Construction Of Plant Expression Vectors Harboring Bt Insecticidal Cry1Ba & Cry3A Genes And Obtaining Of Pest-Resistant Potato Transformants

Potato is the 4th largest food crop in the world. Colorado potato beetle (CPB) is a worldwide quarantine pest, which feeds on potato, elm, tomato, eggplant and other Solanacearum species. CPB has caused severe damage to potato production in the northern region of Xinjiang province during the past years. Most severely, CPB is spreading to inland at a speed of about 100 km per year. Chemical insecticides have been used for the protection from CPB, but they are high cost and not effective enough. Moreover, use of chemical insecticides in large dosage will cause many problems such as environmental pollution and increasing of insecticide-tolerance of CPB. The most effective way to protect from CPB is to develop CPB-resistant plants. Modern biotechnology based on recombinant DNA technology has made it possible to introduce new traits into plants. In this study, we have tried to develop CPB-resistant potato plants by introducing Bt insecticidal gene into potato cultivar. Many studies have demonstrated that Bt strains can express different crystal proteins with specific toxicity to coleopteran insects. Bt is currently the source of insecticidal proteins in commercial insect-resistant transgenic plants and will remain the most important source during the next decade. With the large scale introduction of Bt crops, insect resistance to Bt Cry toxins is the main problem. Only one species, the diamondback moth, has evoled a resistance to Bt-based formulations under field conditions. However, many other insect species were selected for resistance under laboratory conditions, indicating that there is a potential for evolution of resistance in most major pests. Consequently, delaying resistance development in insect populations are the main challenges to be overcome. A consensus has developed that transformant expressing multiple toxin genes with different modes of action can not only avoid of cross-resistance but also extend the pest-resistant spectrum and improve the insecticidal activities. In this study, Bt crylBa gene from pT-lBa was cloned. Plant expression vector harboring crylfia and bi-vector harboring cry3Aa & crylBa genes were constructed and transformed into the potato cultivar Desiree by Agrobactrium tumefaciens-mediated transformation. Thirty potato transformants were obtained. PCR assay and Southern blotting analysis indicated that cry3Aa and crylBa genes had been integrated into potato genome. The mortality of CPB was 64% after feeding with transgenic potato harboring cry1Ba for 3 days and l00% aller4 days.