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1
Thomashow, Linda S. „Biological control of plant root pathogens“. Current Opinion in Biotechnology 7, Nr. 3 (Juni 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 und Stefan Scheu. „Plants Respond to Pathogen Infection by Enhancing the Antifungal Gene Expression of Root-Associated Bacteria“. Molecular Plant-Microbe Interactions® 24, Nr. 3 (März 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 und James D. Bever. „Root pathogen diversity and composition varies with climate in undisturbed grasslands, but less so in anthropogenically disturbed grasslands“. ISME Journal 15, Nr. 1 (21.09.2020): 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 und James P. Kerns. „Characterization and Aggressiveness of Take-All Root Rot Pathogens Isolated from Symptomatic Bermudagrass Putting Greens“. Phytopathology® 112, Nr. 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 und Terri Simmons. „Fire Ant Venom Alkaloids: Possible Control Measure for Soilborne and Foliar Plant Pathogens“. Pathogens 10, Nr. 6 (27.05.2021): 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., und B. D. Bruton. „Quantitative Response of Cucumis melo Inoculated with Root Rot Pathogens“. Plant Disease 85, Nr. 1 (Januar 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 und Young Cheol Kim. „Root-Associated Bacteria Are Biocontrol Agents for Multiple Plant Pests“. Microorganisms 10, Nr. 5 (19.05.2022): 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, Nr. 5 (Mai 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 und N. A. R. Gow. „Oomycete Plant Pathogens Use Electric Fields to Target Roots“. Molecular Plant-Microbe Interactions® 15, Nr. 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 (31.12.1995): 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.
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Windisch, Saskia, Anja Walter, Narges Moradtalab, Frank Walker, Birgit Höglinger, Abbas El-Hasan, Uwe Ludewig, Günter Neumann und Rita Grosch. „Role of Benzoic Acid and Lettucenin A in the Defense Response of Lettuce against Soil-Borne Pathogens“. Plants 10, Nr. 11 (29.10.2021): 2336. http://dx.doi.org/10.3390/plants10112336.
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Soil-borne pathogens can severely limit plant productivity. Induced defense responses are plant strategies to counteract pathogen-related damage and yield loss. In this study, we hypothesized that benzoic acid and lettucenin A are involved as defense compounds against Rhizoctonia solani and Olpidium virulentus in lettuce. To address this hypothesis, we conducted growth chamber experiments using hydroponics, peat culture substrate and soil culture in pots and minirhizotrons. Benzoic acid was identified as root exudate released from lettuce plants upon pathogen infection, with pre-accumulation of benzoic acid esters in the root tissue. The amounts were sufficient to inhibit hyphal growth of R. solani in vitro (30%), to mitigate growth retardation (51%) and damage of fine roots (130%) in lettuce plants caused by R. solani, but were not able to overcome plant growth suppression induced by Olpidium infection. Additionally, lettucenin A was identified as major phytoalexin, with local accumulation in affected plant tissues upon infection with pathogens or chemical elicitation (CuSO4) and detected in trace amounts in root exudates. The results suggest a two-stage defense mechanism with pathogen-induced benzoic acid exudation initially located in the rhizosphere followed by accumulation of lettucenin A locally restricted to affected root and leaf tissues.
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Ma, Ka-Wai, Yulong Niu, Yong Jia, Jana Ordon, Charles Copeland, Aurélia Emonet, Niko Geldner et al. „Coordination of microbe–host homeostasis by crosstalk with plant innate immunity“. Nature Plants 7, Nr. 6 (24.05.2021): 814–25. http://dx.doi.org/10.1038/s41477-021-00920-2.
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AbstractPlants grown in natural soil are colonized by phylogenetically structured communities of microbes known as the microbiota. Individual microbes can activate microbe-associated molecular pattern (MAMP)-triggered immunity (MTI), which limits pathogen proliferation but curtails plant growth, a phenomenon known as the growth–defence trade-off. Here, we report that, in monoassociations, 41% (62 out of 151) of taxonomically diverse root bacterial commensals suppress Arabidopsis thaliana root growth inhibition (RGI) triggered by immune-stimulating MAMPs or damage-associated molecular patterns. Amplicon sequencing of bacterial 16S rRNA genes reveals that immune activation alters the profile of synthetic communities (SynComs) comprising RGI-non-suppressive strains, whereas the presence of RGI-suppressive strains attenuates this effect. Root colonization by SynComs with different complexities and RGI-suppressive activities alters the expression of 174 core host genes, with functions related to root development and nutrient transport. Furthermore, RGI-suppressive SynComs specifically downregulate a subset of immune-related genes. Precolonization of plants with RGI-suppressive SynComs, or mutation of one commensal-downregulated transcription factor, MYB15, renders the plants more susceptible to opportunistic Pseudomonas pathogens. Our results suggest that RGI-non-suppressive and RGI-suppressive root commensals modulate host susceptibility to pathogens by either eliciting or dampening MTI responses, respectively. This interplay buffers the plant immune system against pathogen perturbation and defence-associated growth inhibition, ultimately leading to commensal–host homeostasis.
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Posada-Vergara, Catalina, Stefan Vidal und Michael Rostás. „Local Competition and Enhanced Defense: How Metarhizium brunneum Inhibits Verticillium longisporum in Oilseed Rape Plants“. Journal of Fungi 9, Nr. 8 (28.07.2023): 796. http://dx.doi.org/10.3390/jof9080796.
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Metarhizium brunneum is a soil-borne fungal entomopathogen that can be associated with plant roots. Previous studies have demonstrated that root colonization by beneficial fungi can directly affect soil-borne pathogens through competition and antibiosis and can activate a systemic response in plants, resulting in a primed state for a faster and/or stronger response to stressors. However, the mechanisms by which Metarhizium inoculation ameliorates symptoms caused by plant pathogens are not well known. This study evaluated the ability of M. brunneum to protect oilseed rape (Brassica napus L.) plants against the soil-borne pathogen Verticillium longisporum and investigated whether the observed effects are a result of direct interaction and/or plant-mediated effects. In vitro and greenhouse experiments were conducted to measure fungal colonization of the rhizosphere and plant tissues, and targeted gene expression analysis was used to evaluate the plant response. The results show that M. brunneum delayed pathogen colonization of plant root tissues, resulting in decreased disease symptoms. Direct competition and antibiosis were found to be part of the mechanisms, as M. brunneum growth was stimulated by the pathogen and inhibited the in vitro growth of V. longisporum. Additionally, M. brunneum changed the plant response to the pathogen by locally activating key defense hormones in the salicylic acid (SA) and abscisic acid (ABA) pathways. Using a split-root setup, it was demonstrated that there is a plant-mediated effect, as improved plant growth and decreased disease symptoms were observed when M. brunneum was in the systemic compartment. Moreover, a stronger systemic induction of the gene PR1 suggested a priming effect, involving the SA pathway. Overall, this study sheds light on the mechanisms underlying the protective effects of M. brunneum against soil-borne pathogens in oilseed rape plants, highlighting the potential of this fungal entomopathogen as a biocontrol agent in sustainable agriculture.
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Egamberdieva, Dilfuza, Farkhod Eshboev, Oybek Shukurov, Burak Alaylar und Naveen Kumar Arora. „Bacterial Bioprotectants: Biocontrol Traits and Induced Resistance to Phytopathogens“. Microbiology Research 14, Nr. 2 (22.05.2023): 689–703. http://dx.doi.org/10.3390/microbiolres14020049.
