Characterization and toxicity of Bacillus thuringiensis isolates from warehouses to Spodoptera exigua (Lep., Noctuidae)

Bacillus thuringiensis was isolated from 122 of 413 samples obtained from w arehouses. Eighty-seven (71.31%) of these B. thuringiensis isolates were to xic to Spodoptera exigua, causing more than 60% mortality. Twenty-seven iso lates were highly toxic to S. exigua, causing more than 95% mortality. Isol ates 133, 47 and 58, which belonged to serotype H-7, H-4, H-4, respectively , were more active than the other isolates and their 50% lethality concentr ation (LC50) values were 17.93, 14.78 and 15.55 mug/ml, respectively. The i solate 133, 47 and 58 were analyzed by sodium dodecyl sulphate-polyacrylami de gel electrophoresis and polymerase chain reaction. The results showed th at they contained similar to 135 and 65 kDa crystal proteins, that were sim ilar with reference strain HD-1. Isolate 133 contained the cryIA(a), cryIA( b), cryIA(c), cryIE and cryII genes whereas both isolate 47 and 58 containe d the cryIA(b), cryIA(c), cryIE and cryII genes; but they did not contain c ryIII gene.