Blast pathogens of wild annual ryegrass (Lolium multiflorum Lam.) in the Shonai District, Yamagata Prefecture, northern Honshu Island, Japan.

Abstract

A total of 27 blast isolates from wild annual ryegrass were evaluated to clarify the pathogenicity of the fungi on plants in the Shonai District of Yamagata Prefecture. After plants were sprayed with individual isolates, 25 of the 26 tested caused compatible-type lesions on commercial annual ryegrass, and 25 of 27 formed the same type of lesions on crabgrass. None formed such lesions on rice. Isolates pathogenic on crabgrass produced pyrichalasin H, the characteristic toxin of the crabgrass blast fungus, and their DNA was amplified by Digitaria-specific primers for PCR. Their RFLP bands for the β-tubulin gene matched those of Pyricularia grisea. The patterns for 2 isolates that were nonpathogenic on crabgrass matched those of P. oryzae. Thus, the wild annual ryegrass blast pathogens consisted of 2 species, P. grisea and P. oryzae, in the Shonai District of Yamagata Prefecture in northern Honshu Island.