Molecular phylogeny and infrageneric classification of Actinidia (Actinidiaceae)

Nuclear ribosomal DNA internal transcribed spacers (ITS) and chloroplast matK gone were sequenced for 23 species of Actinidia, the genus of kiwifruit. Neither ITS nor matK phylogeny supports monophyly of any of the four sections of the genus. Species of section Leiocarpae form a paraphyletic group at the base of both gene trees, Species of sections Maculatae, Strigosae, and Stellatae plus A. rufa of section Leiocarpae form a monophyletic group, which is consistent with the morphological feature of presence of lenticels on fruit exocarps. Within this clade, however, each of the three sections is polyphyletic on both gene phylogenies. Polymorphic ITS sequences were cloned from 17 of 27 accessions sampled in this study. The polymorphic sequences that are distantly related on the phylogeny may have derived from hybridization or introgression. The infrageneric classification of Actinidia should be revised on the basis of a robust phylogenetic reconstruction inferred from additional molecular, morphological, and cytological data.