Phylogenetic Relationships Among Taxa Of The Genus Actinidia Based On AFLP Marks

Actinidia is one of important fruit resources native to China. Conserving genetic resources of Actinidia is a vital issue for the long-term sustainability of the kiwifruit industry both in China's and in the world. The national germplasm repository for Actinidia and breeding programs for kiwifruit cultivar improvement were established at the Wuhan Institute of Botany, The Chinese Academy of Sciences, with the goals of conserving natural resources of Actinidia in China and developing superior cultivars. As part of our long-term commitment for Actinidia genetic conservation and germplasm management, a better understanding of taxonomy system and phylogenetic relationships in Actinidia is needed for formulating an effective conservation strategy.The AFLP technique was used for purpose of developing a molecular marker system in assistance to Actinidia genetic conservation. A total of 96 entries conserved in the repository, including 38 species, 17 varieties, three undetermined taxa and one outgroup taxon, were selected and subjected to AFLP analysis. Four selective AFLP primer pairs generated 105 reliable AFLP markers, of which 103 were polymorphic, revealing 98% of polymorphic markers in the genus and 27.0% of mean polymorphic markers in taxon. A high level of genetic diversity was found both in inter- and intra-taxon, and 81.51% genetic diversity found between taxa was much higher than 18.49% within taxon. However, the result need to be considered with cautions and also revealed problems that entries with each taxon were not sufficient enough to encompass the genetic diversity of the taxon and some taxa were mislabeled. Further collection and conservation of Actinidia germplasm is needed to enhance integrity of the repository management.Genetic similarity among taxa was analyzed using reliable AFLP markers by NTSYS-pc software. For phylogenetic relationships among taxa, genetic distances were calculated and used for constructing a dendragram by UPGMA clustering analysis and for establishing a strict consensus tree by Wagner Wanger parsimony method using PHYLIP software. The results indicated: 1) Genetic relationships revealed by the clustering analysis is generally consistent with that by traditionallymorphological classification; 2) The strict consensus tress supports section Leiocarpae as monophyletic group but rejects other three sections in traditional classification; 3) Clustering taxa by geographic distribution was supported by both methods, suggesting a positive correlation between genetic distance and geographic distribution. It appears that geographic condition has played an important role in speciation of the genus and that genetic divergence is still underway in shaping the phylogenetic relationships with the genus; 4) The current taxonomic system ofActinidia needs to be revised and some taxa need to be combined. The paper also discussed application and significance of AFLPs in genetic evaluation and taxonomic revision of Actinidia and AFLPs should be considered a useful and important tool for study of genetic diversity but also suitable for phylogeny construction. Subdivision of the genus into sections and series as well as some undetermined taxonomic relationships were further discussed.