The genome of Magnaporthe grisea (Magnaporthe oryzae) 70-15 (MG8) was sequenced by the BROAD Institute. In order to allow comparative analyses with other fungi, a copy of the genome of M. grisea is incorporated into MycoCosm. The following text was copied from the BROAD website:
Magnaporthe oryzae, the causal agent of rice blast disease, is one of the most devasting threats to food security worldwide. Conservatively, each year enough rice is destroyed by rice blast disease to feed 60 million people (Zeigler et al. 1994). Indeed, the Centers for Disease Control and Prevention has recently recognized and listed rice blast as a significant biological weapon. No part of the world is now safe from this disease. It was long thought of as being confirned to developing nations, but over the past decade it has emerged as a serious problem in the United States. A major epidemic occurred in the Southern US following the widespead introduction of the susceptible cultivar Newbonnet (Marchetti 1994).
The impact of this fungus is beginning to be felt in other ways. Certain strains are able to attack other domesticated grasses, including barley, wheat, pearl millet and turf-grass. Limited outbreaks on wheat have been reported in South America (Valent and Chumley 1994). Widespread devastation of golf courses, particularly in the Midwest, where it has been attacking cool season grasses, is of particular concern (Landschoot and Hoyland 1992).
Like many foliar plant pathogens, M. oryzae is well adapted to attack and penetrate its host. All aerial parts of the plant are subject to invasion, but losses are most devastating when the panicle or node at the base of the panicle is infested and killed resulting in loss of grain set (Ou 1985). The infection process is similar to that of many other fungal pathogens and is mediated by the formation of a specialized infection cell, the appressorium (Emmet and Parberry 1975). Although much has been learned, it remains largely a mystery how the emerging germ tube recognizes it is on a suitable surface and sets in motion a series of elaborate development steps that culminate in infection (Dean 1997).
Management of rice blast disease is most precarious (Bonman and MacKill 1988). While in the past, control was mainly through use of expensive and potentially hazardous chemicals (when affordable) the focus has shifted, as it has for most diseases, to more environmentally friendly and potentially less expensive approaches, principally mediated through host resistance. The rice blast genome appears to be quite unstable and in some instances new races appear relatively quickly. A key to developing effective and durable resistance is through a comprehensive understanding of the host-pathogen interaction, which in turn requires a thorough understanding of both the host and the pathogen.
Magnaporthe oryzae is an excellent model organism for studying fungal phytopathogenicity and host-parasite interactions. M. oryzae is a haploid, filamentous Ascomycete with a relatively small genome of ~40 Mb contained in 7 chromosomes (Talbot et al. 1993; Orbach 1996). The majority of fungal pathogens belong to this taxonomic class or exist as related asexual forms (Agrios 1997). M. oryzae is also closely related to the non-pathogen Neurospora crassa, a leading model organism for the study of eukaryotic genetics and biology (Taylor et al. 1993). Unlike many phytopathogenic fungi such as mildews and rusts, the rice blast fungus can be cultured on defined media, facilitating biochemical and molecular analyses. Significantly, early stages of the infection process including germination, appressorium formation and penetration can be studied ex planta (Hamer et al. 1988; Bourett and Howard 1990; Howard and Valent 1996; Dean 1997).
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