Transgenic insect-resistant maintainer line (IR68899B) for improvement of hybrid rice

Heterosis has helped to increase rice yield in F-1 hybrids by 15-20% beyond the level of inbred semi-dwarf varieties. For stable yield performance ric e hybrids must also possess genetic resistance to biotic stresses. One of t hese, stem borer, reduces the expected yield of hybrid rice. The truncated synthetic cryIA(b) gene from Bacillus thuringiensis is known to be effectiv e in controlling stem borer. The development of transformation techniques h as provided the technology for incorporating this bacterial gene into the r ice genome, which has not been possible by conventional breeding methods. W e have introduced a new approach of using a transgenic maintainer line for developing an insect-resistant hybrid rice. An elite IRRI maintainer line ( IR68899B) has been transformed with the cryIA(b) gene driven by the 35S con stitutive promoter using the biolistic method. The integration and expressi on of the cryIA(b) gene could be demonstrated through Southern and Western blot analyses that have been carried out so Far up to the T-2 generations. Insect bioassay data showed an enhanced resistance to yellow stem borer in the Bt(+) transgenic plants. This is the first report of the development of a transgenic maintainer line for use in hybrid rice improvement.