The bioassay with neonate larvae of bollworm were used to test the resistance of 2 000 Bt transgenic cotton plants in R 1,R 2 and R 3 generations in 1994-1995. 80% reduction of damage as well as mortality were taken as criterion of resistance. 11 plants in R 1, 15 lines in R 2 and 375 plants in R 3 were selected as resistant lines which was 6 21%,13 89% and 71 29% in respective generations .Then 12 lines from R 3 were repeated ...