Dissecting the role of rootstock in drought adaptation: from breeding to agronomic perspectives

Abstract

The response of grapevine to drought is a complex trait that involves several morphological adaptations and physiological pathways. In modern viticulture, this response is mediated by the rootstock genotype, which can induce tolerance rather than susceptibility to the scion. Thus, the selection of drought-tolerant rootstocks is considered an effective and sustainable strategy to face future climate scenarios. However, physiological strategies adopted by tolerant rootstock remain unclear, showing a strong interaction with the growing conditions and the water stress dynamic. Traditionally, the most common drought-tolerant rootstocks maximize water uptake by developing extensive and deep root systems, but they also induce high vigor in the scion, causing an increase in water loss through transpiration. The new breeding for drought-tolerant rootstocks aims to limit water loss by reducing the induced vigor and improving water use efficiency. In this study, different drought-tolerance strategies were characterized by comparing the performance of two tolerant rootstocks (i.e., 1103 Paulsen and M4) under a wide range of growing conditions, including controlled and open field conditions, own-rooted and grafted vines, various grafting combinations, and different climate and soil conditions. Physiological response to drought induced by the two rootstocks differed for root plasticity, scion vigor, stomatal control, xylem vessel modifications and hydraulic conductance. In field conditions, the different tolerance strategies led to differences in grape ripening and production. Results of these studies enhance our understanding of rootstock-induced drought-tolerance, leading to the development of new ideotypes for future breeding selection.