Preharvest methyl jasmonate application regulates ripening, colour development and improves phytochemical quality of fruits: A review

Jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA), are increasingly being recognised as unique phytohormones, linked to a variety of physiological and molecular functions. Endogenous concentrations of jasmonates (JAs) vary among plant parts, stages of fruit development, maturity, ripening and during the postharvest period. MeJA expresses prime cellular responses, where as an elicitor of secondary metabolite production, aids in inter-plant communications, regulates the biosynthesis of associated phytohormones, supports plant defence systems against pathogenic infections, and helps in abiotic stress conditions. The potential of MeJA has been extensively studied in modulating fruit ripening, enhancing colour development, and improving the phytochemical profile, particularly for antioxidants in fruit crops. Preharvest application of MeJA regulates ethylene biosynthesis during fruit maturation and ripening. Preharvest MeJA sprays have been shown to significantly increase the biosynthesis of phytochemicals such as phenolics, flavonoids, anthocyanins, carotenoids, enzymatic and non-enzymatic antioxidants, as well as essential nutrients. Preharvest MeJA application also upregulates the production of aroma volatiles in fruits. Preharvest spray of MeJA is reported to alleviate chilling injury in cold-stored fruits. This review explores: the biosynthesis of JAs, their influence on tree growth; fruit ripening physiology; colour development; regulation of biosynthesis of pigments; fruit firmness and modulation of biochemical attributes, including antioxidant compounds, during the ripening process, at harvest, and during postharvest periods; therby bridging gaps towards a more comprehensive understanding.