Identification and validation of an over-dominant QTL controlling soybean seed weight using populations derived from Glycine max x Glycine soja

Heterosis, or hybrid vigour, has been used to improve seed yield in several important crops for decades and it has potential applications in soybean. The discovery of over-dominant quantitative trait loci (QTL) underlying yield-related traits, such as seed weight, will facilitate hybrid soybean breeding via marker-assisted selection. In this study, F-2 and F-2:3 populations derived from the crosses of Jidou 12' (Glycine max)xZYD2738' (Glycine soja) and Jidou 9' (G.max)xZYD2738' were used to identify over-dominant QTL associated with seed weight. A total of seven QTL were identified. Among them, qSWT_13_1, mapped on chromosome 13 and linked with Satt114, showed an over-dominant effect in two populations for two successive generations. This over-dominant effect was further examined by six subpopulations derived from Jidou12'xZYD2738'. The seed weight for heterozygous individuals was 1.1- to 1.6-fold higher than that of homozygous individuals among the six validation populations examined in different locations and years. Therefore, qSWT_13_1 may be a useful locus to improve the yield of hybrid soybean and to understand the molecular mechanism of heterosis in soybean.