Inheritance of resistance to Helicoverpa armigera of 3 kinds of transgenicBt strains available in upland cotton in China

There are 3 kinds of transgenic Bt strains, Shanxi 94-24, Zhongxin 94, and R19, in upland cotton in China. Their transgenic Bt insect-resistance culti vars or hybrids have been developed and grown by farmers. Genetic studies i ndicate that the resistance of the 3 transgenic Bt cotton strains to Helico verpa armigera is controlled by one pair of non-allelic dominant genes. Lin kage relationship between the resistant genes of R19 and Shanxi 94-24 trans genic Bt strains shows that they may be inserted in the same chromosome. F- 1 hybrids crossed among the 3 strains show that high levels of protection f rom feeding damage are the same as that of their parents. Therefore, there is no co-suppression phenomenon in many transgenic plants. The results pres ented here afford a fundamental reliance in developing transgenic Bt insect -resistant cultivars and exploiting the heterosis of hybrids in upland cott on.