Effect of prohexadione-Ca on leaf chlorophyll content, gas exchange, berry size and composition, wine quality and disease susceptibility in Vitis vinifera L. cv Xinomavro

In this study, prohexadione-Ca was applied at bloom and postbloom stages to field-grown cultivar Xinomavro to evaluate the effects on leaf chlorophyll content, water potential, photosynthesis, grape, berry size and composition and wine quality. The results showed that prohexadione-Ca increased the chlorophyll contents and net photosynthesis in early growth stages (berry set, veraison). Its effect was gradually reduced in later growth of stages. In addition, prohexadione-Ca affected the stomatal conductance mainly at later stage. In contrast, it did not show any effect on the water potential. It was also shown that the prohexadion - Ca reduced the berry size and increased skin anthocyanin and phenolic compounds. Wines provided from treated vines had improved colour and sensory attributes. Applications with prohexadione-Ca improved the resistance of grapes to Botrytis bunch rot in the first year of experiments. In contrast, no significant difference on susceptibility of grapes to Botrytis bunch rot was found in the second year of experiments. No effect of prohexadione-Ca on the susceptibility of vines to downy mildew and powdery mildew was found.