Genetic Dissection Of Grain Yield And Its Component Using Selected Introgression Lines In Rice (Oryza Sativa L.)

Rice is the most important food for us. Great success of genetic and molecular dissection forhigh grain yield have been achieved with the development of molecular marker in rice science 20years ago. Although the development of molecular marker has greatly enhanced our ability tounderstand individual rice genes and their biological roles on rice high GY, it remains a tremendouschallenge facing all plant scientists to determine the relationships among individual rice genes.Furthermore, the separation between QTL mapping and breeding practice always standing the way ofmarker assistant selection in rice breeding.To facilitate breeding for high grain yield potential in rice, two BC3F5 selected introgressionpopulations, derived from two crosses between Feng-Ai-Zhan No.1 (the recurrent parent) and twodonors (Khazar and IR64), were genotyped with 89 and 99 polymorphic SSR markers and evaluatedin 4 environments (early season, late seasons, late season with drought stress in Guangzhou and,single season in Wuhan) to further study QTL underlying grain yield (GY), panicle number per plant(PNP), filled grain number per panicle (GNP) and 1000 grain weight (TGW) on the level of geneticnetwork, and study the interaction between genotype and environment as well. 2 major result werederived as follow and pave the way of molecular breeding for rice high grain yield.First, elite rice lines of high grain yield and of high grain yield combining with drought tolerancewere developed. There were 24, 11, 5, and 19 lines with higher grain yield than the recurrent parentsignificantly in population FAZ/Khazar in respective early season, late season, late season withdrought stress in Guangzhou, and single season in Wuhan progeny test, while there were 17, 9, 11,and 14 lines were selected from population FAZ/IR64 for there significant high grain yield.Nevertheless, there were 33 lines in total out-yielding their recurrent parent in at least 2environments.Second, QTL underlying GY, PNP, GNP, KGW, plant height (PH), and heading date (HD) byχ2-test based on genetic hitch-hiking and one-way ANOVA were detected, and interactions betweengenotype and environment were studied.Selection on GY and its component within or among ILs can shift the population mean value toanother level, the variation and heterozygosity of selected lines, however, did not varied, in otherword, there wasn't genetic diversity exhausting observed after selection within or among ILs. Sothere was a conclusion that it was the interaction between genotype and environment that maintainthe genetic diversity in plant.Converge the result ofχ2-test and one-way ANOVA in 4 environments there were 25 and 32, 22and 27, 20 and 30, 29 and 23 and, 23 and 24 QTL underlying GY, PNP, GNP, KGW, PH, and HD inpopulation FAZ/Khazar and FAZ/IR64 respectively, and there were 18, 14, 14, 11, 14, and 12 QTL were detected from both 2 populations. These QTL were not separated along the chromosomesrandomly but in cluster. 19 interesting genomic regions on chromosomes were noted, which wereassociated with GY and 3 of its components. Detailed analyses indicated that both pleiotropy andlinkage could be responsible for the observed associations.Third, according to molecular biology and population genetics, and basing on pairwise linkagedisequilibrium analyses we revealed the network underlying GY, PNP, GNP, and KGW in differentenvironments using extreme lines in population FAZ/Khazar and FAZ/IR64. The results indicate thatQTL were affected positively or negatively by each other in a complex network of hierarchy. Manyloci were significantly associated with target traits by one-way ANOVA, as conformed the reliabilityof these genetic networks. Many loci were heterozygosity which implied that dominant oroverdominant effect were responsible for high grain yield and heterosis.Genetic network of the same trait in different environment were overlapped which indicate theinteraction between genotype and environment on a depth. In rice high grain yield breeding practicemarker assistant selection on branches existed in different environments in the network can result instability lines, while selected on branches only presented in one environment in the network candevelop specific high grain yield lines.Our results provided useful information to our current understanding of the genetic basis of GYin rice, and a new strategy of using IL populations for both QTL discovery and breeding.