Analysis Of Epistasis Among QTLs On Heading Date Based On Multiple Segment Substitution Lines In Rice

Heading date in rice is an important agronomic trait which directly determines the planting district and season,and is also one of complex quantitative traits with interactions among genes.Therefore,to explore the genetic mechaniss of heading date has great theoretical and practical significance.Limited to research materials and methods,epistatic effects can not be efficiently estimated at present.This thesis based on the experimental materials of single segment substitution lines and the methods to construct mapping populations by half diallel crossing,estimated different epistatic components among four Q TLs on heading date which generatedthe main results as follows:1)The SSSLs used in this study were confirmed truly carrying with significant additive and/or dominant effects of QTLs on heading date.O nly was QTL3 with the early-maturing alleles,while the others were late-maturing,with the additive and/or dominant effects ranged from1.7~21.0 that appeared significant differences between the late season and the early season.2)Epistatic interrections among multiple Q TLs on heading date exsited frequently.The significant epistatic components for dual Q TLs,triple QTLs and quadruple QTLs accounted for74.4%,64.2%and 48.8% respectively.3)Epistatic interactions played a important role on heading date.67.5% epistatic estimation exhibited positiveeffects,and the effectvalues of dual Q TLs,triple QTLs and quadruple QTLs ranged from three to thirty days,from fiveto twenty-fiveday and from ten to thirty-four day srespectively.which significantly differed across the two cropping seasons.4)The previous two paths of flowering confirmed again.O ne path was Hd1,the other was the path by Ehd1.All genes formed a photosensitive network structure associated each other.5)The QTLs on heading date appeared pleiotropic effects or linkages with QTLs on other traits,The QTLs on heading date and their interactions were related to another traitsat least.Thecorrelations between of different Q TLs led to those between of genotypes and between phenotypes.6)Some combinations of QTLs could be considered as components for breeding by designs,Those such as Q TL1/QTL4,QTL1/QTL2/Q TL3,QTL5/QTL2/QTL3,QTL5/QTL2/Q TL1,QTL1/QTL2/QTL3/Q TL4,QTL5/Q TL2/QTL3/Q TL1,which appeared earlymaturing and/or highyield,could be applied to molecular pyramiding breeding.The results would contribute to reveal the genetic mechanisms ofheading date in rice,and excavate genetic materials for polymer breeding,and then provid the bases and components for molecular design breeding in rice.