Effect of Uniconazole on the Control of Plant Height and Fruit Yield of Potted Tomato, Pepper, and Eggplant

Two experiments were conducted to evaluate the effect of the plant regulator uniconazole on plant height, flowering, and fruit yield of vegetable transplants. In the first experiment, seedlings of tomato (Solanum lycopersicum 'Early Girl'), pepper (Capsicum annuum 'Jalapeno'), and eggplant (Solanum melongena 'Millionaire), were sprayed with water (untreated control) or with 2.5, 5, and 10 mg.L-1 of uniconazole. Five weeks after treatment (WAT), application of 2.5 mg.L-1 of uniconazole reduced the height of tomato by 17%, and of 5 and 10 mg.L-1, by 25%. The effect of 10 mg.L-1 of uniconazole on tomato plant height persisted until 13 WAT, but did not affect fruit yield. 'Early Girl' tomato plants treated with 10 mg.L-1 of uniconazole were still shorter than the untreated control at this time, but there were no significant differences in the number or weight of the fruit produced by the plants treated with 10 mg.L-1 of uniconazole, and the untreated controls. In contrast, as the rate of uniconazole increased, the height of 'Jalapeno' pepper and 'Millionaire' eggplant decreased. Application of uniconazole had no effect on the number of fruit produced by 'Millionaire' eggplant. However, treatment with 10 mg.L-1 of uniconazole reduced the number of fruit produced by pepper plants by 50%, and reduced the total weight of fruit produced by pepper and eggplant plants by 30% and 50%, respectively, compared with the untreated control. The second experiment analyzed the effects of 5, 8, and 10 mg.L-1 of uniconazole on two cultivars of tomato with different growth habit, Early Girl (determinate) and Sun Sugar (indeterminate). Application of all rates of uniconazole decreased plant height but not the final fruit yield of the two tomato cultivars.