant health through the systemic induction of defenses against pathogen attack and abiotic stress in the plant; metabolites in the beneficial microbial cocktail function in triggering the plant defenses. The review discusses a wide range of metabolites involved in plant protection through biocontrol in the rhizosphere. The focus is on the beneficial firmicutes and pseudomonads, because of the extensive studies with these isolates. The review evaluates how culture conditions can be optimized to provide formulations containing the preformed active metabolites for rapid control, with or without viable microbial cells as plant inocula, to boost plant productivity in field situations.
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Hanson, L. E. "Interaction of Rhizoctonia solani and Rhizopus stolonifer Causing Root Rot of Sugar Beet." Plant Disease 94, no. 5 (May 2010): 504–9. http://dx.doi.org/10.1094/pdis-94-5-0504.
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In recent years, growers in Michigan and other sugar beet (Beta vulgaris) production areas of the United States have reported increasing incidence of root rot with little or no crown or foliar symptoms in sugar beet with Rhizoctonia crown and root rot. In addition, Rhizoctonia-resistant beets have been reported with higher levels of disease than expected. In examining beets with Rhizoctonia root rot in Michigan, over 50% of sampled roots had a second potential root rot pathogen, Rhizopus stolonifer. Growing conditions generally were not conducive to disease production by this pathogen alone, so we investigated the potential for interaction between these two pathogens. In greenhouse tests, four of five sugar beet varieties had more severe root rot symptoms when inoculated with both pathogens than when inoculated with either pathogen alone. This synergism occurred under conditions that were not conducive to disease production by R. stolonifer. Host resistance to Rhizoctonia crown and root rot reduced diseases severity, but was insufficient to control the disease when both pathogens were present. This raises concerns about correct disease diagnosis and management practices and indicates that a root rot complex may be important on sugar beet in Michigan.
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van West, P., B. M. Morris, B. Reid, A. A. Appiah, M. C. Osborne, T. A. Campbell, S. J. Shepherd, and N. A. R. Gow. "Oomycete Plant Pathogens Use Electric Fields to Target Roots." Molecular Plant-Microbe Interactions® 15, no. 8 (August 2002): 790–98. http://dx.doi.org/10.1094/mpmi.2002.15.8.790.
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Plant roots generate electrical currents and associated electrical fields as a consequence of electrogenic ion transport at the root surface. Here we demonstrate that the attraction of swimming zoospores of oomycete plant pathogens to plant roots is mediated in part by electrotaxis in natural root-generated electric fields. The zones of accumulation of anode- or cathode-seeking zoospores adjacent to intact and wounded root surfaces correlated with their in vitro electrotactic behavior. Manipulation of the root electrical field was reflected in changes in the pattern of zoospore accumulation and imposed focal electrical fields were capable of overriding endogenous signals at the root surface. The overall pattern of zoospore accumulation around roots was not affected by the presence of amino acids at concentrations expected within the rhizosphere, although higher concentrations induced encystment and reduced root targeting. The data suggest that electrical signals can augment or override chemical ones in mediating short-range tactic responses of oomycete zoospores at root surfaces.
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Traquair, James A. "Fungal biocontrol of root diseases: endomycorrhizal suppression of cylindrocarpon root rot." Canadian Journal of Botany 73, S1 (December 31, 1995): 89–95. http://dx.doi.org/10.1139/b95-230.
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Many reviews in the past decade outline the need to understand the complex interactions between fungal pathogens of roots, mycorrhizal fungi, mycorrhizosphere associates, and various climatic and edaphic factors to develop stable mycorrhizal biocontrol strategies. Cylindrocarpon root rot caused by Cylindrocarpon destructans is a good example of a replant disorder that is amenable to this type of control in nurseries and new or renovated orchard sites. Cylindrocarpon root rot was reduced by endomycorrhizal colonization of potted peach rootstocks with Glomus aggregatum under controlled environment conditions using Turface or natural, untreated orchard soils. Several mechanisms of suppression are discussed including tolerance to the pathogen through increased host vigor and reduced exudation, competition for space and nutrients, and induced host resistance. Technical innovations and new concepts of fungal community ecology are improving the odds of developing effective biocontrols with mycorrhizae. Exploitation of natural and integrated disease management using multiple mechanisms of pathogen inhibition may offset the difficulties in inoculum preparation. Key words: Cylindrocarpon destructans, antagonism, competition, rhizosphere, mycorrhizosphere.
Dissertations / Theses on the topic "Plant root pathogens"
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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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Matheron, Michael E., Kevin M. Crosby, and 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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Matheron, Michael E., and 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, and 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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Levenfors, Jens. "Soil-borne pathogens in intensive legume cropping - Aphanomyces spp. and root rots /." Uppsala : Dept. of Plant Pathology and Biocontrol Unit, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a393.pdf.
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Olsen, M., M. McClure, and 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.
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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.
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Matheron, Michael E., and 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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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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Martin, Dana. "Investigation of the Biocontrol Activity in vitro and in planta of Different Pseudomonas Species Against Important Crown, Stem, Foliar and Root Pathogens of Ornamental Crops." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503063395390704.
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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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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.
Books on the topic "Plant root pathogens"
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L, Campbell C., and Benson D. M. 1945-, eds. Epidemiology and management of root diseases. Berlin: Springer-Verlag, 1994.
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Capretti, Paolo, Cecilia Comparini, Matteo Garbelotto, and Nicola La Porta, eds. XIII Conference "Root and Butt Rot of Forest Trees" IUFRO Working Party 7.02.01. Florence: Firenze University Press, 2013. http://dx.doi.org/10.36253/978-88-6655-353-3.
