Methods to dissect grapevine rootstocks responses to drought stress

The tolerance to drought stress is a particularly important goal of grapevine rootstocks breeding. The quality of phenotyping is crucial to achieve the targets of selection. The application of high-throughput phenotyping techniques like infrared thermography has been widely used over the last few years, allowing the study of plant-environment interactions through the development of specific algorithms based on canopy temperatures. In the framework of a larger and long lasting program, the evaluation and characterization of the new rootstock selections performance and the development-validation of non-destructive phenotyping techniques, have been carried out also to provide data for genetic association studies (GWAS). In 2012, 96 genotypes of Vitis spp., including a genus core-collection, commercial rootstock and four new rootstocks (M series), were monitored during a dry down experiment under semi-controlled conditions. The physiological responses to water deficit were evaluated over 30 days considering leaf stomatal conductance (Gs) and leaf temperature (Tl) using a steady state porometer (Licor Li-1600) and Thermal Camera (InfRec) respectively. Data analysis consisted in the analysis of 5742 thermal imagines using the software InfraRecAnalyzer to obtain the thermal indices correlated with stomatal conductance. At the same time the growth of the plants (stems and leaves) were monitored. During the experiment the procedure for reducing the time for phenotyping was validated. Combining the stomatal conductance and the growth data, all genotypes were classified by different physiological characteristics and behaviors under drought stress. The application of thermography allows for rapid phenotyping and permits the screening of a large number of genotypes. The use of this tool requires special attention during the calibration phase.