Plant & Animal Genomes XIV Conference Plant & Animal Genomes XIV ConferenceJanuary 14-18, 2006
Town & Country Convention Center
San Diego, CA
Magnaporthe grisea is a species complex that includes six or more species, some as yet undescribed. The M. grisea genome initiative has enormously expedited resolution of these taxonomic issues. Rigorous phylogenetic analysis of multi-locus DNA sequencing aimed at identifying divergence at genus, species, and intra-species haplotype levels now tells us exactly what the rice blast fungus is. It is Magnaporthe oryzae, amply distinguished as a monophyletic clade from M. grisea. M. oryzae comprises a set of multi-locus haplotypes, each associated with only one host. Barley remains an exception, with a major, ancestral rice haplotype also recovered from this host. There are two ancestral rice haplotypes that are sampled at high frequency and have broad geographical distributions. All rice haplotypes appear to be asexual and the distribution of mating types and three AVR genes among the haplotypes will be discussed. The phylogenetic relationships of haplotypes on all hosts sampled provide important clues for crosses that should be made to tease out the genetics of host specificity in the rice blast system. There are clues to working out the origins of the epidemic on wheat, as well as that on turf. It is clear that at genus level, Magnaporthe is typified by a species of Gaeumannomyces and will require conservation with a newly designated type species. A synopsis of species comprising the M. grisea complex will be presented as a work-in-progress.