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Plant growth and nutrition are adversely affected by various factors such as water stress, high temperature, and plant pathogens. Plant-associated microbes play a vital role in the growth and development of their hosts under biotic and abiotic stresses. The use of a rhizosphere microbiome for plant growth stimulation and the biological control of fungal disease can lead to improved crop productivity. Mechanisms used by plant-growth-promoting rhizobacteria (PGPR) to protect plants from soilborne pathogens include antibiosis, the production of lytic enzymes, indole-3 acetic acid production, decreasing ethylene levels by secreting 1-aminocyclopropane-1-carboxylate deaminase, competition for nutrients and niches, parasitism and induced systemic resistance. In this review, we emphasize the biological control of plant pathogens by root-associated microbes and discuss traits involved in pathogen reduction. Future research should focus on the effect of root exudation on plant–pathogen interactions under various abiotic factors. Moreover, the development of microbial fungicides with longer shelf lives will help farmers to opt for organic agriculture, reducing the use of chemical fertilizers. This trend is expected to drive the adoption of biological control methods in agriculture. The future prospects for the biological control of plant diseases are bright and are expected to play an increasingly important role in sustainable agriculture.
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Poole, Grant J., Martin Harries, D. Hüberli, S. Miyan, W. J. MacLeod, Roger Lawes und A. McKay. „Predicting Cereal Root Disease in Western Australia Using Soil DNA and Environmental Parameters“. Phytopathology® 105, Nr. 8 (August 2015): 1069–79. http://dx.doi.org/10.1094/phyto-07-14-0203-r.
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Root diseases have long been prevalent in Australian grain-growing regions, and most management decisions to reduce the risk of yield loss need to be implemented before the crop is sown. The levels of pathogens that cause the major root diseases can be measured using DNA-based services such as PreDicta B. Although these pathogens are often studied individually, in the field they often occur as mixed populations and their combined effect on crop production is likely to vary across diverse cropping environments. A 3-year survey was conducted covering most cropping regions in Western Australia, utilizing PreDicta B to determine soilborne pathogen levels and visual assessments to score root health and incidence of individual crop root diseases caused by the major root pathogens, including Rhizoctonia solani (anastomosis group [AG]-8), Gaeumannomyces graminis var. tritici (take-all), Fusarium pseudograminearum, and Pratylenchus spp. (root-lesion nematodes) on wheat roots for 115, 50, and 94 fields during 2010, 2011, and 2012, respectively. A predictive model was developed for root health utilizing autumn and summer rainfall and soil temperature parameters. The model showed that pathogen DNA explained 16, 5, and 2% of the variation in root health whereas environmental parameters explained 22, 11, and 1% of the variation in 2010, 2011, and 2012, respectively. Results showed that R. solani AG-8 soil pathogen DNA, environmental soil temperature, and rainfall parameters explained most of the variation in the root health. This research shows that interactions between environment and pathogen levels before seeding can be utilized in predictive models to improve assessment of risk from root diseases to assist growers to plan more profitable cropping programs.
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Persson, L., L. Bødker und M. Larsson-Wikström. „Prevalence and Pathogenicity of Foot and Root Rot Pathogens of Pea in Southern Scandinavia“. Plant Disease 81, Nr. 2 (Februar 1997): 171–74. http://dx.doi.org/10.1094/pdis.1997.81.2.171.
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The occurrence of root pathogens of vining pea was determined in field surveys in Sweden and Denmark from 1989 to 1994. The most serious yield-reducing root pathogen, Aphanomyces euteiches, was found in approximately one-third of the sampled fields in both Sweden and Denmark. In a few fields severely infested with this pathogen, there was a total crop failure. The most frequently isolated pathogens were Phoma medicaginis var. pinodella and Fusarium solani; the latter also was isolated from vascular tissue up to the seventh node level. Other pathogens isolated from roots were F. avenaceum, F. oxysporum, F. culmorum, Chalara elegans, Pythium irregulare, and Mycosphaerella pinodes. In greenhouse pathogenicity tests, A. euteiches caused the most severe root damage and plant death of pea, followed by F. avenaceum and P. irregulare. There was an inverse relationship between field disease severity index and yield for fields infested with A. euteiches.
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Delavault, Philippe. „Are root parasitic plants like any other plant pathogens?“ New Phytologist 226, Nr. 3 (Mai 2020): 641–43. http://dx.doi.org/10.1111/nph.16504.
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Kim, Dohyun, Taiying Li, Jungkwan Lee und Seung-Ho Lee. „Biological Efficacy of Endophytic Bacillus velezensis CH-15 from Ginseng against Ginseng Root Rot Pathogens“. Research in Plant Disease 28, Nr. 1 (31.03.2022): 19–25. http://dx.doi.org/10.5423/rpd.2022.28.1.19.
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Ginseng is an important medicinal plant cultivated in East Asia for thousands of years. It is typically cultivated in the same field for 4 to 6 years and is exposed to a variety of pathogens. Among them, ginseng root rot is the main reason that leads to the most severe losses. In this study, endophytic bacteria were isolated from healthy ginseng, and endophytes with antagonistic effect against ginseng root rot pathogens were screened out. Among the 17 strains, three carried antagonistic effect, and were resistant to radicicol that is a mycotoxin produced by ginseng root rot pathogens. Finally, Bacillus velezensis CH-15 was selected due to excellent antagonistic effect and radicicol resistance. When CH-15 was inoculated on ginseng root, it not only inhibited the mycelial growth of the pathogen, but also inhibited the progression of disease. CH-15 also carried biosynthetic genes for bacillomycin D, iturin A, bacilysin, and surfactin. In addition, CH-15 culture filtrate significantly inhibited the growth and conidial germination of pathogens. This study shows that endophytic bacterium CH-15 had antagonistic effect on ginseng root rot pathogens and inhibited the progression of ginseng root rot. We expected that this strain can be a microbial agent to suppress ginseng root rot.
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Martin, F. N., und C. T. Bull. „Biological Approaches for Control of Root Pathogens of Strawberry“. Phytopathology® 92, Nr. 12 (Dezember 2002): 1356–62. http://dx.doi.org/10.1094/phyto.2002.92.12.1356.
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Soil fumigation with methyl bromide plus chloropicrin is used as a preplant treatment to control a broad range of pathogens in high-value annual crop production systems. In California, fumigation is used on approximately 10,125 ha of strawberry production to control pathogens ranging from Verticillium dahliae to root pruning pathogens such as Pythium, Rhizoctonia, or Cylindrocarpon spp. In addition to pathogen control, fumigation also causes an enhanced growth response of the plant and reduces weed pressure. The development of successful, long-term cost effective biocontrol strategies most likely will require the development of an integrated systems approach that incorporates diverse aspects of the crop production system. Although application of single microbial inoculants may provide some level of control for specific production problems, it will be a challenge to provide the broad spectrum of activity needed in production fields.
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Porto, Maria Alice Formiga, Márcia Michelle de Queiroz Ambrósio, Selma Rogéria de Carvalho Nascimento, Beatriz Letícia Silva da Cruz und Taffarel Melo Torres. „Interaction of Fusarium solani, Macrophomina phaseolina and Rhizoctonia solani as root rot pathogens of Cucumis melo“. Summa Phytopathologica 45, Nr. 4 (Oktober 2019): 355–60. http://dx.doi.org/10.1590/0100-5405/182687.
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ABSTRACT Root diseases represent one of the main reasons for yield loss in melon crops, especially root and stem rots caused by pathogens like the fungi Fusarium solani (Fs), Macrophomina phaseolina (Mp) and Rhizoctonia solani (Rs), frequently observed in muskmelon either alone or in combination. The objective of this study was to evaluate the effect of the interaction between the pathogens Fs, Mp and Rs on the incidence and severity of root rot and muskmelon development. Two greenhouse experiments were performed using plastic pots with substrate infested with each pathogenic agent alone or in combination. The second experiment was conducted in the same pots that were used in the first experiment. In the first experiment, the disease incidence was higher for the treatment with Fs alone. In the second experiment, the disease incidence and severity were greater for treatment Fs + Rs than for Fs alone. Macrophomina phaseolina was the most commonly isolated pathogen when applied to the plants in a paired mixed inoculum (Fs + Mp and Mp + Rs) in the first experiment. In the second experiment, Fs was more prevalent than the other studied pathogens. Soil infested with Fs had the lowest fresh weight of muskmelon. The pathogens Fs and Mp were more competitive than Rs.
