LAUSR

BACKGROUND The plant growth regulator gibberellic acid (GA3 ) is often used to obtain enlarged table grape berries and induce seedlessness in them. However, the effects of GA3 on rachis elongation and bunch compactness have seldom been reported in wine grape production. We assessed the effects of GA3 spraying on wine grape inflorescences and bunches and their practical implications for viticulture in Jiaodong Peninsula, China. RESULTS Various GA3 concentrations were sprayed on field-grown Vitis vinifera L. 'Cabernet Franc' (CF) and 'Cabernet Sauvignon' (CS) grapevines before anthesis in Jiaodong Peninsula, China, in 2015 and 2016. Inflorescence length during berry development was measured and flavonoids and aroma compounds in the fruit were detected by HPLC-MS and GC-MS, respectively. For both cultivars, 50 mg/L and 100 mg/L GA3 caused significant elongation of the rachis, whereas there was no significant effect on inflorescence growth and berry seed number. Anthocyanin, flavonol, and flavan-3-ol levels in mature berries were not significantly influenced by GA3 spraying, while C13 -norisoprenoids were modified. CONCLUSION 50-100 mg/L GA3 application prior to grapevine anthesis caused elongation of inflorescences and bunches and eased cluster compactness in CF and CS, while no negative effects were observed on the yield and seed number. The contents and compositions of flavonoids and most aroma compounds were not influenced, except that the norisoprenoids were increased by 50 mg/L GA3 applications. This article is protected by copyright. All rights reserved.