Phylogenetic relationships among Mexican species of the genus Sechium (Cucurbitaceae)

Abstract

The genus Sechium includes 11 species, which are highly related to the genus Sicyos. Sechium is native to Mesoamerica, but only S. edule and S. tacaco have been domesticated. Sechium edule is the most exploited species of the genus due to its broad phenotypic variability. A total of 68 samples from the species S. chinantlense, S. compositum, S. hintonii and S. edule were evaluated, as well as their respective varietal complexes (albus, nigrum and virens groups), thereby amplifying the loci of mitochondrial DNA (CoxIII), chloroplast DNA (rbcL) and the nuclear ribosomal ITS1-5.8S-ITS2 region. This was done with the aim of establishing phylogenetic relationships that help to understand evolutionary processes, which, in turn, will contribute to the taxonomy of the Mexican clade of Sechium and its exploitation in breeding. Phylogenetic trees obtained from Bayesian inference and the maximum parsimony show that S. chinantlense, S. compositum, and S. edule form a cluster with a high phylogenetic kinship. Sechium chinantlense and S. compositum could possibly be populations or varieties derived from S. edule.