Variations in Seed Yield and Related Traits in Onion (Allium cepa L.) Germplasm Collections

Knowledge of genetic variations is important for the development of efficient breeding programs in onion. The objective of this study was to evaluate seed yields and related traits in 80 onion germplasms, and to select the best accessions for breeding and seed production programs. Among the eleven traits studied, seed yield showed the highest variation (64.1%), followed by the number of scapes center dot plant(-1) (42.8%). Among the 80 accessions evaluated, 90% bolted within the range of 131.0 to 160.0 days and 20% showed more than 50% sterile male plants. The number of scapes center dot plant(-1) and the scape height showed a highly significant (p < 0.01) positive correlation with the seed yield. Based on the eleven traits, a cluster analysis classified 80 germplasms into four groups, clusters 1, 2, 3 and 4, which contained 22, 50, six and two accessions, respectively. Cluster 2 accessions produced a higher average seed yield (12.8 g center dot plant(-1)) than clusters 1, 3 and 4. Clusters 2 and 1 had the highest number of accessions (12 and 3, respectively) and consisted of more than 50% sterile male plants. A principal component analysis (PCA) revealed that the first five principal components (PCs) explained 75.82% of the total variation. Days to 50% flowering, seed yield, days to flowering initiation, seed size, and scape height accounted for 28.53% of the total variation in PC1, whereas the scape diameter, days to bolting, 1,000 seed weight, and days to flowering contributed to 19.94% in PC2. Thus, the phenotypic characterization of onion germplasms may provide the best insights to the breeders for the selection of potential accessions in cultivar development and seed production programs.