Abstract:

【Objective】 The phylogeny of mulberry (Morus) was investigated by using ITS sequences and it will provide useful information for mulberry breeding, germplasm DNA fingerprint identification, classification and evolution. 【Method】 Seventy-three mulberry (Morus) resources were collected from different localities in China and sequenced ITS for all samples by sanger dideoxy method. Furthermore, other ITS sequences of Moraceae and Morus were also downloaded from GenBank and aligned with the sequences obtained in this study by Clustalx1.83c software. Then, the G+C content, divergence and similarity among sequences were analyzed by DNAstar software. Finally, based on the ITS sequences, phylogenetic trees were reconstructed by PAUP Version4.0b10 and Mrbayes softwares. 【Result】 Seventy-three complete internal transcribed spacer (ITS) sequences of Morus were obtained. The length of Morus ITS sequences is 576 bp, and its G + C content is 59.55% (thereinto, ITS1:174 bp, G+C:61.49%, ITS2:302 bp, G+C:62.25%, 5.8S:100 bp, G+C:48.00%). It has 166 variable sites in total (thereinto, ITS1: 100, ITS2: 66, 5.8S: 0), some variable sites are species-specific and can be used as DNA molecular markers of mulberry (Morus) resources. The largest divergence is 4.0. Compared with the other cultivated species, the variation of M. bombycis is bigger, which has differences ranging from 0.9 to 1.4 to the others. Based on the ITS system position of Morus, M. bombycis is between Milicia excelsa (MEU93585) and Streblus glaber (DQ499105) and mulberry (Morus) and Milicia excelsa (MEU93585) have a closest relationship. In addition, Xinjiang M. nigra and North America M. murrayana (FJ605515) are the most primordial species. The evolutionary order of Morus is as M. nigra and M. murrayana→M. alba→M. cathayana →M. wittiorum. 【Conclusion】 ITS is suitable for phylogenetic analysis of Morus. The results of the length of ITS, the content of G+C%, and the variation sites have provide a molecular biological basis for the classification, phylogeny, DNA fingerprinting and cross breeding parentage choice of mulberry. Morus derived from Laurasia move from north to south. The phylogeny of Morus can be reflected indirectly by geographical distribution.

Key words: mulberry (Morus), ITS, fingerprint identification, phylogeny