High level expression of soybean trypsin inhibitor gene in transgenic tobacco plants failed to confer resistance against damage caused by Helicoverpaarmigera

Helicoverpa armigera is a major pest of many tropical crop plants. Soybean trypsin inhibitor (SBTI) was highly effective against the proteolytic activ ity of gut extract of the insect. SBTI was also inhibitory to insect growth when present in artificial diet. The gene coding for SBTI was cloned from soybean (Glycine max, CV Birsa) and transferred to tobacco plants for const itutive expression. Young larvae of H. armigera, fed on the leaves of the t ransgenic tobacco plants expressing high level of SBTI, however, maintained normal growth and development. The results suggest that in certain cases t he trypsin inhibitor gene(s) may not be suitable candidates for developing insect resistant transgenic plants.