Induction of postharvest resistance in melon using pulsed light as abiotic stressor

Abstract

The aim of this study was use the pulsed light (PL) as tool to booster the postharvest resistance in melons. Cantaloupe melons at mature stage were submitted to the treatments as follows: control, pulsed light (PL; 9 J cm−2), 1-methylcyclopropene (1-MCP; 600 nL L-1) and 1-MCP + PL (600 nL L-1 + 9 J cm−2). Postharvest resistance measurements according survival analysis developed at 4 °C, included: ethylene production, 1-aminocyclopropane-l-carboxylic acid (ACC) oxidase activity, ACC synthase activity, firmness, pH, soluble solids, titratable acidity, SS/AT ratio, soluble sugars, vitamin C, total polyphenols, phenylalanine ammonia lyase (PAL) activity, colour epicarp, free polyamines (putrescine-Put, spermine-Spe and spermidine-Spd) and total polyamines (TPo). Combined effect of the PL+1-MCP promoted an additional of 12 days in the shelf life of melons. PL limited the ethylene biosynthesis leading to an immediate upregulation of polyamines (Put + Spe + Spd), hence, associated with high amounts of TPo (56%). PL treatment promoted an increase of PAL activity (67%) that synthesized high content of phenolic compounds (55%). The results suggest that PL with a fluence of 9 J cm−2 stimulate the postharvest defense mechanisms in melon, due to the ethylene production limitation, which was influenced by the increased polyamines, maintaining the quality attributes.