Analysis Of Genetic Basis Of The Plant Type And Panicle Traits In Backcross Recombinant Inbred Lines Of Rice

Ideal plant type is one of the physiological bases of high yield potential in crops. Improvement of the plant type may play an important role for super-high yield breeding of rice. In this study, a population consisting of 244 BC₁F₈ lines (backcross recombinant inbred lines) derived from the cross of 9311 and Zhenshan97B, both elite indica hybrid rice parents, were developed for quantitative trait loci (QTL) mapping. A genetic linkage map was constructed using this population, and phenotypic data of eight plant type traits such as flag leaf length, distance between flag leaf and second-leaf, panicle exsertion and five panicle traits such as panicle weight in this population were collected from two year trials. The main results of the QTL mapping are as follows:1. Two hundred forty-four lines of the BRILs (backcross recombinant inbred lines) were analyzed by 122 SSR (simple sequence repeat) and 2 InDel (insert-deletion marker) to construct a genetic linkage map, which covers a total of l,349.3cM with an average interval of 10.9cM between adjacent loci. Among the 124 marker loci, the allele frequency at 87 loci is according with the ratio of 1:3, meanwhile, the allele frequency of 37 loci (29.8%) are significantly skewed from the ratio as tested by Chi-square (p<0.05). Moreover, there are obvious hot chromosomal spots of the distorted segregation loci, which distribute on all of the 12 chromosome excluding chromosome 5 and 9, and 16 of the loci distort to zhenshan97B, only one of them distorts to the parent 9311.2. Coefficients of pairwise correlations between 8 plant type traits (PH,FW,FL,FS,FA,FD,PL,PNL) and panicle weight (PW) are highly significant excluding FA; There are also significant correlations within the plant type traits and the panicle traits, which suggest that improvement of the plant type traits may be a good way to increase yield potential in rice.3. Sixty two QTLs for the eight plant type traits are detected (LOD>2.4) in the two year trials, and distribute mainly on the chromosome 1,3,7,8,11. Among of the QTLs, qFS-1a for flag leaf area has the largest effect with the explained phenotypic variation of 37.73% in Hainan and 26.62% in Wuhan, and the allele from Zhenshan97B can reduce the flag leaf area about 5.60cm and 9.20cm in Hainan and Wuhan respectively. 4. Thirty four QTLs for panicle traits (PBN,SBN,GL,GW,PW) are identified, and mapped on almost all the chromosomes except of chromosome 9. The qGW-5 for grain width has the largest phenotypic variation with 65.37% in Hainan and 56.90% in Wuhan, and the allele from 9311 reduces the grain width about 0.2cm in Hainan and Wuhan trials.5. Eighteen pleiotropic or overlapping QTLs regions in the 12 chromosomes are also observed, of which 12 affected the plant type traits and the panicle traits simultaneously, 4 QTL regions each involve the different panicle traits, and 2 pleiotropic QTLs regions affected the different plant type traits. For instance, the marker interval RM151-RM8083 on chromosome 1 controlling simultaneously the five traits (FL,FW,FS,SBN and PW), and the range of the explained phenotypic variation is 7.28% to 37.73%. The results are consistent with the highly significant correlations among the five traits, suggesting that the pleiotropic QTLs should be the genetic basis of the significant correlation of the investigated traits.