Morphological and Molecular Evaluation of Genetic Diversity of Wild Tunisian Oregano, Origanum vulgare L. subsp. glandulosum Desf. Ietswaart

Abstract

Aim: The objective of this work was the search for morphological and molecular markers useful for the analysis of genetic diversity of Origanum vulgare L. subsp. glandulosum in the northern region of Tunisia. Study Design: The study of genetic diversity of Origanum vulgare L. subsp. glandulosum was assessed using RAPD- PCR, sequence analysis of the internal transcribed spacer, and eleven quantitative traits. Place and Duration of Study: Five oregano populations were identified and collected in four governorates of Tunisia, Plant specimens of Origanum vulgare L. subsp. glandulosum were collected during the full flowering period in 2015 in their natural habitats. Methodology: The five Tunisian Origanum vulgare L. subsp. glandulosum populations were first characterized and evaluated based on phenotypic characteristic and RAPD- PCR. We carried out PCR amplifications of the ITS1 region of the total cellular DNA extracted either from the seeds or fresh leaves of Origanum vulgare L. subsp. glandulosum. Results: The studied populations were highly variable in all evaluated traits (P < 0.05). The dendrogram estimated for the morphological traits revealed two main clusters. In total, 30 individuals from 5 Origanum wild populations were assessed using RAPD - PCR method coupled with sequence analysis of the internal transcribed spacer (ITS1) and ITS (ITS1 + 5.8S + ITS2) rDNA regions. The separation of amplification products from the total ITS region shows a single band of 700 bp in the oregano populations. This result shows that all the Tunisian populations of Origanum vulgare L. subsp. glandulosum studied have a common genetic basis and they all belong to the same subspecies. The Principal components analysis and the dendrogram using RAPD markers grouped Origanum vulgare L. subsp. glandulosum populations into 2 main clusters. This classification brings together the geographically closest populations. Conclusion: Tunisian Origanum vulgare L. subsp. glandulosum is growing wild in the mountains of North Africa. Therefore, it has been shown that it is possible to discriminate Tunisian oregano populations on the basis of their morphological and molecular characteristics that can be used as identification tools in breeding and biodiversity conservation programs.