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López-Sánchez, Aida, Miquel Capó, Jesús Rodríguez-Calcerrada, Marta Peláez, Alejandro Solla, Juan A. Martín und Ramón Perea. „Exploring the Use of Solid Biofertilisers to Mitigate the Effects of Phytophthora Oak Root Disease“. Forests 13, Nr. 10 (24.09.2022): 1558. http://dx.doi.org/10.3390/f13101558.
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Oak forests are facing multiple threats due to global change, with the introduction and expansion of invasive pathogens as one of the most detrimental. Here, we evaluated the use of soil biological fertiliser Biohumin® to improve the response of Quercus ilex L. to the soil-borne pathogen Phytophthora cinnamomi Rands by using one-year-old seedlings fertilised at 0, 12.5, and 25% concentrations of Biohumin® (v/v). Our hypothesis was that plant vigour and response to the pathogen would improve with Biohumin®. The effects of soil infestation and fertilisation were tested by assessing plant survival, growth, and physiology. The soil infested with P. cinnamomi negatively affected all the studied traits. We observed that a moderate concentration of Biohumin® (12.5%) increased plant survival. However, a high concentration (25%) reduced the survival compared with the control, probably as a result of the stress caused by both biotic (infection) and abiotic (soil toxicity) factors. Biohumin® at the highest concentration reduced the plant height-to-stem diameter ratio (H/D) and negatively affected plant biomass and physiological activity. Combined biofertilisation and infection induced synergistic negative effects in the leaf water potential compared with infection and fertilisation applied alone. A higher concentration of Biohumin® may favour pathogens more than plants. Further studies should explore the causes of the negative effect of the high concentration of Biohumin® observed here and evaluate if lower concentrations may benefit plant survival and physiology against soil pathogens.
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van West, Pieter, Alex A. Appiah und Neil A. R. Gow. „Advances in research on oomycete root pathogens“. Physiological and Molecular Plant Pathology 62, Nr. 2 (Februar 2003): 99–113. http://dx.doi.org/10.1016/s0885-5765(03)00044-4.
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Graham, James H. „What do root pathogens see in mycorrhizas?“ New Phytologist 149, Nr. 3 (März 2001): 357–59. http://dx.doi.org/10.1046/j.1469-8137.2001.00077.x.
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AVAN, Meltem, Gülsüm PALACIOĞLU, Tülin SARIGÜL ERTEK, Yakup Zekai KATIRCIOĞLU, Harun BAYRAKTAR, Rıza KAYA und Salih MADEN. „Sugar beet root rot caused by oomycetous pathogens in Turkey and their control by seed treatmen“. TURKISH JOURNAL OF AGRICULTURE AND FORESTRY 44, Nr. 6 (08.12.2020): 631–41. http://dx.doi.org/10.3906/tar-1910-55.
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The aim of this study was to determine the oomycetous pathogens causing root rot on sugar beet and test their control by seed treatment in Konya Province, Turkey. Oomycetous fungus-like pathogens of sugar beet were investigated using 866 plant samples collected at 2 growth stages, early seedling and late root, from fields in the Konya region of Turkey and 1 sample from the Thrace region. Herein, 10 oomycetous species belonging to 3 genera: Aphanomyces cochlioides, Phytophthora cryptogea, Ph. pseudocryptogea, Ph. megasperma, Ph. inundata, Pythium aphanidermatum, Py. helicoides, Py. heterothallicum, Py. sylvaticum, and Py. ultimum var. ultimum (Globisporangium ultimum var. ultimum) were discovered at various times with in the 2 growth periods, all of which were the first records for Turkey. A. cochlioides was the most serious pathogen, both in terms of its wide distribution and aggressiveness. The pathogen produced more than 90% disease severity when tested by soil infestation at the seedling stage, although it also occurred at the late root growth stage. Pythium species were also ascommon, such as A. cochlioides, the majority of which were very aggressive, producing more than 84% disease severity at the seedling stage, except for Py. aphanidermatum. Half-strength potato dextrose agar medium was found to be very useful for the isolation of all of the pathogens from the plant samples at both stages. Morphological features of all of the pathogens were abundantly produced when the pathogens were grown on amended grated carrot agar medium and culture disks of fungal growth of this medium were submerged in sterile and nonsterile soil extracts. Out of the 15 fungicide mixes tested, 2 mixes, thiram+metalaxyl+hymexazole and thiram+metalaxyl+hymexazole+ pyraclostrobin reduced seedling root rot caused by both A. cochlioides and Pythium ultimum var. ultimum, while the standard seed treatment fungicide mix of thiram+hymexazole was not effective against either of the pathogens.
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Shcherbakova, Larisa, Maksim Kartashov, Natalia Statsyuk, Tatyana Pasechnik und Vitaly Dzhavakhiya. „Assessment of the Sensitivity of Some Plant Pathogenic Fungi to 6-Demethylmevinolin, a Putative Natural Sensitizer Able to Help Overcoming the Fungicide Resistance of Plant Pathogens“. Antibiotics 9, Nr. 12 (25.11.2020): 842. http://dx.doi.org/10.3390/antibiotics9120842.
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Agricultural fungicides contaminate the environment and promote the spread of fungicide-resistant strains of pathogenic fungi. The enhancement of pathogen sensitivity to these pesticides using chemosensitizers allows the reducing of fungicide dosages without a decrease in their efficiency. Using Petri plate and microplate bioassays, 6-demethylmevinolin (6-DMM), a putative sensitizer of a microbial origin, was shown to affect both colony growth and conidial germination of Alternaria solani, A. alternata, Parastagonospora nodorum, Rhizoctonia solani, and four Fusarium species (F. avenaceum, F. culmorum, F. oxysporum, F. graminearum) forming a wheat root rot complex together with B. sorokiniana. Non- or marginally toxic 6-DMM concentrations suitable for sensitizing effect were determined by the probit analysis. The range of determined concentrations confirmed a possibility of using 6-DMM as a putative sensitizer for the whole complex of root rot agents, other cereal pathogens (A. alternata, P.nodorum), and some potato (R. solani, A. solani) and tomato (A. solani) pathogens. Despite the different sensitivities of the eight tested pathogens, 6-DMM lacked specificity to fungi and possessed a mild antimycotic activity that is typical of other known pathogen-sensitizing agents. The pilot evaluation of the 6-DMM sensitizing first confirmed a principal possibility of using it for the sensitization of B. sorokiniana and R. solani to triazole- and strobilurin-based fungicides, respectively.
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Liu, Yunpeng, Lin Chen, Gengwei Wu, Haichao Feng, Guishan Zhang, Qirong Shen und Ruifu Zhang. „Identification of Root-Secreted Compounds Involved in the Communication Between Cucumber, the Beneficial Bacillus amyloliquefaciens, and the Soil-Borne Pathogen Fusarium oxysporum“. Molecular Plant-Microbe Interactions® 30, Nr. 1 (Januar 2017): 53–62. http://dx.doi.org/10.1094/mpmi-07-16-0131-r.
