Studies On Molecular Marker Of Fusarium Wilt Physiological Race 2 Resistance Gene In Watermelon [Citrullus Lanatus (Thunb.) Mansf.]

Fusarium wilt is resulted in Fusarium oxysporum f.sp.niveum. As one of the main disease of watermelon, it commonly occur all over the world, which brings great loss to production. At present, three physiological race are discovered, which are 0, 1 and 2. Compared to the other two, physiological race 2 was more infested. Meanwhile, Charleston Gray have resistance to physiological race 0, Calhoun Gray have resistance to physiological race 1.However, there is no resistance variety of physiological race 2 as yet. Since wild watermelon PI296341 is universally recognized as the antigen of Fusarium wilt of three physiological race, the resistance of the present variety will probably be improved by utilizing the vital hardiness of wild watermelon. Wild watermelon PI296341 were studied to obtain molecular markers linked to the resistant genes by technique of RAPD (Random ampilied polymorphic DNA). It has provided a solid basis for effectively exploiting the stress resistance of wild watermelon germplasm and make location and cloning of stress resistant genes possible.the results were reported as follows:1. Many key factors that affect the stability of RAPD were completely analysed and thorough discussed. It included template DNA, Mg²⁺ and Taq DNA polymerase. The result showed the optional concentration of template DNA was 15ng, Mg²⁺ 2.0mM, dNTPs 0.8mmol/L, Taq DNA polymerase 1 unit, and primer 0.15mmol/L in the RAPD system.2. The CTAB extraction method that this experiment advanced can acquire the good quantity of DNA. It had many advantages of rapidity, simplicity, low cost, and raised the efficiency. The simple RAPD-PCR procedure was set, by a systematic examination of effects of the length of each step on RAPD patterns. The time for the PCR program can be reduced to 3.30 hours without changing the RAPD patterns obtained from genomic DNA of watermelon.3. From surveying the Fusarium wilt resistance of F2 population consisted by the introgression of Fusarium wilt resistant gene from PI296341 into the susceptible inbred M17 by using root-dip inoculation, the result showed, resistant plants are 70, susceptible plants are 35. It was tested that resistance/susceptibility basic match 3︰1 comparison of segregation. This experiment certificated the Fusarium wilt resistant gene is controlled by single dominant gene.4. RAPD were employed as a tool to detect molecular marker linked to Fusarium wilt resistant gene in the watermelon wild germplasm. Only one primer OPG13(5'CTCTCCGCCA3')was singled out from 630 10mer primers to detect diversity between pool of Fusarium wilt resistance and susceptibility. In pool of Fusarium wilt resistance a specific 530bp DNA segment was amplified with primer OPG13, but in Fusarium wilt susceptibility was not, and the same as in the different single plant in F2 segregation.5. It was discussed in relation to molecular marker of main gene character and possiblity of make location and cloning of resistant gene. These has availed to clarify the mechanism of Fusarium wilt resistance, and provided the new strategy and methods to improve Fusarium wilt resistance in watermelon.