Induction of phytoalexins in adzuki bean after inoculation with <Emphasis Type="Italic">Phytophthora vignae</Emphasis> f. sp. <Emphasis Type="Italic">adzukicola</Emphasis>

To identify phytoalexins of adzuki bean elicited in response to attempted infection of Phytophthora vignae f. sp. adzukicola, we isolated compounds from adzuki bean and evaluated their antifungal activity. Seven flavonoids (daidzein, genistein, 2′-hydroxygenistein, coumestrol, dalbergioidin, kievitone, and phaseol) were identified from epicotyls wound-inoculated with a mycelial suspension of an avirulent race of P. vignae f. sp. adzukicola. Of those compounds, kievitone and dalbergioidin accumulated to higher levels in incompatible interactions compared to compatible interactions 48 h after inoculation. Kievitone strongly inhibited the germination of encysted zoospores, and dalbergioidin were slightly suppressive. From these results, we concluded that kievitone and dalbergioidin are phytoalexins in adzuki bean.