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The present Proceedings comprise the contributions that were presented at the 13th International Conference of the IUFRO W. Party 7.02.01 “Root and Butt Rot of Forest Trees” that was held in Italy from the 4th to the 10th of September 2011. The Conference started in Firenze than moved to FEM Research Centre, S. Michele all’Adige, Trento and continued in San Martino di Castrozza, Dolomite region. Root and Butt Rot of Forest Trees have a high biological and economic impact in forestry. The Proceedings were organized under seven headings: Genomics and Plant-Pathogen Interactions; Systematics, Taxonomy and Phylogeography; Ecology; Population Genetics; Etiology and Epidemiology; Disease Management and Control; New Reports, Diagnostics and Research on the Application of new Diagnostic Methods.
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Peterson, Michael James. Sanitation of styroblocks to control algae and seedling root rot fungi. Victoria, B.C: Forestry Canada, 1990.
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Thies, Walter Gene. Laminated root rot in Western North America. Portland, Or: U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Research Station, 1995.
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Geiger, Jean-Paul. Maladies racinaires de l'hévéa: Biochimie et physiologie des relations hôte-parasite. Paris: Editions de l'ORSTOM, 1987.
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Stirling, Graham, Helen Hayden, Tony Pattison, and Marcelle Stirling. Soil Health, Soil Biology, Soilborne Diseases and Sustainable Agriculture. CSIRO Publishing, 2016. http://dx.doi.org/10.1071/9781486303052.
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Our capacity to maintain world food production depends heavily on the thin layer of soil covering the Earth's surface. The health of this soil determines whether crops can grow successfully, whether a farm business is profitable and whether an enterprise is sustainable in the long term. Farmers are generally aware of the physical and chemical factors that limit the productivity of their soils but often do not recognise that soil microbes and the soil fauna play a major role in achieving healthy soils and healthy crops.
Soil Health, Soil Biology, Soilborne Diseases and Sustainable Agriculture provides readily understandable information about the bacteria, fungi, nematodes and other soil organisms that not only harm food crops but also help them take up water and nutrients and protect them from root diseases. Complete with illustrations and practical case studies, it provides growers and their consultants with holistic solutions for building an active and diverse soil biological community capable of improving soil structure, enhancing plant nutrient uptake and suppressing root pests and pathogens.
The book is written by scientists with many years' experience developing sustainable crop production practices in the grains, vegetable, sugarcane, grazing and horticultural industries.
This book will be useful for: growers, consultants, agronomists and soil chemists, extension personnel working in the grains, livestock, sugarcane and horticultural industries, professionals running courses in soil health/biological farming, and students taking university courses in soil science, ecology, microbiology, plant pathology and other biological sciences.
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Dommergues, Y. R. Interactions Between Non-Pathogenic Soil Microorganisms and Plants. Elsevier, 2012.
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Marsden, M. A. Sensitivity of the western root disease model: inventory of root disease. 1992.
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Laminated root rot in Western North America. [Portland, Or.]: U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Research Station, 1995.
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Kirchman, David L. Symbioses and microbes. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0014.
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The book ends with a chapter devoted to discussing interactions between microbes and higher plants and animals. Symbiosis is sometimes used to describe all interactions, even negative ones, between organisms in persistent, close contact. This chapter focuses on interactions that benefit both partners (mutualism), or one partner while being neutral to the other (commensalism). Microbes are essential to the health and ecology of vertebrates, including Homo sapiens. Microbial cells outnumber human cells on our bodies, aiding in digestion and warding off pathogens. In consortia similar to the anaerobic food chain of anoxic sediments, microbes are essential in the digestion of plant material by deer, cattle, and sheep. Different types of microbes form symbiotic relationships with insects and help to explain their huge success in the biosphere. Protozoa are crucial for wood-boring insects, symbiotic bacteria in the genus Buchnera provide sugars to host aphids while obtaining essential amino acids in exchange, and fungi thrive in subterranean gardens before being harvested for food by ants. Symbiotic dinoflagellates directly provide organic material to support coral growth in exchange for ammonium and other nutrients. Corals are now threatened worldwide by rising oceanic temperatures, decreasing pH, and other human-caused environmental changes. At hydrothermal vents in some deep oceans, sulfur-oxidizing bacteria fuel an entire ecosystem and endosymbiotic bacteria support the growth of giant tube worms. Higher plants also have many symbiotic relationships with bacteria and fungi. Symbiotic nitrogen-fixing bacteria in legumes and other plants fix more nitrogen than free-living bacteria. Fungi associated with plant roots (“mycorrhizal”) are even more common and potentially provide plants with phosphorus as well as nitrogen. Symbiotic microbes can provide other services to their hosts, such as producing bioluminescence, needed for camouflage against predators. In the case of the bobtail squid, bioluminescence is only turned on when populations of the symbiotic bacteria reach critical levels, determined by a quorum sensing mechanism.
Book chapters on the topic "Plant root pathogens"
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Termorshuizen, Aad J. "Root Pathogens." In Interactions in Soil: Promoting Plant Growth, 119–37. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-017-8890-8_6.
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Okubara, Patricia A., and Timothy C. Paulitz. "Root defense responses to fungal pathogens: A molecular perspective." In Plant Ecophysiology, 215–26. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/1-4020-4099-7_11.
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Fallath, Thorya, Ahmad Bin Rosli, Brendan Kidd, Lilia C. Carvalhais, and Peer M. Schenk. "Toward Plant Defense Mechanisms Against Root Pathogens." In Agriculturally Important Microbes for Sustainable Agriculture, 293–313. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-5343-6_10.
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Pinhey, Sally, and Margaret Tebbs. "The role of fungi." In Plants for soil regeneration: an illustrated guide, 23–27. Wallingford: CABI, 2022. http://dx.doi.org/10.1079/9781789243604.0005.
