Molecular phylogenetic studies based on rDNA ITS, cpDNA trnL intron sequence and cladode characteristics in nine Protasparagus taxa

摘要

The genus Asparagus comprises three subgenera of cladode bearing plants: Protasparagus, Asparagus, and Myrsiphyllum. The interspecific delimitation of the subgenus Protasparagus is ill-defined till date. In the present study, interspecific phylogenetic relationships among nine taxa of Protasparagus based on ribosomal DNA internal transcribed spacer region (ITS1-5.8S-ITS2) sequence and the chloroplast DNA trnL intron sequence conservation with their cladode morphology, anatomy, and stomatal characteristics have been analyzed for the first time. The monophyletic subgenus Protasparagus could be resolved into four strongly supported distinct subclades (I, II, III and IV) suggesting that the rDNA and cpDNA molecular phylogenies are explicitly congruent with the cladode characteristics of the subgenus Protasparagus. The present study also confirms the existing subgeneric classification of the genus Asparagus with the monophyletic origin of the dioecious subgenus Asparagus. The present work brings out phylogenetic and taxonomic relationships within the studied taxa of the subgenus Protasparagus therefore providing important background information for further studies on biogeography of a wide range of species.