Construction Of An RFLP-SSR Linkage Map And Mapping Of QTLs Underlying Grain Quality Traits In Rice

Weng Qingmei et al. (2000) constructed an RFLP marker lingkage map (designated RFMAP) of rice based on a doubled haploid (DH) population derived from a cross between an indica rice variety Gui-630 and ajaponica rice variety Taiwan)ing. The map contains 175 RFLP markers and covers a total length of 1224.6cM with an average distance of 7.0cM between adjacent markers. But the RFLP markers on the map are not evenly distributed and there are two breaking points on chromosomes 4 and 8. This study was to avoid the two breaking points and make markers distributed denser and more evenly by adding some SSR markers into the RFMAP. A total of 361 pairs of SSR primers published by Cornell University were used to screen polymorphic markers between the parents. 183 (55.97%) pairs of the primers showed polymorphism and 57 SSR markers were added into the RFMAP. The new map (designated RSMAP) covers a total length of 1811.2cM with an average distance of 7.8cM between adjacent markers, and the markers are distributed more evenly. However, the two breaking point still exist, suggesting that the two regions are less polymorphic and of high recombination frequency.Mapping of QTLs underlying amylose content (AC), chalkiness rate (CR) and chalkiness score (CS) was performed using the method of composite interval mapping (CIM). A total of 33 QTLs were detected, 8 for AC, 12 for CR and 13 for CS, whichcould explain 59.22%, 64.90% and 67.50% of phenotypic variances of the traits, respectively.