James T. Yeager

Flowering and fruiting in ‘Patterson’ apricot (Prunus armeniaca) in response to postharvest application of gibberellic acid

Abstract In July or August of 1988 and 1989 which was approximately 2 or 6 weeks, respectively, after fruit harvest, cultivar ‘Patterson’ apricot (Prunus armeniaca) trees were sprayed with a single spray of either 10, 50 or 100 p.p.m. gibberellic acid (gibberellin A3, GA). GA sprays of 100 p.p.m. applied in early July reduced flower number per centimeter of limb length in the year following treatment. Flower number per centimeter of limb circumference was reduced by sprays of 50 and 100 p.p.m. GA applied in July. Fruit set was not affected by GA sprays. The yield and fruit number of hand thinned trees was equivalent to that found on trees treated with 50 and 100 p.p.m. GA sprays in July. Individual fruit weight (size) was increased by GA sprays of 50 and 100 p.p.m. in July compared to hand thinned trees. Fruit maturity was advanced when yields were reduced by GA sprays. In July, GA sprays of 10 p.p.m. resulted in increased individual fruit weight without reduced total yields per tree compared to non-thinned control trees. Results showed that the use of GA sprays the year before flowering (July) decreased flower numbers, eliminating the need for chemical or hand fruit thinning of ‘Patterson’ apricot.

Use of gibberellin to delay maturity and improve fruit quality of 'French' prune.

Summary Gibberellin (GA) increased firmness of ‘French‘ prune (Prunus domestica L.) when applied preharvest at a rate of 31 or 62 mg 1‒1 in 1997,1998 and 1999. Most effective application dates corresponded with a fruit soluble solids (SS) of 11% to 13% in 1997 and 1998, but with 15% in 1999. The development of SS was temporarily delayed by some of the GA treatments, but was generally similar to the control by harvest time. In 1997, fruit firmness remained higher than the control and extended fruit maturity for up to 7 d by either 31 or 62 mg 1‒1 GA applied at 13% SS, or by 62 mg 1‒1 GA applied at 16% SS. In 1998, fruit firmness was increased by treatment with either 31 or 62 mg 1‒1 GA at 11.5% SS or 31 mg 1‒1 at 16% SS. In 1999, harvest was extended by 3 d due to greater fruit firmness by 31 mg 1‒1 GA applied at 11% or 13% SS, or by 62 mg 1‒1 GA applied at 13% or 15% SS. GA treatments did not affect fruit drop, dried fruit size, or yield. Bloom was delayed by application of GA in 1997 and 1998, particularly with later treatments and with the higher rate. Return bloom in 1998 was not affected by GA treatment in 1997. In 1999,31 mg 1‒1 GA at 11.5% SS resulted in greater return bloom than the control, but bloom of other treatments had similar return bloom as the control. Fruit set was unaffected by the application dates and concentrations tested.