Insecticidal characteristics of Bacillus thuringiensis strain CYZ-4 with high activity.

A Bacillus thuringiensis(Bt)isolate CYZ-4,which was high lethal to some pests of Lepidoptera and Diptera,was screened by bioassay and DPS analysis.And its gene types of cry1,cry2,cry3,cry7,cry8,cry9,vip3A and the protein types were identified by PCR-RFLP and SDS-PAGE.The bioassay result indicated that the isolate was more lethal to these pests compared with Bt subsp.kurstaki HD1.The LC50 of Bt CYZ-4 isolate against Mythimna separate was 6.6×106 cells/mL in 48 hours.The LC50 values of the isolate against 1st larvae of Hyphantria cunea(Drury),Spodoptera exigua,and Helicoverpa armigera were 2.9×106,2.25×105,and 4.7×106 cell/mL,and that against 2nd larvae of Clostera anachoreta was 1.7×106 cells/mL in 72 hours;while it also had insecticidal activity against Culex pipiens pallens,and the LC50 was 2.01×105 cells/mL in 24 hours.The genotypes of the Bt isolate were identified by the methods of PCR-RFLP and SDS-PAGE.vip3A,cry1Ac,cry1Ab and cry2Ab were identified in Bt CYZ-4,and cry3,cry7,cry8,cry9 were not found,while other genes still need to be identified.SDS-PAGE analysis also showed that the strain produced crystal proteins of 130,70,57 and 27 ku,and 88 ku at vegetative stage.Results prove that Bt CYZ-4 is a potential wild strain against some pests in practice.