Protein hydrolysates effects on grapevine (Vitis vinifera L., cv. Corvina) performance and water stress tolerance

The effects of animal- and plant-derived protein hydrolysates (PHs), namely casein (Cas), soybean (Soy) and lupin (Lup), in improving grapevine performance and inducing water stress tolerance were evaluated in the field on the wine grape cultivar Corvina. PHs were applied every ten days and for three times from fruit-set to bunch closure by spraying at two concentrations (1.6 and 6.4 g L-1 equivalent to 0.5 and 2.0 kg/ha, respectively); water treatment was used as control. Overall, data clearly pointed out the effect of biostimulants in enhancing grapevine yield and quality and in reducing conductance index (IG), with differences in efficiency, depending on the biostimulant origin and concentration. With regards of yield, Soy and Cas at 6.4 g L-1 reached 5.57 and 5.39 kg/vine, respectively, with an increase of 24 and 21% with respect to the control treatment (4.25 kg/vine). Total soluble solids content was significantly increased by PHs application, with values ranging from 19.05 (control) up to 22.80 degrees Brix (Lup at 1.6 g L-1). All PHs significantly ameliorated the total anthocyanin content of berries with respect of the control (132 g L-1). The best effect was obtained by Cas treatment at the lower dose with an anthocyanin content of 373 g L-1. Generally, canopy temperature of treated vines remained significantly higher than untreated control of 1-3 degrees C degrees. Regarding water stress tolerance, the lowest dose of Soy- and Cas-PHs showed great ability to reduce the stress index IG (proportional to stomatal conductance). This 5-year study showed the role of PHs, as natural biostimulants, to ameliorate fruit parameters and reduce water loss and Soy- and Lup-PHs can be considered for a commercial application.