Rockmelon (Cucumis melo L.) fruit ripening and postharvest quality following application of aminoethoxyvinylglycine

ReTain (Valent BioScience Corporation, Sydney) plant growth regulator is a commercial formulation of aminoethoxyvinylglycine (AVG). This compound is known to competitively inhibit the activity of the enzyme ACC (1- aminocyclopropanecarboxylate) synthase which is the rate-limiting enzyme in the metabolic cycle of ethylene production. Ethylene is a naturally occurring plant hormone that stimulates ripening in climacteric melon fruit, such as rind colour change, flesh softening and production of volatiles. Pre-harvest application of ReTain at the concentration of 125 ppm on rockmelon plants 2 weeks before harvest inhibited postharvest ethylene production. Melons harvested from plots treated with ReTain had lower rates of ethylene production at harvest and after cold storage than melons harvested from control plots. The ethylene inhibition resulted in a delay of fruit ripening of about 2 days. ReTain-treated fruit had a firmer flesh than untreated fruits. In addition, delayed fruit maturity showed less incidence of disease. The results suggest that application of ReTain has major benefits as a harvest management tool for rockmelon production, allowing growers to regulate fruit ripening, improve fruit quality and reduce postharvest rot severity.