GA3 Applications for Inflorescence Elongation, Seedless Induction, and Berry Enlargement in ‘White Malaga’ Grape

Abstract

White Malaga’ grape has been popularly consumed in Thailand. Research data for its problems as short peduncle, small and various berry sizes, have been limited. This research aimed to solve the problems using gibberellic acid (GA₃) applications. The experiments were 1) to elongate the peduncle with GA₃ spraying of 2, 4, and 6 mg/L at 15, 20, and 25 days after pruning (DAP) compared to untreated inflorescence (control). Spraying 4 mg/L GA₃ at 20 DAP increased the peduncle length up to 119 %. 2) To induce seedless with GA₃ spraying of 25, 50, 100 mg/L at -3, 0, 3, and 6 days after flowering (DAF) compared to untreated inflorescence (control). GA₃ spraying on a flowering day at any concentrations induced 100% seedless. 3) To enlarge the berry size with GA₃ spraying alone of 25, 50, and 100 mg/L or added with 5 mg/L forchlorfenuron (CPPU) at 2 weeks after flowering. The 50 mg/L of GA₃ + 5 mg/L CPPU yielded larger berries, as 1.82 cm wide, 3.35 cm long, 7.58 g in berry weight, and bunch weight of 376.37 g, with 20.37 % TSS and 0.80 % TA. These indicated that spraying GA₃ with suitable concentrations and correct times can elongate the peduncle, induce seedless, and enlarge the berry size of the ‘White Malaga’ grape.