Pre-Harvest Strategy for Improving Harvest and Post-Harvest Performance of Kale and Chicory Baby Leaves

A greenhouse trial was conducted in Southern Italy to examine the effects of foliar applications of two substances, methyl-jasmonate (MeJA) and a zeolite, on the harvest and post-harvest performance of two hydroponically grown baby leaf genotypes (leafy chicory 'Cicoria costa rossa'; kale 'Cavolo nero'). MeJA is a phyto-hormone primarily studied for fruit and post-harvest applications, while zeolite is typically used for pest and disease biological control. MeJA (Sigma-Aldrich Merck KGaA, Darmstadt, Germany), and a commercial zeolite (Big-Zeo, Agricola Internazionale s.r.l., Pisa, Italy) (BigZeo) were sprayed twice at the second and fourth true leaf stages (BigZeo, 5 kg ha^-1; MeJA, 250 µM). Bio-physiological (yield, dry matter DM, chlorophyll CHL, weight loss WL) and qualitative (nitrate, carotenoids, phenols, flavonoids, anthocyanins, antioxidant activity) traits were evaluated in both raw and fresh-cut (7 day-cold-stored) products. Treatments did not significantly affect yield (1.0 kg m^-2), while plant responses to the substances concerning other traits were genotype-dependent. MeJA enhanced greenness (CHL), texture (DM), and antioxidant activity (by increasing carotenoids and flavonoids) in chicory. In contrast, zeolite improved greenness, texture, and antioxidant activity (by increasing carotenoids, anthocyanins, and phenols), and reduced nitrate in kale. Treatments did not affect weight loss (2.2 g 100 g^-1 f.w., on average). After 7 days of storage, MeJA-treated chicory and zeolite-treated kale exhibited improved textural and nutritional quality.