Exogenous application of gibberellic acid and brassinosteroids: Synergistic effects on Nutmeg's growth, yield and color attributes

This study evaluates the effects of preharvest spray applications of gibberellic acid (GA3) and brassinosteroids on the growth, fruit drop, fruit set, yield and colour characteristics of nutmeg. Treatments included combinations of GA3 and brassinosteroids with boric acid and calcium nitrate, applied during the flowering stage. The experiment followed a randomized block design with seven treatment combinations; each replicated three times. Among the treatments, the application of GA3 at 75 ppm combined with 0.3 % boric acid yielded the most favourable results. This combination significantly enhanced vegetative growth parameters, including plant height (8.9 m), leaf length (14.5 cm) and leaf width (5.5 cm). It also resulted in the highest fruit set percentage (80.95 %) and the lowest fruit drop rate (43.63 %). Furthermore, this treatment produced the highest yield, with 680 fruits per tree, amounting to 54.46 kg per tree. It also maximized both fresh and dry aril yields (3.19 kg and 2.58 kg per tree, respectively) as well as nut yields (9.08 kg fresh and 6.78 kg dry per tree). In addition, it improved the brightness and vibrancy of the aril colour, achieving the highest values for L* (66.2), a* (53.8) and b* (31.2). Overall, these findings highlight the potential of GA3 and brassinosteroids, especially in combination with boric acid, to enhance mace yield, quality and colour stability offering a promising strategy for improving nutmeg production and postharvest quality.