Influences of gibberellins A4, A4+7, and A4+iso—A7on apple fruit quality and tree productivity. I. Effects on fruit russet and tree yield components

Abstract

Mature ‘Golden Delicious’ apple trees in British Columbia (B.C.) and Quebec, Canada and Cox’s Orange Pippin apple in Canterbury, New Zealand were sprayed weekly for four weeks, commencing at petal fall, with formulations of GA4, GA4+7 mixture (1:1) or GA4+iso—GA7 (a less active isomer). This study was predicated on previous work suggesting that GA4 is more effective than GA7 for fruit russet control and is less likely than GA7 to inhibit return flowering. It was hypothesized that conversion of GA7 in the GA4+7 mixture to iso—GA7 might ameliorate the expected negative effect of the GA treatment on return flowering. Surface russet was prevalent on Quebec ‘Golden Delicious’ and all GA treatments reduced its severity. Stem-end russet was reduced by GA4+iso—GA7 in the B.C. ‘Golden Delicious’ trial but none of the treatments influenced stem-end russet of New Zealand ‘Cox’s Orange Pippin’. All G As and GA mixtures reduced fruit set and seed number per fruit and increased average fruit weight in one or more exper...