QTL Analysis For Some Traits Of Rice (Oryza Sativa L.) By Recombinant Inbred Line

Heading date,yield component traits and grain shape related traits have been shown to be quantitatively inherited.Therefore,the use of marker-assisted selection(MAS) may provide a more efficient approach for improving these quality traits than classical breeding alone.The first step of MAS that to be carried out is mapping major loci.However,most of the studies were conducted in a single environment of only a few traits,the stability of the resultant QTL and the important chromosome regions that control different traits could not be evaluated.In this study,a set of 111 recombinant inbred lines(RIL) population derived from a rice cross between Nikken 2 and Milyang 23 through successive selfing for six and seven generations were used to investigate the QTLs of heading date,plant height,nine yield component traits in 2005 and 2006.We also investigate the QTLs of 4 grain shape traits in 2006.The main results were as follows:1.We detected eleven traits including heading date,plant height,panicle length, primary branch number,secondary branch number,spikelet numbers per panicle,number of filled grains per panicle,seed setting rate,number of panicles per plant,1000-grain weight and grain yield per plant in both two years.A total of 38 QTLs were identified on chromosome 1,2,3,4,6,7,8 and 10.We detected 22 QTLs in 2005 and 27 QTL in 2006. Of which 11 QTLs were detected in the two years.These QTL were identified on chromosome 1,3,4,6,8 and 10.The stable QTLs were qHD8,qPH8,qPH10,qPL6a, qPBN8,qSBN4,qPNP1,qSP4,qSP8a,qFGP8 and qGWP8b,whose averge PVEs were 24.2%,15.92%,12.94%,9.24%,20.83%,14.16%,17.27%,13.76%,17.91%,13.28%, 22.86%,with average LOD scores of 7.83,5.84,3.18,3.44,6.90,4.79,5.19,3.69,6.46, 4.36,7.17,respectively.2.In 2006,we analysis the QTLs of four grain shape traits including grain length,grain width,grain thickness and length/width ratio.A total of twelve QTLs distributed on five chromosomes were detected.QTL mapping showed that on chromosome 2 grain width shared the same chromosome region with 1000-grain weight,which closed to qGT2.This result was consistent with the result of correlation analysis in which grain weight was closely correlated with grain width(0.631),and then with grain thickness(0.487).In conclusion,a total of 50 QTLs for fifteen traits including heading date,plant height, yield component traits and grain shape traits.Of which qHD8,qPH8,qPH10,qPL6a, qPBN8,qSBN4,qPNP1,qSP4,qSP8a,qFGP8 and qGWP8b were detected in two years. Some QTLs controlling different traits shared the same marker interval in the chromosome with each other,which is consistent with their significant phenotypic correlations.A QTL cluster for grain width,1000-grain weight and grain thickness was located on chromosome 2.We also found a QTL cluster on chromosome 4(RM303-RM280),which including 4 QTL--qPH4,qSBN4,qFGP4 and qSP4.The most important chromosome region we found in this research is the QTL cluster on chromosome 8(RM5556-RM331) which concluding qGWP8b,qHD8,qPH8,qPBN8,qSP8a and qFGP8.These results will provide useful information for elite rice breeding by MAS.