Application Of SSR Technique On Cucumber Genetic Diversity And Purity Test

Cucumber(Cucumis sativus L.) is one of the important vegetable crops with an adundant germplasms. The study on the genetic diversity of cucumber can benefit the conservation, classification, identification, genetic enhancement and effective utilization of the cucumber germplasm resource. In this study, genetic diversity in 59 cucumber accessions from different countries or regions was assessed using morphological and SSR makers, and the genetic relationship among the accessions was revealed by cluster analysis at various levels. In morphological assessment, the average coefficient of variation and the average diversity index among the accessions was 0.59 and 1.26 based on the data of 59 morphological characters. 59 accessions were clustered into 7 groups based on morphological data: American processing type group,mixed group,European greenhouse type group,The Xishuangbanna cucumber D59,D28,South China ecotype group and North China ecotype group. It was apparent that there was some association between morphological similarity and geographical distribution.62 pairs of SSR primers generated 213 storable bands among 59 accessions, 170 (79.8%) of which were polymorphic. A mean of 3.74 bands and 2.74 polymorphic bands per primer pair was detected. 62 pairs of SSR primers were composed of genome SSR and the EST-SSR, 66% of which belonged to middle and high Polymorphism locus. In this study, EST-SSR was firstly used for studying cucumber genetic diversity, and the result showed that EST-SSR had better polymorphic lever than genome SSR. Some primers can amplify specific bands in certain accessions. Except Japanese ecotype accessions, other six ecotypes can amplify specific bands. The accession D59 amplify most specific bands. 59 accessions were clustered based genetic distance matrix by SSR markers, the genetic distance value range from 0.04 to 0.54, and the average value was 0.26. 59 accessions were clustered into 7 groups: namely European greenhouse ecotype group,American ecotype group,Xishuangbanna cucumberD59,The white fruited accession D38,mixed materials group,The leaf color mutant materials D28,North China ecotype group. Results obtained from the morphologic method were consistent with those from the SSR markers, which were in according with the ecotypic taxonomy on cucumber.Seeds are very important for agricultural production. The hybrid purity identification can examine the seed quality effectively and ensure crop production. Morphological characters were usually used for cucumber seed purity identification, but it was time-consuming and long cycle. In this study, parents complementary primers CS24,CS06 and CSWTA16 screened from 271 pairs of SSR primer were used for examining purity of Zhongnong No.8,Zhongnong No.10 and Zhongnong No.16 hybrid. The result showed that either of them can examine hybrid purity accurately, but SSR marker was more feasibility than morphological characters because of it operating easily and timesaving.