QTL Mapping For Total Starch, Amylopectin And Amino Acid Content In Milled Rice (Oryza Sativa L.)

Rice grain quality is a very important objective in rice breeding programs. Total starch, amylopectin and amino acids are the three critical factors affecting rice eating and nutritional quality. In this study, a recombinant inbred line population derived from D50/HB277 and its genetic linkage map were used to identify the QTLs controlling eating and nutritional quality traits in 2006 and 2007. The results are summarized as follows:1. QTL mapping analysis for the total starch and amylopectin content was carried out By WinQTL Cartographer 2.0. In 2006 and 2007, two putative QTLs (qTS6 and qTS10) for the total starch content with significant additive effects were identified, each of them explained a total phenotypic variation of 5.25% and 7.29%, respectively. In 2006, two QTLs for amylopectin content with significant additive effects were identified, and explained a total phenotypic variation of qAPs5 and qAPs6 is 7.99% and 59.5%, respectively.2. Amino acid content is a very important nutrient quality trait, too. The identification of QTL for amino acid content was conducted using WinQTL Cartographer 2.0. In 2006 and 2007, a total of 53 putative QTLs affecting amino acid content were detected, among them, only 11 loci were detected commonly in both years. The contribution of each QTL to the phenotypic variation ranged from 4.12% to 26.66%. Twenty one QTLs with significant additive effects for thirteen amino acids were identified in the interval of RM578-RM111 on chromosome 6, and ten of these QTLs exhibited significant additive effects in both years. In addition, 11 QTLs for eleven amino acids were mapped in the interval of RM305-RM178 on chromosome 5, nine and seven QTLs were identified in the interval of RM168-RM143 and RM130-RM148 on chromosome 3, respectively, indicating the regions probably play significant roles for amino acid metabolism.3. The results showed that amylopectin content was also mainly controlled by the same region near the Wx loci on chromosome 6, and it was also an important region determining the amino acids content. Nearby this region, 21 QTLs for the content of 13 amino acids were detected, in which 10 QTLs controlling Thr,Val,Ile,Phe,Met,Ser,Glu,His,Arg and Pro were detected in both years. Our results indicated that to improve both cooking and nutrient quality simultaneously was complicated and need further studies.