Abstract: Xishuangbanna cucumber (Cucumis sativus L.var.xishuangbannanesis Qi et Yuan) is a special variation in our country. Simple sequence repeat ( SSR) analyses were conducted to assess the genetic diversity of 30 germplasm resources collected in Xishuangbanna prefecture in 1979 and 1980, which showed that relatively abundant genetic diversity existed in Xishuangbanna cucumber population. The percentage of polymorphic loci, Nei's gene diversity ( H ) and Shannon information index ( I ) of 273 samples were 92.86%, 0.1818 and 0.2972, respectively. The indexes of genetic diversity of 30 germplasm showed that the genetic variation among germplasm was 54.06% and that within germplasm was 45.94%. The genetic diversity of No.17 germplasm was the highest among 30 germplasm (H = 0.1376, I = 0.2032, percentage of poly
morphic loci = 37.21% ). Cluster analysis showed that the result of classification of most germp lasm was consistent with fruit skin color and flesh color. Among 5 populations according to accession source, the genetic diversity of Jinghong population was the highest, whose polymorphic loci, H value and I value were 76.19% ,0.1562 and 0.2516 respectively. Genetic identity of 5 populations was between 0.9071 and 0.9889. Cluster analyses suggest that the difference of genetic background existed in 5 populations with different collecting source. The coefficient of genetic differentiation (Gst) and gene flow (Nm )were 0.2201 and 1.7718, which indicated that the genetic differentiation was relatively low, with relatively larger gene flow in C.sativus L.var. xishuangbannanesis.

Key words: cucumber, Cucumis sativus L.var. xishuangbannanesis, genetic diversity, SSR, population