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Colonization of plant growth–promoting rhizobacteria (PGPR) is critical for exerting their beneficial effects on the plant. Root exudation is a major factor influencing the colonization of both PGPR and soil-borne pathogens within the root system. However, the tripartite interaction of PGPR, plant roots, and soil-borne pathogens is poorly understood. We screened root exudates for signals that mediate tripartite interactions in the rhizosphere. In a split-root system, we found that root colonization of PGPR strain Bacillus amyloliquefaciens SQR9 on cucumber root was significantly enhanced by preinoculation with SQR9 or the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum, whereas root colonization of F. oxysporum f. sp. cucumerinum was reduced upon preinoculation with SQR9 or F. oxysporum f. sp. cucumerinum. Root exudates from cucumbers preinoculated with SQR9 or F. oxysporum f. sp. cucumerinum were analyzed and 109 compounds were identified. Correlation analysis highlighted eight compounds that significantly correlated with root colonization of SQR9 or F. oxysporum f. sp. cucumerinum. After performing colonization experiments with these chemicals, raffinose and tryptophan were shown to positively affect the root colonization of F. oxysporum f. sp. cucumerinum and SQR9, respectively. These results indicate that cucumber roots colonized by F. oxysporum f. sp. cucumerinum or SQR9 increase root secretion of tryptophan to strengthen further colonization of SQR9. In contrast, these colonized cucumber roots reduce raffinose secretion to inhibit root colonization of F. oxysporum f. sp. cucumerinum.
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Weiland, Jerry E., Carolyn F. Scagel, Niklaus J. Grünwald, E. Anne Davis, Bryan R. Beck und Val J. Fieland. „Variation in Disease Severity Caused by Phytophthora cinnamomi, P. plurivora, and Pythium cryptoirregulare on Two Rhododendron Cultivars“. Plant Disease 102, Nr. 12 (Dezember 2018): 2560–70. http://dx.doi.org/10.1094/pdis-04-18-0666-re.
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Rhododendrons are an important crop in the ornamental nursery industry, but are prone to Phytophthora root rot. Phytophthora root rot is a continuing issue on rhododendrons despite decades of research. Several Phytophthora species are known to cause root rot, but most research has focused on P. cinnamomi, and comparative information on pathogenicity is limited for other commonly encountered oomycetes, including Phytophthora plurivora and Pythium cryptoirregulare. In this study, three isolates each of P. cinnamomi, P. plurivora, and Py. cryptoirregulare were used to inoculate rhododendron cultivars Cunningham’s White and Yaku Princess at two different inoculum levels. All three species caused disease, especially at the higher inoculum level. P. cinnamomi and P. plurivora were the most aggressive pathogens, causing severe root rot, whereas Py. cryptoirregulare was a weak pathogen that only caused mild disease. Within each pathogen species, isolate had no influence on disease. Both P. cinnamomi and P. plurivora caused more severe disease on Cunningham’s White than on Yaku Princess, suggesting that the relative resistance and susceptibility among rhododendron cultivars might be similar for both pathogens. Reisolation of P. cinnamomi and P. plurivora was also greater from plants exhibiting aboveground symptoms of wilting and plant death and belowground symptoms of root rot than from those without symptoms. Results show that both P. cinnamomi and P. plurivora, but not Py. cryptoirregulare, are important pathogens causing severe root rot in rhododendron. This study establishes the risks for disease resulting from low and high levels of inoculum for each pathogen. Further research is needed to evaluate longer term risks associated with low inoculum levels on rhododendron health and to explore whether differences among pathogen species affect disease control.
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Loit, Kaire, Liina Soonvald, Alar Astover, Eve Runno-Paurson, Maarja Öpik und Leho Tedersoo. „Temporal and Cultivar-Specific Effects on Potato Root and Soil Fungal Diversity“. Agronomy 10, Nr. 10 (09.10.2020): 1535. http://dx.doi.org/10.3390/agronomy10101535.
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The soil fungal community plays an important role in determining plant growth and health. In this study, we investigated the fungal diversity and community composition in the roots and soil of 21 potato (Solanum tuberosum L.) cultivars using high-throughput sequencing at three different time points across the growing season. In soil and roots, the fungal richness and relative abundance of pathogens and saprotrophs were mainly affected by sampling time. While sampling time affected fungal composition in soil, root fungal communities were also significantly affected by cultivar. The cultivar had the strongest effect on diversity of pathogens and abundance of particular pathogen species. Our results demonstrate changes in soil and root fungal communities of potato over the growing season, as well as highlighting the importance of potato cultivar on root fungal communities and abundance of pathogens.
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Sommermann, Loreen, Doreen Babin, Jan Helge Behr, Soumitra Paul Chowdhury, Martin Sandmann, Saskia Windisch, Günter Neumann et al. „Long-Term Fertilization Strategy Impacts Rhizoctonia solani–Microbe Interactions in Soil and Rhizosphere and Defense Responses in Lettuce“. Microorganisms 10, Nr. 9 (26.08.2022): 1717. http://dx.doi.org/10.3390/microorganisms10091717.
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The long-term effects of agricultural management such as different fertilization strategies on soil microbiota and soil suppressiveness against plant pathogens are crucial. Therefore, the suppressiveness of soils differing in fertilization history was assessed using two Rhizoctonia solani isolates and their respective host plants (lettuce, sugar beet) in pot experiments. Further, the effects of fertilization history and the pathogen R. solani AG1-IB on the bulk soil, root-associated soil and rhizosphere microbiota of lettuce were analyzed based on amplicon sequencing of the 16S rRNA gene and ITS2 region. Organic fertilization history supported the spread of the soil-borne pathogens compared to long-term mineral fertilization. The fertilization strategy affected bacterial and fungal community composition in the root-associated soil and rhizosphere, respectively, but only the fungal community shifted in response to the inoculated pathogen. The potential plant-beneficial genus Talaromyces was enriched in the rhizosphere by organic fertilization and presence of the pathogen. Moreover, increased expression levels of defense-related genes in shoots of lettuce were observed in the soil with organic fertilization history, both in the absence and presence of the pathogen. This may reflect the enrichment of potential plant-beneficial microorganisms in the rhizosphere, but also pathogen infestation. However, enhanced defense responses resulted in retarded plant growth in the presence of R. solani (plant growth/defense tradeoff).
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Ma, Jianbing, Juan Jaraba, Terrence L. Kirkpatrick und Craig S. Rothrock. „Effects of Meloidogyne incognita and Thielaviopsis basicola on Cotton Growth and Root Morphology“. Phytopathology® 104, Nr. 5 (Mai 2014): 507–12. http://dx.doi.org/10.1094/phyto-06-12-0120-r.
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Effects of the root-knot nematode Meloidogyne incognita and the fungal pathogen Thielaviopsis basicola on cotton seedling growth and root morphology were evaluated in controlled environmental experiments. Four pathogen treatments, including noninfested soil, soil infested with M. incognita, soil infested with T. basicola, and soil infested with both pathogens were evaluated at soil bulk densities (BDs) of 1.25 and 1.50 g/cm3. Plant growth and the morphology of the root systems were evaluated 44 days after planting. Infestation with M. incognita and T. basicola together significantly reduced seedling emergence, number of stem nodes, and root system volume compared with either pathogen alone. Either M. incognita or T. basicola reduced plant height, root fresh weight, top dry weight; root parameters total root length, surface area, and links; and root topological parameters magnitude, altitude, and exterior path length. M. incognita infection increased root radius. Root colonization by T. basicola increased with the presence of M. incognita at the lower soil BD. In contrast to previous research with Pythium spp., root topological indices (TIs) were similar with all of the treatments. Root TIs were near 1.92, indicating a herringbone (less branching) root architectural structure. Studying root architecture using a topological model offers an additional approach to evaluating fungi and nematodes and their interactions for soilborne-pathogen systems.
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Msikita, W., B. Bissang, B. D. James, H. Baimey, H. T. Wilkinson, M. Ahounou und R. Fagbemissi. „Prevalence and Severity of Nattrassia mangiferae Root and Stem Rot Pathogen of Cassava in Bénin“. Plant Disease 89, Nr. 1 (Januar 2005): 12–16. http://dx.doi.org/10.1094/pd-89-0012.
