Author : Pracha Boonsompong

Summary : The study was conducted to determine the optimum concentration and most suitable time to apply GA3 as well as their effects on the seedlessness of 'Brazilian Hybrid' grape. The application timings were pre-bloom, full-bloom, and post-bloom while the different concentrations of GA3 were 0 ppm (control), 50 ppm (control), 50 ppm, 100 ppm, 150 ppm, and 200 ppm. Results revealed that application of 150-200 ppm of GA3 at full-bloom can reduce the number of seeds in the berry by 0.63, which is significantly lower than the number of seeds in the control berries with 2.73 seeds. Moreover, berries with less seeds are longer than berries with more seeds but with reduced diameter. Fruit setting also decreased when GA3 was applied. However, it was better to apply GA3 at the later stage of flowering because higher fruit setting was recorded at post-bloom. In terms of yield, control plants and Post-bloom application outyielded the rest of the treatments. In general, however, the ratio between TSS to TA in all treatments and treatment combinations is high indicating better quality fruits.