Strategies for the utilization of USDA mungbean germplasm collection for breeding outcomes

Global and mid-west U.S. agriculture requires diversification and new sources of protein for sustainable crop production. Mungbean as a legume crop has a long cultivation history in Asia; however, its potential lays hitherto underexplored in the U.S. As a first step towards exploring mungbean for crop diversification in northern latitudes, crop germplasm centers that harbor worldwide crop resources need to be utilized. This study explores the potential of mungbean in the U.S. northern latitudes through the utilization of the United States Department of Agriculture (USDA) germplasm resources. Complete collection of USDA mungbean germplasm was screened under Iowa field conditions in 2017, to shortlist 482 accessions to create an Iowa mungbean panel. The Iowa mungbean 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 traits - 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 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 indicates potential for mungbean improvement to suit mid-western U.S. cultivation.