Improved Cry1Ac expression levels during Bt cotton cultivation

Decreasing resistance to insecticidal proteins from transgenic crops is a major strategy of insect management. Increased resistance is a major problem nowadays in insects' pests which reduces efficiency of insecticidal proteins from Bacillus thuringiensis (Bt) produced by transgenic crops such as Bt cotton (Bollgard-II). Cultivation of Bt cotton with refuge nBt cotton is a strategy to delay resistance of lepidopteran insect pests. During this present study, field trails with four treatments with varying nBt refuge crops for quantification of Cry1Ac were done. Results showed that 50% Bt with 50% nBt treatment has highest Cry1Ac expression in lower leaves (8.249 mu g/gm) followed by upper leaves (7.407 mu g/gm), sepals (0.988 mu g/gm) and boll bracts (0.987 mu g/gm) respectively. The Cry1Ac expression decreased consistently as the plant age increased in all the treatments. The morphological and yield parameters were recorded and highest plant height was found in 90% Bt with 10% nBt treatment such as 123.8669cm and 99.200 cm. It was also recorded that highest yield like boll size (gm/plant) and lint index were found in 75% Bt with 25% nBt treatment as 14.449, 9.979 (gm/plant) and 11.647, 9.426 respectively. We have concluded that highest morphology and yield depend upon number of Bt and nBt plants present in all treatments. This combination is a better option to farmers to increase their income and good strategy to defend the resistance in insect.