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Poster: Diseases of Plants: New & Emerging Diseases


Wheat blast is caused by multiple Pyricularia species, including Pyricularia graminis-tritici sp. nov.
V. CASTROAGUDIN (1), S. Moreira (2), D. Pereira (3), S. Moreira (4), P. Brunner (3), J. Maciel (5), P. Crous (6), B. McDonald (3), E. Alves (7), P. Ceresini (4) (1) University of Sao Paulo State, Brazil; (2) Federal University of Lavras, Brazil; (3) Insti

Presently, Pyricularia oryzae pathotype Oryza (Po-O) is considered the widely distributed rice blast pathogen, whereas P. oryzae pathotype Triticum (Po-T) is the South American wheat blast pathogen. In this study, we investigated whether Po-O and Po-T were distinct at species level. We also described a new Pyricularia species causing blast on several Poaceae, including wheat, from Brazil. Bayesian phylogenetic analyses were conducted on 10 genes from an extensive sampling (N = 128) of populations of Pyricularia adapted to rice, wheat and other Poaceae. Isolates were grouped into two major clusters (Clusters I and II, P=0.99). Cluster I contained isolates from wheat and another Poaceae (P=0.98). Cluster II was sub-divided in three clades (P>0.75). Clades 1 and 2 grouped wheat-derived isolates, and Clade 3 contained rice-derived isolates. The Clusters I and II corresponded to two distinct species: Pyricularia graminis-tritici sp. nov. (Pgt), newly described here, and Pyricularia oryzae (Po). The clades of Po concurred with Po-T and Po-O, and were not distinct at species level. Among species, morphological differences were not recorded; however, a distinctive pathogenicity spectrum was observed. Pgt and Po-T were highly virulent on wheat, barley, signal grass, and oats. Po-O was highly virulent on rice, wheat, barley, and oats, but not on signal grass. We demonstrated that blast disease on wheat and other Poaceae from Brazil is caused by multiple Pyricularia species.