Defoliation alleviates cold-induced oxidative damage in dormant buds of grapevine by up-regulating soluble carbohydrates and decreasing ROS

Abstract

The number of pre-bloom, bloom and fruit-set source leaves are the most important determinant of tolerance of buds to low temperatures during winter. In this study, we tested whether pre-bloom (LR-PB), bloom (LR-FB) and fruit-set (LR-FS) hand defoliation are effective in interacting the cold hardiness and biochemical parameters in dormant buds (basal-medium and apical buds) of a high-yielding cultivar Karaerik during period of 2-year field study. In the LR-PB contrary to control (C) was found that basal-medium buds showed high-temperature exotherm (HTE) values and low-temperature exotherm (LTE) values at high temperatures than apical buds; therefore, basal-medium buds (1st, 2nd, 3rd, 4th and 5th) had less tolerance to low temperature than apical buds (6th, 7th, 8th, 9th and 10th). Additionally, the contents of the soluble carbohydrates increased in buds apical after the LR-PB treatment, while malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide radical (O2·−) were decreased. The results from defoliation indicated that the LTE values are positively correlated with water content, MDA, H2O2 and O2·− and are negatively correlated with soluble carbohydrates content. Particularly, LR-PB treatment played the key role to explain the difference of cold hardiness between basal-medium and apical buds. Therefore, since LR-PB treatment does not have a negative effect on basal bud survival and increases the survival of apical buds in cool climatic regions, it could be used as a powerful technique for grape cultivars with poor basal buds fruitfulness.