对国产 29 个瓠瓜[ Lagenaria siceraria ( Molina) Standl.]品种的 ITS 序列进行了扩增及测序,并结合引自GenBank 的国产 9 个瓠瓜品种以及国外 6 个瓠瓜品种和 3 个同属种类的 ITS 序列,对它们的 ITS 序列长度和 GC 含量以及变异位点进行比较,在此基础上构建系统发育树并对 47 个样本间的遗传关系进行研究。 结果显示:供试 47个样本的 ITS 序列均由 ITS1、5. 8S rDNA 及 ITS2 组成,各样本间的 ITS 序列长度、GC 含量以及变异位点差异明显。国产 38 个瓠瓜品种的 ITS 序列(包括 ITS1、5. 8S rDNA 及 ITS2)长度为 619 ~ 627 bp、GC 含量为 58. 00% ~ 63. 32% ;国外 9 个样本的 ITS 序列长度为 591 ~ 626 bp,GC 含量为 54. 17% ~ 63. 26% 。 序列比对结果显示:国产 38 个瓠瓜品种的 ITS 序列同源率为 84. 6% ~ 100. 0% ,包含 221 个变异位点;其中,来源于山东的品种‘砧木 2’ (‘ ZhenmuNo. 2’)的 ITS 序列包含的变异位点最多,与其他品种间的同源率也最低。 在系统发育树上,国产 38 个瓠瓜品种可分为 3 个分支,来源于山东的品种‘砧木 2’和来源于河南的品种‘西瓜砧木 1’(‘Xiguazhenmu No. 1’)各自聚为第1 和第 2 分支;其余 36 个品种聚为第 3 分支。 而供试的 47 个样本则可分为 2 个分支和 5 个亚组,第 1 分支可分为2 个亚组,包括国产品种‘砧木 2’和产自日本的 2 个品种;第 2 分支包含的 44 个样本则进一步分为 3 个亚组,国产品种‘西瓜砧木 1’和产自法国的品种‘白花瓠瓜’(‘White-flowered gourd’)各自聚为第 1 和第 2 亚组,其余的 42 个样本聚为第 3 亚组。 研究结果表明:供试的不同产地瓠瓜品种间存在丰富的遗传变异和地理分化现象,其 ITS 序列差异与地理分布有一定关系。

ITS sequence of 29 cultivars of Lagenaria siceraria (Molina) Standl. in China was amplified and sequenced, and combined with that of 9 cultivars of L. siceraria in China, 6 cultivars of L. siceraria and 3 congeneric species abroad from GenBank, length, GC content and variation site of their ITS sequence were compared. On this basis, phylogenetic tree was constructed and genetic relationship among 47 samples was researched. The results show that ITS sequence of 47 samples all includes ITS1, 5. 8S rDNA and ITS2, and there are obvious differences in length, GC content and variation site of ITS sequence among different samples. Length of ITS sequence (including ITS1, 5. 8S rDNA and ITS2) of 38 cultivars of L. siceraria in China is 619-627 bp, and their GC content is 58. 00% -63. 32% . While ITS sequence length and GC content of 9 samples abroad are 591 - 626 bp and 54. 17% - 63. 26% , respectively. The result of sequence alignment shows that homological rate of ITS sequence of 38 cultivars of L. siceraria in China is 84. 6% -100. 0% , which includes 221 variation sites. In which there are the most variation sites of ITS sequence and the smallest homological rate in cultivar ‘Zhenmu No. 2’ from Shandong as compared with other cultivars. According to the phylogenetic tree, 38 cultivars of L. siceraria in China can be divided into 3 branches, cultivar ‘Zhenmu No. 2’ from Shandong and cultivar ‘Xiguazhenmu No. 1’ from He’ nan are clustered in the first and second branches, respectively, and other 36 cultivars are clustered in the third branch. While 47 samples tested are divided into 2 branches and 5 subgroups. The first branch can be divided into two subgroups, which includes cultivar ‘Zhenmu No. 2’ in China and two cultivars in Japan; and the second branch includes 44 samples which can be divided into 3 subgroups, in which, cultivar ‘ Xiguazhenmu No. 1’ in China and cultivar ‘ White-flowered gourd’ in France are clustered in the first and second subgroups, respectively, and other 42 cultivars are clustered in the third subgroup. It is suggested that there are rich genetic variations and geographic divergences among cultivars of L. siceraria from different origins, and difference of their ITS sequences is related to geographical distribution.