Identification of a new wheat yellow mosaic virus strain with specific pathogenicity towards major wheat cultivars grown in Hokkaido [Japan]

Yellow mosaic of wheat was first described in Japan in 1927. Its causal agent was identified as wheat yellow mosaic virus (WYMV). In Canada, the virus responsible for a similar disease of wheat was designated as wheat spindle streak mosaic virus (WSSMV). Later, Usugi and Saito reported that WYMV and WSSMV are strains of the same virus differing only slightly in their serological and pathological characteristics. Both WYMV and WSSMV have filamentous particles with two modal lengths of 250-300 and 550-650 nm, and are transmitted by the soil-inhabiting fungus Polymyxa graminis.