Applications of leaf architecture characters in delineating selected species and infraspecific taxa of Genus Cucumis L. (Cucurbitaceae)

Abstract

Leaf venation characters of twelve (12) Cucumis taxa, comprised of eight species, three subspecies, and three varieties were examined to determine patterns of leaf architectural characters and delineate these accessions at the species, subspecies, and variety level. The leaf architecture of twenty-seven accessions representing six taxa were examined and described in this study. Additionally, data on the leaf architecture of another six taxa (represented by 57 accessions) published by Masungsong et al. (2022) were incorporated in the analysis. Results revealed that the twelve (12) taxa of Cucumis primarily varied in blade class, apex angle, primary vein size, secondary vein spacing, tertiary vein angle to primary vein, and areole development. These variations were found consistent with Cucumis species examined in previous studies. A dichotomous key was constructed for the twelve Cucumis taxa using leaf characters derived. Cluster analysis (based on UPGMA) formed two major clusters at 0.130 Gower distance. Cluster I includes Cucumis melo subsp. melo, C. pustulatus, C. melo var. flexuosus, C. melo subsp. agrestis, and C, melo var. texanus which exhibited secondary vein spacing that increases towards the base. while Cluster II is composed of the remaining Cucumis taxa, all displaying irregular secondary vein spacing. Furthermore, sub-clusters were formed based on tertiary vein angle in relation to primary vein, blade class, apex angle, and primary vein size. Results showed that utilizing leaf architecture is an effective technique to describe, characterize and delineate closely related taxa with many similar characters.