Physiological biochemical and molecular responses of some grape varieties against drought stress

In this study, drought stress tolerance mechanism of 8 different grape varieties (Kabarcık, Manda Gözü, Bilecik İrikarası, Horoz Karası, Rumi, Tekirdağ Çekirdeksizi, Çavuş and Trakya İlkeren) were investigated. Drought application was applied in the form of water constraints, and leaf samples were taken in 4 different periods before the start of the application (control), on the 3rd and 7th days of the water constraint application and after the irrigation at field capacity for 2 days after drought. With the samples of treatments, leaf relative water content (RWC), membrane permeability index (MPI), chlorophyll content (Chlorophyll a, chlorophyll b and carotenoids), proline content, lipid peroxidation (MDA) as well as activities of catalase (CAT) and ascorbate peroxidase (APx) were measured. In all varieties, significant changes weren't noted in RWC with a 3-day drought while RWC significantly decreased after submitting a 7-day drought stress. The responses regarding MDA content varied depending on the varieties. The highest value of MDA was noted in Kabarcık variety in response to drought. MPI values decreased in some varieties after a 3-day drought but a 7-day drought stress caused significant reductions in all varieties. While drought caused increases in APx activities of all cultivars, the responses regarding CAT activity against drought varied depending on variety and duration of stress. Along with the findings of RWC, MPI and MDA, of the varieties, Horoz Karası was relatively tolerant and Kabarcik variety was the most sensitive. For the subsequent and second stage of the experiment, those two cultivars were grafted on their roots and Rupestris du Lot rootstock, which in turn were exposed to drought stress. Then, effects of drought stress on the expression of aquaporin proteins were examined. Accordingly, drought caused a decrease in PIP2-1 aquaporin expression and an increase in TIP1-1 expression in both grafted and non-grafted seedlings of both cultivars.