New Sources of Resistance to Cadophora gregata f. sp. adzukicola and Fusarium oxysporum f. sp. adzukicola in Vigna spp.

Adzuki bean brown stem rot (BSR), caused by Cadophora gregata f. sp. adzukicola, and adzuki bean Fusarium wilt (AFW), caused by Fusarium oxysporum f. sp. adzukicola, are serious problems in Hokkaido, Japan, and have been managed using cultivars with multiple resistance. However, a limited number of adzuki bean varieties are resistant to these pathogens because of the frequent appearance of new races; thus, new sources of resistance have been sought in related Vigna spp., particularly in the section Angulares to which adzuki bean belongs. An analysis of selected Vigna accessions (JP81231 to JP235420) conserved in the Genebank of the National Institute of Agrobiological Sciences, Tsukuba, Japan, revealed wide variation in resistance spectra and resistance combinations, and eight disease response groups (A to H) were identified. Four of eight were newly detected response groups, suggesting the existence of novel resistance genes. Of 252 accessions from 26 species, 28 accessions in Vigna angularis var. nipponensis, V. hirtella, V. minima, and V. tenuicaulis (section Angulares) from group D, which were cross-compatible with adzuki bean, are expected to be potential sources of multiple resistance genes. They were resistant to all races of BSR and AFW pathogens examined.