Implications of Some Foliar Organic Compounds on the Taxonomy of Capsicum L. Species

Abstract

Capsicum L. varieties and species are closely related so much that there have been some confusions among different taxonomists on their taxonomic status. This study aimed to determine the taxonomic standing of Capsicum L. genus members in Nigeria to assess genetic divergences and similarities among them to provide some insight into their identification and the infrageneric classification (INC) of the genus. Seeds of five cultivars of Capsicum spp., collected from various sources and authenticated, were regenerated, and nurtured to fruit. Variations in their foliar organic compounds were identified quantitatively, using Gas Chromatography Mass Spectroscopy (GCMS). A total of 17 organic chemical characters (12 Esters, 2 Alkanols 1 each of Alkanoate, Alkanoic acid, and Alkane) were detected. The percentage peak area values obtained include 1.75 to 21.88 of esters, 2.24 to 11.99 of alkanols, 5.8 of alkanoate, 17.48 to 55.15 of alkanoic acid, and 4.9 of alkane. The cultivars of each genus were hierarchically clustered as operational taxonomic units (OTUs) using squared Euclidean distance computed through PASTatistics software (Ward’s method). Artificial keys were also constructed for the identification of the species in the genus. The categories of chemical characters adopted gave useful insights into the INC of the genus, as their combination was sufficiently diagnostic of the species as evidenced by the artificial keys. The taxonomic status of Nigerian representatives of the genus Capsicum L. was successfully determined in connection to the distribution of their fruit capsaicin concentration (FCC), similar to those that were previously reported of morphology and phytochemicals in Capsicum. The challenge of vague infrageneric boundaries has also been partially resolved in the Nigerian Capsicum spp. studied.