Effects of ethephon on ripening, red colour, and storage performance of Jonathan and Delicious apples

Abstract

Ethephon, at concentrations of 125- 1000 ppm, was applied to Jonathan and Delicious apple trees 3-4 weeks before the anticipated harvest date for untreated apples. Ripening of Jonathan, as measured by increases in red colour and flavour score, was advanced by 6, 10, and 15 d by 250,500 and 1000 ppm ethephon respectively. Softening was not affected. Fruit drop was increased by 1000 ppm only, to 14% of the crop. In Delicious, red colouring and flavour development were advanced by up to 6 d with 1000 ppm ethephon, but yellowing and softening were advanced more, by 7- 14 d with 250 ppm and up to 10- 17 d with 1000 ppm. Softening did not reach unacceptable levels, but three weeks after treatment, yellowing and water core reached unacceptable levels. Red colouring, as measured by anthocyanin concentration or area of red skin, was increased up to two-fold in Jonathan with 1000 ppm, and by up to 50% in Delicious with 1000 ppm. Ethephon also advanced the rise in susceptibility of both cultivars to storage disorders, breakdown and brownheart, in air or controlled atmosphere cold storage. However, if the treated apples were harvested when ripe, 7- 15 d before the controls, their quality after storage was the same as that of controls harvested later.