Preliminary Studies On Risk Of Rice Leaffolder, Cnaphalocrocis Medinalis (Lepidoptera: Pyralididae Resistant To Bt Rice And Its Management)

The risk of rice leaffolder, Cnaphalocrocis medinalis(Lepidoptera: Pyralididae) resistance to Btrice and its management were studied and discussed in this paper.1 Susceptibility of Cnaphalocrocis medinalis to Cry1Ab and its transgenic riceThe susceptibility of different C. medinalis population to Cry1Ab was bioassayed using the leaf-immersion method. The LC₅₀ values of Cry1Ab to C. medinalis populations ranged from 20.00 ng/cm² (Hangzhou population) to 69.60 ng/cm² (Ningbo population). The diagnostic dose of Cry1Ab to the field population of C. medinalis was estimated as 620ng/cm² using the multi-dose LP-p line. Finally, the frequence distribution of susceptibility in the field population of C. medinalis to Cry1Ab and transgenic cry1Ab rice were measured using iso-female analysis method.2 Susceptibility of rice lepidopterans to four insecticidal proteins from Bacillus thuringiensisThe susceptibility of the neonates of rice lepidopterans, striped stem borer, Chilo suppressalis (Walker), pink stem borer, Sesamia inferens (Walker), and leaffolder, Cnaphalocrocis medinalis (Guenee) to four Cry proteins, i.e. Cry1Ab, Cry1Ac, Cry1C, and Cry2A, from Bacillus thuringiensis were bioassayed using diet-feeding method and leaf-immersion method. The LC₅₀ values of Cry1Ab, Cry1Ac, Cry1C, and Cry2A to C. suppressalis were 1.739ng/mg, 2.645ng/mg, 2.794ng/mg, and 15.965ng/mg, respectively; and those for S. inferens were 2.455ng/mg, 10.046ng/mg, 11.803ng/mg, and 35.359ng/mg, respectively; and for C. medinalis, 4.000μg/ml, 1.611μg/ml, 69.031μg/ml,and 12.708μg/ml, respectively.3 Construction of new fusion genes based on cry geneThe pBDIIA vector was constructed by combining the domain 11 sequence of cry1Ab and anti-microbic peptides (AMPs) using the modern biotechnique. Despite the insecticidal activity of the expression products of recombinants still to be further bioassayed, it provides a new strategy for sustainable pest resistance in genetically enhanced crops.