Wind and deficit irrigation affect Malbec and Cabernet Sauvignon differently

ALONSO R.; ROIG PUSCAMA F.; FONTANA A.; PICCOLI P.; BOTTINI R.; BERLI F.

Cádiz

Congreso; XLIV World Congress of Vine and Wine, XXI General Assembly of the OIV,; 2023

OIV

Due to global warming Argentina’s vineyards are expanding towards Southern latitudes. Patagonia is the southernmost winegrowing region in the world and is characterized by a high frequency of strong winds. Wind is an environmental signal and a stressful condition, especially to exotic species, that triggers increases in secondary metabolites, although this effect on the grapevine has not been extensively studied. In turn, deficit irrigation (DI) is a management tool commonly used in arid region vineyards, which stimulates the production of secondary metabolites (many of them related to wine quality), although its effectiveness depends on the particular climatic conditions of each region/growing season. Malbec (Mb) and Cabernet Sauvignon (CS) are the red varieties most cultivated in Argentina as per area basis. They have different phenotypic plasticity, i.e., the ability to express different phenotypes under changing environmental conditions. To evaluate the effects of wind, deficit irrigation, and their interactions, a field trial was carried out with Mb and CS during the 2021-22 growing season in an experimental vineyard in the windy locality of Casa de Piedra. Treatments were: protected plants (close to a poplar windbreak) and exposed plants (farther from the windbreak). In each sector, from veraison on, half of the plants were subjected to DI, while the other half was normally irrigated. At the beginning of the experiment, trunk wood samples were taken and the width of the growth rings was analyzed, which allows evaluating the effect of environmental conditions on plant growth from the moment of planting (2011). At harvest time, vegetative growth, yield components and enological quality of the berries were measured. One of the main effects observed was that Mb and CS plants exposed to wind had a lower cumulative growth of the ring width compared to those growing protected from wind. Under this wind-exposed environment, CS plants reduced vegetative growth of their canopy (shoot length, leaf number and leaf area), but clusters weight and yield were increased. This vegetative/reproductive imbalance affected berry ripening, and CS/wind-exposed plants showed lower sugar content. Polyphenol profiles and contents in the berry skins were modified by the treatments and varied between varieties. Generally, wind exposure negatively affected polyphenols concentration in CS, may be through a diluting effect since yield increases, while they increased in Mb plants. On the otherhand, DI increased polyphenols concentration in both varieties and decreased cluster weight in CS. The wind/DI treatments interact in Mb, where protected plants with normal irrigation (lower stress) had the highest vegetative growth and the lowest cluster weight and yield (berries with high sugar levels); while the other treatment combinations did not differ. The wind/DI treatments no interact in CS for any of the measured variables. In conclusion, it was observed that the environmental factorsstudied affect both varieties differently. Deficit irrigation has a positive effect for both Mb and CS, as it increases desired compounds in wine; while wind balances vegetative/reproductive growth, which is beneficial from an agronomic standpoint.