Strategies for the utilization of the USDA mung bean germplasm collection for breeding outcomes

Global and midwestern U.S. agriculture requires diversification and new sources of protein for sustainable crop production. Mung bean [Vigna radiata (L.) R. Wilczek] as a legume crop has a long cultivation history in Asia; however, its potential lays hitherto underexplored in the United States. As a first step towards exploring mung bean for crop diversification in northern latitudes, crop germplasm centers that harbor worldwide crop resources need to be used. This study explores the potential of mung bean in the U.S. northern latitudes through the utilization of the USDA germplasm resources. Complete collection of USDA mung bean germplasm was screened under Iowa field conditions in 2017, to shortlist 482 accessions to create an Iowa mung bean panel. The Iowa mung bean panel was further characterized for field adaptability traits in 2018 and 2019 and genotyped using genotype-by-sequencing (GBS) to conduct association mapping of important traits. Genetic markers were identified for both quantitative trait (days to flowering [DTF], plant height [PHT], leaf drop at maturity [LDMS], 100-seed weight [SDWT], and Fusarium wilt score [WS]) and qualitative traits (seed color [SC], seed-coat texture [ST], hypocotyl color [HC], and pod color [PC]). We report FERONIA, a known flowering-pathway gene, as the candidate gene for the quantitative trait locus (QTL) with largest effect on DTF. In addition, important epistatic interactions were also uncovered for WS and SDWT. Further, accessions with desirable magnitude of traits were identified as potential parents. Diversity analyses and field phenotypic data indicate potential for mung bean improvement to suit midwestern U.S. cultivation.