The inhibition of flower bud differentiation in ‘Crimson Gold’ nectarine with GA3 as an alternative to hand thinning

The reduction of flower bud density by gibberellin sprays, to adjust the cropping level, is a novel approach to fruit thinning of peach and nectarine. A linear reduction in the number of flowers developed per unit of shoot length was found following the spray application of increasing concentrations of GA₃, in the nectarine cultivar ‘Crimson Gold’. These reductions in flower number led to reductions in yield at harvest, and increases in mean fruit weight. Flowering was slightly delayed by the GA₃ treatments, but no differences in ripening were detected at harvest, this depending rather on fruit size. The yield obtained by the application of 200 mg l⁻¹ GA₃ corresponded to that obtained with a very good thinning level, as established by hand thinning. No secondary effects on vegetative growth followed either the application of GA₃ or the reductions in crop load by means of hand thinning. Decreasing crop-loads have resulted in an increase in fruit size and an advance of fruit ripening, measured by greater levels of soluble solids and lower flesh firmness. A good commercial quality fruit size was obtained for crop-loads of 300 fruits per tree or less.