Epistasis and complementary gene action adequately account for the genetic bases of transgressive segregation of kilo-grain weight in rice

Transgressive segregation is a common phenomenon in plant species. In this study, transgressive segregation for kilo-grain weight (KGW) was observed in a recombinant inbred line (RIL) population derived from the cross between an indica variety, Teqing, and a wide compatible japonica variety, 02428, in three environments. A genetic linkage map with 154 single sequence repeat markers (SSR) was developed. Effects on KGW of quantitative trait loci (QTLs), digenetic epistasis, and their environmental interaction (QE) were determined using a mixed linear model approach. 13 QTLs with additive effects and 8 digenetic interactions involving 16 loci were identified. Eight QTLs were involved in interactions. Two QTLs and one epistasis showed QE. 30.0 and 14.0% of variation was explained by the additive effects and epistasis, respectively, which were much greater than the 4.4% of variation explained by QE. According to the model used, predicted KGW values of extreme phenotypes in the RIL population were very close to their observed values. This indicated that complementary action of additive QTLs and epistasis can adequately account for the important genetic bases of transgressive segregation for KGW in the rice RIL population.