Abstract: Random amplified polymorphic DNA markerswere used to analyze the genetic relationship among 39 cucumber inbred lines. One hundred and seventy-eight arbitrary primers were selected and 49 primers could amplify 378 bands, among them 137 were polymorphic. Based on these data the resulted dendrogram was coincident with the morphology. The genetic distance (GD) between the inbred lines varied from 0.0645 to 0.5992 with the mean value of 0.2458, which showed a wide genetic diversity existed in these inbred lines.
The parental combination with higher, medium and lower genetic distances were selected and 60 crosses were made. Heterosis was found to be significant for yield and its components, which varied from - 39% to 136%.
The association between genetic distance of parents and heterosis for yield and its components is only significant in the crosses in which the GD of parents varied from 0.19 to 0.27. The correlation coefficient with the total yield, average fruitmass and the total number of fruit was 0.6207, 0.5012 and 0.3918. According to the rule the parental combination with the GD varying from 0.24 to 0.27 were selected and 58 crosses were made. The possibility of hybrids with the yield 10% higher than‘Jinchun 2’and‘Jinyou 10’were significantly increased compared to random crosses.

Key words: Cucumis sativus L., RAPD markers, Genetic distance (GD), Heterosis, Yield