Metabolites changes after pre-bloom gibberellic acid (GA3) application for inducing seedless grape

Gibberellic acid (GA3) treatment is a useful method for inducing seedless grape berries in the seeded grape bunch before flowering. In this work, we applied 100 ppm of GA3 on ‘Tamnara’ grape flower cluster at 14 days before flowering to find metabolites significantly related to seedlessness. Three bunches of grape flower samples were collected at nine different stages (Day before full bloom; DBF13, 10, 7, 5, 2, flowering (0) and day after full bloom; DAF 2, 5, 9). Metabolites of each collected sample were analyzed using GC-MS with derivatization method (MSTFA). Metabolite contents of GA3 treatment flower were compared with non-treated controls in all stages and analyzed using Partial least squares discriminate analysis (PLS-DA). As a result, five sampling times (DBF 13, 10, 2, 0, DAF 9) showed significance differences using GA3 treatments. Total of 13 metabolites were recognized to relate to differences in five specific sampling times and mainly affected the initial stages (DBF 13 and 10). Tartaric acid, D-glucose, phosphoric acid, and D-mannose, inositol were increased by GA3 treatment at the early-flower developing stage. Dehydroascorbic acid, caffeic acid, citric acid, and gluconic acid were mainly increased at the time of GA3 treatment but decreased approaching full bloom. All stages of GA3 treatment, L-glutamine, L-serine, and D-allose was decreased, but fructose increased. In particular, the metabolite contents before GA3 treatment provides new clues on the role of GA3 in the early stage of grape berry development