Genetic Analysis And QTL Mapping Of Fusarium Wilt Resistance Of Sea Island Cotton

The materials of this study were 63 introduced and cultivated Sea island cotton breed in Xinjiang, genetic diversities were evaluated by field phenotypic traits and molecular markers analysis, and F2 mapping population was constructed with screened disease resistant materials and susceptible materials by crossing, genetic rule of fusarium wilt on Sea island cotton were analyzed and study of molecular marker was developed. Molecular markers related to fusarium wilt on Sea island cotton were found and our research can provided a theoretical, methodical and material support for anti-disease breeding on Sea island cotton. It also has important practical significant for selection of disease resistant materials, identification of disease resistant breeds, reliability and purity examination of generalized varieties, as well as accelerating the disease resistant breeding process of Sea island cotton and improving Xinjiang Sea island cotton production. The following results were obtained from this study:l.The study of genetic diversity on 63 Sea island cotton varieties using agronomic characters and molecular markers (SRAP and RGA)was showed that Sea island cotton had big differences in total and the diversity was rich; The result of RGA clustering was showed that genetic diversity of Sea island cotton varieties on resistance was relatively narrow. We found that the three clustering results were performed certain consistency in big classified groups, while big differences within groups by comparing agronomic characters and molecular markers clustering results.2.The existence of additive-dominant effects, no epistasis of Sea island cotton resistance was showed by preparing complete diallel cross design using the known resistant Sea island cotton varieties and the susceptible Sea island cotton varieties by Hayman analyze.The resistance presented in compelete dominance on the basis of additive effect; The generalized genetic ratio of average fusarium wilt rate was 74.28% and the narrow genetic ratio was 67.82% which specified that resistance parents have stronger ability in passing to generation and have higher genetic ratio.3.The combining ability was analyzed by Griffing method and GGE biplot. The analyzing results of the two method were basically consistent and preliminary showed that the resistant×susceptible type combinations was more suitable distribution.4. It was showed that the occurrence of fusarium wilt has obvious effect on production and quality of Sea island cotton by relative analysis. The plant will be dwarfing after pathogeny, and the productivity traits such as pod-branch, total ball number and single ball weight will be obviously decreased, so does the fiber length and strength. 5.122 polymorphic locus were screened from F2 mapping population constructed with fusarium wilt susceptible varieties Xinhai 14 and fusarium wilt resistant varieties 06-146 by crossing. The average distance of the linkage map was 10.7 cM, the full length was 923.6 cM and the cotton genomic coverage was 16.63%. 17 linkage groups were obtained and 10 chromosomes of cotton were covered.6.3 possible resistant QTLs which are separately situated on LG1(Chr.26),LG3,LG17(Chr.8)were identified and their contribution rate was 33.60%,2.15% and 21.46% respectively. We can preliminary come to the conclusion that qFw1 and qFw3 are two major genes and the qFw2 is a minor genes. In this study the susceptible Xinhai 14 was as a female parent and the resistant materials 06-146 were as male parents. Among the three qFw1,qFw2 and qFw3 QTLs, the additive effects of qFw1 and qFw2 were negative, which indicates that these two enhancing allele were came from resistant parents, but the contribution rate of qFw2 was lower which preliminary thought that the qFw1 has utility value in Molecular maker assistant breeding. The additive effect of qFw3 was positive which indicates that qFw3 enhancing allele was came from the susceptible parent.7. Genetic linkage analysis was carried out between molecular marker and fusarium wilt gene by using BSA method. In the end, the m12e15a and Gbrga14a genes whose genetic distance with fusarium wilt gene of Sea island cotton are 12.97cM,15.92 cM respectively. In locating resistant gene, these two markers situated separately on side of qFw1 and qFw2 which indicates that the three QTLs tested in this study have certain reliability and the results will lay a good foundation on follow-up verification of resistant gene.