55th Annual Conference of AMI AMI-EMMT-2014 TNAU (Nov 12-14, 2014) POSTER ABSTRACT AM 128 Isolation of chimeric Cry2AX1 protein from recombinant Bt and its toxicity against rice leaf folder R Manikandan, A Naveenkumar, N Balakrishnan and V Udayasuriyan* Department of Plant Biotechnology, Tamil Nadu Agricultural University, Coimbatore 641 003, India * e mail : [email protected] Bacillus thuringiensis (Bt) is a Gram-positive, spore forming bacterium that produces parasporal crystal proteins during the stationary phase of its growth cycle. It is a key source of insecticidal genes for transgenic expression to provide pest resistance in plants. However, the continuous use of similar Bt toxins against a target insect pest can lead to breakdown of resistance in plants. In this direction a potent chimeric cry2AX1 gene was constructed earlier in TNAU by using part of coding sequences of cry2Aa and cry2Ac, cloned from Indian isolates of Bt. In this present study, the chimeric Cry2AX1 protein isolated from recombinant Bt was tested for efficacy against rice leaf folder through coated leaf bioassay. The cry2AX1 gene was expressed in recombinant Bt by cry2Aa promoter. The recombinant Bt-Cry2AX1 protein at the concentration of 13.33 ng/µl recorded 86.70 per cent mortality against neonate larvae of rice leaf folder. There was no mortality on control leaf bits coated with water as well as with triton X 100 and major portion of the leaf material was consumed by the surviving larvae over a period of five days. These results indicated that the Cry2AX1 protein isolated from recombinant Bt was effective against rice leaf folder even at a very low concentration. Hence, further efforts can be made for developing transgenic rice with cry2AX1 gene to impart insect resistance. ASSOCIATION OF MICROBIOLOGISTS OF INDIA