Objective This study aimed to evaluate the resistance to blight disease and genetic diversity of different cucumber (Cucumis sativus L.) germplasm resources from around the world, providing a basis and reference for cucumber resistance breeding.

Method The resistance of these resources was evaluated by artificial inoculation with Phytophthora melonis. The important agronomic traits of 90 cucumber germplasm resources were recorded. Two hundred pairs of SSR primers were designed based on the whole genome to screen molecular markers and analyze genetic diversity.

Result Different types of cucumber materials had significant differences in blight disease resistance. There were 4 highly resistant materials and 10 resistant materials, most of which were South China type cucumbers. There were 38 susceptible materials and 38 highly susceptible materials. The results of SSR analysis showed that a total of 142 alleles were amplified from 90 cucumber resources using 45 primer pairs, with a range from 2 to 4 alleles and an average of 3.22 alleles amplified per a pair of primers. The effective allele number ranged from 1.0225 to 3.0840 with an average of 1.6684. The Nei’s genetic diversity index ranged from 0.0610 to 1.1728 with an average of 0.5816. The average Shannon diversity index was 0.2402. The genetic similarity coefficient ranged from 0.0556 to 1.0000 with an average of 0.5783. The cluster analysis showed that at the genetic similarity coefficient of 0.5500, these 90 cucumber germplasms could be clustered into 9 groups. The resistant germplasm resources were concentrated in groups Ⅰ, Ⅱ and Ⅺ, predominantly South China type cucumbers.

Conclusion Through artificial inoculation of 90 cucumber materials with P. melonis, 14 resistant materials were identified. The 45 SSR primer pairs with high polymorphism were screened out, which could effectively cluster 90 cucumber germplasm materials. This study provides the materials and theoretical basis for screening and evaluating excellent cucumber germplasm resources and resistance breeding.