Differentiation and phylogenetic relationship among different cultivars of asparagus bean (Vigna unguiculata ssp sesquipedalis) assessed using ISSR markers

Asparagus bean, one of the three subspecies of Vigna unguiculata, has a long cultivation history in China. The genetic diversity was analyzed based on the 66 landraces and cultivars cultivated in China by using ISSR molecular markers, with which 192 amplification loci were obtained 32.3% of them being polymorphic. The genetic differentiation analysis revealed a very high genetic diversity in the Chinese landraces, which confirmed that China is the secondary origin centre of the asparagus bean. The commercial cultivars bred in China were genetically highly homogenous, suggesting that the breeding process has resulted in disappearance of some of the genetic variation. A cluster analysis at 0.17 of Nei genetic distance divided the 66 landraces and cultivars into 9 groups. Their clustering pattern basically matches the phylogeny of those cultivars, and also corresponds to their geographical origin and morphological traits.