Involvement of Ethylene in the Pedicel in Preharvest Abscission of 'Tsugaru' Apple

Abstract

The involvement of ethylene in the pedicel in preharvest fruit drop and the relationship between ethylene in the pedicel and its production in the flesh and the seed were investigated in 'Tsugaru' apple. The induction of pedicel abscission was achieved by the injection of ethylene with a syringe, whereas it was inhibited by 2, 5-norbornadiene (NBD), an antagonist of ethylene action. The injection of ethephon into the fruit core, or the spray on the bourse resulted in increasing ethylene content in the pedicel and subsequent fruit abscission. The treatment with aminoetoxy-vinylglicine (AVG) of the fruit core, the inhibitor of ethylene synthesis, reduced the fruit abscission and ethylene content in the pedicel. Ethylene production of the seed and the flesh, and its content in the pedicel in 'Tsugaru' greatly increased before the rapid increase in fruit drop. Fruit of 'Jonagold' usually do not exhibit preharvest drop, the ethylene production and ethylene content are low; they increased little before harvest. Therefore, ethylene likely originates in the flesh and seeds and is translocated to the pedicel where it acts to induce fruit abscission.