Blast caused by Magnaporthe grisea ( Pyricularia grisea) is a disease that occurs in many important gramineous plants in Brazil such as rice, wheat, triticale and barley. In 2005, the presence of this disease was reported on black oat ( Avena strigosa) at different locations of Parana state. Due to little information of M. grisea that is infecting this host, this work aimed to characterize it at molecular, sexual and pathogenic level. DNA analysis showed that M. grisea from black oat formed a homogenous and genetic distinct group of its own, different from other hosts, including rice, wheat, triticale and barley. Isolate 15720 was an exception, because it was similar to wheat isolate. There was no sexual compatibility between M. grisea from oat and other tested hosts. In pathogenic terms, isolates of M. grisea from oat infected triticale, wheat, rye, millet, barley, sorghum and rice; cross-inoculation was positive with wheat, triticale, rice and barley.
