Qtl-based Study Of Relationship Between Rice Quality And Grain Yield Of Indica Rice

Currently,high yield and quality is one of important aims for rice hybrid breeding. A set ofrecombinant inbred line (RIL) population characterized by a relative narrow range of heading date anddeveloped from crosses between Teqing and IRBB lines was utilized to analyze the genetic relationshipbetween rice quality involving13indexes and6grain yield-related traits of indica rice with theassistance of molecular linkage map and phenotypic data. Theoretically, the effect of ecologicalenvironment on assay results due to various heading date among the lines was diminished, as a result,the genetic relationship between rice quality and grain yield was reflected objectively.In this study, a total of7chromosomal regions related to both rice quality and grain yield weredetected. They were mainly distributed on chromosome3,5,6,7,8and10, on which QTLsconditioning rice quality and grain yield were clustered together. Surveying the additive directions ofthese QTLs, we found that alleles for increasing rice quality and grain yield were often from differentparents. That is, grain yield were improved due to a certain multi-function region followed bydeleterious effects on rice quality. This may be the main cause for cultivating some elite agronomictraits at the expense of deleterious agronomic traits, that is, genetic drag in rice hybrid breeding practice.RM15139-RM16region on chromosome3: QTLs for4grain yield-related traits including1000-grain weight (TGW), number of grains per panicle (NGP), number of spikelets per panicle (NSP)and spikelet fertility (SF) were detected as well as QTLs for rice quality involving rice milled quality,appearance quality and grain shape in this region. Allele for increasing TGW in this region was fromIRBB while the enhancing alleles of NGP and NSP were from Teqing, which means that this regionincreased TGW with NGP and NSP decreased simultaneously. QTLs conditioning brown rice ratio(BRR), grain length (GL), ratio of grain length to grain width (LWR), percentage of chalky grain (PCG),degree of chalkiness (DC) and the endosperm transparency (ET) were also detected in this region andall QTLs had the enhancing alleles from IRBB, however, QTLs detected in this region for head riceratio (HRR) and grain width (GW) both had the enhancing alleles from Teqing.RM15139-RM16region on chromosome5: QTLs for TGW and SF were the only two grainyield-related QTLs detected in this region and the enhancing alleles were from Teqing and IRBB,respectively. QTLs detected for rice quality involved3aspects including rice milled quality, appearancequality and grain shape in this region. This region increased TGW, DC, BRR, milled rice ratio (MRR),GW and PCG with SF, GL, LWR and ET decreased simultaneously.Wx region on chromosome6: In additional to3QTLs conditioning3indexes for cooking andeating quality respectively were detected in this region, QTL for GW, TGW, BRR, MRR and chalkinesswere also detected in this region. All QTLs except QTL for gel consistency (GC) had enhancing allelesfrom Teqing.Alk region on chromosome6: QTLs conditioning alkali-spread score (ALK), GC, NGP and NSPwere detected in this region and all QTLs except QTL for ALK had enhancing alleles from Teqing. RM70-RM18region on chromosome7: QTLs conditioning NSP, BRR, ET and amylose content(AC) were detected in this region and all QTLs except QTL for NSP had enhancing alleles from IRBB.RM5647-RM22755region on chromosome8: In our study, the short arm of chromosome8was amultifunction region and controlled7rice traits including NGP, NSP, SF, GW, LWR, BRR and PCG.All QTLs except QTLs for LWR and SF had enhancing alleles from Teqing.RM6100-RM3123region on chromosome10: QTLs conditioning TGW, PCG, DC, BRR, GW andET were detected in this region and all QTLs except QTL for ET had enhancing alleles from Teqing.Additionally, a total of29couple epistatic QTLs involving with all chromosomes exceptchromosome1were detected in this study. These epistatic QTLs had a relative small genetic effect andthe phenotypic variation explained by them was often under1%. One locus usually interacted withmany loci and generated genetic effects, for example, main-effect QTL qTGW2.2located on the distalof long arm of chromosome2interacted with many main-effect QTLs for TGW. Among the29coupleepistatic QTLs, interactions between main-effect QTLs accounted for a most part.