Studies On The Physiologic Races Of The Rice Blast Fungus, Piricularia Oryzae Cav. Part I

Abstract

1) Nineteen races of Piricularia oryzae Cay., were characterized from 293 isolates of the blast fungus obtained during 1964-1966. Among them., 17 races representing 259 isolates-showed the pathogenic patterns which had already been detected. The two newly chara eterized races (races 26 and 27) showed T race group patterns. Race 24 was the most prevalent race in 1964, being encountered 64 times. Another prevalent races of the period were races 17, 2, 3, 26, and 21. 2) Nine isolates representing six U.S. races and eleven isolates representing eight Japanese races were tested for their pathogenicity on the Taiwan differentials. Among the 16 Taiwan differentials, indica type varieties seemed more valuable as the differentials for the U.S. races than the japonica type varieties. Isolates of the same Japanese races did not give identical reactions on the Taiwan differentials. The pathogenic patterns on the Taiwan differentials, induced by Japanese race C-1 (Ken 60-19), N-1 (Hoku 373), N¡X4 (Ina-168) and N¡XS (Naga 61-14) were identical to those by Taiwan race 23, 22, 24 and 26, respectively.