Development Of Single Segment Substitution Lines And QTL Analysis In Main Parents Of Rice (Oryza Sativa L.)

Rice (Oryza sativa L .) is the world's most important food crop,and its most traits are quantitative traits,which are controlled by polygene. It is very important for rice genetics and breeding to identify and map quantitative trait loci(QTL). Single segment substitution line contains only one chromosome segment from donor,and eliminates the interference of the genetic background.SSSL is a important test material to identify and finely map.The present research has developed 113 SSSLs which substituted segments from three-line hybrid rice restorer line Shuhui527(donor parent) were introgressed into an elite genetic background of two-line hybrid rice restorer line 93-11 (recipient parent),using backcross and marker-assisted selection(MAS).This study identified and analyzed the QTL for heading date (Hd),effective panicle number (Epn) and spikelet setting density (Ssd) using 42 Single segment substitution lines selected from SSSL population. The main results are as follows:1. The polymorphism between donor parent Shuhui527 and recipient parent 93-11 was detected by using 359 microsatellite markers.81 molecular markers which presented clear banding pattern showed definite polymorphism between parents. The average interval distance between adjacent markers is 14.44 cM. The percent of polymorphism is 22.56% between parents.2. 113 single segment substitution lines with the 93-11 genetic background have been developed in BC₃F₃ and BC₂F₄ generations. 113 SSSLs contain 17 repetitive segment substitution lines and 13 nonrepetitive segment substitution lines,30 different SSSLs in all. Substituted segments of these SSSLs distribute on 9 chromosomes of rice, but the distribution is uneven on 9 chromosomes, and most candidate SSSLs which number are 35 are on NO.5 chromosome.The total length of all substituted segments is 3910.88cM, and the average length of each substituted segment is 34.61cM. The total coverage length of substituted segments of 113 SSSLs is 368.70cM in the rice genome,to account 24.13% of rice genome's total length.3. This study have analyzed genetic background of candidate SSSLs using SSR and ISSR molecular marker. The average background similar percent is 97.27%,and the average covered percentage of donor parent's residual segments is 0.46% on the genetic background.4. 17 QTLs for 3 important agronomic traits of rice have been detected in 42 SSSLs through t-test(P≤0.001) between the SSSL and recipient. These 17 QTLs contain 9 QTLs for heading date (Hd),7 QTLs for spikelet setting density (Ssd) and 1 QTL for effective panicle number (Epn). Hd-3,Hd-6-1,Hd-8-2 and Hd-11 identified in the present research are similar with the previous studies,the other 13 QTLs are the new study.5. There are 7 segment-overlapping groups in 42 SSSLs used to identify QTL.Several QTLs were mapped in a shorter segment through substitution mapping. Hd-9 for heading date was mapped between RM23785 and RM23918 that the length of the segment is 1.62cM. Hd-8-3 for heading date have been identified in a segment which length is 17.75cM through substitution mapping.SSSLs of rice have been developed in the present research,and QTLs of 3 important agronomic traits on substituted segments have been analyzed. This study lays a certain foundation for molecular marker-assisted breeding and rice varieties' genetic improvement.