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Abstract This chapter focuses on the role of fungi. Fungi are a vital part of the mixture of microorganisms found in healthy soil. Fungal associations between plant roots and beneficial fungi are known as mycorrhizae (meaning 'fungus' and 'root'), and form a beneficial or symbiotic relationship with plants growing in the soil. Mycorrhizal fungi also facilitate plant interactions with other soil microbes. These include pathogens, and bacteria that produce vitamins and protect against attack. The most common of the mycorrhizae are divided into the following: (1) ectomycorrhizae; (2) endomycorrhizae; (3) arbuscular mycorrhizae; (4) ericoid mycorrhizae; and (5) orchid mycorrhiza. The role of saprophytes, pathogens and actinomycetes are also discussed.
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da Silva Campos, Maryluce Albuquerque. "Applications of Arbuscular Mycorrhizal Fungi in Controlling Root-Knot Nematodes." In Arbuscular Mycorrhizal Fungi and Higher Plants, 225–37. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-8220-2_10.
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AbstractMeloidogyne nematodes cause diseases in economically important plants. These sedentary endoparasites modify plant roots, creating feeding sites and leading to the formation of root galls. Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with many plants, enhancing nutrient uptake and overall plant health. AMF can also provide protection against pathogens, making them valuable for biocontrol. Studies have shown that AMF can reduce the number of Meloidogyne galls and eggs while improving plant growth and nutrient absorption, potentially outperforming chemical pesticides. AMF affect Meloidogyne infection at various stages, such as making roots less attractive to nematodes and reducing giant cell formation in galls. There is an increase in the production of protective molecules, compounds, and defense genes in mycorrhizal plants infected by Meloidogyne, standing out phenolic compounds and defense enzymes like peroxidase and polyphenol oxidase. The activation of defense genes and pathways is suggested to play a role in the tolerance of mycorrhizal plants to Meloidogyne. However, there is still a need for further research to understand the physiological and genetic modifications that occur in plants infected by Meloidogyne and associated with AMF.
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Kroschel, Jürgen, and Dorette Müller-Stöver. "Biological Control of Root Parasitic Weeds with Plant Pathogens." In Weed Biology and Management, 423–38. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-94-017-0552-3_21.
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Bruggen, Ariena H. C., and Niklaus J. Grünwald. "Tests for Risk Assessment of Root Infection by Plant Pathogens." In SSSA Special Publications, 293–310. Madison, WI, USA: Soil Science Society of America, 2015. http://dx.doi.org/10.2136/sssaspecpub49.c17.
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Hafez, Saad L., and Sundararaj Palanisamy. "Integrated nematode management of root-knot and root lesion nematodes in Idaho potatoes: major economic limiting factors." In Integrated nematode management: state-of-the-art and visions for the future, 340–46. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789247541.0047.
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Abstract More than 68 species of plant parasitic nematodes belonging to 24 genera are associated with potato fields from different parts of the world. Among all, two groups of nematodes are important in potato production in Idaho, USA. These include root-knot nematodes (Meloidogyne spp.) and root lesion nematodes (Pratylenchus spp.). This chapter discusses the symptoms and damage, distribution, host range, recommended integrated management (including chemical, cultural and host resistance methods) and interactions with other pathogens of root-knot and root lesion nematodes.
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NISHIMURA, HIROYUKI, and ATSUSHI SATOH. "ANTIMICROBIAL AND NEMATICIDAL SUBSTANCES FROM THE ROOT OF CHICORY(Cichorium intybus)." In Allelochemicals: Biological Control of Plant Pathogens and Diseases, 177–80. Dordrecht: Springer Netherlands, 2006. http://dx.doi.org/10.1007/1-4020-4447-x_9.
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Roberts, Philip A. "Integrated management of root-knot and other nematodes in food legumes." In Integrated nematode management: state-of-the-art and visions for the future, 132–37. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789247541.0019.
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Abstract This chapter focuses on the economic importance, host range, distribution, symptoms of damage and biology and life cycle of root-knot and other nematodes in food legumes, such as cowpeas, common beans and lima beans, among others. Some information on their interactions with other nematodes and plant pathogens, the efficacy and optimization of some recommended integrated nematode management systems and future outlook and research requirements are also presented.
Conference papers on the topic "Plant root pathogens"
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Yin, Chuntao. "Disease-induced changes in the rhizosphere microbiome reduced root disease." In IS-MPMI Congress. IS-MPMI, 2023. http://dx.doi.org/10.1094/ismpmi-2023-5r.
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Rhizosphere microbiota, referred to as the second genome of plants, are crucial to plant health. Increasing evidence reveals that plants can change their rhizosphere microbiome and promote microbial activity to reduce plant disease. However, how plant and phytopathogens factor in combination to structure the rhizosphere microbiome and govern microbial selection for adaptation to disease stress remains incompletely understood. In this study, rhizosphere microbiota from successive wheat plantings under the pressure of the soilborne pathogen Rhizoctonia solani AG8 were characterized. Amplicon sequence analyses revealed that bacterial and fungal communities clustered by planting cycles. The addition of AG8 enhanced the separation of the rhizosphere microbiota. The alpha diversity of bacteria and fungi significantly decreased over planting cycles. Compared with rhizosphere bacterial communities, AG8 was a major driver structuring fungal communities. Pathogen-infected monocultures enriched a group of bacterial genera with potential antagonistic activities or abilities for plant growth promotion or nitrogen fixation. Further, eleven bacterial species exhibited antagonistic activities toward Rhizoctonia spp., and four of them displayed broad antagonism against multiple soilborne fungal pathogens. These findings support the potential to improve plant health through manipulating rhizosphere microbiota.
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Mihnea, Nadejda. "Reacția unor linii de tomate la izolatele fungului Alternaria alternata." In VIIth International Scientific Conference “Genetics, Physiology and Plant Breeding”. Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2021. http://dx.doi.org/10.53040/gppb7.2021.64.
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The paper presents the results of the appreciation of some tomato lines based on the resistance to the fungal pathogen Alternaria alternata. Culture filtrates (CF) of pathogen in the most cases did not significantly influence for the seed germination. A more obvious impact was manifested in the case of the root and the stem, the deviations from the control constituting -38.2…. -69.6% for the root and -40.7… -72.6% - for the stem. It was found that the greatest importance in the reaction to A. alternata isolates for seed germination had the genotypic factor, and for root and stem growth - the isolation factor - 95.7-91.0%.
