Effects of BA, GA4+7, and Daminozide on Fruit Set, Fruit Quality, Vegetative Growth, Flower Initiation, and Flower Quality of ‘Golden Delicious’ Apple

Abstract

Five repeat spray applications at full bloom (FB) + 11 days through FB + 61 days of 50 ppm 6-benzylamino purine (BA) and/or gibberellins A 4+7 (GA 4+7 ) were made on limbs receiving 0 or 2000 ppm butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) at FB + 11 days. Similar repeat applications of BA and GA 4+7 were made at FB + 4 through FB + 57 days on limbs where all blossom clusters were removed at FB or all blossom clusters were retained. GA 4+7 depressed flower bud formation, whereas BA not only increased bloom but also overcame some of the inhibitory effects of GA 4+7 on flowering. The daminozide and BA combination increased flowering more than when each was applied separately. BA increased lateral flower development in the blossom cluster and increased the number of “king” flowers surviving several mid-April freezes. Russeting was increased by BA, decreased by GA 4+7 , and unaffected when BA and GA 4+7 were combined. BA increased fruit weight, length, and diameter when treatments were started at FB + 4 days. GA 4+7 increased fruit length but fruit weight was increased only when treatments were started at FB + 11 days. GA 4+7 decreased seed number, and when combined with BA, seed number was reduced even further.