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Ethylene induces postharvest problems in many fruits, including members of the Cucurbitaceae. The effects of ethylene and its antagonist 1-methylcyclopropene (1-MCP) were studied on cucumber fruit, a cucurbit harvested immature. Beit Alpha cucumbers (cv. Manar) were harvested and exposed to 0.5 or 1.0 μL·L^-1 1-MCP prior to exposure to ethylene at 10 μL·L^-1 at 15 °C. Fruit exposed to ethylene exhibited significant quality loss upon exposure to ethylene, including epidermal yellowing, a 40% reduction in firmness and, following longer exposure (6 d), epidermal sloughing and placental watersoaking. After 8 d, cucumbers exhibited a 75% reduction in firmness and acute pathogen incidence. Control fruit (no ethylene, no 1-MCP) were visually acceptable but firmness had declined 30% compared with initial values. Fruit exposed to 1-MCP were resistant to applied ethylene, with firmness declining 10 (1.0 μL·L^-1 1-MCP) to 20% (0.5 μL·L^-1) during storage for 14 d at 15 °C. Firmness of fruit treated with 1-MCP at 1.0 μL·L^-1 was 28% higher than controls receiving only air, suggesting that ethylene production contributes to softening of cucumber during storage. The softening and watersoaking of fruit treated with ethylene was accompanied by downshifts in pectin mol mass. Fruit exposed to 1-MCP showed significantly reduced mol mass downshifts. The data indicate that cucumber show a PCD response to ethylene that is largely prevented by suppression of ethylene perception. The response of cucumber to ethylene parallels that for other cucurbits, and provides additional information that the benefits of 1-MCP extend beyond application to climacteric fruits.

The present study was conducted to explore the process of watersoaking seen previously in beit alpha-type cucumber fruit treated with ethylene. Fruit were harvested at four levels of maturity: Immature (4 to 8 days after anthesis, DAA), Mature (10 to 14 DAA), Breaker (16 to 20 DAA), and Yellow (35 to 40 DAA). Fruit were then stored at 13 °C in the presence of air (control) or either 10 μL·L^-1 ethylene or 1300 μL·L^-1 propylene for up to 12 days. The physiological response to ethylene treatment varied with fruit maturity. Immature-stage fruit treated with ethylene for 9 days had mesocarp watersoaking, epidermal sloughing, and lower hue (118°, control 124°), endocarp pH (4.4, control 5.4), and whole fruit firmness (23 N, control 46 N). Mature-stage fruit behaved similarly to Immature-stage fruit, but lacked mesocarp watersoaking. In contrast, after 9 days of ethylene exposure, the Breaker- and Yellow-stage fruit exhibited no watersoaking, accumulated beta-carotene in peel tissue (13.6 μg·g^-1 F.W, control 0.35 μg·g^-1 F.W.) and had a “melon”-like aroma. Ethylene exposure for all maturities increased respiration rate and decay incidence compared to air-treated fruit. Ethylene evolution was only detectable in fruit with visible decay. Decay incidence in response to ethylene treatment was inversely proportional to maturity at harvest. Watersoaking, exhibited exclusively in Immature fruit, spread inward from the epidermis starting after about 6 days of ethylene treatment. Cells in watersoaked tissue stained negatively for viability with fluorescein diacetate and cells proximal to watersoaked cells stained weakly compared to air-treated controls. Current work is focused on identifying the mechanism of cell death.

Nonclimacteric commodities produce low levels of ethylene yet remain quite sensitive to the growth regulator. 1-Methylcyclopropene (1-MCP; SmartFresh Quality System), an inhibitor of ethylene action, allows analysis of the effects of endogenous ethylene on the senescence of nonclimacteric commodities during storage. Two commercial cultivars (Thoroughbred and Carlo) of fresh green beans (Phaseolus vulgaris L.) were treated with 0.5 μL·L⁻¹ 1-MCP followed by storage at 7 °C. 1-MCP was effective in delaying color change, brown spot incidence, and watersoaking in both cultivars. 1-MCP was effective at delaying yellowing as indicated by a decline in surface hue and chroma; however, lightness was not significantly different between control and 1-MCP-treated beans. Respiration in both cultivars was suppressed, but ethylene production was stimulated late during storage in response to 1-MCP. The appearance of brown spot, a surface disorder possibly reflecting low-temperature injury, was delayed by ≈5 days, and the progression of the disorder was reduced in 1-MCP-treated beans. The incidence of watersoaking in ‘Carlo’ was reduced by 50% in 1-MCP-treated compared with control beans. 1-MCP alleviated symptoms of senescence and chill injury of green beans during long-term storage, implicating a role for endogenous ethylene in the senescence of nonclimacteric commodities after harvest.