Effect of some protein hydrolysates against gray mould of table and wine grapes

The efficacy of eight protein hydrolysates (PHs) of different origins, i.e., soybean (SoyA and SoyB), lupin (LupF and LupP), pea (Pea), yeast (Yeast), casein (Cas), and malt (Cer), in controlling gray mould of grapes, caused by Botrytis cinerea, was evaluated. In in vitro trials, the different PHs did not affect pathogen growth. Whereas, in in vivo trials, wound applications of SoyA, SoyB, LupP, and Cas showed significant effect in reducing rots on table grapes. SoyA and Cas were further tested at different concentrations against B. cinerea. A dose effect was observed, with the best activity recorded at 0.8 g/l, reducing gray mould of 67 and 54 % by SoyA and Cas, respectively. To simulate a commercial application, the experiment was repeated under natural infections, applying PHs at different doses by spray on detached berries. All doses induced a significant reduction of rots, and in general, there were no significant differences among the doses ≤6.4 g/l. Finally, the two hydrolysates were tested on wine grapes cv. Corvina. When applied in the field during growth phase until véraison, SoyA and Cas significantly reduced gray mould incidence by 65 and 92 %, as compared to water control, respectively. Whereas, a combination of pre- and postharvest application of SoyA and Cas reduced storage rots by 56 and 40 %, respectively. Overall SoyA proved to be the best treatment. Although the obtained results need further confirmation, they support the role of Cas and particularly SoyA as safe and effective alternative to traditional fungicides against gray mould of grapes, to be applied in the field and/or during postharvest phase.