Exogenous application of chemical elicitors affects crop yield and nutraceutical potential of yellow summer squash ( <i>Cucurbita pepo</i> L. var. <i>cylindrica</i> ) fruits

ABSTRACT The aim of this study was to evaluate the effects of applying chitosan (CHT), methyl jasmonate (MeJA), and salicylic acid (SA) during cultivation of yellow summer squash on selected nutraceutical properties. Plants treated with SA (3 mM) increased the number of fruits, fruit weight, and crop yield by 91.6, 51.4, and 188.8%, respectively ( p ≤ 0.05). SA (3 mM) and MeJA (1.5 mM) increased the total phenolic content (TPC) by 19.3 and 39.8%, respectively. SA (3 mM) also increased total flavonoid content (TF) by 28.2% and the antioxidant capacity (AC) by 15.5–60.5%. The three elicitors CHT (1.5 g/L), MeJA (1.5 mM) and SA (3 mM) increased (13.3–17.4%) the cellular antioxidant activity (CCA) compared to the control. Among the treatments, SA (3 mM) was the most effective in enhancing crop yield and key nutraceutical properties while preserving postharvest quality. Although pronounced, CHT (1.5 g/L) and MeJA (1.5 mM) also contributed to crop yield, TPC, and CAA, underscoring their potential as complementary strategies to optimise the production and quality of yellow summer squash.