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

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 degrees C even though the chilling requirement had been met by storage at -1 degrees C. Treating fruit with 100 mu l l(-1) ethylene at 20 degrees C for 3 days, followed by 14 days of a simulated transit period at -1 degrees C, induced normal ripening at 20 degrees 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 mu l 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 degrees 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 degrees 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 degrees C. (C) 1997 Elsevier Science B.V.