Abstract: Bt22 is a new type of rice that has been genetically modified to express Cry1Ab protein, we explored a new method based on PCR to screen the homozygous transgenic offspring. The primers were designed on the flanking sequence of the exogenous gene and the specificity and sensitivity of the primers were tested by experiment. Then we established multiPCR methods to screen homozygous plant from numerous transgenic offspring. Our results showed that this method is simple, efficient and convenient．

Key words: genetically modified rice, eventspecific qualitative PCR, multiplex PCR, zygosity testing