Phylogenetic relationships in Actinidia as revealed by RAPDs and PCR-RFLPs of mtDNA

Phylogenetic relationship in Actinidia was investigated using RAPD and PCR-RFLPs of mtDNA. Forty taxa of 31 species, encompassing all four sections and six series of the genus, and 2 species of related genus were analyzed with 22 pre-screened random decamers out of a total of 144 primers. A total of 220 DNA scorable bands were amplified across all samples, and 204 DNA scorable bands were amplified within Actinidia, of which 188 (92.16%) were polymorphic. Meanwhile, Thirty-four taxa of Actinidia were investigated through PCR-RFLP analysis of two mtDNA fragments, including nad1/B-C gene (approximately 1,565 bp) and nad4/1-2 gene (approximately 2,061 bp). Digestion of these two fragments by seven restriction endonucleases yielded twenty polymorphic restiction fragments. The phylogenetic analysis revealed a clear indication that section Leiocarpae was a monophyletic group, but subdividing other three traditional sections was poorly supported by RAPDs; however, none of four sections was a monophyletic group in PCR-RFLPs of mtDNA. Both UPGMA phenogram and the strict consensus tree showed that majority of the species were clustered into geographic subgroups of Yangtzi River, southeastern, southern and southwestern region of China in accordance with their natural distribution. The intrageneric subdivisions of Actinidia appeared to be difficult, but could be more appropriate by taking into account the geographic distribution of species, particularly for species of Liang’s sections of Maculatae and Stellatae. The results of phylogenetic analysis with RAPD data suggest to divide the genus into two sections of Leicarpae and Maculatae and to divide the latter section into four series of Yangtzi River, southeastern, southern and southwestern China. The phylogenetic relationships among several species with taxonomic uncertainty have been also discussed on the basis of the results of RAPD and mtDNA data. The results obtained in the present study supplements our understandings of the Actinidia taxonomy obtained from the morphological characters.