Abstract
Scientific investigations are being increasingly devoted to biostimulant effects on vegetable yield and quality, with the perspective of sustainable crop management. Two farming systems (conventional or organic) in factorial combination with two biostimulant treatments (tropical plant extract (PE); legume-derived protein hydrolysate (PH)) plus a non-treated control were compared in terms of tomato fruit yield, yield components, mineral composition, functional and nutritional indicators. PE- and PH-based biostimulants resulted in higher plant biomass, PH even in higher leaf area index, compared to non-treated control. Marketable yield was not significantly affected by farming system. PH and PE gave higher yield than non-treated control. PH treatment led to higher fruit number than the control, whereas PE incurred significant increase in yield only under organic farming. The mean fruit weight attained the highest value upon PE application under conventional management. Colour component a* (redness) was higher with the conventional system compared to the organic one, whereas an opposite trend was shown by the organic acids malate, oxalate and isocitrate. Irrespective of the farming system, the soluble solids, fruit brightness (L*) and redness as well as the target organic acids malate, oxalate, citrate and isocitrate were significantly higher than untreated plants by 10.1%, 16.1%, 19.8%, 18.9%, 12.1%, 13.5% and 26.8%, respectively, with no significant differences between the PH- and PE-based biostimulants. Higher lipophilic activity and total ascorbic acid concentration but lower lycopene were recorded under organic management. PE and PH application resulted in higher total phenol and ascorbic acid as well as in lycopene content, and lipophilic antioxidant activity than the non-treated control. Biostimulants proved to be an effective sustainable tool for enhancing tomato fruit yield and functional quality both under conventional and organic vegetable systems.
Highlights
Organic horticulture has been increasing worldwide for the past two decades, as a result of rising demand of consumers for healthy and safer food [1], accounting for 3.5 million ha in 2014, which is almost twofold compared to 2008 [2]
Protein hydrolysates (PHs) are mainly made of amino acids, polypeptides and oligopeptides derived from proteins of animal or plant origin upon partial hydrolysis [15] and can be applied to seeds, leaves or soil in several forms [12]
The application of protein hydrolysate (PH)-based biostimulant resulted in the highest yield but plant extract (PE) biostimulant gave a significantly higher yield compared to non-treated control (+18.7% and +11.2%, respectively); these outcomes stemmed from the combined effects of fruit number and mean weight (Table 1)
Summary
Organic horticulture has been increasing worldwide for the past two decades, as a result of rising demand of consumers for healthy and safer food [1], accounting for 3.5 million ha in 2014, which is almost twofold compared to 2008 [2]. The rate of major minerals such as nitrogen and phosphorus released from organic fertilizers and crop residues do not often meet the crop demand during the highest rate plant growth, leading to significant yield reduction [9]. Within both conventional and organic farming systems, the use of naturally derived plant biostimulants is a promising sustainable approach [10,11], aiming to enhance (i) plant nutrient availability/uptake/assimilation and use efficiency, (ii) abiotic stress tolerance as well as (iii) product quality [12,13,14]. Protein hydrolysates (PHs) are mainly made of amino acids, polypeptides and oligopeptides derived from proteins of animal or plant origin upon partial hydrolysis [15] and can be applied to seeds, leaves or soil in several forms (liquid or granular) [12]
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