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

Abstract

Gibberellin A4A7 (GA4-7) and benzyladenine (BA) were applied to ‘Starkrimson Delicious’ apples from 1969 through 1972. In initial tests, GA4-7 + BA (50 to 200 ppm each) increased fruit length, fruit wt and length/diam ratio (L/D) but did not alter diam or fruit color. Firmness and seed numbers were reduced only at 200 ppm. At concn above 50 ppm flower initiation was substantially reduced. Concentrations of 25 ppm were as effective as 50 ppm but concentrations below 25 ppm were not effective. To be most effective, these materials must be applied between full bloom and petal fall. In general, a single application was more effective than split applications. Repeated annual applications of 50 ppm resulted in continued good response and no adverse effects. In one of the 4 years tested, fruit set but not commercial crop, was significantly reduced by applications of GA4-7 + BA. Air blast applications were as effective as hand gun applications even when the amount of spray mixture/acre was substantially reduced. The average fruit weight response in all experiments reported was 12 and 20% at 25 and 50 ppm, respectively. The improved fruit shape and increased fruit mass could justify the use of GA4-7 + BA in apple producing areas where post bloom temp conditions reduce “typiness”.

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

“…Fruit weight was increased in the absence of thinning when either GA4 + 7 or B A ^e re applied starting at FB + 11 days but not when used in combination (Table 3). Sprays of GA4 + 7 and BA can increase fruit weight of 'Delicious' primarily by elongation of the calyx end, and maximum response appears to be when applied during the bloom period (23). However, Looney (14) has reported that treatments on 'Spartan' with GA4 + 7 and BA increased the L/D ratio and especially fruit weight for at least 5 weeks after bloom.…”

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

“…Reports of increased fruit weight following GA4 + 7 + BA application (8,11) were not confirmed here (Tables 2 and 3). This may be due in part to the GA4 + 7 + BA concentrations used in this study, which were generally above those which are recommended commercially.…”

“…Also, Miller (8) has reported that geographical location can modify the response to GA4 + 7 + BA. GA4 + 7 + BA increases fruit size in the warmer regions of the United States such as North Carolina (11) and Georgia (8), but confirmation in northern states is lacking. 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).…”

“…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.…”