Stem rot

About: Stem rot is a research topic. Over the lifetime, 2199 publications have been published within this topic receiving 27639 citations.

Sclerotinia sclerotiorum (Lib.) de Bary: biology and molecular traits of a cosmopolitan pathogen.

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.

Potato diseases caused by soft rot erwinias : an overview of pathogenesis

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.

Phytophthora sojae: root rot pathogen of soybean and model oomycete

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