Abstract
1-Methylcyclopropene (1-MCP) is a gaseous ethylene binding inhibitor used to control or delay ethylene-related postharvest problems in a range of horticultural commodities. To evaluate the potential of 1-MCP to prevent unwanted defoliation and fruitlet loss when using ethephon to loosen mature citrus fruit, canopy sector tests were conducted in 'Valencia' orange [Citrus sinensis (L.) Osb.] using 400 mg L-1 ethephon (2-chloro-ethyl-2-phosphonic acid) in combination with 1, 2.5 and 5 mM concentrations of 1-MCP. Although there was no difference in loosening of mature fruit by ethephon and ethephon + 1-MCP treatments, 1-MCP reduced defoliation caused by ethephon. Studies on the effect of 1-MCP + ethephon application on flower and fruitlet abscission demonstrated that unwanted abscission in these organs could also be reduced. The results suggest that ethephon-induced phytotoxicity can be reduced with 1-MCP, but the gaseous nature of 1-MCP is an impediment to uniform application. A sprayable 1-MCP formulation is needed for preharvest use in many horticultural crops.
