Amelioration effects of plant-derived protein hydrolysates on growth and yield of four greenhouse lettuce cultivars

Biostimulant application is increasingly capturing the interest of the scientific community and the production industry, as a strategy to endorse the sustainability of agricultural production systems. Protein hydrolysates (PHs), mainly produced by chemical and/or enzymatic hydrolysis from animal or plant matrices, are used more often due to their undisputed beneficial effects on crop productivity. Lettuce (Lactuca sativa L.) is definitely among the most grown and consumed leafy vegetable. Its fast growing cycle with the feasibility of growing it all year round (between open field and greenhouse conditions), in addition to its high phytochemical benefits, makes it constantly present in the daily human diet. The aim of our research was to compare the different productive and colorimetric responses (CIELab) of four hydroponically grown lettuce cultivars (‘Ballerina’, ‘Maravilla De Verano Canasta’, ‘Opalix’, and ‘Integral’) grown in a greenhouse, evaluating the impact of a commercial vegetable PH (Trainer^®). Our results showed an improvement in production performance due to the foliar application of this vegetal derived biostimulant, other than a modulation of the SPAD index and the colorimetric parameters of green and red cultivars of lettuce. The obtained results are of major importance for defining the best combination of genotype × biostimulant applications aiming to improve productivity and appealing color parameters of vegetable commodities.