Promotion of ripening of `Gebhard' red `d'Anjou' pears by treatment with ethylene

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Pears (Pyrus communis L., `d'Anjou'), `Gebhard' red strain, harvested at commercial maturity with flesh firmness (FF) of 64.5 N, did not ripen normally at 20°C even though the chilling requirement had been met by storage at −1°C. Treating fruit with 100 μl l−1 ethylene at 20°C for 3 days, followed by 14 days of a simulated transit period at −1°C, induced normal ripening at 20°C, with a climacteric-like rise in ethylene production, fruit softening, and reduction of extractable juice. Fruit did not ripen under these conditions without the ethylene treatment. A 3 day treatment with 100 μl l−1 ethylene readily induced pulp tissue to convert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, regardless of the length of chilling. Tissue conversion of ACC to ethylene was also induced by holding fruit at −1°C for 2 months or longer. ACC synthase activity was induced only by ethylene treatment, and did not increase until the fruit had been transferred to 20°C for 3 days. Promotion of normal ripening in `Gebhard' red `d'Anjou' pears by ethylene treatment could be primarily attributed to the coordinate induction of ACC to ethylene conversion and ACC synthase, followed by increasing ACC synthase activity at 20°C.