Gibberellic Acid Inhibits Flowering and Reduces Hand Thinning of 'Redhaven' Peach

• Published in: HortScience Vol. 41; no. 7; pp. 1596 - 1601
• Main Authors: Coneva, E, Cline, J.A
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Society for Horticultural Science 01.12.2006
• Subjects: Agronomy. Soil science and plant productions; application rate; application timing; Biological and medical sciences; crop management; Cropping systems. Cultivation. Soil tillage; cultivars; firmness; flowering; fruit quality; fruit set; fruit thinning; fruits (plant anatomy); Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; gibberellic acid; orchards; peaches; plant growth substances; Prunus persica; ripening; seasonal variation; Tending. Growth control; Tillage. Tending. Growth control; tree growth; tree trunk; Ontario; Deblossoming; Horticulture; Rosaceae; Arboriculture; Growth regulator treatment; Defruiting; hand thinning; Dicotyledones; Angiospermae; Plant growth substance; Flowering; flower inhibition; Fruit tree; Inhibition; Organic compounds; Cultural practice; Terpenoid; Flower; Fruit set; Fruit; Stone fruit; Manual operation; peach; Gibberellin; Dimension; Prunus persica; fruit size; Fruit crop; Spermatophyta; Gibberellic acid; Cultivar; Fructification
• ISSN: 0018-5345; 2327-9834
• DOI: 10.21273/hortsci.41.7.1596

Adjusting the crop load of peaches [Prunus persica (L.) Batsch] by hand thinning is currently required to ensure marketable size of most cultivars grown in Ontario. A novel approach to adjust cropping by inhibiting flowering using gibberellic acid (GA3) was tested in an orchard experiment in which GA3 was applied at 7, 10, and 13 weeks after full bloom to mature `Redhaven' peach trees. Late GA3 treatments increased soluble solids concentration (SSC) in the season of application. A significant interaction between GA3 rate and time of application was observed on increased fruit firmness in the current season. Increasing rates of GA3 decreased flowering the following season in a quadratic fashion, resulting in a 41% to 90% diminished requirement for hand thinning. This translated into lower crop loads and yields for GA3-treated trees at harvest compared with untreated control trees. However, GA3-treated trees had larger mean fruit size and improved fruit size distribution the year after GA3 application. Advanced fruit ripening was also evident by increased fruit SSC and decreased fruit firmness, likely an indirect effect of GA3 on crop load. GA3 application timing significantly increased overall tree growth measured by the changes in trunk cross-sectional area.