Two field experiments were conducted at the Experimental and Research station Farm of the Faculty of Agriculture at Moshtohor, Benha University during 2012& 2013 seasons to study the effect of spraying some growth regulators paclobutrazol (PP333) (Cultar25%sc), at rates of 30, 40 and 50 mg/l and Mepiquat chloride 5%sc )Pix ( at rates of 100,200 and 300 mg/l on yield, fiber and yarn properties of Giza 86 cotton variety and promising crosse (Giza 86x10299) compared with Control.
A split plot design with three replicates was used whereas cotton genotypes were allocated in main plots while growth regulators in the sub-plots. The spraying time was at 60, 80, and 100 days after sowing. Results showed that, genotypes (Giza 86x10299) gave the best reading in some growth attributes such as, plant height, number of leaves /plant, total leaves area /plant and total chlorophyll in both seasons and some yield components i.e., seed cotton yield /plant, and Lint percentage, in the first season only. This strain superior in micronaire reading, Fiber and coefficient of variation length C.v% in both seasons. Genotype (Giza 86x10299) superior Giza 86 in skein strength, and number of neps /100 meter.
Use of 200 mg/l pix gave the highest average of plant height, number of leaves /plant, reflectance (Rd %) and coefficient of variation length )C.v% (in both seasons, but use 300 mg/l pix gave the best reading in number of leaves /plant, total dry weight /plant, total chlorophyll, skein strength, and number of thin, thick places /100 meter and number of neps /100 meter in both seasons. Giza 86 cotton varity with 200 mg/l pix gave the highest average of yield and its components and fiber properties, but Genotype (Giza 86x10299) with 300 mg/l pix gave the best reading in yarn properties.