A novel system for evaluating drought-cold tolerance of grapevines using chlorophyll fluorescence

Background: Grape production in continental climatic regions suffers from the combination of drought and cold stresses during winter. Developing a reliable system to simulate combined drought-cold stress and to determine physiological responses and regulatory mechanisms is important. Evaluating tolerance to combined stress at germplasm level is crucial to select parents for breeding grapevines. Results: In the present study, two species, namely, Vitis amurensis and V. vinifera cv. 'Muscat Hamburg', were used to develop a reliable system for evaluating their tolerance to drought-cold stress. This system used tissue-cultured grapevine plants, 6% PEG solution, and gradient cooling mode to simulate drought-cold stress. V. amurensis had a significantly lower LT50 value (the temperature of 50% electrolyte leakage) than 'Muscat Hamburg' during simulated drought-cold stress. Thus, the former had higher tolerance than the latter to drought-cold stress based on electrolyte leakage (EL) measurements. Moreover, the chlorophyll fluorescence responses of V. amurensis and 'Muscat Hamburg' were also analyzed under drought-cold stress. The maximum photochemical quantum yield of PS II (Fv/Fm) exhibited a significant linear correlationship with EL. The relationship of EL with Fv/Fm in the other four genotypes of grapevines under drought-cold stress was also detected. Conclusions: A novel LT50 estimation model was established, and the LT50 values can be well calculated based on Fv/Fm in replacement of EL measurement. The Fv/Fm-based model exhibits good reliability for evaluating the tolerance of different grapevine genotypes to drought-cold stress.