QTL Mapping Of Traits Related To Yield Using Advance Backcrossing Introgression Lines And Identification Of DTH6 For Heading Date In Rice(Oryza Sativa L.)

The high yield and stable production of rice is of great significance to ensure the food security of our country.In recent years,the narrowing genetic basis of varieties has become the bottleneck to improve rice potential yield.Jiangsu province is a typically planting area of japonica varieties,and excavation of yield-related quantitative trait loci(QTL)/genes is of great importance to breed japonica variety and improve the potential yield of japonica varieties in Jiangsu province.In this study,a set of advanced backcrossing introgression lines were constructed using Huanghuazhan as donor and Wuyujing3 with the resistance to rice stripe virus(R-Wuyujing3)as receptor,and the traits related to rice yields of the introgression lines were investigated for many years.The introgression lines were resequenced by using the specific length amplified fragment sequencing(SLAF-seq)technology,and the introgression segments in each line were analyzed.QTL analysis for the yield-related traits were conducted on data of traits and SNPs,and effect of Gnla in japonica varieties with erect panicle was further analyzed of and new QTL/genes location,these results laid the foundation for molecular breeding of yield related traits and mapping and cloning of new QTL/genes.The main results were as follows:1.A set of advanced backcrossing introgression lines consisting of 210 lines were constructed by crossing and backcrossing with the strategy of trait priority and 133 lines including 56 BC4F4 and 77 BC3F5 lines were selected by the pedigrees and resequencing data to be investigated on 16 traits related to rice yields during the 2014 and 2015.2.A total of 244,683 SLAF labels were developed,and 25,784 effective polymorphism markers were gained,which accounted for 10.54%polymorphism.For subsequent analysis,10,103 high quality SLAF labels were sifted from the polymorphism markers,and these high quality labels were evenly distributed on 12 chromosomes.There was the most labels on chromosome 2,and the number of the markers was about 1328.Additionally,there was the least labels on chromosome 12,and the number of labels was 296.3.A total of 120 QTLs for the 16 traits related to rice yield were mapped in QTL IciMapping V4.0 software,includingll,6,4,6,3,11,9,4,5,6,6,12,3,12,13 and 9 QTLs for heading date(HD),plant height(PH),number of panicles per plant(PP),yield per plant(YPP),panicle length(PL),primary branch number(PBN),primary spikelet number(PSN),secondary branch number(SBN),secondary spikelet number(SSN),spikelet of main axis(SM),setting rate(SR),thousand-grain weight(TGW),grain length(GL),grain width(GW),grain thickness(GT)and grain length-width ratio(GLW),respectively.Among these QTLs,18 QTLs were repeatedly detected in the two years,and 12 QTLs,locating in the similar physical intervals and having effects with the same direction during two years,were also detected,which might be considered as the same QTL.Additionally,these were six QTL clusters that affected two or more traits detected in this study.4.Compared with the advanced backcrossing introgression lines without Gnla and R-Wuyujing3,those lines carrying Gnla exhibited significant secondary branch number,secondary spikelet number,panicle length,primary branch number,grain width and thousand-grain weight but the significant decreased number of panicles per plant and length-width ratio,resulting in no significant difference on the yield per plant between the lines with different genotypes.Additionally,the lines carrying Gnla showed the increased chalkiness.Therefore,other yield related genes would be need to pyramid with Gnla for improving the yield in japonica rice with erect panicle.5.Using the F2 population from the cross between R-Wuyujing3 and Tl,a advanced backcross introgression line showing heading-date 20d earlier than that of R-Wuyujing3,a new dominant heading date gene DTH6 was mapped to an interval of 500 kb on chromosome 6,and DTH6 was identified to be from Dualr,an indica rice varietie used as the donor to improve the RSV level of Wuyujing3.Heading-dates of lines carring DTH6 were shorter than that of R-Wuyujing3 under long day condition of Yangzhou,but the heading-dates of the lines were about 82 days at Yangzhou and Hainan,indicating that could be weaken the photonasty of lines.