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Root rot pathogens were found through diagnostic surveys in all departments (regions) of Bénin, West Africa, to affect 86 to 100% and 96 to 100% of cassava fields during the dry and rainy seasons, respectively. Disease incidence in individual fields ranged between 0 and 53%, and averaged 16 to 27% per department. Nattrassia mangiferae was consistently the most frequently isolated root rot pathogen (56% in the dry season and 22 to 52% in the rainy season). Pathogenicity of N. mangiferae was confirmed on four cultivars of cassava using stem cuttings and storage roots. For all four cultivars, N. mangiferae significantly reduced the number of roots. Lesions (3 to 15 cm long) formed on the lower stem portion of all inoculated plants, whereas control plants remained symptom free. On storage roots, the disease profile was similar to that formed on stem cuttings. Other root rot pathogens detected during the dry season were Macrophomina phaseolina (14.2%), Fusarium spp. (11.8%), Botryodiplodia theobromae (7.7%), and Pythium spp. (2.9%). During the rainy season, Fusarium spp. were the second most commonly isolated root rot pathogens in three departments (Atlantique, Borgou, and Mono). In Oueme and Zou, B. theobromae was the second most isolated root rot pathogen (ranging between 24 and 28%) during the rainy season. During the same season, Pythium spp. were pronounced in Borgou (18%), followed by Mono (11%), Atlantique (9%), Atacora (8%), Oueme (5%), and Zou (6%). Results of the study are discussed with a view to creating awareness of the destructive power of N. mangiferae, a hitherto poorly recognized root rot pathogen of cassava in Bénin and West Africa in general.
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Coles, Donovin W., Sean L. Bithell, Meena Mikhael, William S. Cuddy und Jonathan M. Plett. „Chickpea Roots Undergoing Colonisation by Phytophthora medicaginis Exhibit Opposing Jasmonic Acid and Salicylic Acid Accumulation and Signalling Profiles to Leaf Hemibiotrophic Models“. Microorganisms 10, Nr. 2 (02.02.2022): 343. http://dx.doi.org/10.3390/microorganisms10020343.
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Hemibiotrophic pathogens cause significant losses within agriculture, threatening the sustainability of food systems globally. These microbes colonise plant tissues in three phases: a biotrophic phase followed by a biotrophic-to-necrotrophic switch phase and ending with necrotrophy. Each of these phases is characterized by both common and discrete host transcriptional responses. Plant hormones play an important role in these phases, with foliar models showing that salicylic acid accumulates during the biotrophic phase and jasmonic acid/ethylene responses occur during the necrotrophic phase. The appropriateness of this model to plant roots has been challenged in recent years. The need to understand root responses to hemibiotrophic pathogens of agronomic importance necessitates further research. In this study, using the root hemibiotroph Phytophthora medicaginis, we define the duration of each phase of pathogenesis in Cicer arietinum (chickpea) roots. Using transcriptional profiling, we demonstrate that susceptible chickpea roots display some similarities in response to disease progression as previously documented in leaf plant–pathogen hemibiotrophic interactions. However, our transcriptomic results also show that chickpea roots do not conform to the phytohormone responses typically found in leaf colonisation by hemibiotrophs. We found that quantified levels of salicylic acid concentrations in root tissues decreased significantly during biotrophy while jasmonic acid concentrations were significantly induced. This study demonstrated that a wider spectrum of plant species should be investigated in the future to understand the physiological changes in plants during colonisation by soil-borne hemibiotrophic pathogens before we can better manage these economically important microbes.
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Šišić, Adnan, Jelena Baćanović-Šišić, Fernanda M. Gamba und Maria R. Finckh. „Didymella pinodella: An Important Pea Root Rot Pathogen in France to Watch Out For?“ Journal of Fungi 10, Nr. 1 (05.01.2024): 44. http://dx.doi.org/10.3390/jof10010044.
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Root rot pathogens restrict pea and wheat production globally. In the EU, pea and pea-based cereal mixtures are being promoted; however, root rot pathogen dynamics in such mixtures are poorly understood. Winter pea and wheat were grown either in pure stands or in mixtures in the field in western France, and the severity of root rot in pea, wheat, and their mixtures, as well as the key pathogens associated with these crops, were assessed. Disease severity was moderate in pea and low in wheat, with no effect of sowing pattern. Didymella pinodella, a previously unreported pathogen in the pea–root rot complex in France, emerged as the most dominant pathogen in pea. It also occurred in low frequencies in wheat. Subsequent greenhouse aggressiveness tests showed that ten of the commonly grown pea cultivars in France lack resistance to D. pinodella. Among the Fusarium spp. isolated, F. avenaceum was the most frequent, occurring at similar frequencies in pea and wheat. In conclusion, D. pinodella may be an important pea root rot pathogen in France and there is a lack of resistance in the tested pea cultivars. In addition, F. avenaceum is a shared pathogen of wheat and pea.
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Gossen, Bruce D., Robert L. Conner, Kan-Fa Chang, Julie S. Pasche, Debra L. McLaren, Maria A. Henriquez, Syama Chatterton und Sheau-Fang Hwang. „Identifying and Managing Root Rot of Pulses on the Northern Great Plains“. Plant Disease 100, Nr. 10 (Oktober 2016): 1965–78. http://dx.doi.org/10.1094/pdis-02-16-0184-fe.
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Pulse crops (annual grain legumes such as field pea, lentil, dry bean, and chickpea) have become an important component of the cropping system in the northern Great Plains of North America over the last three decades. In many areas, the intensity of damping-off, seedling blight, root rot, and premature ripening of pulse crops is increasing, resulting in reduction in stand establishment and yield. This review provides a brief description of the important pathogens that make up the root rot complex and summarizes root rot management on pulses in the region. Initially, several specific Fusarium spp., a range of Pythium spp., and Rhizoctonia solani were identified as important components of the root rot disease complex. Molecular approaches have recently been used to identify the importance of Aphanomyces euteiches on pulses, and to demonstrate that year-to-year changes in precipitation and temperature have an important effect on pathogen prevalence. Progress has been made on management of root rot, but more IPM tools are required to provide effective disease management. Seed-treatment fungicides can reduce damping-off and seedling blight for many of the pathogens in this disease complex, but complex cocktails of active ingredients are required to protect seedlings from the pathogen complex present in most commercial fields. Partial resistance against many of the pathogens in the complex has been identified, but is not yet available in commercial cultivars. Cultural practices, especially diversified cropping rotations and early, shallow seeding, have been shown to have an important role in root rot management. Biocontrol agents may also have potential over the long term. Improved methods being developed to identify and quantify the pathogen inoculum in individual fields may help producers avoid high-risk fields and select IPM packages that enhance yield stability.
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Nicomrat, Duongruitai, Pattarika Soongsombat, Nednapa Suenonmueng und Ninlawan Marjang. „An Antagonism of Isolates of Root-Associated Bacteria Consortia Habituating in Banana Rhizosphere“. Applied Mechanics and Materials 879 (März 2018): 83–88. http://dx.doi.org/10.4028/www.scientific.net/amm.879.83.
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Microbial diversity based on plant-microbe interaction as well as most fungal diseases which are such multipathogen complexes have been long researched. Most beneficial microbes promote the growth of the plant but inhibit the growth of plant pathogen as biocontrol agents and are reported for their establishment being microbial communities associated to the plant roots. We were interested in understanding the antagonistic activity of root-associated bacterial communities in the rhizospheres. In this experiment, common bacteria associated with banana root exudation that were cultivated and isolated harbored specific antagonistic to common pathogen. In the experiments, the root (rhizosphere), and interior of the pseudostem (endosphere) samples were high CFU counts in the extracted endosphere than in rhizosphere of banana roots (6-8 and 4-5 CFU/ g, respectively). Antibacterial activity as bioactive agents were detected from these microbes as antagonis activity against plant pathogens that wereBacillus indicus, Pseudomonas palleroniana, Penicilliumspp andFusarium oxysporum. both mixed consortia could control Fusarium, fungal pathogen in banana. From this study, the isolates of indigenous bacteria obtained from banana rhizosphere can be potential for agricultural uses as further as disease-suppressive microorganisms provides promising perspectives for sustainable plant protection.
