Field experiment was conducted to study the influence of sowing time and moisture regimes on cry protein concentration at Agriculture Research Station, Dharwad for two years (2005-06 and 2006-07) under irrigated conditions.Early sowing of Bt-cotton (June) shown significantly higher cry protein expression than late sowings (July and August).
Bollworm incidence increased with delayed sowing. Increased incidence of bollworm to late sowing may be attributed to decreased level of cry protein concentration. Higher SPAD readings and leaf N concentration were observed in early sown crop at 60, 120 and 150 DAS. Early sown crop might have better nitrogen uptake as indicated by higher leaf N concentration, which has probably altered the cry protein level by improving protein synthesis and metabolism in Bt-cotton. Cry protein expression in Bt-cotton from 90 to 150 days after sowing (DAS) as influenced by different moisture regimes indicated that 0.8 IW/CPE recorded significantly higher cry protein concentration as compared to other regimes. Effect of moisture regimes on pest incidence was little and not significant at early stages (60 and 90 DAS). However, pest incidence was significantly affected with moisture regimes at 120 DAS, owing to the decreased level of cry protein and increased effect of soil moisture.