Transgenic Bt Cotton hybrids expressing cry toxins with different events are available in India for cultivation offering resistance to bollworms. In the present investigation the impact of Bt Cotton hybrids derived from different events were studied in the laboratory on the growth and development of tobacco caterpillar, Spodoptera litura. The larval mortality when fed on leaves and squares of RCH 2 BG-II featuring Cry 1 AC + Cry 2 Ab was highest compared to other Bt Cotton hybrids with corresponding events. The susceptibility level of S. litura to RCH2 BG-II varied instar wise and the late instars had very little effect on the survival and developmental bioLogyof the insect. The development of S. litura was drastically affected as indicated by lowest growth and survival indices. The cry protein content was estimated from different plant parts of different events of transgenic Bt cotton hybrids at 60, 90, 120 and 150 DAS during the seasons.
Key words: Spodoptera litura, Bt cotton, survival, expansion, cry 1 AC + Cry 2 Ab.
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