Impacts and Interactions of Abscisic Acid and Gibberellic Acid on Sovereign Coronation and Skookum Seedless Table Grapes

Abstract

Gibberellic acid (GA; 0, 15, or 30 mg/L) and abscisic acid (ABA; 0, 150, and 300 mg/L) treatments were applied alone and in combination to Sovereign Coronation (Coronation) and Skookum Seedless (Skookum) table grapes in 2013 and 2014 to assess their effects on cluster and berry size, berry composition, and sensory characteristics, alone and in combination. Two sites (Hipple, Lambert) were used for Coronation and one (Lambert) for Skookum. Trials were randomized complete block designs with factorialized treatment arrangements containing four blocks and 12-vine treatment replicates. GA was applied three times (prebloom, seven days postbloom, and 14 days postbloom). ABA was applied twice, one and two weeks preveraison). Treatments were assessed for yield components (yield, cluster weight, and berry weight), berry composition [Brix, titratable acidity (TA), pH, color intensity, and anthocyanins], and sensory variables. GA increased yield, cluster weight, and berry weight in Coronation. GA reduced Brix, color, and anthocyanins and reduced TA (both sites). ABA increased berry pH (both sites) and color intensity and anthocyanins (Hipple in 2013). Yield was reduced by GA in Skookum, but cluster weight increased in 2013. Brix and berry pH increased and TA decreased with increasing GA in Skookum, while ABA increased Brix and pH. In Coronation, GA enhanced several sensory variables (cluster attractiveness, color intensity, and juiciness at Hipple; cluster attractiveness, color intensity, and labrusca flavor at Lambert). ABA enhanced sensory variables (cluster attractiveness, color intensity, and labrusca flavor). In Skookum, GA enhanced the sensory variables (flesh firmness, fruity flavor, and juiciness), and ABA enhanced cluster attractiveness, golden color, and visual liking. GA consistently increased yield components with minimal impacts on berry composition, while ABA increased Brix, pH, color, and anthocyanins, but decreased TA.