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Sasco, Elena. "Variabilitatea patogenității unor agenți fungici ai putregaiului de rădăcină la grâul comun de toamnă." In International Scientific Symposium "Plant Protection – Achievements and Prospects". Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2020. http://dx.doi.org/10.53040/9789975347204.08.
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The study established different reactions of the growth characters of the autumn common wheat seedlings to the treatment of seeds of genotypes Moldova 614, Moldova 66 and L Selania / Accent with the culture filtrates of the strains of Alternaria alternata, Drechslera sorokiniana and Fusarium solani. The 3 strains of the F. solani pathogen produced concomitant repression of root and stem in Moldova 614 and Moldova 66, but differentiated in L Selania / Accent, being identified as the most aggressive in this study. The highest sensitivity was recorded by L Selania / Accent in the case of the root under the action of Alternaria alternata strains.
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Cers, I. D., V. Yu Gorshkov, R. F. Gubaev, N. E. Gogoleva, and Yu V. Gogolev. "Pathogen-induced changes in gene expression of tobacco plants with development of soft rot caused by Pectobacterium atrosepticum." In IX Congress of society physiologists of plants of Russia "Plant physiology is the basis for creating plants of the future". Kazan University Press, 2019. http://dx.doi.org/10.26907/978-5-00130-204-9-2019-461.
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Стратулат, Татьяна, Татьяна Щербакова, Штефан Кручан, and Андрей Лунгу. "Пораженность листвы древесных насаждений города Кишинева комплексом гнилей летом 2021 года." In VIIth International Scientific Conference “Genetics, Physiology and Plant Breeding”. Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2021. http://dx.doi.org/10.53040/gppb7.2021.92.
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To determine the complex of fungi that cause rot on the leaves and needles of tree species in the green spaces of Chisinau, foliage was collected in four sectors of the city. It was determined by microbio-logical methods that the complex of pathogens on the leaves differs little in different sectors. The main leaf rot fungi present on the affected leaves and needles are Alternaria sp., Aspergillus sp., Fusarium sp., Penicillium sp. For the treatment of the green spaces of Chisinau against diseases, it is advisable to carry out phytosanitary measures with biological products.
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Mikhalev, E. V., and D. D. Khilov. "INFLUENCE OF VARIOUS TYPES OF ORGANIC WASTE OF AGROINDUSTRIAL COMPLEX ON PRODUCTIVITY OF ROW CROPS IN THE CONDITIONS OF THE NIZHNY NOVGOROD REGION." In STATE AND DEVELOPMENT PROSPECTS OF AGRIBUSINESS Volume 2. DSTU-Print, 2020. http://dx.doi.org/10.23947/interagro.2020.2.494-497.
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The introduction of unprocessed organic waste into the soil leads to the accumulation of nutrition elements for their subsequent assimilation by plants in the land-use system from the organomineral complexes of the soil, which will significantly increase the yield of agricultural crops. However, for 2- 3 years with constant introduction of "raw" manure, soil degradation occurs. So, with the constant introduction of "fresh" litter will be the oppression of cultivated plants by "osmosis" and the subsequent destruction of their root rot due to its high content of raw litter of pathogenic organisms and high level of Pro-infectious potential, which reduces fungistasis soil, leading to lower yields. The cardinal way out of this situation is to add composted manure to the soil. In addition to increasing the content of organic matter in the soil, including humus. Due to this, there is a decrease in osmosis and phytopathogenic load. The biological activity of the soil when composting will be slightly lower than when applying " raw " manure. However, due to this fact, in the following years, when using complex compost, the soil will contain more organic matter compared to the control. In addition," full "composting reduces "osmosis", kills weed seeds and destroys potentially dangerous pathogens of agricultural crops. Based on the above, it can be assumed that the introduction of new organic fertilizers should have a multi-sided effect on the agronomic properties of the soil, which in the end, with the correct use of complex compost, dramatically increases the yield of crops, including cereals.
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Крым, Инесса. "Определение устойчивости картофеля к бурой бактериальной гнили в лабораторных условиях." In VIIth International Scientific Conference “Genetics, Physiology and Plant Breeding”. Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2021. http://dx.doi.org/10.53040/gppb7.2021.79.
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The resistance (sensibility) study of potato plant’s aboveground part to brown rot causative agent conducted in laboratory conditions. The used technique for infecting plants growing on artificial substrate allowed to standardize experiment conducting and to decrease the hazard of pathogen spread. The re-ceived data in such way may use in breeding for the search of resistant parents forms to disease.
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Kuznetsov, M. A., A. A. Scherbakov, S. V. Ivashchenko, E. A. Gorelnikova, and N. S. Chervyakova. "Identification black rot pathogen Xanthomonas campestris pv. campestris with biochemical tests." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.147.
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Govender, Nisha. "In silico identification of Dicer-like proteins in Gaderma boninense, the basal stem rot of oil palm pathogen." In ASPB PLANT BIOLOGY 2020. USA: ASPB, 2020. http://dx.doi.org/10.46678/pb.20.1052033.
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Scerbacova, Tatiana, Alina Lungu, Boris Pinzaru, and Leonid Volosciuc. "Testarea preparatului biologic SCLEROTSYD® pentru protecția florii soarelui de putregaiul alb." In Scientific International Symposium "Plant Protection – Achievements and Perspectives". Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2023. http://dx.doi.org/10.53040/ppap2023.32.
