Genetic and Flower Volatile Diversity in Natural Populations of Origanum vulgare subsp. hirtum (Link) Ietsw. in Bulgaria: Toward the Development of a Core Collection.

Marina Alekseeva,Ivan Atanassov,Tzvetelina Zagorcheva,Krasimir Rusanov,Mila Rusanova

doi:10.3389/fpls.2021.679063

Abstract

We studied the genetic and flower volatile diversity in natural populations of Origanum vulgare subsp. hirtum (Link) Ietsw. in Bulgaria using simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) markers and gas chromatography/mass spectrometry (GC/MS) analysis of flower volatiles from individual plants. Two regions, including the Kresna Gorge and Eastern Rhodopes, typical for the species comprising eight populations and 239 individual plants were included in this study. An analysis with 11 SSR markers and eight SRAP primer combinations showed that SRAP markers were substantially more informative than the SSR markers and were further used for genetic diversity analysis. The results showed low-range to mid-range genetic differentiation between the populations with pairwise fixation index (Fst) values ranging between 0.0047 and 0.11. A total of 10 genetic clusters were identified. An analysis of the flower volatile diversity identified a total of 63 compounds with the vast majority of plants belonging to the carvacrol chemotype and just a single plant to the thymol chemotype. Large deviations were observed for individual compounds within each region as well as within the populations. Hierarchical clustering showed a clear sample grouping based on the two different regions. In addition, an in-depth analysis identified six major and 23 minor metabolite clusters. The overall data set and cluster analysis were further used for the development and testing of a simple and straightforward strategy for the selection of individual plants for the development of a core collection representing the sampled natural populations for this species in Bulgaria. The proposed strategy involves precise genetic clustering of the tested plants followed by the selection of a minimal set from each genetic cluster representing the different metabolite clusters. The selected core set was further compared with a core set extracted by the PowerCore software. A comparison of the genetic and metabolic affiliation of the members of both sets showed that the reported approach selected representatives from each genetic cluster and minor metabolic cluster, whereas some metabolic clusters were unrepresented in the PowerCore set. The feasibility and efficiency of applying the pointed strategy for the development of a core collection representing both the genetic and metabolite diversity of natural populations in aromatic and medicinal plants toward subsequent steps of selection and breeding are discussed.

Highlights

The common name “oregano” refers to a number of species from the Lamiaceae family that produce essential oils with a characteristic scent mostly due to the high concentration of phenolic monoterpenoids like carvacrol and thymol
Considering the fact that sequence-related amplified polymorphism (SRAP) markers could be universally applied to a wide range of plant species, and the methods for general metabolite analysis [gas chromatography/mass spectrometry (GC/MS) and/or liquid chromatography/MS (LC/MS)] are largely available for most of the medicinal and aromatic plants, we propose that the pointed strategy could be routinely applied for the development of core collections from natural populations of a wide range of medicinal and aromatic plants, which are of interest for breeding and industrial cultivation
The currently available expressed sequence tags (ESTs)-derived simple sequence repeat (SSR) markers do not provide enough resolution to allow for genetic differentiation of the populations, and further efforts will be necessary to identify SSR markers, which are suitable for population genetics studies in this species

Summary

Introduction

The common name “oregano” refers to a number of species from the Lamiaceae family that produce essential oils with a characteristic scent mostly due to the high concentration of phenolic monoterpenoids like carvacrol and thymol. Hirtum essential oil has been successfully used as a herbicide (Araniti et al, 2018), an antibacterial agent in the food industry (Govaris et al, 2011; Asensio et al, 2012; AlHijazeen et al, 2016), and a potential treatment for chronic diseases linked to oxidative stress such as Alzheimer and diabetes (Sarikurkcu et al, 2015; Vujicic et al, 2015). All these properties make the oregano essential oil an attractive product for the food, cosmetics, and pharmaceutical industries, which have been constantly looking for sources of natural and safe agents

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Conclusion