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Stem rot

About: Stem rot is a(n) research topic. Over the lifetime, 2199 publication(s) have been published within this topic receiving 27639 citation(s). more


Journal ArticleDOI: 10.1111/J.1364-3703.2005.00316.X
Abstract: Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen causing disease in a wide range of plants. This review summarizes current knowledge of mechanisms employed by the fungus to parasitize its host with emphasis on biology, physiology and molecular aspects of pathogenicity. In addition, current tools for research and strategies to combat S. sclerotiorum are discussed. Taxonomy: Sclerotinia sclerotiorum (Lib.) de Bary: kingdom Fungi, phylum Ascomycota, class Discomycetes, order Helotiales, family Sclerotiniaceae, genus Sclerotinia. Identification: Hyphae are hyaline, septate, branched and multinucleate. Mycelium may appear white to tan in culture and in planta. No asexual conidia are produced. Long-term survival is mediated through the sclerotium; a pigmented, multi-hyphal structure that can remain viable over long periods of time under unfavourable conditions for growth. Sclerotia can germinate to produce mycelia or apothecia depending on environmental conditions. Apothecia produce ascospores, which are the primary means of infection in most host plants. Host range: S. sclerotiorum is capable of colonizing over 400 plant species found worldwide. The majority of these species are dicotyledonous, although a number of agriculturally significant monocotyledonous plants are also hosts. Disease symptoms: Leaves usually have water-soaked lesions that expand rapidly and move down the petiole into the stem. Infected stems of some species will first develop dark lesions whereas the initial indication in other hosts is the appearance of water-soaked stem lesions. Lesions usually develop into necrotic tissues that subsequently develop patches of fluffy white mycelium, often with sclerotia, which is the most obvious sign of plants infected with S. sclerotiorum. more

Topics: Sclerotinia sclerotiorum (72%), Sclerotinia (59%), Sclerotium (54%) more

729 Citations

Open accessJournal ArticleDOI: 10.1016/J.MICRES.2004.08.004
Abstract: Although plant growth-promoting rhizobacteria (PGPR) have been reported to influence plant growth, yield and nutrient uptake by an array of mechanisms, the specific traits by which PGPR promote plant growth, yield and nutrient uptake were limited to the expression of one or more of the traits expressed at a given environment of plant-microbe interaction. We selected nine different isolates of PGPR from a pool of 233 rhizobacterial isolates obtained from the peanut rhizosphere on the basis of ACC-deaminase activity. The nine isolates were selected, initially, on the basis of germinating seed bioassay in which the root length of the seedling was enhanced significantly over the untreated control. All the nine isolates were identified as Pseudomonas spp. Four of these isolates, viz. PGPR1, PGPR2, PGPR4 and PGPR7 (all fluorescent pseudomonads), were the best in producing siderophore and indole acetic acid (IAA). In addition to IAA and siderophore-producing attributes, Pseudomonas fluorescens PGPR1 also possessed the characters like tri-calcium phosphate solubilization, ammonification and inhibited Aspergillus niger and A. flavus in vitro. P. fluorescens PGPR2 differed from PGPR1 in the sense that it did not show ammonification. In addition to the traits exhibited by PGPR1, PGPR4 showed strong in vitro inhibition to Sclerotium rolfsii. The performances of these selected plant growth-promoting rhizobacterial isolates were repeatedly evaluated for 3 years in pot and field trials. Seed inoculation of these three isolates, viz. PGPR1, PGPR2 and PGPR4, resulted in a significantly higher pod yield than the control, in pots, during rainy and post-rainy seasons. The contents of nitrogen and phosphorus in soil, shoot and kernel were also enhanced significantly in treatments inoculated with these rhizobacterial isolates in pots during both the seasons. In the field trials, however, there was wide variation in the performance of the PGPR isolates in enhancing the growth and yield of peanut in different years. Plant growth-promoting fluorescent pseudomonad isolates, viz. PGPR1, PGPR2 and PGPR4, significantly enhanced pod yield (23-26%, 24-28% and 18-24%, respectively), haulm yield and nodule dry weight over the control in 3 years. Other attributes like root length, pod number, 100-kernel mass, shelling out-turn and nodule number were also enhanced. Seed bacterization with plant growth-promoting P. fluorescens isolates, viz. PGPR1, PGPR2 and PGPR4, suppressed the soil-borne fungal diseases like collar rot of peanut caused by A. niger and PGPR4 also suppressed stem rot caused by S. rolfsii. Studies on the growth patterns of PGPR isolates utilizing the seed leachate as the sole source of C and N indicated that PGPR4 isolate was the best in utilizing the seed leachate of peanut, cultivar JL24. Studies on the rhizosphere competence of the PGPR isolates, evaluated on the basis of spontaneous rifampicin resistance, indicated that PGPR7 was the best rhizoplane colonizer and PGPR1 was the best rhizosphere colonizer. Although the presence of growth-promoting traits in vitro does not guarantee that an isolate will be plant growth promoting in nature, results suggested that besides ACC-deaminase activity of the PGPR isolates, expression of one or more of the traits like suppression of phytopathogens, solubilization of tri-calcium phosphate, production of siderophore and/or nodulation promotion might have contributed to the enhancement of growth, yield and nutrient uptake of peanut. more