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For the purpose of sunflower's protection from white mold (pathogen Sclerotinia sclerotiorum), it was tested biologic preparate Sclerotsyd®. The fungicide was used by spraying the working suspension with subsequent incorporation into the soil. Were used three application rates: 1) Sclerotsyd® - 0.5 l/ha, 2) Sclerotsyd® - 1.0 l/ha, 3) Sclerotsyd ® - 2.0 l/ha, control – without applying any products. The purpose of the research is to test the consumption rates and determine the biological effectiveness of the biological product in the control of sunflower’s root and head white mold. As a result, it was established that the most effective use rate of the biopreparation Sclerotsyd® for suppressing the development of sunflower’s mold and white head mold it is recommended the rate of 2.0 l/ha with a biological efficiency of 86.2-87.0%.
Reports on the topic "Plant root pathogens"
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Katan, Jaacov, and 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, October 1993. http://dx.doi.org/10.32747/1993.7568089.bard.
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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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Cytryn, Eddie, Mark R. Liles, and Omer Frenkel. Mining multidrug-resistant desert soil bacteria for biocontrol activity and biologically-active compounds. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598174.bard.
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Control of agro-associated pathogens is becoming increasingly difficult due to increased resistance and mounting restrictions on chemical pesticides and antibiotics. Likewise, in veterinary and human environments, there is increasing resistance of pathogens to currently available antibiotics requiring discovery of novel antibiotic compounds. These drawbacks necessitate discovery and application of microorganisms that can be used as biocontrol agents (BCAs) and the isolation of novel biologically-active compounds. This highly-synergistic one year project implemented an innovative pipeline aimed at detecting BCAs and associated biologically-active compounds, which included: (A) isolation of multidrug-resistant desert soil bacteria and root-associated bacteria from medicinal plants; (B) invitro screening of bacterial isolates against known plant, animal and human pathogens; (C) nextgeneration sequencing of isolates that displayed antagonistic activity against at least one of the model pathogens and (D) in-planta screening of promising BCAs in a model bean-Sclerotiumrolfsii system. The BCA genome data were examined for presence of: i) secondary metabolite encoding genes potentially linked to the anti-pathogenic activity of the isolates; and ii) rhizosphere competence-associated genes, associated with the capacity of microorganisms to successfully inhabit plant roots, and a prerequisite for the success of a soil amended BCA. Altogether, 56 phylogenetically-diverse isolates with bioactivity against bacterial, oomycete and fungal plant pathogens were identified. These strains were sent to Auburn University where bioassays against a panel of animal and human pathogens (including multi-drug resistant pathogenic strains such as A. baumannii 3806) were conducted. Nineteen isolates that showed substantial antagonistic activity against at least one of the screened pathogens were sequenced, assembled and subjected to bioinformatics analyses aimed at identifying secondary metabolite-encoding and rhizosphere competence-associated genes. The genome size of the bacteria ranged from 3.77 to 9.85 Mbp. All of the genomes were characterized by a plethora of secondary metabolite encoding genes including non-ribosomal peptide synthase, polyketidesynthases, lantipeptides, bacteriocins, terpenes and siderophores. While some of these genes were highly similar to documented genes, many were unique and therefore may encode for novel antagonistic compounds. Comparative genomic analysis of root-associated isolates with similar strains not isolated from root environments revealed genes encoding for several rhizospherecompetence- associated traits including urea utilization, chitin degradation, plant cell polymerdegradation, biofilm formation, mechanisms for iron, phosphorus and sulfur acquisition and antibiotic resistance. Our labs are currently writing a continuation of this feasibility study that proposes a unique pipeline for the detection of BCAs and biopesticides that can be used against phytopathogens. It will combine i) metabolomic screening of strains from our collection that contain unique secondary metabolite-encoding genes, in order to isolate novel antimicrobial compounds; ii) model plant-based experiments to assess the antagonistic capacities of selected BCAs toward selected phytopathogens; and iii) an innovative next-generation-sequencing based method to monitor the relative abundance and distribution of selected BCAs in field experiments in order to assess their persistence in natural agro-environments. We believe that this integrated approach will enable development of novel strains and compounds that can be used in large-scale operations.
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Cytryn, E., Sean F. Brady, and O. Frenkel. Cutting edge culture independent pipeline for detection of novel anti-fungal plant protection compounds in suppressive soils. Israel: United States-Israel Binational Agricultural Research and Development Fund, 2022. http://dx.doi.org/10.32747/2022.8134142.bard.
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Fusarium oxysporum spp. causes Panama disease in bananas and crown and root rot in an array of vegetables and field crops, but increased regulations have restricted the use of many conventional chemical pesticides, and there are a limited number of commercially available products effective against them. The soil microbiome represents a largely untapped reservoir of secondary metabolites that can potentially antagonize fungal pathogens. However, most soil bacteria cannot be cultivated using conventional techniques and therefore most of these compounds remain unexplored. The overall goal of this two-year project was to extract and characterize novel secondary metabolites from "unculturable" soil microbiomes that antagonize Fusarium and other fungal plant pathogens. Initially, the Cytryn lab at the Volcani Institute (ARO) identified candidate biosynthetic gene clusters (BGCs) encoding for potentially novel antifungal compounds (specifically non-ribosomal peptides and polyketides) in soil and plant root microbiomes using cutting-edge metagenomic platforms. Next, the Brady lab at Rockefeller University (RU) screened archived soil metagenomic cosmid libraries for these BGCs, and heterologously expressed them in suitable hosts. Finally, the Frenkel and Cytryn labs at ARO assessed the capacity of these heterologous expressed strains to antagonize Fusarium and other fungal plant pathogens. Initially tomato and lettuce were analyzed, and subsequently roots of cucumbers grown in suppressive (biochar amended) soils were targeted. We found that the composition of tomato and lettuce root BGCs are similar to each other, but significantly different from adjacent bulk soil, indicating that root bacteria possess specific secondary metabolites that are potentially associated with rhizosphere competence. BGC linked to known metabolites included various antimicrobial, (e.g., streptazone E, sessilin), antifungal (heat-stable antifungal factor- HSAF, II and ECO-02301), and insecticidal (melingmycin, orfamide A) compounds. However, over 90% of the identified BGCs were moderately to significantly different from those encoding for characterized secondary metabolites, highlighting the profusion of potentially novel secondary metabolites in both root and soil environments. Novel BGCs that were abundant in roots and remotely resembled those of antifungal compounds were transferred to RU for subsequent screening and five were identified in RU soil metagenomic cosmid libraries. Two of these clusters (BARD-1711 BARD-B481) were heterologously-expressed in a Streptomyces albus J1074 strain, and transferred to ARO. The strain harboring BARAD-B481 was found to antagonize Fusarium significantly more than the host strain, indicating that this BGCs product has antifungal activity. Future studies will need to work on chemically characterizing the BARAD-B481 BGC and progress with the above described pipeline for other interesting BGCs.
