ABA and ethephon alleviated to a different extent the impact of elevated temperatures on grape berry composition

Abstract

The Intergovernmental Panel on Climate Change (IPCC) forecasts an increase in global temperature and a decrease in relative humidity (RH) in the coming decades, which may have implications for berry ripening and composition. The objective of this study was to evaluate the use of two phytoregulators, abscisic acid (ABA) and ethephon (an ethylene releasing compound), to counteract the negative effects of increased temperature on the accumulation of anthocyanins in grapes. Grapevine fruit-bearing cuttings of Tempranillo (TE) and Cabernet sauvignon (CS) were grown from fruit set in two greenhouses under two temperature/RH regimes: 24 °C / 14 °C and 55% / 70% RH, day/night (T) and 28 °C / 18 °C and 43% / 58% RH (T+4), simulating the changes expected for 2100. Just before the onset of veraison the bunches of plants from both temperature/RH regimes were sprayed with ABA (400 mg L-1), ethephon (480 mg L-1), and distilled water (control). The application was repeated 7 days after the first application. T+4 conditions reduced the must acidity and the concentration of berry skin anthocyanins, increasing the proportion of malvidin, in both TE and CS. The concentration of total amino acids tended to increase under T+4 compared with T in both varieties. ABA was more effective than ethephon as a mitigation compound, increasing the concentration of anthocyanins in both TE and CS and alleviating the decrease induced by T+4. Ethephon reduced must acidity in both varieties and regardless of the temperature/RH regime. In CS, ethephon also decreased the concentration of total amino acids, but increased aromatic precursor amino acids. In conclusion, the application of ABA alleviated the negative effects of elevated temperature on anthocyanins. Ethephon was less effective than ABA, even negatively affecting must acidity.