EFFECT OF GROWTH REGULATORS ON BOLTING IN ONION (Allium cepa L.)

Floral stem emission (bolting) on onion, reduces the quality bulb and yield. A practice that can reduce this problem is the use of plant growth regulators. The objective of this research was to evaluate the effect of growth regulators on the reduction of bolting in onion. This experiment was carried out during the 2008-2009 fall-winter season in Imuris, Sonora, Mexico. The growth regulators evaluated were: Apogee (Prohexadione Ca, 50 ppm), Cultar 25 SC (Paclobutrazol, 10 ppm), Ethrel (Ethephon, 5000 ppm), Pix Plus (Mepiquat chloride, two applications of 42 ppm), Moddus 250 (Trinexapac-etil, two applications of 250 ppm) and Agromil V (1556 ppm) which were applied as foliar in a volume of 500 l ha(-1). The results showed significant differences among the plant growth regulators evaluated. The treatments applied with Ethrel and Pix Plus exhibited the best response in reducing this problem with 10,5% of bolting, versus 30,7% of control. On the other hand, Ethrel treatment obtained the highest yield with 61,8 t ha(-1). Conclusion: The growth regulators application is a good alternative to decrease the floral stem emission problem in onion.