Quantitative Trait Loci Affecting Fruit Ascorbic Acid Content In Tomato And Germ Plasm Screening

Tomato(Lycopersicon esculentum Mill), an annual or perennial herbage of Lycopersicon of Solanaceae, is one of the most important fruit vegetable and extensively planted in the world. Vitamin C content is one of the most important traits in tomato quality measurement. High vitamin C content tomato can satisfy most tomato quality traits for most people’s requirements. Vitamin C could not be produced by the body whether human or most mammals, and must be supplied by the diet. Therefore, research of vitamin C content in tomato is very important:firstly, it can be very useful for the tomato breeding to distinguish inheritance of vitamin C; secondly, using the method of molecular markers to obtain the markers which associated with the vitamin C content in tomato can provide theoretical basis for the further research in molecular marker-assisted selection. This experiment used the method of molecular biology to construct the genetic linkage map for tomato and found the SSR and AFLP markers which tightly link with the sugar content in watermelon, analyzed the QTLs. These SSR and AFLP markers linked to QTLs could provide the reference data of genes localization and vitamin C content genes isolation in tomato.In this experiment, we used high vitamin C content tomato12680and low vitamin C content tomato12574as the female and male parent, respectively, to establish six generations and263F2population. Then the content of vitamin C was measured and the inheritance and vitamin C content related QTLs were analyzed.1The results indicated that the content of vitamin C of F2showed continuous variation with normal distribution. The results exhibited an obviously characteristics of quantitative character inheritance, controlling by the poly-gene.2Using the method of SSR and AFLP molecular markers, we obtained41pairs of polymorphism primers through185pairs of tomato SSR markers and256pairs of tomato AFLP markers with the two parents. The rate of polymorphism in SSR markers is12.97%while in AFLP markers is6.64%.3To analyze the F2population using the24pairs of SSR markers and17pairs of AFLP markers, a genetic map with42molecular markers and6linkage groups was developed, which spanning1358.93cM with a mean marker interval of32.35cM.4QTLs associated with vitamin C content were detected and named Qvc1, Qvc2, Qvc3and Qvc4, respectively. There was1,2and1QTL distributed in1,2and5linkage groups, respectively, and they were all additive effects. Their LOD values were4.09,2.54,3.99and3.21, respectively. The4QTLs were able to explain4.88%,18.39%、7.94%、26.04%of total phenotypic variation, respectively. Qvc1had negative additive effects while Qvc2, Qvc3and Qvc4had positive additive effects on vitamin C content in tomato.8markers (SSR246, SSR222, M12E1-5, M2E2, M8E4, M12E14, TGS2393, TGS1476) were detected which associated with te vitamin C content in tomato. Otherwise, the markers M8E4, TGS2393and TGS1476were far from QTL and could hardly be applied in practice.4The SSR molecule markers SSR246was used to screen50tomato germ plasm, and compare with Field identification,the inosculation rate is up to94%.