U.S.-Japan cooperative research on the international pathogenic races of the rice blast fungus, Piricularia oryzae Cav., and their international differentials

Abstract

Research studies were conducted in Japan and the United States under a 3-year cooperative project in order to select an international set of rice varieties for differentiating the pathogenic races of Piricularia oryzae. Initially, the 39 varieties comprising the former United States, Japan and Taiwan differentials were used. As the studies progressed, 12 candidate varieties were selected. A total of 59 races were differentiated through use of the 12 varieties. Eight of the 12 candidate varieties were selected as the final set of international differentiating varieties: Raminad Str. 3; Zenith; NP-125; Usen; Dular; Kanto 51; Sha-tiao-tsao-S; and Caloro. Among P. oryzae isolates from several rice-producing countries, 32 international races were characterized.