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Harman, Gary E., and Ilan Chet. Enhancement of plant disease resistance and productivity through use of root symbiotic fungi. United States Department of Agriculture, July 2008. http://dx.doi.org/10.32747/2008.7695588.bard.
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The objectives of the project were to (a) compare effects ofT22 and T-203 on growth promotion and induced resistance of maize inbred line Mol7; (b) follow induced resistance of pathogenesis-related proteins through changes in gene expression with a root and foliar pathogen in the presence or absence of T22 or T-203 and (c) to follow changes in the proteome of Mol? over time in roots and leaves in the presence or absence of T22 or T-203. The research built changes in our concepts regarding the effects of Trichoderma on plants; we hypothesized that there would be major changes in the physiology of plants and these would be reflected in changes in the plant proteome as a consequence of root infection by Trichoderma spp. Further, Trichoderma spp. differ in their effects on plants and these changes are largely a consequence of the production of different elicitors of elicitor mixtures that are produced in the zone of communication that is established by root infection by Trichoderma spp. In this work, we demonstrated that both T22 and T-203 increase growth and induce resistance to pathogens in maize. In Israel, it was shown that a hydrophobin is critical for root colonization by Trichoderma strains, and that peptaibols and an expansin-like protein from Ttrichoderma probably act as elicitors of induced resistance in plants. Further, this fungus induces the jasmonate/ethylene pathway of disease resistance and a specific cucumber MAPK is required for transduction of the resistance signal. This is the first such gene known to be induced by fungal systems. In the USA, extensive proteomic analyses of maize demonstrated a number of proteins are differentially regulated by T. harzianum strain T22. The pattern of up-regulation strongly supports the contention that this fungus induces increases in plant disease resistance, respiratory rates and photosynthesis. These are all very consistent with the observations of effects of the fungus on plants in the greenhouse and field. In addition, the chitinolytic complex of maize was examined. The numbers of maize genes encoding these enzymes was increased about 3-fold and their locations on maize chromosomes determined by sequence identification in specific BAC libraries on the web. One of the chitinolytic enzymes was determined to be a heterodimer between a specific exochitinase and different endochitinases dependent upon tissue differences (shoot or root) and the presence or absence of T. harzianum. These heterodimers, which were discovered in this work, are very strongly antifungal, especially the one from shoots in the presence of the biocontrol fungus. Finally, RNA was isolated from plants at Cornell and sent to Israel for transcriptome assessment using Affymetrix chips (the chips became available for maize at the end of the project). The data was sent back to Cornell for bioinformatic analyses and found, in large sense, to be consistent with the proteomic data. The final assessment of this data is just now possible since the full annotation of the sequences in the maize Affy chips is just now available. This work is already being used to discover more effective strains of Trichoderma. It also is expected to elucidate how we may be able to manipulate and breed plants for greater disease resistance, enhanced growth and yield and similar goals. This will be possible since the changes in gene and protein expression that lead to better plant performance can be elucidated by following changes induced by Trichoderma strains. The work was in, some parts, collaborative but in others, most specifically transcriptome analyses, fully synergistic.
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MacDonald, James D., Aharon Abeliovich, Manuel C. Lagunas-Solar, David Faiman, and John Kabshima. Treatment of Irrigation Effluent Water to Reduce Nitrogenous Contaminants and Plant Pathogens. United States Department of Agriculture, July 1993. http://dx.doi.org/10.32747/1993.7568092.bard.
Full textAbstract:
The contamination of surface and subterranean drinking water supplies with nitrogen-laden agricultural wastewater is a problem of increasing concern in the U.S. and Israel. Through this research, we found that bacteria could utilize common organic wastes (e.g. paper, straw, cotton) as carbon sources under anaerobic conditions, and reduce nitrate concentrations in wastewater to safe levels. Two species of bacteria, Cellulomonas uda and a Comamonas sp., were required for dentitrification. Celulomonas uda degraded cellulose and reduced nitrate to nitrite. In addition, it excreted soluble organic carbon needed as a food source by the Comamonas sp. for completion of denitrification. We also found that recirculated irrigation water contains substantial amounts of fungal inoculum, and that irrigating healthy plants with such water leads to significant levels of root infection. Water can be disinfected with UV, but our experiments showed that Hg-vapor lamps do not possess sufficient energy to kill spores in wastewater containing dissolved organics. Excimer lasers and Xenon flashlamps do possess the needed power levels, but only the laser had a high enough repetition rate to reliably treat large volumes of water. Ozone was highly efficacious, but it's use as a water treatment is probably best suited to moderate or low volume irrigation systems. This research provides critical data needed for the design of effective water denitrification and/or pathogen disinfection systems for different growing operations.
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Hoitink, Harry A. J., Yitzhak Hadar, Laurence V. Madden, and Yona Chen. Sustained Suppression of Pythium Diseases: Interactions between Compost Maturity and Nutritional Requirements of Biocontrol Agents. United States Department of Agriculture, June 1993. http://dx.doi.org/10.32747/1993.7568755.bard.
