Response of Cotton (Gossypium hirsutum L.) Cultivars to Topping and Plant Growth Regulator

To study response of cotton (Gossypium hirsutum L.) cultivars to topping and pix as a plant growth regulator an experiment was conducted in Parsabad, Moghan region of Iran with four cultivars included Sahel, Varamin, Bakhteghan and Mehr and topping at 30 days after flowering (DAF), pix spraying at 15 and 30 DAF, and a treatment with neither pix nor topping as control. Results indicated that Sahel had good response to pix spraying at 30 DAF and could increase lint yield up to 210 kg ha-1 when compared to the control. For Sahel cultivar that was sprayed and topped at 30 DAF, cotton plants matured earlier, but other treatments especially control plots matured later. Pix sprayings and topping had no-significant effect on plant height of Varamin, and there was not significant difference among treatments for earliness. Bakhteghan sprayed with pix at 30 DAF was earlier by 78%. Response of Mehr to spraying was better than topping, and after treatment its yield improved (1015 kg ha-1) as compared to the control. Mehr in topping at 30 DAF with 78% earliness was earlier than other cultivars. It is concluded that cotton stem topping of 10-15 cm and pix spraying may decrease plant height and increase earliness and yield of Sahel, Bakhteghan and Mehr cotton cultivars.