Understanding genetic variability in the mungbean (Vigna radiataL.) genepool

Mungbean or green gram (Vigna radiataL. Wilczek) is a major pulse crop of Southeast Asia. This is the most liked pulse in India because of its good palatability, nutritional quality and easy digestibility. It is mainly grown in subsistence farming systems in India. The crop species has evolved in a diverse range of agroclimatic conditions and therefore the local germplasm has rich genetic diversity. However, this diversity has not been explored to identify useful traits and germplasm to utilise in crop improvement programmes. Therefore, a study was performed on 1,232 mungbean accessions using 8 quantitative, 18 qualitative traits and 4 seed morphometric traits to understand genetic diversity of the crop and identify trait-specific germplasm. Wide range of variation was observed for days to flowering, days to maturity, pod length, number of seeds/pod and 100-seed weight. Relative high phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was observed for 100-seed weight, flowering period, seed length and seed breadth. Broad sense heritability (h(2)) analysis indicated that days to 50% flowering, flowering period, days to 80% maturity, 100-seed weight and seed-dimension-related traits are highly suitable for mungbean breeding programmes. Agglomerative hierarchical clustering analysis based on morphological quantitative traits indicates that the diversity in the mungbean germplasm has no significant relationship with respect to their geographical origin. Principal component analysis (PCA) revealed that the first five principal components (PCs) explained 91.4% of total variation. The maximum variance was explained by PC1 (44.61%) followed by PC2 (21.15%). Plotting of observations in two-dimensional space corresponding to PC1 and PC2 revealed wide distribution of accessions, and certain accessions were found associated with variables. The agromorphological variability and its genetic nature revealed from this study may prove very useful in ongoing and future breeding programmes.