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Ehwarieme, D. A., Blessing Offuah und E. M. Ilondu. „EVALUATION OF THE PHYTOCHEMICAL AND ANTIMICROBIAL ACTIVITY OF Kalanchoe pinnata AGAINST PLANT PATHOGENS ISOLATED FROM DISEASED PLANT PATHOGENS“. FUDMA JOURNAL OF SCIENCES 5, Nr. 3 (03.11.2021): 310–14. http://dx.doi.org/10.33003/fjs-2021-0503-755.
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The antimicrobial activity of Kalanchoe pinnata (Syn Bryophyllum pinnatum) against clinical pathogen is well documented in literature but there is paucity of information on its effect against plant pathogens. This work attempts to evaluate inhibitory activity of Kalanchoe pinnata (Syn Bryophyllum pinnatum) on selected plant pathogens. Aqueous, acetone, ethanol and methanol leaf, stem and root extracts of Kalanchoe pinnata (Syn Bryophyllum pinnatum) were prepared using standard techniques. Extracts were tested against bacteria and fungi isolated from some diseased plants, both singly and in combination with standard antimicrobials. Inhibitory activity was determined using agar well diffusion technique as well as broth dilution technique. Results indicate that the leaf ethanol extract was most effective against the plant pathogens. Zones of inhibition (mm) ranged from [19.0 ± 0.32] for Aspergillus flavus to [23.5 ± 0.22] for Xanthomonas campestris. Meanwhile, the Minimum inhibitory concentration (MIC) reduced from 6.25 mg/mL to 3.13 mg/mL (for Xanthomonas oryzae and Xanthomonas campestris) when leaf extract was used in combination with streptomycin. Furthermore, MIC reduced from 1.56 mg/mL to 0.78 mg/mL (for Aspergillus flavus and Aspergillus niger) when extract was used in combination with cycloheximide. Ethanol leaf extract of Kalanchoe pinnata (Syn Bryophyllum pinnatum) was most effective against selected plant pathogens. Also, effectiveness of extract was enhanced when used in combination with regular antimicrobial. Kalanchoe pinnata (Syn Bryophyllum pinnatum) may become useful as a biological control agent for plant disease pathogens
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Gautam, R., SK Singh und V. Sharma. „Suppression of soil-borne root pathogens of arid legumes by Sinorhizobium saheli“. SAARC Journal of Agriculture 13, Nr. 1 (15.07.2015): 63–74. http://dx.doi.org/10.3329/sja.v13i1.24181.
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The productivity of arid legumes in arid and semi-arid tracks remains virtually stagnant over decades because of their susceptibility to root diseases. The information on interaction of beneficial nitrogen fixing rhizobia with particular reference to arid legumes of the region is limited. Systematic studies on predominant species Sinorhizobium saheli in management of root pathogens in arid legumes were undertaken. In-vitro interactions of root pathogens and S. saheli isolated from arid legumes significantly suppressed the growth of all fungal pathogens in presence of S. saheli. In addition the growth of Rhizobium was stimulated in presence of different root pathogens. A field experiment on integrated disease managementexhibited that the maximum root nodulation with the maximum seed yield of 1325 kg/ha was observed from treatment where seeds were treated with S. saheli. Whereas, the minimum root nodulation was recorded in treatment, where a mixture of isolated fungal root pathogens were co-inoculated with S. Saheli was recorded from cowpea. The minimum seed yield was recorded from treatment wherein the mixture of isolated root pathogens of arid legumes was co-inoculated with S. Saheli due to increased disease pressure. The results of in-vitro and in-vivo efficacy of S. saheli strains suggest that their co-inoculation with PGPRs can not only reduce the use of chemical fertilizers but also can significantly enhance yields by increasing plant growth and suppressing soil borne plant pathogenic fungi.SAARC J. Agri., 13(1): 63-74 (2015)
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Roberson, Amanda, Carla Spence und Harsh P. Bais. „Underground communication: Belowground signalling mediates diverse root–root and root–microbe interactions“. Biochemist 36, Nr. 5 (01.10.2014): 32–35. http://dx.doi.org/10.1042/bio03605032.
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Plants are stationary organisms, generally restricted to one location for the duration of their growth and development, which is why the need for clear means of information exchange becomes paramount. Above-ground, plants readily emit pungent volatile substances to signal danger of eminent attack to their relatives or to attract the enemy of their enemies. However, most plant communication is occurring below the ground, where plants are secreting compounds from their roots to send messages to neighbouring plants, microbes and insects in the rhizosphere. Although we think of plants as silent and autonomous, they are actually having very complex and specific conversations to communicate with kin, shape their microbiome, and deter invasive plants and pathogens from taking up residence. Rather than blindly fumbling through the soil matrix in hopes of encountering the conditions for ideal growth, plant roots are actively exploring and modulating their surroundings. Root communication is not only critical in terms of an individual plant's success, but it is becoming clear that this activity has consequences to plant populations at the community and ecosystem scale. This article discusses belowground plant communication via root secretion and the resulting ecological significance.
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Ziedan, El-Sayed, Ibrahim Elewa, Mostafa Mostafa und Ahmed Sahab. „Application of Mycorrhizae for Controlling Root Diseases of Sesame“. Journal of Plant Protection Research 51, Nr. 4 (01.10.2011): 355–61. http://dx.doi.org/10.2478/v10045-011-0058-0.
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Application of Mycorrhizae for Controlling Root Diseases of Sesame Vesicular arbuscular mycorrhizae fungi (VAM) was evaluated as a biotic agent for controlling wilt and root-rot diseases of sesame caused by Fusarium oxysporum f. sp. sesami (Zap.) Cast and Macrophomina phaseolina (Moubl) Ashby pathogens can infect sesame plant at any growth stage causing considerable losses of seed yield. Spores of VA mycorrhizae fungi (Glomus spp.) were collected from the soil around the root systems of sesame plants then propagated on roots of Suddan grass (Sorghum vulgare var. sudanese). Under green house and field conditions, two hundreds sporocarps of Glomus spp. were added as a soil drench beside the sesame plant. Glomus spp. (VA mycorrhizae) significantly reduced wilt and root-rot incidence of sesame plants. Lums spp. (VA mycorrhizae) also significantly increased plant morphological characters such as plant height, number of branches and number of pods for each plant. Application of Glomus spp. to protect sesame plants by colonizing the root system, significantly reduced colonization of fungal pathogens in sesame rhizosphere as well as pathogenic activity of fungal pathogens increased lignin contents in the sesame root system were also observed. Furthermore, mycorrhizae treatment provided selective bacterial stimulation for colonization on sesame rhizosphere. These bacteria belonging the Bacillus group showed highly antagonistic potential to fungal pathogens. Application of mycorrhizae together with other biocontrol agent such as Trichoderma viride or Bacillus subtilis significantly effected than individual treatments for controlling these diseases incidences and increasing morphological characters and seed yield of sesame.
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Xue, Allen G. „Biological Control of Pathogens Causing Root Rot Complex in Field Pea Using Clonostachys rosea Strain ACM941“. Phytopathology® 93, Nr. 3 (März 2003): 329–35. http://dx.doi.org/10.1094/phyto.2003.93.3.329.
