Objective This study aims to analyse the genetic diversity of 50 cucumber core germplasm resources from all over the countryto provide a basis and reference for cucumber breeding.

Method In this study, 66 pairs of SSR primers were designed to screen 50 cucumber materials for molecular markers and cluster analyses of genetic diversity.

Result 50 cucumber core germplasms tested showed diversity in rind color, papilloma, and fruit stripe. The results showed that 32 of the 66 primer pairs were effective to amplify clear and stable polymorphic markers among different cucumber core germplasms, and the 32 pairs of SSR primers amplified a total of 280 allelic fragments, of which 216 were polymorphic, accounting for 77.1% of the total fragments. It indicated that 32 pairs of SSR primers screened have high genetic polymorphism and are suitable for genetic diversity analysis of cucumber germplasm materials. The clustering results were consistent with the results of the investigated germplasm resources. The lowest genetic similarity coefficient of 50 cucumber core germplasms was 0.62, and the highest was 1.00. At the genetic similarity coefficient of 0.754, 50 cucumber germplasm materials were clustered into 7 groups, that is, 9 South China type materials were clustered into 6 groups: Ⅰ, Ⅲ, Ⅳ, Ⅴ, Ⅵ, Ⅶ, of which Ⅳ included one intermediate material and No.9 South China type material. 40 North China cucumber materials were clustered into one class: class Ⅱ. This indicated that the similarity coefficient between North China type cucumber materials and South China type cucumber materials was low and the genetic relationship was far. The cucumber materials of North China type had high similarity coefficient, close genetic relationship, narrow genetic background and poor genetic diversity. The similarity coefficient between the South China cucumber materials is low, the genetic relationship is far, the genetic background is wide, and the genetic diversity is rich.

Conclusion 32 pairs of SSR primers were screened out, which could effectively cluster the 50 cucumber core germplasm materials. The 50 cucumber materials at the genetic similarity coefficient of 0.754 were clustered into 7 groups, and the results were consistent with the results of trait investigation. In addition, the genetic background of North China cucumber is narrow with poor genetic diversity. The genetic background of South China cucumber is relatively wide with rich genetic diversity.