Genetic diversity analysis of 51 antivirus and susceptible germplasm resources of watermelon by SRAP molecular markers

【Objective】To provide theoretical referencefor acceleratingthe breeding process of antivirus varieties of watermelon, the genetic diversity of 51 germplasm resources of antivirus watermelon were analyzed by SRAP molecular markers.【Method】The polymorphic primers were selected to amplify 51 antivirus and susceptible germplasm resources of watermelon.The genetic similarity coefficients were calculated by unweighted pair group method with arithmetic average(UPGMA) by NTsys-pc 2.1e. Genetic diversity parameters of different types of watermelon were calculated by PopGene Version 3.2.【Result】Eighteenpairs of primers with clear and stable bands and high amplified polymorphism were selected from 500 pairs of SRAP primers, and a total of 402 clearly identifiable bands were amplified, among which 271 were polymorphic bands. And 22.33 stable and clear bands were amplified on average with each pair of primers, including 15.06 polymorphic bands, with an average polymorphism rate of 67.41%. The observed number of alleles(Na) was 1.6766, the effective number of alleles(Ne) was 1.3033, the diversity index of Nei's gene(H) was 0.1878, and the Shannon's information index(I) was 0.2931. Except the Na of susceptible watermelon germplasmswas higher than that of antivirus watermelon germplasms, the other genetic diversity indexes of antivirus watermelon germplasms was higher than that of susceptible watermelon germplasms. The results showed that the genetic diversity of antivirus watermelon germplasms was higher than that of virus susceptible watermelon germplasms. The genetic consistency and genetic distance of the virus resistant and susceptible watermelon germplasms were 0.8924 and 0.1138 respectively. The genetic similarity coefficients of the experimental watermelon germplasms were between 0.62-0.95. With the genetic similarity coefficient of 0.78 as the boundary, 51 watermelon germplasms were divided into four groups. Antiviral type of watermelon germplasms were in groupsⅠ and Ⅱ, and virus susceptible type of watermelon germplasms were concentrated in groups Ⅲ and Ⅳ, and wild watermelon materials and other watermelon varieties showed the most distantly related.The correlation between the genetic similarity coefficient matrix and the UPGMA clustering matrix was obvious(r=0.914), which accurately reflected the genetic relationship among the watermelon germplasms.【Conclusion】The selected SRAP primer combinations have good ability of variety identification and can be used for the analysis of watermelon germplasm genetic diversity. The germplasm of antivirus and virus susceptible type are closely related, so the genetic diversity is not high. Excellent disease-resistant germplasms should be explored to broaden the genetic base of watermelon.