Effect of Gibberellins and 6-Benzyladenine on the Shape and Fruit Set of ‘Delicious’ Apples1

Abstract

The cytokinin 6-benzyladenine (BA) and gibberellins A4 + A7 (GA4+7), but not GA3, increased the fruit length-diam (L/D) ratio of ‘Delicious’ apples. Prominence of the points near the fruit calyx was increased more by BA than by GA4+7, but increased most when the 2 were combined. Sprays during bloom were more effective than either postbloom or prebloom sprays. A bloom spray combining GA4+7 and BA at 100 ppm each decreased fruit set of open pollinated flowers in one year, but not in another. Concentration of 50 ppm or less altered fruit shape without any significant effect on the number of seed, fruit set, firmness, or fruit size.

The Commercial Implications of Gibberellin A4A7 Plus Benzyladenine for Improving Shape and Yield of ‘Delicious’ Apples1

“…Thus, for max effectiveness, GA4-7 + BA should be applied between FB and PF. This agrees with Stembridge and Morrell's findings (3).…”

“…Stembridge and Morrell (3) reported that while both GA4-7 and BA applications increased L/D ratio and the prominence of calyx lobing, combined application of the 2 materials was most effective. Sprays applied during bloom were more effective than pre or post bloom sprays.…”

Microdroplet Application of GA4+7 + BA: Sites of Absorption and Effect on Fruit Set, Size, and Shape of ‘Delicious’ Apples

“…Looney reported that GA4 + 7 + BA increased the size of 'Spartan' apples in British Columbia but the response occurred only when applications were made a week or more after bloom (7). It is known that GA4 + 7 + BA sprays of 50 ppm or greater can cause fruit thinning (5,9,11) and we have observed previously that a 500-ppm foliar spray applied at bloom can completely defruit 'Delicious' trees. However, in this present investigation, no GA4 + 7 + BA treatments reduced fruit set even though seed numbers were reduced substantially (Table 3).…”

“…Increased L/D ratio was due to a combination of increased fruit length and decreased fruit diameter. Reduced fruit diameter and weight were attributed to a lower seed number.A proprietory formulation of GA4 +7 + BA (Promalin; Abbott Laboratory, North Chicago, IL 60064) is applied commercially to 'Delicious' apples during the bloom period to elongate fruit and increase fruit weight (8,9,11). In the Northeast, increased length/diameter (L/D) ratio has been observed but the response often is less than expected.…”

“…A proprietory formulation of GA4 +7 + BA (Promalin; Abbott Laboratory, North Chicago, IL 60064) is applied commercially to 'Delicious' apples during the bloom period to elongate fruit and increase fruit weight (8,9,11). In the Northeast, increased length/diameter (L/D) ratio has been observed but the response often is less than expected.…”