Phylogeny of the selected members of family Cornaceae as inferred from PCR-RFLP analysis of chloroplast DNA (cpDNA) and internal transcribed spacer (ITS)

Abstract

PCR-RFLP (polymerase chain reaction–restriction fragment length polymorphism) analysis of cpDNA and PCR-RFLP of rDNA were performed to assess the phylogenetic relationship in seven species of the family Cornaceae. Four pairs of primers, trnD/trnT, trnH/trnK, psaA/trnS and rbcL/ORF106, and one restriction enzyme (HinfI) were used for RFLP-PCR of cpDNA, and two primer pairs ITS5/ITS2 and ITS3/ITS4 with one restriction enzyme (HhaI) were used for ITS1 and ITS2 regions of rDNA, successively. Restriction products produced by trnH/trnK-HinfI and psaA/trnS-HinfI for cpDNA and ITS5/ITS2-HhaI and ITS3/ITS4-HhaI for rDNA, generated very informative bands from all of the seven species studied. A total of 147 scores were recorded and used in PHYLIP (phylogeny inference package) to generate a combined phylogenetic tree. The family was divided into two clades: the Aucuba clade and the cornaceous clade. The cornaceous clade further divided into two subclades: the previously suggested blue- or white-fruited dogwoods (C. walteri and C. macrophylla) and the Cornelian cherries (C. officinalis), and the big-bracted dogwoods (C. kousa and C. florida). The opposite-leaved blue- or white-fruited dogwoods were found to be close sisters to the alternate-leaved blue- or white-fruited dogwoods and all sisters to the Cornelian cherries. C. kousa and C. florida were found to be close sisters under big-bracted dogwoods. Based on the topology portrayed by the phylogenetic tree obtained, it is possible to conclude that big-bracted dogwoods are the most primitive member followed by the intermediates – the cornelian cherries, and the blue- or white-fruited dogwoods are the most advanced members, while the Aucuba clade is the most primitive in the family.