Analysis Of Epistasis Among QTLs On Heading Date And Yield-related Traits In Rice

Rice(Oryza sativa L.)is one of the most important food crops,and its yield relates to food security,which is the fundamental of human existence.Heading date and yield related traits are important agronomic traits.Different heading date determines the growth environment and planting mode of rice,which is the guarantee of the ideal yield of rice.Different yield related traits directly affect the yield.Epistasis is an important genetic component of complex quantitative traits and plays an important role in rice heading date and yield related traits.In this study,single segment substitution lines were used as experimental materials to culture multiple segment pyramiding lines for analysis of epistasis on heading date and yield-related traits among QTL in rice.The main results are as follows:(1)The five single segment substitution lines that carried with QTL on heading date were divided into three types of early-ripening QTL(OsMADS50),medium-ripening QTL(those with small effects,Ehd1-1 and Hd1)and late-ripening QTL(DTH8 and Hd3a-1).These QTL were consistent in effect directions but different in effect sizes between the early season and the late season.Each single segment substitution line was related to at least 2 yield-related traits.(2)The additive effects of polymerization lines for heading date QTL were significant and showed mainly positive.With the increase of QTL numbers polymerized,the aggregation effects would increased gradually.The smallest and the largest estimations for QTL effects on heading date were-12.6d on line DTH8/Hd3a-1 and 39.0d on line Ehd1-1/Hd3a-1///OsMADS50 occured in the early season,respectively.Five heading date genes were regulated by each other.Each polymerization line was related to at least 2yield-related traits.(3)The epistases among QTL on heading date and yield-related traits were one ofimportant and universal genetic components,mainly with negative effects.The negative epistases involved at least in one positive QTL participated in,while the positive epistases one negative QTL.There was no direct correlation between the epistatic effects and the participation QTL effects in size,and it was possible to have specific interaction effects on QTL combinations regardless of the effects of QTL themselves.This study indicated that the variations on heading date and yield-related traits in these research materials were mainly caused by different genotypes.Some common features of epistases were detected as one of ubiquitous and important genetic components with different effects in directions and in sizes,opposite direction and larger effects compared with the addditives,and different interaction effects among dual-,tri-and tetra-QTLs.These conclusions were helpful to deepen the knowledge of the genetic model,and provided bases and materials for the design breeding on heading date and yield-related traits.