Variability of responses to 1-methylcyclopropene by banana: influence of time of year at harvest and fruit position in the bunch

Abstract

To examine the effect of early-climacteric (postripening) 1-methylcyclopropene (1-MCP) exposure on the shelf-life and quality of green Cavendish bananas ('Musa acuminata' cv. Williams) from the middle section of the bunch, bananas were harvested bimonthly and treated with 100 μL L−¹ ethylene for 2 consecutive days prior to exposure to 0, 100, 300, 1000, 3000 or 10 000 nL L−¹ 1-MCP for 24 h prior to storage at 22°C. 1-MCP treatment at a concentration of 300 nL L−¹ or above increased banana shelf-life significantly compared with the control, regardless of the month in which fruit were harvested except March where a higher concentration was needed (3000 nL L−¹). Fruit harvested in May were the most responsive with a greater than twofold increase in shelf-life. To examine the effect of fruit position in the bunch on 1-MCP efficacy, green fruit from the top or bottom of bunches were treated with 100 μL L−1 ethylene for 2 consecutive days prior to early-climacteric 1-MCP (300 nL L−1) exposure for 24 h at 22°C. In spring and autumn but not in summer, application of 1-MCP to early-climacteric fruit was more effective in fruit from the top than in those treated from the bottom of the bunch, increasing shelf-life. Firmness of 1-MCP-treated fruit was up to 19% greater than that of the control across the year, except in fruit from the bottom of the bunch. Given that 1-MCP is less effective in extending the shelf-life of summer-harvested fruit (particularly those from the bottom of the bunch), we conclude that preharvest conditions and fruit position in the bunch affect their responsiveness to ethylene and their behaviour during the ripening process.