Effect of variety and ambient conditions on the physiological profile of grapes

Grapes can be classified as drought-resistant crops. However, water deficit, albeit required to produce a quality crop, negatively affects the growth, development, longevity, and resistance of grapes to diseases and low temperatures. High temperatures can also reduce crop quality. Therefore, the resistance of the particular grape variety determines the extent to which abiotic factors influence its productivity. In general, the plant responses to the effects of water deficit and temperature fluctuations are quite conservative; nevertheless, the genotype has a significant influence on the metabolic changes that ensure plant functioning under suboptimal conditions. A comprehensive understanding of the key factors that determine the response of grapes to external influences can identify an effective strategy for breeding, variety selection, or placement under suitable agroecological conditions. The paper aims to explore the leading factor in metabolic changes of grapes under the stress of drought and high temperature. The studies were carried out under controlled conditions. The influence of modeled drought, high temperature, as well as their combination on physiological reactions of the Cabernet-Sauvignon , Kutuzovsky , and Morozko varieties was analyzed. Variety and temperature effects were the leading factors of metabolic changes in grapes, while drought impacted the least number of physiological and biochemical parameters, probably due to a rather high drought resistance of grapes. The low level of cell damage (changes compared the control were about 5%), pigment apparatus (chlorophyll stability index more than 90 %), relatively low MDA content (31 and 33 μmol/g crude weight) can characterize the Kutuzovsky variety as more stable in comparison with Morozko and Cabernet-Sauvignon varieties. Adaptive processes were provided by adaptive degradation of starch, an increase in the content of soluble carbohydrates, high peroxidase activity, and an increase in the content of phenolic compounds. The combined effect of drought and high temperature caused inhibition of peroxidase activity, decrease in starch degradation, higher intensity of oxidative processes, and damage to grape tissues.