Phylogenetic relationships in Cucumis (Cucurbitaceae) revealed by SSR and RAPD analyses
采用SSR和RAPD标记研究黄瓜属(葫芦科)的系统发育关系

Cucumis hystrix is the first wild Cucumis species possessing 12 basic chromosomes ever found in Asia. This discovery has posed a challenge to the current subgeneric division of this genus which was made mainly based on the differences in basic chromosome numbers and geographical distribution. The subgenus Cucumis with the basic chromosome number of x=7 is distributed in Asia, whereas the subgenus Melo with x=12 is distributed in eastern Africa. In this study, RAPD and SSR markers were used to investigate the phylogenetic relationships among 22 accessions in Cucumis . The genetic distance (GD) values between C. hystrix and C. sativus var. sativus ascribed by SSR and RAPD matrices were 0.59 and 0.57, respectively. The GDs are smaller than those between C. hystrix and C. melo var. melo , 0.87 and 0.70, respectively. The phylogenetic relationships calculated using SSR and RAPD makers agree well with each other, and the correlation between the GDs of SSR and those of RAPD was r =0.94, though the GD value obtained from SSR was higher than that from RAPD and the equation was y =0.859 x +0.141. One hundred and nine SSR and 398 RAPD primed sites were used in cluster analysis. Twenty-two accessions were clustered into two main groups. The CS group consisted of C. sativus var. sativus , var. hardwickii , C. hytivus , and C. hystrix and the CM group included C. melo var. melo , var. conomon , C. melo ssp. agrestis , and C. metuliferus .