Effect of Square Removal on Growth, Yield and Fibre Quality of Transgenic Bt Cotton Hybrids

A plant type with a good morphoframe would sustain more boll load with synchronous boll development and boll burst. In Bt cotton the plant morphoframe doesn't develop fully due to retention of early formed squares. Thus an attempt was made to improve Bt plant morphoframe by removing the early formed squares. Twenty treatments, consisting of five cotton hybrids viz. RCH 2 Bt, JKCH 99 Bt, NCEH 2R Bt, Mallika Bt and non Bt G. Cot Hy10, two concentration of ethylene (i.e. 30 and 45 ppm at square initiation), one time hand removal of squares besides untreated control was tested in factorial randomised block design with three replications. The results indicated that all Bt and non Bt hybrids, following spray of 45 ppm ethylene attained significant increase in plant height, number of fruiting forms, number of sympodia, boll weight, seed cotton yield and biomass. Mechanical square removal was also found to be effective and at par with ethylene treatments for many of parameters. The fibre quality parameters, uniformity ratio and maturity coefficient reduced marginally with square removal treatments, yet it met specified norms of fibre quality. Thus, the application of 45 ppm ethylene as a square removal treatment or mechanical square removal treatment significantly improved growth and yield of Bt cotton.