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) andlupin (Lup), in improving grapevine performance and inducing water stress tolerance were evaluated in thefieldon the wine grape cultivar Corvina. PHs were applied every ten days and for three times from fruit-set to bunchclosure by spraying at two concentrations (1.6 and 6.4 g L−1equivalent 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 enhancinggrapevine yield and quality and in reducing conductance index (IG), with differences in efficiency, depending onthe biostimulant origin and concentration. With regards of yield,SoyandCasat 6.4 g L−1reached 5.57 and5.39 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 °Brix (Lupat 1.6 g L−1). All PHs significantly ameliorated the total anthocyanin content ofberries with respect of the control (132 g L−1). The best effect was obtained byCastreatment at the lower dosewith an anthocyanin content of 373 g L−1. Generally, canopy temperature of treated vines remained significantlyhigher than untreated control of 1–3 °C degrees. Regarding water stress tolerance, the lowest dose ofSoy-andCas-PHs showed great ability to reduce the stress index IG(proportional to stomatal conductance). This 5-yearstudy showed the role of PHs, as natural biostimulants, to ameliorate fruit parameters and reduce water loss andSoy-andLup-PHs can be considered for a commercial application