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Pea root rot complex (PRRC), caused by Alternaria alternata, Aphanomyces euteiches, Fusarium oxysporum f. sp. pisi, F. solani f. sp. pisi, Mycosphaerella pinodes, Pythium spp., Rhizoctonia solani, and Sclerotinia sclerotiorum, is a major yield-limiting factor for field pea production in Canada. A strain of Clonostachys rosea (syn. Gliocladium roseum), ACM941 (ATCC 74447), was identified as a mycoparasite against these pathogens. When grown near the pathogen, ACM941 often was stimulated to produce lateral branches that grew directly toward the pathogen mycelium, typically entwining around the pathogen mycelium. When applied to the seed, ACM941 propagated in the rhizosphere and colonized the seed coat, hypocotyl, and roots as the plant developed and grew. ACM941 significantly reduced the recovery of all fungal pathogens from infected seed, increased in vitro seed germination by 44% and seedling emergence by 22%, and reduced root rot severity by 76%. The effects were similar to those of thiram fungicide, which increased germination and emergence by 33 and 29%, respectively, and reduced root rot severity by 65%. When soil was inoculated with selected PRRC pathogens in a controlled environment, seed treatment with ACM941 significantly increased emergence by 26, 38, 28, 13, and 21% for F. oxysporum f. sp. pisi, F. solani f. sp. pisi, M. pinodes, R. solani, and S. sclerotiorum, respectively. Under field conditions from 1995 to 1997, ACM941 increased emergence by 17, 23, 22, 13, and 18% and yield by 15, 6, 28, 6, and 19% for the five respective pathogens. The seed treatment effects of ACM941 on these PRRC pathogens were greater or statistically equivalent to those achieved with thiram. Results of this study suggest that ACM941 is an effective bioagent in controlling PRRC and is an alternative to existing chemical products.
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Dufresne, Marie, und Anne E. Osbourn. „Definition of Tissue-Specific and General Requirements for Plant Infection in a Phytopathogenic Fungus“. Molecular Plant-Microbe Interactions® 14, Nr. 3 (März 2001): 300–307. http://dx.doi.org/10.1094/mpmi.2001.14.3.300.
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Although plant diseases are usually characterized by the part of the plant that is affected (e.g., leaf spots, root rots, wilts), surprisingly little is known about the factors that condition the ability of pathogens to colonize different plant tissues. Here we demonstrate that the leaf blast pathogen Magnaporthe grisea also can infect plant roots, and we exploit this finding to distinguish tissue-specific and general requirements for plant infection. Tests of a M. grisea mutant collection identified some mutants that were defective specifically in infection of either leaves or roots, and others such as the map kinase mutant pmk1 that were generally defective in pathogenicity. Conservation of a functional PMK1-related MAP kinase in the root pathogen Gaeumannomyces graminis was also demonstrated. Exploitation of the ability of M. grisea to infect distinct plant tissues thus represents a powerful tool for the comprehensive dissection of genetic determinants of tissue specificity and global requirements for plant infection.
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Crow, William T. „Diagnosis of Trichodorus obtusus and Paratrichodorus minor on Turfgrasses in the Southeastern United States“. Plant Health Progress 6, Nr. 1 (Januar 2005): 20. http://dx.doi.org/10.1094/php-2005-0121-01-dg.
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“Stubby-root” nematodes are of agricultural importance as plant-pathogens and as vectors for plant viruses. Two species of stubby-root nematode have been identified as pathogens on warm-season turfgrasses in the southern U.S.: Paratrichodorus minor and Trichodorus obtusus. Both are pathogens of bermudagrass and St. Augustinegrass, with T. obtusus more damaging than P. minor. Methods for distinguishing these species are described that do not require mounting of specimens and can be used at ×100 magnification or less. Accepted for publication 24 November 2004. Published 21 January 2005.
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Ayala-Doñas, Alejandro, Miguel de Cara-García, Miguel Talavera-Rubia und Soledad Verdejo-Lucas. „Management of Soil-Borne Fungi and Root-Knot Nematodes in Cucurbits through Breeding for Resistance and Grafting“. Agronomy 10, Nr. 11 (24.10.2020): 1641. http://dx.doi.org/10.3390/agronomy10111641.
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Soil-borne pathogenic fungi (SBPF) and root-knot nematodes (RKN) co-exist in the rhizosphere and are major pathogens causing root diseases in cucurbits. Current knowledge on soil-borne pathogens of cucurbit crops grown under protected cultivation, their host-pathogen interactions, and mechanisms of resistance has been reviewed. Plant resistance is an effective and sustainable method to control soil-borne diseases and the available resistant cultivars and rootstocks to key soil-borne pathogens are reported. The importance of proper pathogen diagnosis in the right choice of cultivar or rootstock is highlighted because of the specificity in the response of the cucurbit crops to fungal and nematode species and races. Plants protect themselves through common mechanisms of resistance against SBPF and RKN including hardening of their cell walls, pathogenesis-related (PR) proteins, and production of antimicrobial molecules. The activity of some enzymes, such as peroxidases and phenylalanine lyase, is increased after pathogen infection and is higher on SBPF and RKN resistant than susceptible cucurbits. Plant hormones such as salicylic acid, jasmonic acid, and ethylene are involved in the response of cucurbits to SBPF. Most mechanisms of resistance to RKN affect post-infection development of the nematode, which results in a delay or disruption of the life cycle. Traditional and biotechnological tools used for breeding for resistance in cucurbits are described. Grafting is an effective non-host resistance method to control primarily Fusarium wilt but not to control RKN. However, new rootstocks with resistance to both pathogens have been developed recently and their effects on fruit quality and yield stability need additional studies. The impact of grafting on yield in pathogen-infested soils is discussed.
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You, Ming Pei, Jay Ram Lamichhane, Jean-Noël Aubertot und Martin J. Barbetti. „Understanding Why Effective Fungicides Against Individual Soilborne Pathogens Are Ineffective with Soilborne Pathogen Complexes“. Plant Disease 104, Nr. 3 (März 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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Rekah, Yael, D. Shtienberg und J. Katan. „Spatial Distribution and Temporal Development of Fusarium Crown and Root Rot of Tomato and Pathogen Dissemination in Field Soil“. Phytopathology® 89, Nr. 9 (September 1999): 831–39. http://dx.doi.org/10.1094/phyto.1999.89.9.831.
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The spatial distribution and temporal development of tomato crown and root rot, caused by Fusarium oxysporum f. sp. radicis-lycopersici, were studied in naturally infested fields in 1996 and 1997. Disease progression fit a logistic model better than a monomolecular one. Geostatistical analyses and semivariogram calculations revealed that the disease spreads from infected plants to a distance of 1.1 to 4.4 m during the growing season. By using a chlorate-resistant nitrate nonutilizing (nit) mutant of F. oxysporum f. sp. radicis-lycopersici as a “tagged” inoculum, the pathogen was found to spread from one plant to the next via infection of the roots. The pathogen spread to up to four plants (2.0 m) on either side of the inoculated focus plant. Root colonization by the nit mutant showed a decreasing gradient from the site of inoculation to both sides of the inoculated plant. Simulation experiments in the greenhouse further established that this soilborne pathogen can spread from root to root during the growing season. These findings suggest a polycyclic nature of F. oxysporum f. sp. radicis-lycopersici, a deviation from the monocyclic nature of many nonzoosporic soilborne pathogens.
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Toth, Ronald, Deborah Toth, David Starke und David R. Smith. „Vesicular–arbuscular mycorrhizal colonization in Zea mays affected by breeding for resistance to fungal pathogens“. Canadian Journal of Botany 68, Nr. 5 (01.05.1990): 1039–44. http://dx.doi.org/10.1139/b90-131.
