Abstract: The phylogenetic relationship and genetic diversity of melon germplasm in Xinjiang were investigated by comparing 32 phenotypic traits of the 121 melon landraces（Cucumis melo L.）collected from various areas of Xinjiang，China. The results showed that 121 landraces varied significantly in 5 phenotypic traits，including number of branches，leaf length，main stem thickness，fruit weight and thickness of fruit flesh. Landraces from different areas varied significantly in 4 phenotypic traits，including leaf length，petiole length，flesh texture and taste，but not in the other traits screened．Shannon’s genetic diversity index of 121 landraces reached to 0.74，and the extent of genetic diversity between areas was distinctly different，which indicated that Xinjiang would be the second diversity center of cultivated melon. The average Euclidean genetic distance（EGD）between any two pairs of all landraces was 0.42 ± 0.13. On average，‘Hami Wild Melon’was most distinct to the other landraces，with the highest EGD value of 0.76 ± 0.11. The clustering results showed that‘Hami Wild Melon’was clustered in only one branch and  the other landraces were clustered in 3 groups and subsequently 7 sub-groups，which indicated that the genetic background of‘Hami Wild Melon’was completely dissimilar to any landrace examined. Landraces between different groups or sub-groups showed little genetic affinity，which indicated that the genetic background of different groups or sub-groups were independent from each other. These results indicated that‘Hami Wild Melon’belongs to Cucumis melo L. ssp. agrestis and all the other landraces in Xinjiang belong to two botanical varieties or groups，C. melo L. var. cantalupensis and C. melo L. var. inodorus.

Key words: melon, landraces, Xinjiang, phenotypic character, genetic diversity