Taxonomic relationships among the genera of subfamily Cucurbitoideae (family Cucurbitaceae) from India inferred from ITS sequences of nuclear ribosomal DNA

Abstract

The internal transcribed spacer (ITS) region of nuclear ribosomal DNA was analyzed from 18 species of the subfamily Cucurbitoideae (family Cucurbitaceae) to assess phylogenetic relationships. The ITS sequence data resolves three major clades. Benincasa, Coccinia, Cucumis, Diplocyclos, Lagenaria and Solena, which belong to the tribe Benincaseae, are grouped in a single clade (78% bootstrap support). This group is further distinguishable into two subgroups. Benincasa forms a clade (80% bootstrap support) with Cucumis species. Lagenaria is closely related to Diplocyclos-Coccinia-Solena subgroup (78% bootstrap support). Trichosanthes and Luffa are grouped in a single clade (93% bootstrap support). Edgaria darjeelingensis (tribe Herpetospermeae), though nested within Trichosanthes-Luffa clade (50% bootstrap support), is distinct from members of tribes Benincaseae and Joliffeae included in the present study. Momordica cymbalaria (=Luffa tuberosa) forms a clade with Momordica dioica (80% bootstrap support).