Heritability Analysis And Qtl Mapping For Resistant Starch Content In Wheat

Resistant starch (RS) is the sum of starch not absorbed by amylase in the small intestine. It's the focus of carbohydrate researches recently, and the unique physical function of RS has aroused many researchers' concern. The objective of this study is helping to select new wheat cultivar with high resistant starch content. In the study, three wheat cultivars with high resistant starch content and three wheat cultivars with low resistant starch content were selected to cross without reciprocals, and the inheritance of resistant starch content was analyzed by six wheat cultivars and their F1 combinations. A wheat cultivar (M344) with higher resistant starch content and the other wheat cultivar (Wuchun 3) with lower resistant starch content were selected to obtain recombinant inbred lines (RILs), which was used to construct genetic map and quantitative trait loci (QTL) analysis for resistant starch content. The main results were summarized as follows:1,In the study, three wheat cultivars with high resistant starch content and three wheat cultivars with low resistant starch content were selected to obtain 15 F1 combinations from a diallel cross without reciprocals, and the inheritance of resistant starch content was analyzed by six wheat cultivars and their F1 combinations. The results showed that Annong 90202 and D68-20 were the best among all test wheat cultivars for general combining ability of resistant starch content and it could increase the resistant starch content in its crossing progeny significantly or extremely significant. The specific combining ability of Annong 90202×04 Dan 28 and 06-5×D68-20 were the best among all of the F1 combinations. Their values of specific combining ability effects were higher than other combinations significantly. The inheritance of resistant starch content which degree of dominance was super dominance fitted in the additive-dominance model and was controlled by both additive and dominant effects. The alleles increasing resistant starch content were recessive genes, which were more than dominant genes in high resistant starch content parents. The distribution of increasing or reducing alleles among 6 parents was different. Annong 90202 and 04 Dan 28 had more recessive genes controlling resistant starch content, while Ningchun 18 and Xinchun 5 had more dominant genes in the study. The narrow sense heritability of resistant starch content was 36.49%.2,A wheat cultivar (M344) with higher resistant starch content and the other wheat cultivar (Wuchun 3) with lower resistant starch content were selected to recombinant inbred to obtain F2:3 Lines. The relation ship between the resistant starch content and the other starch quality characters (total starch content, amylose content and swelling power) in wheat was analyzed by correlation, regression and path analyses. The result showed that resistant starch content positively correlated with amylase content extremely significant(r=0.18,p≤0.01), which also positively correlated with total starch content significant(r= 0.151,p≤0.05) and negatively correlated with swelling power (r=-0.57). Path analysis showed total starch content could improve resistant starch content and the direct path modulus between them was 0.169.The regression equation among resistant starch content(Y), total starch content(X1),amylose content(X2) and swelling power(X3) was Y=0.289+0.007X1+0.037X2-0.033X3, which could provide a 7% explanation for the phenotypic variations and also explained that resistant starch content extremely related with amylase content and then was total starch content.3,A wheat cultivar (M344) with higher resistant starch content and the other wheat cultivar (Wuchun 3) with lower resistant starch content were selected to obtain recombinant inbred lines (RILs) containing 231 lines, which was used to quantitative trait loci (QTL) analysis for resistant starch content, total starch content, amylose content and swelling power of F2;3lines. A genetic map was constructed based on 163 SSRs and 33 linkage groups distributing in 18 chromosomes by using Joinmap3.0, which spanned 1622.5cM with an average genetic distance of 9.95cM per marker.8 main-effect QTLs and 19 epistatic QTLs were detected by using QTLNetwork 2.0. The results showed that two additive QTLs were detected for resistant starch content, one additive QTL for total starch content, one additive QTL for amylose content, one additive QTL and three dominance QTLs for swelling power. The QTLs above were located on chromosome 4A,4A, 1D,5D, 1D, 1B,3A and 6A, the phenotypic variance which could explain were 11.47%,12.53%,5.34%,8.49%,11.3%,99.96%,100% and 3.3%. In addition, two epistatic QTLs were detected for resistant starch content, eight epistatic QTLs for total starch content, five epistatic QTLs for amylose content and four epistatic QTLs for swelling power, the total phenotypic variance which could explain were 8.3%,7.78%,8.13% and 3.87%. What's more, it was found that a QTL on Xwmc453.3-Xcfd44.2 of chromosome 2B controlling resistant starch content and total starch content, a QTL on Xgwm296-Xgwm455.2 of chromosome 2D controlling resistant starch content, total starch content and amylose content, which showed that resistant starch content has related with total starch content and amylase content.