Investigating the role of endophytes in enhancing grapevine resilience to drought

Grapevine (Vitis vinifera) has been a key perennial crop in temperate regions since its domestication. Its products, particularly wine, table grapes, and raisins, hold significant socio-economic value not only in producing countries, but also worldwide. In recent decades, the demand for grapes has increased due to factors such as globalization, shifting consumer preferences, and expansion of the wine industry. To enhance grapevine productivity, farmers have turned to more intensive cultivation practices that often depend on considerable water resources, leading to an over-extraction of water from local ecosystems, and ultimately compromising the environmental water balance. Concurrently, the rising temperatures and decreasing precipitation levels due to climate change are triggering more frequent and severe drought conditions. These climatic shifts further threaten water availability, making it increasingly difficult for vineyards to maintain their production levels, both in terms of quantity and quality, thereby creating a precarious situation for farmers. As a result, viticulture is becoming more vulnerable both ecologically and economically. This vulnerability highlights the urgent need to enhance the resilience of grapevine by adopting sustainable practices that encourage a more efficient use of natural resources. Recent research has emphasised the crucial role of endophytes – microorganisms that reside within plant tissues without causing damage – in promoting plant growth under both optimal and stressful conditions. In this context, the aim of my PhD project was to investigate the potential use the natural endophyte biodiversity as a sustainable strategy to enhance the resilience of grapevine plants to water deficit environmental conditions. For this study, field grapevine plants growing in arid regions of Italy and Algeria were used as endophyte source. The first step was to characterize the bacterial endophyte communities of these field plants, including their culturable fractions. To evaluate the impact of endophytes on grapevine plants, selected bacterial isolates were inoculated into endophyte-free grapevine plantlets. Subsequently, consortia of these endophytes were developed and inoculated into endophyte-free grapevine plantlets for a drought stress experiment. The effects of the endophytes on the grape plantlets were assessed at physiological, transcriptomic, and epigenetic levels to elucidate their role under both optimal and water deficit conditions. Additionally, the possibility of using the grafting technique to transfer endophytes between grapevines was explored as an alternative method to inoculation.