Genetic Analysis And Preliminary QTL Mapping Of Heat Tolerance In Cucumber(Cucumis Sativus L.)

Cucumber (Cucumis sativus L.) is an important climbing annual herbaceous plants belonging to cucurbitaceae. It is one of the main vegetable crop cultivated in many parts of China. With the global temperatures rising, heat injury has become an important environmental factors affecting the cultivation and production of cucumber. The research of heat tolerance of cucumber genetics and gene mapping is still less. Therefore, breeding in heat tolerance of cucumber progress slowly, useful heat resistant gene directional trandfer is lack of reliable technical support. Exploration of heat tolerance genetic regular in cucumber, fine mapping related gene of resistant, cloning and breeding in heat tolerance of cucumber.In this study, suitable heat resistance identification method and subordinate function analysis was used to select the heat tolerance parents of the cucumber. The six generation of the population derived from’GY2’(heat tolerance)×’Biyu3’(heat sensitive) was applied to separate and analysis the genetic system of heat tolerance of cucumber. Based on this, the F2population was used as the mapping population, parents and F2population were identifyed on there heat phenotype, and the genetic linkage map was constructed with SSR markers, heat tolerance related QTL ananlysis was performed with composite interval mapping(CEM). The main results are as followed:1. Identifying the heat tolerance by using subordinate function analysis method on different varieties of cucumber seedlings, the results show that:each part of GY2seedlings had the highest membership degree on heat injury index, conductivity and relative chlorophyll content of membership degree was also higher, the average highest membership degree was0.961, between0.8-1.0, belongs to the strong heat-resistant varieties; average degrees of Biyu3was the minimum0.116, between0-0.2, belongs to the heat sensitive cultivars.2. The heat tolerance of cucumber was controlled by two additive-dominance-epistatic major genes plus additive-dominant polygene, and also affected by environment, heat tolerance genetic rate of major genes in the BC1, BC2and F2population were28.67%,17.24%and39.78%of cucumber seedling, among that the genetic rate of major genes in F2was higher; heat tolerance genetic rate of polygen in the BC1, BC2and F2population were28.36%、44.87%and36.81%of cucumber seedling, among that the genetic rate of major genes in F2was higher; Environment has certain effect on heat resistance performance, respectively42.97%,37.90%and23.41%in the BC1, BC2and F2population. The above results showed that, selection of heat tolerance effect in subsequent generations of F2will be better in the cucumber heat tolerance breeding.3. The genetic linkage map which contains35SSR markers and7linkage groups was constructed.7linkage groups were located in7chromosomes. The total length of linkage group was191.2cM, average marker spacing was5.46cM, the minimum distance between markers was1.0cM, the maximum distance of46.0cM. According to the construction of the linkage group, QTL location of heat tolerance was analysised using composite interval mapping method.1heat tolerance related QTL were been found, it was located in the5chromosome, named HT5-1, which explained11.0%of variation. Additive effect was negative indicating from the strong heat resistant parent allele of GY2performance enhancing effect of heat resistance.