Polymerization And Epistatic Analysis Of Genes On Grain Shape Based On SSSL In Rice

High-yield and good-quality varieties in rice are of great significance for food security and meeting human needs.Grain shape is an important agronomic trait,which closely related to yield and quality in rice.It is also one of complex quantitative traits,determined by multiple gene system companying with additive,dominance and epistasis,as well as their interacting with environments.Therefore,studying the genetic mechanism of grain shape has important theoretical and practical significance in rice.This thesis based on the experimental materials of single segment substitution lines in rice and the methods to construct mapping populations by half diallel crossing,estimated different epistatic components in various levels among four genes on grain shape in order to explore genetic patterns and to excavate valuable genes,providing the basis and materals for molecular pyramiding and design breeding.The main results showed as follows.1.The four SSSLs did truly carry with genes on grain shape.In the three seasonal environments,the four SSSLs possessed significant additive effects and partial dominant effects on grain shape traits.Where gene GW5 shortened grain length,and the others extended.All of them involved in multiple traits on grain shape and expressed stably between the early season and late season.2.Significant pyramiding effects appeared among genes on grain shape.All pyramiding lines changed significantly grain length and grain width,excepting for no connection between GW5/gw8 and grain length,between gs3/GW7,gs3/GW5/gw7,gs3/GW5/gw8 and grain width.The lines of gs3/GW7,gs3/gw8,gs3/GW5/gw8,gs3/GW7/gw8 showed the best effects on ratio of grain length to grain width.3.Epistatic interaction existed extensively among genes on grain shape.All of gene combinations generated significant interaction with mostly additive-additive epistasis and involved in multiple traits,which were sensitive to seasonal environments.Epistatic interations among multiple genes seemed more common and exhibited larger effects.4.The feature of epistasis depended on the component genes.Positive epistasis involved at least in one negative genes participaed,and negative epistasis at least one positive gene.Epistasis appeared mainly nagetive effects(ocuppying 72.1%),perhap owing to positive componets of genes.5.The interaction of granular genes had significant pleiotropy.Most of the granular QTL combinations not only affected grain shape,but also at least 4 traits of yield and yield components.The epistasis of gs3/GW5 and gs3/GW5/gw8 increased significantly yield per plant.6.The genetic correlation between traits was closely related to the correlation of genes effects.The genetic correlation between grain length and grain width was caused by additive and dominant effects and no epistasis.While those between grain length,grain width and ratio of grain length to grain width were determined by additive,dominant and epistasis jointly.The results above revealed the genetic mechnism of genes on grain shape and screened out some of valuable pyramiding lines as the basis and materials for molecular breeding by design on grain shape in rice.