Proposal of a New Method for Differentiating Races of Pyricularia oryzae Cavara in Japan

Many reports have been published in Japan on the pathogenic specialization of rice blast fungus, Pyricularia oryzae.Especially, Goto and his co-workers1,2) have established the method to identify blast fungus races.Their differential varieties consist of 12 varieties belonging to the following 3 groups.T group (varieties having rice blast resistance genes of indica rice) Te-tep, Tadukan, and Usen C group (varieties having resistance genes of Chinese varieties) Chokoto, Yakeiko, and Kanto 51 N group (other common Japanese varieties) Ishikari-shiroke, Homare-nishiki, Ginga, Norin 22, Aichi-asahi, and Norm 20 According to their method, blast fungus isolates found in Japan are classified into N, C, and T groups.N group races are defined as the races virulent only to N (Japanese) varieties in the differentials.C group races are virulent to C (Chinese), but not to T varieties in the differentials, irrespective of the virulence to N varieties.T group races are virulent to T (indica) varieties, irrespective of the virulence to C and N differentials.Then each race is numbered in the order of the identification in each race group, such as T-1 or C-3.With this procedure, 3 races of T, 9 races of C, and 6 races of N race group have been differentiated until now.This procedure was adopted widely in Japan, and the situation of pathogenic specialization of rice blast fungus in Japan has been clarified1-3).