Alleviation of drought stress in grapevine by foliar-applied strigolactones.

Drought is one of the major abiotic stress factors that affect grape growth and yield, which in turn negatively affects the grape and wine production industry. Developing effective approaches to improve grapevine tolerance to drought stress is a priority for viticulture. Strigolactones, a newly discovered class of carotenoid-derived phytohormones, have been found to participate in various physiological processes. Herein, the effect of strigolactones (SLs) on grape seedlings under drought stress was investigated. Two-year-old grape seedlings (Vitis vinifera L.) were sprayed with 3 doses of rac-GR24 (1 μM, 3 μM and 5 μM), a synthesized strigolactone, and then were subjected to 7% (w/v) polyethylene glycol (PEG-6000) to simulate the drought conditions. Synthetic GR24 treated plants showed higher tolerance to drought stress with regard to lower electrolyte leakage, stomatal opening, reactive oxygen species (ROS), and higher relative water content, chlorophyll content, photosynthesis rate and malondialdehyde (MDA) content. GR24 application also decreased the levels of indoleacetic acid (IAA) and zeatin riboside (ZR), while increasing the level of abscisic acid (ABA), both in the roots and leaves under drought stress. These results suggested that foliar application of GR24 could ameliorate the adverse effects of drought due to its regulation of stomatal closure through ABA or ROS, and modulation of chlorophyll components and photosynthesis, as well as activation of the antioxidant defense capacity. Cross-talk with other hormones, especially ABA, was also suggested to be one of the important mechanism during this process. This study contributes to our current understanding of GR24-induced drought tolerance in grapevines.