Brazil is a host spot of blast disease in winter crops, where reports of severe epidemics in wheat, barley, oat, and triticale are documented. Genotype replacement is the most employed method to their control, but has had limited success due to high pathogen diversity. Sexual recombination is suggested for the diversity of wheat blast pathogen due to high mating ability of isolates, presence of both mating type with even distribution; there is little information on sexual traits of M. oryzae from other hosts. This work employed biological and molecular tools to examined sexual characteristics of M. oryzae associated with blast disease of wheat, barley, oat and triticale. Mating type distribution of 600 isolates of M. oryzae (150 from each of the four hosts) was examined ‘in vitro’ assay in oat meal agar medium with two fertile parental strains collected from wheat; PCR approach employed primers L1/L2 (MAT1-1) and T1/T2 (MAT1-2). Our data showed existence of only one mating type among 150 M. oryzae isolates from barley (MAT1-1), black oat (MAT1-2), and wheat (MAT1-1, but one). Only M. oryzae from triticale showed a 1:1 rate (72:78) supporting hypothesis of sexual recombination in this field. Nevertheless, lab assay showed low mating ability of M. oryzae from all four hosts as no ascospore was formed. Only 16 isolates from barley and 3 from wheat crossed with fertile wheat isolates. Therefore, our study suggest that recombination does not play any role in M. oryzae from these fields, even when a 1:1 mating type distribution was found.

Grant: FAPESP (2017/18587-9)