Full textAbstract:
Several procedures were developed that predict maturity (stability) of composts prepared from municipal solid wastes (MSW). A respirometry procedure, based O2 uptake by compost, predicted (R2=0.90) the growth response of ryegrass in composts and an acceptable level of maturity. Spectroscopic methods (CPMAS13-NMR and DRIFT spectroscopy) showed that the stabilizing compost contained increasing levels of aromatic structures. All procedures predicted acceptable plant growth after approximately 110 days of composting. MSW compost suppressed diseases caused by a broad spectrum of plant pathogens including Rhizoctonia solani, Pythium aphanidermatum and Fusarium oxysporum. A strain of Pantoea agglomerans was identified that caused lysis of hyphae of R. solani. Evidence was obtained, suggesting that thermophilic biocontrol agents also might play a role in suppression. 13C-NMR spectra revealed that the longevity of the suppressive effect against Pythium root rot was determined by the concentration of readily biodegradable carbohydrate in the substrate, mostly present as cellulose. Bacterial species capable of inducing biocontrol were replaced by those not effective as suppression was lost. The rate of uptake of 14C-acetate into microbial biomass in the conducive substrate was not significantly different from that in the suppressive substrate although specific activity was higher. The suppressive composts induced systemic acquired resistance in cucumjber roots to Pythium root rot and to anthracnose in the foliage. Composts also increased peroxidase activity in plants by the conducive substrate did not have these effects. In summary, the composition of the organic fraction determined bacterial species composition and activity in the substrate, which in turn regulated plant gene expression relative to biological control.
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Hoitink, Harry A. J., Yitzhak Hadar, Laurence V. Madden, and Yona Chen. Sustained Suppression of Pythium Diseases: Interactions between Compost Maturity and Nutritional Requirements of Biocontrol Agents. United States Department of Agriculture, June 1993. http://dx.doi.org/10.32747/1993.7568746.bard.
Full textAbstract:
Several procedures were developed that predict maturity (stability) of composts prepared from municipal solid wastes (MSW). A respirometry procedure, based O2 uptake by compost, predicted (R2=0.90) the growth response of ryegrass in composts and an acceptable level of maturity. Spectroscopic methods (CPMAS13-NMR and DRIFT spectroscopy) showed that the stabilizing compost contained increasing levels of aromatic structures. All procedures predicted acceptable plant growth after approximately 110 days of composting. MSW compost suppressed diseases caused by a broad spectrum of plant pathogens including Rhizoctonia solani, Pythium aphanidermatum and Fusarium oxysporum. A strain of Pantoea agglomerans was identified that caused lysis of hyphae of R. solani. Evidence was obtained, suggesting that thermophilic biocontrol agents also might play a role in suppression. 13C-NMR spectra revealed that the longevity of the suppressive effect against Pythium root rot was determined by the concentration of readily biodegradable carbohydrate in the substrate, mostly present as cellulose. Bacterial species capable of inducing biocontrol were replaced by those not effective as suppression was lost. The rate of uptake of 14C-acetate into microbial biomass in the conducive substrate was not significantly different from that in the suppressive substrate although specific activity was higher. The suppressive composts induced systemic acquired resistance in cucumjber roots to Pythium root rot and to anthracnose in the foliage. Composts also increased peroxidase activity in plants by the conducive substrate did not have these effects. In summary, the composition of the organic fraction determined bacterial species composition and activity in the substrate, which in turn regulated plant gene expression relative to biological control.
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Chamovitz, A. Daniel, and Georg Jander. Genetic and biochemical analysis of glucosinolate breakdown: The effects of indole-3-carbinol on plant physiology and development. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597917.bard.
Full textAbstract:
Genetic and biochemical analysis of glucosinolate breakdown: The effects of indole-3-carbinol on plant physiology and development Glucosinolates are a class of defense-related secondary metabolites found in all crucifers, including important oilseed and vegetable crops in the Brassica genus and the well-studied model plant Arabidopsis thaliana. Upon tissue damage, such as that provided by insect feeding, glucosinolates are subjected to catalysis and spontaneous degradation to form a variety of breakdown products. These breakdown products typically have a deterrent effect on generalist herbivores. Glucosinolate breakdown products also contribute to the anti-carcinogenic effects of eating cabbage, broccoli and related cruciferous vegetables. Indole-3-carbinol, a breakdown product of indol-3-ylmethylglucosinolate, forms conjugates with several other plant metabolites. Although some indole-3-carbinol conjugates have known functions in defense against herbivores and pathogens, most play as yet unidentified roles in plant metabolism, and possibly also plant development. At the outset, our proposal had three main hypotheses: (1) There is a specific detoxification pathway for indole-3-carbinol; (2) Metabolites derived from indole-3-carbinol are phloem-mobile and serve as signaling molecules; and (3) Indole-3-carbinol affects plant cell cycle and cell-differentiation pathways. The experiments were designed to enable us to elucidate how indole-3-carbinol and related metabolites affect plants and their interactions with herbivorous insects. We discovered that indole-3- carbinol rapidly and reversibly inhibits root elongation in a dose-dependent manner, and that this inhibition is accompanied by a loss of auxin activity in the root meristem. A direct interaction between indole-3-carbinol and the auxin perception machinery was suggested, as application of indole-3-carbinol rescued auxin-induced root phenotypes. In vitro and yeast-based protein interaction studies showed that indole-3-carbinol perturbs the auxin-dependent interaction of TIR1 with Aux/IAA proteins, supporting the notion that indole-3-carbinol acts as an auxin antagonist. Furthermore, transcript profiling experiments revealed the influence of indole-3-carbinol on auxin signaling in root tips, and indole-3-carbinol also affected auxin transporters. Brief treatment with indole-3-carbinol led to a reduction in the amount of PIN1 and to mislocalization of PIN2. The results indicate that chemicals induced by herbivory, such as indole-3-carbinol, function not only to repel herbivores, but also as signaling molecules that directly compete with auxin to fine tune plant growth and development, which implies transport of indole-3- carbinol that we are as yet unsuccessful in detecting. Our results indicate that plant defensive metabolites also have secondary functions in regulating aspects of plant metabolism, thereby providing diversity in defense-related plant signaling pathways. Such diversity of of signaling by defensive metabolites would be beneficial for the plant, as herbivores and pathogens would be less likely to mount effective countermeasures. We propose that growth arrest can be mediated directly by the herbivory-induced chemicals, in our case, indole-3-carbinol. Thus, glucosinolate breakdown to I3C following herbivory would have two outcomes: (1) Indole-3-carbinaol would inhibit the herbivore, while (2) at the same time inducing growth arrest within the plant. Thus, our results indicate that I3C is a defensive phytohormone that modulates auxin signaling, leading to growth arrest.
