Utilization of natural hybridization and intra-cultivar variations for improving soybean yield, seed weight, and agronomic traits

Soybean (Glycine max) is a highly self-pollinated species, but cross-pollination occasionally occurs and variations within cultivars can be observed under certain conditions. To explore the potential uses of natural hybridization and intra-cultivar/advanced line variations, 78 of breeding lines derived from the segregants of natural hybridization and the intra-cultivar/line variations and their 17 source cultivars/lines were evaluated over four crop seasons for yield, seed weight, and other agronomic traits. All the lines were also genotyped using BARCSoySNP6K assays to compare the genetic similarities between the new lines and the source genotypes. Analysis of variance results indicated that genotypic differences, year effects, and genotype × year interactions were significant for all the traits. The broad-sense heritability of the traits was estimated to be 67.22%–98.80%, suggesting that the traits were mainly affected by genetic factors. Compared with the source materials, yield of 34 breeding lines exceeded by >5%, and 17 of them had yield increases of 11.85%–41.59%. Seed weight increased significantly in 24 lines, and 11 lines showed improvements in both seed weight and yield, although there was a negative correlation between these two traits. In addition, 36 and 29 lines showed a shortened period of flowering and maturity, respectively. Plant height of 20 lines decreased by >8.5 cm. Genotypic matching rate between the new lines and the source materials varied from 48.86% to 99.90%. These results demonstrated that both segregations resulting from natural crossing and intra-cultivar/line variations could be used to improve important traits in soybean.