Effect of Gibberellic Acid Concentration on the Growth and Development of Two Tomato Varieties in Kano State, Nigeria

This study examined the effect of Gibberellic acid (GA₃) on the growth and yield of two tomato varieties, Diva and Padma, at the Teaching and Research Farm of the Centre for Dryland Agriculture, Bayero University, Kano. Two factors experiment was laid out in Complete Randomized Design (CRD) with three replications. Five treatments were applied: a control (0 ppm GA₃) and four GA₃ concentrations (100, 200, 300, and 400 ppm). Growth parameters, including leaf number, branch number, plant height, stem diameter, flower production, and chlorophyll content, were measured. Yield data were recorded across five harvests. For the Padma variety, GA₃ application had minimal effects on growth parameters, with no statistically significant differences observed. The highest number of leaves (73) occurred at 100 ppm, while plant height peaked at 200 ppm (61.91 cm). Stem diameter decreased with increasing GA₃ concentration, suggesting excessive GA₃ may lead to weak stems. The highest fruit production was recorded at 300 ppm, but overall, 200 ppm was identified as the optimal concentration for improved yield (1500 g), whereas excessive application (400 ppm) led to a decline. Similarly, for the Diva variety, GA₃ had little impact on growth parameters, with leaf number, plant height, and branching showing no significant trends. The highest total yield (890 g) was recorded at 200 ppm GA₃, while excessive application (400 ppm) resulted in reduced yield (645 g). Excessive GA₃ concentrations appeared to inhibit reproductive traits rather than enhance them. Overall, GA₃ application at moderate concentrations (200–300 ppm) showed potential to enhance tomato yield, but excessive use (400 ppm) may be counterproductive. Further research is needed to optimize GA₃ use in tomato cultivation under local conditions