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Davis, Eric L., Yuji Oka, Amit Gal-On, Todd Wehner, and Aaron Zelcer. Broad-spectrum Resistance to Root-Knot Nematodes in Transgenic Cucurbits. United States Department of Agriculture, June 2013. http://dx.doi.org/10.32747/2013.7593389.bard.
Full textAbstract:
Root-knot nematodes (RKN), Meloidogyne spp., are extremely destructive pathogens of cucurbit crops grown in the United States and Israel. The safety and environmental concerns of toxic nematicides, and limited sources of natural cucurbit resistance to the four major species of Meloidogyne that threaten these crops in Israel and the U.S., have emphasized the use of biotechnology to develop cucurbits with novel RKN resistance. The U.S. scientists have identified over 40 unique RKN parasitism genes that encode nematode secretions involved in successful plant root infection by RKN, and they have demonstrated that expression of a double-stranded RNA (dsRNA) complementary to a RKN parasitism gene (called 16DIO) in Arabidopsis thaliana induced RNA interference (RNAi)-mediated silencing of the RKN16DlO gene and produced transgenic plants with strong resistance to all four major RKN species. The expression 8D05 parasitism gene was found to coincide with the timing of upregulation of NtCel7 promoter (identified to be upregulated in giantcells by US scientists). NtCel7 promoter was used to express the genes at the right time (early stages of infection) and in the right place (giant-cells) in transgenic plants. US partners produced NtCel7 (nematode-induced promoter)-driven 16DlO-RNAi and 8DOS-RNAi constructs, pHANNIBAL 4D03-RNAi construct and modified 16DlO-RNAi construct (for increased RNAi expression and efficacy) for cucurbit transformation in Israel. In Arabidopsis, some 16DlO-RNAi plant lines show greater levels of resistance to M. incognita than others, and within these lines resistance of greater than 90% reduction in infection is observed among almost all replicates in US. The level of observed nematode resistance is likely to be directly correlated with the level of RNAi expression in individual plants. In Israel, all the RKN parasitism genes-RNAi constructs were successfully transformed into cucumber and melon. The transgenic lines were evaluated for expression of the transgene siRNA in leaves and roots. Those displaying transgene siRNA accumulation were passed on for nematode resistance analysis. Rl seedlings from different lines were subjected to evaluation for resistance to M. javanica. None of the lines was resistant to the nematode in contrast with US partner's results in Arabidopsis. This could be for the following reasons: a) The level of transgene siRNA was insufficient in cucumber and tomato to cause resislance. b) 111e nemalode species on cucwnber IIlay be different ur act in a different manner. c) The assay was performed in soil with a high level of nematode inoculation, and not in petri dish, which may not permit the observation of a low level of resistance.
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Brown Horowitz, Sigal, Eric L. Davis, and Axel Elling. Dissecting interactions between root-knot nematode effectors and lipid signaling involved in plant defense. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598167.bard.
Full textAbstract:
Root-knot nematodes, Meloidogynespp., are extremely destructive pathogens with a cosmopolitan distribution and a host range that affects most crops. Safety and environmental concerns related to the toxicity of nematicides along with a lack of natural resistance sources threaten most crops in Israel and the U.S. This emphasizes the need to identify genes and signal mechanisms that could provide novel nematode control tactics and resistance breeding targets. The sedentary root-knot nematode (RKN) Meloidogynespp. secrete effectors in a spatial and temporal manner to interfere with and mimic multiple physiological and morphological mechanisms, leading to modifications and reprogramming of the host cells' functions, resulted in construction and maintenance of nematodes' feeding sites. For successful parasitism, many effectors act as immunomodulators, aimed to manipulate and suppress immune defense signaling triggered upon nematode invasion. Plant development and defense rely mainly on hormone regulation. Herein, a metabolomic profiling of oxylipins and hormones composition of tomato roots were performed using LC-MS/MS, indicating a fluctuation in oxylipins profile in a compatible interaction. Moreover, further attention was given to uncover the implication of WRKYs transcription factors in regulating nematode development. In addition, in order to identify genes that might interact with the lipidomic defense pathway induced by oxylipins, a RNAseq was performed by exposing M. javanicasecond-stage juveniles to tomato protoplast, 9-HOT and 13-KOD oxylipins. This transcriptome generated a total of 4682 differentially expressed genes (DEGs). Being interested in effectors, we seek for DEGs carrying a predicted secretion signal peptide. Among the DEGs including signal peptide, several had homology with known effectors in other nematode species, other unknown potentially secreted proteins may have a role as root-knot nematodes' effectors which might interact with lipid signaling. The molecular interaction of LOX proteins with the Cyst nematode effectors illustrate the nematode strategy in manipulating plant lipid signals. The function of several other effectors in manipulating plant defense signals, as well as lipids signals, weakening cell walls, attenuating feeding site function and development are still being studied in depth for several novel effectors. As direct outcome of this project, the accumulating findings will be utilized to improve our understanding of the mechanisms governing critical life-cycle phases of the parasitic M. incognita RKN, thereby facilitating design of effective controls based on perturbation of nematode behavior—without producing harmful side effects. The knowledge from this study will promote genome editing strategies aimed at developing nematode resistance in tomato and other nematode-susceptible crop species in Israel and the United States.