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Distribution of Phytophthora vignae f. sp. adzukicola Races in Adzuki Bean Fields in Hokkaido, Japan

Information on the distribution of races of Phytophthora vignae f. sp. adzukicola in Hokkaido, Japan, is important for the management of Phytophthora stem rot of adzuki bean. In all, 107 isolates of P. vignae collected between 1999 and 2001 from 63 fields were evaluated for patho-type using four differentials. In this study, 26, 52, and 28 isolates were identified as races 1, 3, and 4, respectively. One isolate was nonpathogenic on the differentials. Race 4 isolates had the broadest host range and were widely distributed in the adzuki bean-producing regions, especially in central and western Hokkaido. Additional management measures for P. vignae are required if the cultivation area of an agronomically promising cultivar like cv. Syumari (susceptible to race 4) is to be increased.