Genetic Research On Heat Tolerance During Grain-Filling Stage And Main Agronomic And Quality Traits In Rice

Rice is an important food crop in China.With the frequent occurrence of high-temperature weather in the world,heat stress has become a critical factor that threatens the yield and quality of rice.Breeding thermotolerant rice varieties has become the main breeding target.In this study,the heat stress experiment of rice RILs population(ZS97B/IRAT109)has been carried out,to explore the genetic basic related to the thermotolerance of rice during the grain-filling stage.Moreover,QTLs related to agronomic traits(including DSF,PH,EPN,PL,SD,SSR,TGW,YP,SP,and GP)and quality traits(including BR,MR,HR,CGR,CD,GS,GT,GC,and AC)were also analyzed,which will provide a theoretical basis for improving the yield and quality of rice.The main results are as following:1.The genetic linkage map consisting of 315 markers(including 191 InDel and 124 SSR markers)has been constructed using RILs population,which covered 3051.09 cM,and an average interval between neighbouring markers was 9.69 cM.2.Two main-effect QTLs related to the heat-tolerance of rice during grain-filling period were located in the RILs,which distributed on Chromosomes7 and 9 respectively.The qRHI7-1 was located between MRG7006 and PWK16076,explaining 10.69% of phenotypic variation with the LOD value of 2.93,with the additive effect of-4.41,whose favorable allele was derived from the female parent ZS97 B.The qRHI9-1 was located between YY018 and YY194 markers,which explained 9.01% of phenotypic variation with the LOD value of 2.4,with the additive effect of 4.04,whose favorable allele came from the male parent IRAT109.In addition,4 pairs of QTLs with epistasis effects were mapped,which explained about 20% of phenotypic variation.These results indicate that the heat-tolerance of rice at the grain-filling stage is controlled not only by major genes but also by epistasis genes.3.In the RILs population,37 QTLs associated with main agronomic traits were detected in two years.Among them,4,6,3,5,2,4,1,4,5and 3 loci were identified for DSF,PH,EPN,PL,SD,SSR,TGW,YP,GP,and SP respectively.These loci such as qDSF7-1,qPH3-1,qSSR3-2 and qTGW1-1 were detected repeatedly in two years,which showed that those QTLs were inherited stably in different environments and their heritability was high.Most of QTLs related to agronomic traits in this study,such as qDSF7-1,qPH6-1,qEPN7-1,qPL4-1 and qTGW1-1 were also detected in previous reports.Besides,some new agronomic QTLs such as qDSF3-1,qPH1-1,qEPN9-1 and qPL11-1 were firstly detected for further study.4.In the RILs population,a total of 15 quality-related QTL loci were located in 2017.In which 1,1,3,2,1,3,2 and 2 loci were identified for BR,MR,GS,CGR,CD,GT,GC and AC respectively.Among them,many QTLs related to cooking quality were detected on Chr6,which were closely linked.These loci(qAC6-1,qAC6-2,qGC6-1,and qGT6-1)were located near the YY127 markers,with the higher LOD and PVE,where loci qAC6-1 and qAC6-2,controlling amylose content explained more than 80% of phenotypic variation,which consistented with previous report.