Genetic variation in cultivated mungbean germplasm and its implication in breeding for high yield

摘要

We evaluated 9 qualitative and 21 quantitative traits in 340 diverse cultivated mungbean accessions collected at AVRDC-the World Vegetable Center, Taiwan to assess the extent and pattern of their diversity with respect to the traits measured. We also estimated broad-sense heritability (H) and expected genetic advance (GA) from selection of major quantitative traits. The germplasm displayed a wide range of diversity for most of the traits evaluated. High genetic variability, moderate to high H and GA were found in yield components, i.e. 100-seed weight, seed weight per plant, and number of pods per plant. Phenology traits such as plant height, days to flowering, and days to maturity also showed high genetic variability and H, while GA was high for plant height but relatively low for days to flowering and days to maturity. Cluster analysis grouped the germplasm into 5 major and 1 minor clusters. In general, germplasm from India and West Asia were present in all major clusters, while those from Southeast Asia and other origins were mainly grouped into one cluster. Principal component analysis revealed that the first three PCs explained 74.9% of the total variation. The variance explained by PC1 was due to the variation in almost all traits. PC2 originated principally from number of pods per plant, number of branches per plant, pod width and seed length. Two-dimensional plots of PCs revealed that mungbeans from India and West Asia were widely distributed with some overlapping, although they could be partially distinguished. Mungbeans from Southeast Asia were differentiated from those from India and West Asia. Since the mungbeans from India have been most frequently and widely employed in breeding programs, we recommend that the germplasm from West Asia be exploited more in cultivar development to enrich the breeding gene pool. The results from this experiment can help mungbean breeders choose the right combinations of parental genotypes carrying the desirable characters.