Intra-Varietal Variability for Abiotic Stress Tolerance Traits in the Grapevine Variety Arinto

The valorization of genetic intravarietal variability through the identification of the most suitable genotypes for yield and must quality is an adequate strategy for grapevine selection. Currently, climate change affects vine yield and wine quality in numerous ways, but little information is available on intravarietal variability regarding responses to abiotic stresses. In the current work, the intravarietal genetic variability of the Portuguese white variety Arinto was studied for yield, must quality, and for tolerance to abiotic stress, through indirect, rapid, and nondestructive measurements in the field. An innovative approach in selection for abiotic stress tolerance is described. The surface leaf temperature (SLT) of clones under environmental conditions of drought and extreme heat was measured, as were the NDVI (Normalized Difference Vegetation Index); PRI (Photochemical Reflectance Index); and chlorophyll content through the SPAD index, yield, and the characteristics of the must (pH, acidity, and °Brix). The application of this methodology was carried out in an experimental population of 165 Arinto clones for three years. Linear mixed models were fitted to the data from evaluated traits, and the empirical best linear unbiased predictors (EBLUPs) of genotypic effects were obtained, as well as the coefficient of genotypic variation (CVG) and broad-sense heritability. The genotypes were ranked according to their level of tolerance to abiotic stress without loss of yield/quality. SLT enabled the identification of clones that regulate stomata opening during stress, thus correlating positively with yield. SLT appears, thus, to be the most robust and reliable indicator to assess tolerance to stress in large field trials for grapevine selection. The results enabled the selection of a group of ten clones with increased tolerance to stress, compared to the average of the variety which maintained the typical must quality of Arinto.