Phylogenetic relationship of wild Petunia taxa by RFLP analysis of chloroplast DNA

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Phylogenetic relationship among the species of Petunia Juss. was analyzed by restriction fragment length polymorphism (RFLP) of chloroplast DNA digested by 20 restriction enzymes and hybridized with 12 cloned Nicotiana cpDNA fragments as probes. A total of 89 useful RFLPs were detected and one Wagner parsimonious tree was obtained using those data. In the tree, both Petunia sensu Wijsman and Calibrachoa were monophyletic but they showed paraphyletic relationship relative to Nicotiana langsdorffii. Six Petunia Juss. species that are not assigned to Calibrachoa were included in the monophyletic clade composed of all species of Calibrachoa used in this study. Calibrachoa parviflora and C.pygmaea, previously thought to be different from the other species of Calibrachoa, formed a clade within the genus Calibrachoa. Among other Calibrachoa species, one geographical clade emerged that consists of the species found in Uruguay and southern Rio Grande do Sul state in Brazil. The clades of Petunia sensu Wijsman obtained from the RFLP data could not be interpreted as groups that correspond with traditional classification. However, four small clades were formed in which the embraced species had some common characters, such as cross-compatibility, floral morphology, and geographical distribution.