Towards a better understanding of the complex mechanisms involved in adaptation of rootstocks to drought

Abstract

Water is the main factor limiting yield in viticulture. Vine water status also strongly impacts grape quality. In the context of climate change, we consider the rootstocks as a relevant way to cope with water deficit. Although drought tolerant and drought sensitive rootstocks are well identified in the vineyard, the mechanisms involved in drought tolerance are poorly understood. In the frame of the rootstock breeding program developed at INRA Bordeaux, we have been characterizing about fifty rootstocks registered in France or used in others countries, in terms of responses to water deficit and conferred vigor. The experiment was carried out in pots, in a greenhouse. Transpiration was evaluated daily by weighing each pot individually with a 150 scale platform. Irrigation was applied in the mid-morning in order to obtain the desired level of water stress. Leaf area measurements were performed weekly in order to calculate the daily transpiration per unit of leaf area. Water extraction capacity was measured with TTSW. A significant diversity for conferred vigor and for plasticity of growth response to water deficit was observed. The results demonstrated that root dry biomass was not correlated with water extraction capacity. A multivariate analysis revealed the complexity of the mechanisms involved in drought adaptation because all the rootstocks known to be tolerant in the vineyard were not grouped in the same area of the graph. Conferred vigor was independent from transpiration responses to water deficit. This result strengthens and confirms previous conclusions obtained from a quantitative genetic study and from one field experiment.