Effect of fruit maturity on efficiency of 1-methylcyclopropene to delay the ripening of bananas

Three bunches of unripe 'Williams' banana fruit of different maturity, 173, 156 and 71 days from bunch emergence, were harvested. Fruit from the top, bottom and middle hands from each bunch were fumigated for 24 h with 1-meth ylcyclopropene (I-MCP) at 0, 5, 50 or 500 nl l(-1) at 20 degreesC. All frui t were then stored at 20 degreesC in air containing 0.1 mul l(-1) ethylene and the time taken for each fruit to ripen (green life) was noted. The gree n life of fruit treated with 500 nl l(-1) 1-MCP varied with fruit maturity. In the two most mature bunches it was 27.9 +/- 2.3 days, 4-fold longer tha n fruit fumigated with 0 nl l(-1) I-MCP (6.7 +/- 0.6 days). In the least ma ture bunch, green life was 39.7 +/- 3.0 days, 1.5-fold longer than fruit fu migated with 0 nl l(-1) I-MCP (25.7 +/- 2.5 days). Most fruit treated with 500 nl l(-1) 1-MCP showed an unacceptable uneven skin colouration when ripe . There was no significant effect on green life of 1-MCP at 50 nl l(-1) and 5 nl l(-1). Other fruit from these bunches were not exposed to 1-MCP and w ere held in ethylene-free air until ripe. In the two most mature bunches, t hese fruit had a significantly shorter green life (11.2 +/- 5.6 days in han d 1; 18.9 +/- 4.1 days in hands 4 and 6) than fruit that were fumigated wit h 500 nl l(-1) ' 1-MCP. In the least mature bunch, however, these fruit had a significantly longer green life (56.0 +/- 5.9 days) than I-MCP treated f ruit. Since the effectiveness of I-MCP varied with fruit maturity and in an y commercial consignment there is a mixture of fruit maturity, it is conclu ded that I-MCP has limited commercial potential for the storage of unripe ' Williams' bananas. (C) 2000 Elsevier Science B.V. All rights reserved.