Genetic Effect Of QGS5.1 And QGS5.2 On Grain Weight And Grain Size In Rice

Grain weight and grain size are complex traits that controlled by few major QTL and a large number of minor QTL.Previous studies mainly focused on major QTL,while minor QTL also play an important role in the regulation of important agronomic traits in rice.In this study,QTL analysis for grain weight and grain size were performed using populations derived from the crosses of Teqing/IRBB52.Firstly,QTL mapping for grain yield-related traits in rice were performed using Ti52-2 population which derived from a F₇ plant.Then,the RM18927-RM274 region on chromosome 5 was selected for further study.In addition,QTL for yield related traits and heading date were detected by genome-wide association analysis,and explored the effected of minor QTL in natural population.The main results of the research are as follows:1.QTL analysis for yield-related traits in Ti52-2 population was performed by two years data.Totally 16 QTL were identified,including one QTL for number of panicles per plant,five QTL for number of grains per panicle,seven QTL for 1000 grain weight and three QTL for yield per plant.The qTGW5 was located in RM18927-RM274 region on chromosome 5 and showed the highest additive effect and proportion of phenotypic variance in those QTL.Therefore,this QTL were selected for validation and dissection.2.One plant was selected from Ti52-2,and selfed constructing a F_2:3family for validation of qTGW5.The qTGW5 had significant effects on grain weight and grain number,the IRBB52 allele increased 1000 grain weight by 0.26 g and explaining 33.6%of the phenotypic variation,and decrease the number of grains per panicle by 4.3 with R² of 10.0%.Two NIL-F₂ populations were developed for further validation of qTGW5.The effects of qTGW5 were well validated in those two populations.Then,four NIL-F₂populations covering the qTGW5 region were constructed.Homozygous non-recombinants were selected to develop four sets of NIL.By comparing the heterozygous interval and the results of QTL mapping in those populations,two QTL were separated in this interval.qGS5.1 was delimited into an 1896.4-kb region flanked by RM18865 and Fi25273,and qGS5.2 was located in a 388.9 kb region flanked by Fi27293 and Fi27682.The two QTL had significant effects on grain weight and grain number,and direction of additive for grain weight and grain number was opposite.3.For qGS5.2,Seven NIL-F₂ populations with smaller heterozygous interval were developed and mapped to 68.8 kb interval flanked by Fi27369 and Fi27438.There are six annotated genes in the qGS5.2 region,two of them encode proteins with known functional domains and four annotated genes encode expressed proteins.Among the two genes encoding known functional domains,LOC?Os05g47840 not only had missense mutations between parents,but also showed significant expression differences between NILs.While LOC?Os05g47780 had synonym mutations between parents,and the expression difference is not significant in NILs.Among the four genes encode expressed proteins,all of them showed SNP differences between the two parental lines except for LOC?Os05g47830.We obtained some mutants by gene-editing for these annotated genes,laying foundation for cloning of qGS5.2.4.Genome wide association study was performed to identify loci associated with heading date and yield related traits.More than 170 significant loci were identified under Lingshui and Hangzhou environments.Then,the accessions were subdivided into four groups by the different functional haplotypes of GS3 and GW5.qGS5.1 and qGS5.2were detected respectively in GW5/gw5 group by GWAS.There are significant different in grain length and width by comparing the phenotypic of different haplotypes of LOC?Os05g41760,indicating that the LOC?Os05g41760 may be a candidate gene for qGS5.1.