Exogenous application of melatonin suppresses ethylene production and delays changes in cell wall-degrading enzyme activities during ripening of ‘034’ avocado fruit

Abstract Melatonin (N-acetyl-5-methoxytryptamine, MT) is known to play diverse regulatory roles in fruit ripening and senescence. However, its involvement in avocado ripening remains unclear. This study investigated the effects of exogenous MT application (0.1 and 0.5 mM) on ethylene biosynthesis and cell wall metabolism in ‘034’ avocado fruit stored at 22 ± 1 °C and 75–80 % relative humidity. Treatment with 0.5 mM MT (immersion for 2 hours) significantly suppressed ethylene production and reduced the respiration rate. In addition, MT treatment effectively delayed fruit softening by moderating the activities of pectin methylesterase (PME), polygalacturonase (PG), and cellulase (Cx). These results demonstrate that MT can slow ripening-associated physiological and biochemical changes, suggesting its potential as a postharvest strategy to extend the shelf life of avocado fruit.