Phylogenetic Relationships of Sugarcane Related Genera and Species Based on ITS Sequences of Nuclear Ribosomal DNA

Sugarcane related genera and species are important germplasm resources in sugarcane breeding. The internal transcribed spacer (ITS) sequence of 120 Saccharinae accessions that belong to 8 genera and 37 species were used to analyze their genetic relationships and construct phylogentic relationships with Pennisetum purpureum as an outgroup. The results showed that the sequence lengths were 200–208 bp for ITS1, 215–221 bp for ITS2, and 164 bp for 5.8sDNA with variable sites of 91, 93, and 18, respectively. The informative sites were 70, 68, and 9 for ITS1, ITS2, and 5.8sDNA, and the GC contents were 60.4%–69.1%, 66.1%–73.4%, and 54.1%–58.0%, respectively. According to the ratio of the variable sites and the ratio of informative sites to all sites, ITS sequence had richer variance than 5.8sDNA sequence, and the variance of ITS1 sequence was richer than that of ITS2 sequence. The result of genetic distance analysis revealed that that Miscanthus and Triarrhena were the closest genera to Saccharum, followed by Erianthus and Narenga, and genera Microstegium, Spodiopogon, and Imperata represented the furthest relationships with Saccharum. In the phylogenic tree constructed using neighbor-joining and maximum parsimony methods, the sugarcane related genera and species were separated into 10 groups. Erianthus arundinaceus should be classified into Erianthus genus rather than in Saccharum genus. Triarrhena is likely to be involved in Miscanthus. The 2 species from Narenga were sepearted in different groups, of which N. porphyrocoma was grouped with E. rockii, and N. allax was in an independent group. The Erianthus and Miscanthus species went to different groups, indicating the complex genetic relationships within genera.