Molecular Characterization of Mung Bean Germplasm from the USDA Core Collection Using Newly Developed KASP-based SNP Markers

Mung bean [Vigna radiata (L.) Wilczek] is an important, nutritious legume food crop for tropical and subtropical countries with high value in Asia and worldwide potential. However, the genetic improvement of mung bean is slowed by low polymorphism of previous molecular markers, even microsatellites. The goals of this study were to develop Kompetitive Allele Specific Polymerase Chain Reaction (KASP)-based single-nucleotide polymorphism (SNP) markers and use them for characterization of 94 cultivated mung bean genotypes from the USDA originating in 27 countries across 10 regions of the world, all being cultivars rather than wild accessions. We targeted 42 SNPs from previous sequencing and converted them into 20 robust KASP assays. Of these, 18 were polymorphic among the mung bean cultivars, with 38 alleles total and 1.9 alleles per locus average. The polymorphism information content of the newly developed markers ranged from zero for monomorphic markers to 0.375 for the most diverse biallelic polymorphic marker (MBkSNP_ 39) and averaged 0.250 across all loci. Population structure analysis grouped 90% of the accessions into two subpopulations, with 10% belonging to an admixture group, but did not follow geographic origins of the germplasm, suggesting no clear center of origin and blending of the subpopulations. An analysis of molecular variance revealed 22% of genetic variation among subpopulations and 78% within subpopulations. The first two axes of regionwide principle coordinate analysis explained 81.26% variation of total variation, indicating the existence of genetic diversity among groups. The SNP markers of this study can be used in molecular breeding of mung bean and are the first to work with KASP detection.