Phylogenetic informativeness of plastid regions in inferring the species relationships among Cucumis species

Molecular approaches are playing major role in phylogeny reconstruction and species relationship studies. The uniparent inheritance, small size, non recombinant nature and extremely low rate of evolution of chloroplast genome make it an appropriate marker for phylogenetic studies. In the present study, phylogenetic informativeness of two coding regions, rbcL and rpoC1 and two non-coding intergenic spacers psbA-trnH and trnL-F of plastid DNA were analysed for inferring relationships among Cucumis species. Maximum evolutionary divergence was shown by trnL-F followed by psbA-trnH region. The non-coding spacers evolved 1.62 to 9 times faster than coding regions of rbcL and rpoC1. In the phylogenetic analyses, all species of Asian origin showed clear divergence from Cucumis dipsaceus and Cucumis prophetarum, which were African in origin. Mukia maderaspatana and Dicaelospermum ritchiei showed very low evolutionary divergence and are reported close to each other. C. setosus had been confirmed as distinct species and C. callosus was found to be a wild progenitor of C. melo.