| 1. The distribution of Cucumis species in the worldThe data of cucumis species (Cucumis L.) geographic distributions were collected and analyzed. We also constructed sketch map of the cucumis species distributions. The results showed that Cucumis species occurred in a large scale from 38°N to 37°S of the Old World, with more species in the southern hemisphere than in the northern hemisphere. With latitude rising Cucumis species sharply decreased in the northern hemisphere. There were abundant species near the equator. They occurred in about 75 countries, but 90.6% of them were from Ethiopia, Kenya, Somalia, South Africa and Tanzania. Somalia had more rare species in absolute and relative (4 species). 33 in 75 countries only had one species and 23 countries were only distributed C.melo. We also found some interesting distribution pattern like discontinuous distribution, widespread distribution and endemic distribution.2. Molecular phylogenetic of cucumis species based on ITSC.hystrix, two lines of C.sativus var.xishuangbanesis and four ecotypes of C.sativus var. sativus were selected for sequencing ITS (internal transcribed spacer) region. The raw sequences were analyzed using Blastn and Clustalw on line. The results showed the length of C.sativus was constant with the value 640bp; and the accessions of C.sativus were separated in two groups with a transition T/C in the site of 168bp, group one was xishangbanna cucumber with T and group two was hardwickii cucumber with C. The length of C.hystrix was 637bp, and was constant with C.sativus (95% of sequence). The transition of base occurred more often between C.sativus and C.hystrix.Total 32 ITS sequence of 18 cucumis species and two additional Cucurbit species were analyzed and phylogenetic relationships of cucumis species were estimated from the ITS sequences. This analysis included the unique species C.hystrix that had the base chromosome number like C. Subgen.melo, but was found in Asia like C.subgen.cucumis. The results showed that the GC content of C.hystrix was the highest in the test species with the value 64.5%. Alignment of cucumis species sequences showed two insertion/deletions( indels) about 10bp were found in ITS1 and 5 site with one base indels were detected, and three indels with 3-16bp were detected in ITS2 ,and a minor indels was also found in ITS2. Using watermelon and zucchini as outgroups, our dendrogram presented the relationship between subgen.cucumis and subgen.melo was close, the Cmetuliferus was the primary species of genus Cucumis and the subgenCucumis species and C.melo formed one group and a sister group of Africa species. |
