Fumigation of 1-Hexylcyclopropene Inhibit Ethylene Production in Climacteric Fruits at Ambient Conditions

Postharvest losses in fresh horticultural produce account more than 30% in the world. The postharvest life of horticultural commodities is most affected by endogenous ethylene, exposure of produce to external ethylene, or both. Methylcyclopropene (1-MCP) is widely recognized as an ethylene inhibitor, but its application is cumbersome and expensive. Among other 1-substituted cyclopropenes, 1-HCP (1-hexylcyclopropene) is effective in extending vase life on kalanchoe flowers. We investigated the effects of different concentrations of 1-HCP and some other analogues of 1-MCP (isoprene oxide and 1-octyne) on ethylene production and modulation of ripening in climacteric fruits such as ‘Kommeet’ tomato; ‘Black Amber’ and ‘Tegan Blue’ Japanese plum; ‘Fuji’ and ‘Crisp Pink’ apple.  The experiments were conducted on completely randomized design, with three replications and ten fruits in each replication. The treated fruits were kept at ambient conditions (20 ± 2 °C and 70% ± 5% RH) and data were collected on the ripening behavior and qualitative changes of the fruits. 1-HCP (1000 nlL^-1) is more effective in suppressing climacteric ethylene production (1.5-fold) as compared to 500 and 2000 nlL^-1 in tomato. Ethylene production was also supressed (1.5- to > 2-fold) in the plum fruits treated with 1-HCP (250 nlL^-1), as compared to other 1-HCP treatments. The higher concentration (500 to 1000 nlL^-1) of isoprene oxide and 1-octyne enhanced ethylene production ranged from 2.5- to > 370-fold more than 1-HCP treated fruit in ‘Tegan Blue’ plum. In ‘Fuji’ apple, the treatment of 125 nlL^-1 1-HCP delayed the climacteric peak of ethylene up to three weeks as compared to all other treatments. The lower concentration of 1-HCP (125 to 250 nlL^-1) substantially suppressed the ethylene production and respiration in both of the two and four-week cold stored fruit of ‘Crisp Pink’ apples. Our preliminary results showed that 1-HCP (125 to 250 nlL^-1) is an effective anti-ethylene compound on a range of climacteric fruits kept at ambient conditions.