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Inbred lines of Zea mays L. (maize) selected for a range of resistances to a variety of fungal pathogens were assayed for percentage colonization by vesicular–arbuscular mycorrhizal fungi. Inbreds that were generally resistant to a number of fungal pathogens had significantly lower levels of vesicular–arbuscular mycorrhizae, matured more slowly, and had larger root systems. Disease-susceptible inbreds had significantly higher levels of mycorrhizal colonization, matured more rapidly, and had smaller root systems. It is uncertain if a general resistance to fungal pathogens or rate of root development, separately or in combination, may have influenced mycorrhizal colonization levels. Irrespective of cause, present breeding programs for disease resistance in maize do influence the plants ability to form mycorrhizae.
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Basu, Muthuramalingam, und Karuppagnaniar Santhaguru. „Impact of Glomus Fasciculatum and Fluorescent Pseudomonas on Growth Performance of Vigna Radiata (L.) Wilczek Challenged with Phytopathogens“. Journal of Plant Protection Research 49, Nr. 2 (01.06.2009): 190–94. http://dx.doi.org/10.2478/v10045-009-0028-y.
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Impact ofGlomus Fasciculatumand FluorescentPseudomonason Growth Performance ofVigna Radiata(L.) Wilczek Challenged with PhytopathogensFusarium oxysporumandRhizoctonia solaniare the major soil-borne pathogens causing growth and yield depression. The present study focused on the ability of fluorescentPseudomonasandGlomus fasciculatumon growth performance ofVigna radiatain pathogen-infested soil. The percent colonization byG. fasciculatumindicated an increase of the presence of fluorescentPseudomonasand a decrease of the presence ofFusarium oxysporumorRhizoctonia solani. However, the reduction of colonization induced pathogen in percent was alleviated by fluorescentPseudomonas. Inoculation with either fluorescentPseudomonasorG. fasciculatumor both induced a significant increase in root and shoot length, plant vigour index, dry weight and total N and P content in V. radiata as compared to uninoculated control. The impact of inoculation was much pronounced in dual inoculated plants in comparison with those inoculated with eitherG. fasciculatumor fluorescentPseudomonas. In contrast, treatment of plants with eitherF. oxysporumorR. solanidecreased the root and shoot length, plant vigour index, dry weight and total N and P content in the test legume. However, in the presence of fluorescentPseudomonasandG. fasciculatum, the adverse effect on the pathogens on growth ofV. radiatawas alleviated.
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Zitnick-Anderson, Kimberly, Luis E. del Río Mendoza, Shana Forster und Julie S. Pasche. „Associations among the communities of soil-borne pathogens, soil edaphic properties and disease incidence in the field pea root rot complex“. Plant and Soil 457, Nr. 1-2 (22.10.2020): 339–54. http://dx.doi.org/10.1007/s11104-020-04745-4.
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Abstract Background and aims Field pea production is greatly impacted by multiple soil-borne fungal and oomycete pathogens in a complex. The objectives of this research were to 1) identify the soil-borne pathogens associated with field pea in North Dakota and; 2) develop prediction models incorporating the occurrence of the soil-borne pathogen communities, soil edaphic properties and disease incidence. Methods Soil and plants were sampled from 60 field pea fields in North Dakota during 2014 and 2015. Plants (1500 across two years) were rated for both root rot and soil-borne pathogens isolated from roots. Soils were analyzed for edaphic properties. Indicator species analysis was used to identify soil-borne pathogen communities. Logistic regression was used to determine associations and develop prediction models. Results Survey results from 2014 and 2015 indicated that the most prevalent soil-borne pathogens identified in field pea fields were Fusarium spp. and Aphanomyces euteiches. Five soil-borne pathogen communities were identified; three of which had statistically significant associations characterized by (1) Fusarium acuminatum, (3) A. euteiches, and (4) Fusarium sporotrichioides. The occurrence of the three communities were associated with clay content, soil pH, Fe2+, and K+. Disease incidence was associated with the presence of either community 1 or 3 and K+. Conclusions The results generated from this research will contribute to the development of management strategies by providing a soil-borne pathogen community prediction tool.
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Yavdoshchenko, M. P., T. M. Pedash, T. V. Girka und S. S. Semenov. „Pathogenic complex and recovery of cereal agrocenoses in the Steppe of Ukraine“. Scientific Journal Grain Crops 6, Nr. 2 (02.03.2023): 153–60. http://dx.doi.org/10.31867/2523-4544/0245.
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Topicality. Changes in weather and climatic conditions affect the formation of pathogenic complexes of grain agrocenoses and the species composition of pathogens, which are typical for the Steppe zone of Ukraine. At the same time, changes in cultivation technologies accompanying the transition to new forms of management also play a significant role in the formation of pathogenic complexes. It is necessary to find out the features of the pathogenic mycoflora formation and plant immunity in order to scientifically substantiate measures to stabilize the phytosanitary state of agro-cenoses at the current stage of grain production. Purpose. To divide into appropriate groups of grain crop diseases in the Steppe zone in terms of the nature of development, harmfulness and hy-drothermal dependence of their pathogens. Materials and Methods. In 1999–2019, we conducted surveys of wheat (winter and spring), rye, barley (winter and spring), oats and maize for disease in-festation in the Northern Steppe of Ukraine according to generally accepted methods of phytopathological research. Results. Over the years of research, we identified 123 pathogens, which caused 135 diseases in grain crops. The most diverse composition of pathogens was observed on wheat and maize, 64 and 55 pathogens, and, 33 and 41 diseases, respectively. It should be noted a wide range for specialization of the widespread pathogens in the Northern Steppe of Ukraine. The pathogens of smut infects generally a certain type of grain crops, rusts are somewhat less specialized. Less specialized parasites, such as fungi from the genera Fusarium, Helminthosporium, Alternaria cause the same type of diseases in several plant species, and some of them affect different plant organs. Thus, among the pathogens of Fusarium root rot of wheat, rye, barley and maize, the fungus Fusarium moniliforme Sheld. was identified. On the maize, in particular, this pathogen caused seedling mold, root and stem rot, cob rot, and grain mold. Conclusions. It was established that the hydrothermal regime can affect the development of diseases not only due to its compliance with the pathogen's requirements, but also affect the resistance of plants. The problem of agrocenosis recovery can be successfully solved by adapting modern intensive technologies of growing grain crops that aimed to optimally utilized ecological resources by plants in the Steppe of Ukraine, and prevent the spread of harmful organisms. Key words: winter wheat, maize, pathogens, diseases, hydrothermal conditions, harmfulness
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Tegg, Robert S., Ross Corkrey, Herdina Herdina, Alan C. McKay, Nigel S. Crump, Rudolf F. de Boer, Tonya J. Wiechel und Calum R. Wilson. „Modeling Pathogen DNA Content and Visual Disease Assessment in Seed Tubers to Inform Disease in Potato Progeny Root, Stolon, and Tubers“. Plant Disease 99, Nr. 1 (Januar 2015): 50–57. http://dx.doi.org/10.1094/pdis-04-14-0337-re.
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Measurement of pathogens on seed tubers is essential for informing likelihood of subsequent potato disease. Here we utilized quantitative PCR assessment of pathogen DNA and visual assessment of disease to measure seed tuber inoculum and used this to model development of disease in potato grown in pathogen-free soil. Analysis by recursive partitioning and modeling using receiver operating curves indicated both abundance of Rhizoctonia solani AG3 and Streptomyces scabies DNA, and disease symptoms associated with these pathogens on seed tubers could predict subsequent disease in progeny tubers and for R. solani, stolons. In contrast, abundance of Spongospora subterranea DNA and disease symptoms on seed tubers were not consistently associated with powdery scab in progeny tubers. The relationship between S. subterranea DNA and seed tuber symptoms on root galling was stronger. Symptomless seed tubers that carried high levels of S. subterranea DNA were also associated with greater root galling than those with low pathogen DNA levels. There was a modest association between root galling and powdery scab in progeny tubers. These results highlight the importance of using certified seed tubers, and demonstrate a statistical tool for measuring the impact of seed tuber-borne inoculum.