Study On QTL Mapping Of Preharvest Sprouting Resistance Of Wheat Cultivar Frontana

Pre-harvest sprouting in wheat is a natural disaster worldwide. It seriously decreases not only the yield and test weight, but also nutrition and industry quality, as well as seeding values. It can also decline the grain transparency and commodity grade. All these affect wheat production seriously. Setting up scientific methods of evaluation on preharvest sprouting resistance, and developing molecular markers of preharvest sprouting resistance variety, carrying out marker-assisted selection and resistant genes pyramiding are all important for inhancing efficiency of breeding for resistance to preharvest sprouting.A RILs derived from cross of Frontana (resistant to preharvest sprouting) and Inia66 (susceptible to preharvest sprouting) was employed to develop QTLs associated with resistance to preharvest sprouting. Seed germination index , a-amylase activity and index of preharvest sprouting (PHS)in spike level were determined for phenotyping, and SSR markers was used for genotyping. QTLs associated with preharvest sprouting resistance in wheat were mapped, based on combining analysis of Composite Interval Mapping (CIM) method and Multiple Interval Mapping (MIM) method, respectively. The major results are as follows:With CIM, three QTLs associated with dormancy were detected on chromosome 5A and 4A, in which the QTLs on chromosome 5A accounted for 3.6% and 19.8% of the phenotypic variation, respectively, and the QTL on chromosome 4A explained 48.77% of the phenotypic variation. Three QTLs associated with a-amylase activity were mapped on chromosome 5A and 4A, and the QTLs on chromosome 5A explained 16.63% and 12.01% of the phenotypic variation, respectively, while the QTL on chromosome 4A accounted for 18.35% the phenotypic variation. Five QTLs associated with PHS resistance were found on chromosome 5A , 4A and 7A in both 2006 and 2007, in which two QTLs were detected on chromosome 4A and 7A, accounting for 14.1% and 11.75% of the phenotypic variation in 2006 , three QTLs were found on chromosome 5A , 4AL and 7A explaining 5.6%, 5.2% and 7.9% of the phenotypic variation in 2007.The results revealed by MIM are similar to that of CIM, but the way of MIM shows two more QTLs which control a-amylase activity were found on chromosome 7A. One of the QTLs accounted for 29.7% of the phenotypic variation with genetic distances of 0.1 cM from the closest SSR marker Xbarc29.By the two mapping methods it can be seen that the QTLs controlling dormancy, a-amylase activity and PHS were mapped on the same region of chromosome 4A across two years in Frotana, which is only 0.6~1.6cM to the nearest marker Xbarc170, and the QTLs related to preharvest sprouting(PHS)were detected in two years.