Mapping Of Cca-2 Gene Resistant To Cucumber Target Leaf Spot And Transformation Of Corynspora Cassiicola With RFP

In recent years, cucumber target leaf spot caused by Corynespora cassiicola has become an important epidemic disease in China. In this paper, the inheritance and the mapping of gene cca-2 resistant to cucumber target leaf spot were studied based on the Cucumber sativus var. hardwickii PI183967 and Xintaimici lines 931. What’s more, C. cassiicola RFP-tagged transformat were constructed. The main results are as follows.1. According to the phenotype identification, cucumber sativus var. hardwickii PI 183967 was proved to be a broad-spectrum resistant germplasm to different pathogenic level of C. cassiicola.2. Using trypan blue staining method, the infection process of C. cassiicola between the resistant and suceptical materials were observed to be different. Results showed that C. cassiicola grew slowly on resistant material, and spots appearred after 5 days’inoculation. On the contrary, C. cassiicola grew quickly on susceptible cultivar, and spots appearred after 3 days’inoculation.3. The research about the phenotype identification of F9 recombinant inbreeding lines (RILs 164 lines) population showed that the genetic mechanisms of cucumber resistance to Corynespora leaf spot was control by a single recessive gene. In 164 RILs, the ratio of resistant lines to susceptible lines was 41:116, the chi square test was fit with the inheritance of single recessive gene, whose R:S=1:3.4. Using the cca-2 flanking markers, SSR19803 and SSR16890,141 lines out of 1500 F2 plants population were screened. Using the new molecular markers and the phenotype identification of F2 recombinant lines, cca-2 was located between SSR62 and SSR301, and the genetic distances were 1.4 cM and 1.7 cM respectively.5. Using the method of agrobacterium tumefaciens-mediated transformation (ATMT), a RFP-tagged pathogenicity transformant of C. cassiicola was obtained. Its genetic stability, biological characteristics, such as growth rate, colony morphology, spore production and pathogenicity had no differences with the wild isolate.The research about inheritance and resistant gene mapping of Cucumber sativus var. hardwickii PI 183967 to Corynespora leaf spot might lay the foundation for marker assisted selection breeding, fine mapping and the cloning of cca-2. Transformation of C. cassiicola with rfp provides a reference for the construction of other transformant-fungi. Furthermore, this RFP-tagged transformat might speed up the research about the mechanism of C. cassiicola to cucumber or other hosts.