Variability of qualitative and quantitative secondary metabolites traits among wild genetic resources of Lavandula stoechas L.

Lavandula stoechas L. (Lamiaceae) is an attractive shrub native to the Mediterranean regions used for ornamental, melliferous, aromatic and medicinal purposes. Furthermore, this species presents an increasing interest in cosmetics, perfumery and pharmaceutical industries. The variability of qualitative and quantitative metabolic traits among nine wild germplasms representing the distribution area of this species in Tunisia was undertaken. A total of 45 essential oil components were identified in the aerial parts of the studied germplasms. The main essential oil components were camphor (15.32-50.63%), fenchone (6.57-34.70%), 1,8-cineole (0.05-13.45%) and gamma-gurjunene (1.10-12.15%). In addition to the well known chemotypes camphor/fenchone and camphor/1.8cineole, a new chemotype camphor/gamma-gurjunene was detected in Tunisian L. stoechas L. Six phenolic acids (quinic acid, gallic acid, p-coumaric acid, 4,5-di-O-caffeoyquinic acid, salviolinic acid and trans cinnamic acid) and five flavonoids (luteolin-7-o-glucoside, naringin, apegenin-7-o-glucoside, quercetin and kampherol) were identified in the ethanolic extracts. Salviolinic acid (46.30-615.18 mu g/g) and luteolin-7-o-glucoside (5.98-38.54 mu g/g) were the most abundant phenolic compounds. A high significant phytochemical variability (p < 0.01) in the accumulation of volatile and phenolic secondary metabolites among the studied germplasms was recorded. The conducted multivariate (PCA) and clustering (HCA) analyses revealed different classification pattern for essential oil and phenolic compounds. The detected phytochemical polymorphism among the investigated lavender ecotypes didn't show accordance with bioclimatic and geographical areas which suggests genetic background as the main explaining factor. The detected secondary metabolites polymorphism valorises Tunisian L. stoechas L. genetic resources as valuable plant material in further breeding programs. Moreover, an urgent in situ and ex situ conservation measures are required for these wild germplasms threatened by human over-harvesting practices and the occurring dramatic changes in climatic conditions.

Automated summary

This study investigated the variability of volatile and phenolic secondary metabolites among nine wild germplasms of Lavandula stoechas L. in Tunisia, identifying a new chemotype and significant phytochemical polymorphism. Salviolinic acid and luteolin-7-o-glucoside were found to be the most abundant phenolic compounds. The detection of phytochemical polymorphism highlights the genetic background as the main explaining factor, suggesting the value of Tunisian L. stoechas L. genetic resources for breeding programs.