Resolving the polyphyletic nature of Pyricularia (Pyriculariaceae)

Species ofPyricularia(magnaporthe-like sexual morphs) are responsible for major diseases on grasses.Pyricularia oryzae(sexual morphMagnaporthe oryzae) is responsible for the major disease of rice called rice blast disease, and foliar diseases of wheat and millet, whilePyricularia grisea(sexual morphMagnaporthe grisea) is responsible for foliar diseases ofDigitaria.Magnaporthe salvinii, M. poaeandM. rhizophilaproduce asexual spores that differ from those ofPyricularia sensu strictothat has pyriform, 2-septate conidia produced on conidiophores with sympodial proliferation.Magnaporthe salviniiwas recently allocated toNakataea, whileM. poaeandM. rhizophilawere placed inMagnaporthiopsis. To clarify the taxonomic relationships among species that are magnaporthe- or pyricularia-like in morphology, we analysed phylogenetic relationships among isolates representing a wide range of host plants by using partial DNA sequences of multiple genes such as LSU, ITS, RPB1, actin and calmodulin. Species ofPyricularia s. str.belong to a monophyletic clade that includes allP. oryzae/P. griseaisolates tested, defining thePyriculariaceae,which is sister to theOphioceraceae, representing two novel families. These clades are clearly distinct from species belonging to theGaeumannomyces pro parte/Magnaporthiopsis/Nakataeageneric complex that are monophyletic and define theMagnaporthaceae. A few magnaporthe- and pyricularia-like species are unrelated toMagnaporthaceaeandPyriculariaceae. Pyricularia oryzae/P. griseaisolates cluster into two related clades. Host plants such asEleusine, Oryza,SetariaorTriticumwere exclusively infected by isolates fromP. oryzae, while some host plant such asCenchrus, Echinochloa, Lolium, PennisetumorZingiberwere infected by differentPyriculariaspecies. This demonstrates that host range cannot be used as taxonomic criterion without extensive pathotyping. Our results also show that the typical pyriform, 2-septate conidium morphology ofP. grisea/P. oryzaeis restricted toPyriculariaandNeopyricularia, while most other genera have obclavate to more ellipsoid 2-septate conidia. Some related genera (Deightoniella, Macgarvieomyces) have evolved 1-septate conidia. Therefore, conidium morphology cannot be used as taxonomic criterion at generic level without phylogenetic data. We also identified 10 novel genera, and seven novel species. A re-evaluation of generic and species concepts withinPyriculariaceaeis presented, and novelties are proposed based on morphological and phylogenetic data.