Pedunculate oak (Quercus robur L.) is one of the most significant broadleaved tree species in Europe. However, various abiotic and biotic agents have influenced pedunculate oak forests, among which drought stress has been frequently described as the main driver of this species forests decline. In this study we assessed relative expression profile of 11 candidate genes involved in many different metabolic pathways and potentially responsible for oak drought tolerance. The obtained results succeed in partially tackling drought tolerance mechanisms of targeted natural pedunculated oak population. This gene pool may represent a base for adaptation and therefore genetic diversity should be conserved. In this paper we described different expression responses of four pedunculate oak ecological groups, characterized by different physiological status (senescent vs vital) and flowering period (early (var. praecox) vs late (var. tardissima)). The most significant differences in relative gene expression levels are shown between the flowering period (tardissima (8 genes upregulated) vs praecox (3 genes upregulated)), more than a physiological status (sene-scent vs vital). Only three genes wrky53, rd22 and sag21 showed upregulated expression pattern in senescent physiological groups, indicating their possible role in the coping mechanisms of oak in stressed environment. Results showed interesting connections of relative gene expression values of identified drought-tolerance related genes with flowering period and provide further recommendations for adequate conservation and monitoring of this important oak gene pool in its southeast refugium.
