THE EFFECT OF MESOCLIMATE ON THE RIPENING OF NEBBIOLO GRAPES (Vitis vinifera) IN VALLE DE VALLE DE GUADALUPE, BAJA CALIFORNIA, MEXICO

The physiology of vines (Vitis vinifera) is regulated by the mesoscale and large-scale climatic conditions. Valle de Guadalupe is a winegrowing basin where most of Mexico's wine production takes place and presents climatic variations in mesoscale that could influence the grape ripening. The objective of this study was to evaluate the effect of climatic differences on the ripening of the Nebbiolo grape variety, in two winegrowing areas of Valle de Guadalupe. Due to the distance from the coast, finding climatic differences in the valley and in the grape ripening in the study areas was to be expected. Over the course of four seasons, soluble solids concentration, titratable acidity, and pH were evaluated in grapes from the central zone of Valle de Guadalupe and the area nearest to the sea, San Antonio de la Minas (SAM), Baja California, Mexico. In addition, temperature, relative humidity, irradiance, rainfall, wind speed, and wind direction were evaluated from 2012 to 2015. The soluble solids concentration and pH were significantly higher in the Guadalupe grapes' must than in SAM grapes during the four seasons. On the contrary, the concentration of organic acids always was lower in the must of Guadalupe grapes than in the SAM's. The irradiance was similar in both areas, but the daily average temperature and the number of days with extreme temperatures were higher in Guadalupe. On the contrary, relative humidity and precipitation were higher in SAM. The early ripening of Guadalupe's Nebbiolo grapes seems to be the result of higher average temperatures, frequent warm periods, and lower relative humidity in Guadalupe compared with SAM.