Formae speciales differentiation of Phytophthora vignae isolates from cowpea and adzuki bean.

The pathogenicity of 17 isolates of Phytophthora vignae Purss from adzuki beans and 4 isolates from cowpeas was compared. Isolates from adzuki beans were virulent to adzuki beans, but not to cowpeas, while isolates from cowpeas were virulent to cowpeas, but not to adzuki beans. The soluble proteins and isoenzymes patterns of these isolates, compared by zone electrophoresis, showed no qualitative differences between adzuki bean and cowpea isolates. Although the pathogens of both adzuki beans and cowpeas have bean treated as P. vignae, two formae specials are proposed for these two fungi on the basis of their specific pathogenicity: P. vignae f. sp. adzukicola Tsuchiya, Yanagawa et Ogoshi for the former and P. vignae f. sp. vignae Tsuchiya, Yanagawa et Ogoshi for the latter. Furthermore, from differences in pathogenicity to six cultivars of adzuki bean, three races (1, 2 and 3) were recognized within f. sp. adzukicola.