Genetic diversity analysis on ITS sequence of Lagenaria siceraria cultivars from different origins

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) of38 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 ‘Whiteflowered 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.