Physiological and agronomical responses to environmental fluctuations of two Portuguese grapevine varieties during three field seasons

Extensive agricultural losses are attributed to heat, often combined with drought. These abiotic stresses occur in the field simultaneously, namely in areas with Mediterranean climate, where grapevine traditionally grows. The available scenarios for climate change suggest an increase in the frequency of heat waves and severe drought events in summer, also affecting the South of Portugal. In this work we monitored several production-related parameters and evaluated the state of the oxidative stress response apparatus of two grapevine varieties, Touriga Nacional (TN) and Trincadeira (TR), with and without irrigation, during three field seasons (2010 to 2012). Overall, results point to a high correlation of most yield and stress-associated parameters with the specific characteristics of each variety and to each season rather than the irrigation treatments. In the season with the driest winter, 2012, the lack of irrigation significantly affected yield in TR, while in the two other seasons the impact of the irrigation regime was much lower. In 2012, the yield of TN was affected by environmental conditions of the previous season. The irrigation treatments significantly affected berry size rather than quality.