Topics: Rhizobacteria (55%), Rhizosphere (53%), Collar rot (52%) more

685 Citations

Journal ArticleDOI: 10.1046/J.0032-0862.2001.SHORT
M. C. M. Pérombelon1Institutions (1)
01 Feb 2002-Plant Pathology
Abstract: Three soft rot erwinias, Erwinia carotovora ssp. carotovora, E. carotovora ssp. atroseptica and E. chrysanthemi are associated with potatoes causing tuber soft rot and blackleg (stem rot). Latent infection of tubers and stems is widespread. As opportunistic pathogens, the bacteria tend to cause disease when potato resistance is impaired. Pathogenesis or disease development in potato tubers and stems is discussed in terms of the interaction between pathogen, host and environment, microbial competition and recent findings on the molecular basis of pathogenicity. Emphasis is placed on the role of free water and anaerobiosis in weakening tuber resistance and in providing nutrient for erwinias to multiply. Blackleg symptoms are expressed when erwinias predominate in rotting mother tubers, invade the stems and multiply in xylem vessels under favourable weather conditions. Soft rot erwinias tend to out-compete other bacteria in tuber rots because of their ability to produce larger quantities of a wider range of cell wall-degrading enzymes. However, despite extensive studies on their induction, regulation and secretion, little is known about the precise role of the different enzymes in pathogenesis. The putative role of quorum-sensing regulation of these enzymes in disease development is evaluated. The role certain pathogenicity-related characters, including motility, adhesion, siderophores, detoxifying systems and the hrp gene complex, common to most bacteria including symbionts and saprophytes, could play in latent and active infections is also discussed. more

Topics: Stem rot (54%), Pectobacterium atrosepticum (52%)

466 Citations

Journal ArticleDOI: 10.1111/J.1364-3703.2006.00373.X
Brett M. Tyler1Institutions (1)
Abstract: SUMMARY Phytophthora sojae is an oomycete pathogen of soybean, classified in the kingdom Stramenopiles It causes ‘damping off’ of seedlings and root rot of older plants, with an annual cost worldwide of $1–2 billion Owing to its economic importance, this species, along with P infestans, has been developed as a model species for the study of oomycete plant pathogens It is readily transformed with DNA enabling over-expression and silencing of selected genes, genetic maps have been constructed and large expressed sequence tag sequence libraries have been developed A draft genome sequence has recently been completed This review briefly summarizes current information about the pathogenicity, evolution, molecular biology and genomics of P sojae Taxonomy: Phytophthora sojae (Kaufman & Gerdman): superkingdom Eukaryota; kingdom Stramenopila; phylum Oomycota; class Peronosporomycetidae; order Pythiales; family Pythiaceae; genus Phytophthora Host range: Soybean is the only economically important host Several species of lupins have also been reported as hosts Disease symptoms and signs: All parts of the soybean plant are susceptible to infection by P sojae, from germinating seedlings to mature plants In the field, P sojae causes damping off of soybean seedlings and a root and stem rot of established plants Leaves can be infected in the field as a result of rain splash or by deliberate inoculation in the laboratory Damping off can affect germinating seeds or emerged seedlings and is most severe when the spring is very wet and warm (25–30 °C) Established plants can become infected when the soil is wet for extended periods, especially if the soil is poorly drained Both the cortex and the vascular tissue are colonized by P sojae, and the infection can spread rapidly along the vascular tissues in susceptible cultivars Useful websites: http://pmgnvbivtedu, http://phytophthoravbivtedu, http://wwwjgidoegov/Psojae, http://wwwjgidoegov/Pramorum, http://wwwpfgdorg, http://pamgovbivtedu, http://soyvbivtedu, https://wwwvbivtedu/article/articleview/78, http://plantpathosuedu/faculty/dorrancephp more

Topics: Phytophthora sojae (67%), Phytophthora (56%), Root rot (55%) more

332 Citations

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Topic's top 5 most impactful authors

Timothy B. Brenneman

18 papers, 310 citations

Craig R. Grau

15 papers, 583 citations

Martin J. Barbetti

13 papers, 371 citations

Brian W. Diers

10 papers, 594 citations

Jin-Hyeuk Kwon

10 papers, 40 citations

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