1-Methylcyclopropene (1-MCP) strongly inhibits ethylene (C2H4) action in less mature tomato (Lycopersicon esculentum Mill.) fruits, and that control by 1-MCP over C2H4 action limits its commercial use. Our first objective was to determine whether ripening in less mature fruits could be reinitiated by exposure to C2H4 when tomatoes were treated previously with 1-MCP. A second objective was to determine the concentrations of 1-MCP that could be used commercially to retard ripening in tomatoes at less mature stages. For the reinitiation experiments, tomato fruits at the turning stage were treated with 0, 25, 50, 100, 150, or 200 nL·L−1 of 1-MCP. These fruits subsequently were exposed to 100 [mu]L·L−1 of C2H4 on day 3 or day 4 after treatment with 1-MCP. To determine the appropriate low 1-MCP concentrations that may be used without subsequent C2H4 treatment, fruits in the turning stage were treated with 0, 25, 50, 75, 100, or 200 nL·L−1 of 1-MCP, and fruits in the pink stage were treated with 0, 50, 100, 200, 300, or 400 nL·L−1 of 1-MCP. Ethylene treatment on day 3 or day 4 could not reinitiate ripening in turning stage tomato fruits previously treated with any of the 1-MCP concentrations. In tomatoes treated only with lower 1-MCP concentrations, the rate at which ripening proceeded depended upon the 1-MCP concentration and the stage of ripeness at the time of treatment. Arrival at the full red stage of ripening in turning fruits was delayed by 48 h when fruits were treated with 25 nL·L−1 of 1-MCP, 72 h when treated with 50 nL·L−1, and 96 h when treated with 75 nL·L−1, when compared with the control. Ripening of pink fruits was delayed by 24, 48, and 96 h with 50, 100, and 200 nL·L−1 of 1-MCP, respectively, as compared with the control. Tomato ripening could not be reinitiated, but it could be delayed by using lower 1-MCP concentrations that depended upon the stage of ripeness at treatment. This research benefits tomato wholesalers and retailers because they can use 1-MCP to adjust supply and demand cycles. Use of 1-MCP also will reduce losses caused by fluctuating market conditions and during transportation to distant markets
