PCR identification of Cry I genes in Bacillus thuringiensis strains that are efficient against fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Fall armyworm, Spodoptera frugiperda (J. E. Smith), is the most important maize insect pest in Brazil and its damage can reduce yield up to 34%. The objective of this work was to utilize the PCR technique to Identify Bacillus thuringiensis (B.t) strains that control S. frugiperda in maize crops. Bioassays showed that 16 strains were very effective against S. frugiperda, 15 of them collected from soil samples and one (T09) obtained at the Institute Pasteur. The DNA of these strains were probed with cryI general primers and their proteins were analised by SDS-PAGE eletrophoresis. All strains present positive results for cryI genes. To further characterize these strains, specific cryI primers were employed. PCR technique showed that some strains harbour the same cryI genes. The only difference was the amplification of an unexpected fragment of approximately 160bp when a mixture of cryIB and cryID specific primers was used. Analysis by phase contrast microscope showed that crystal proteins produced by these strains were all bipyramidal crystals. Also, eltrophoretic analysis of proteins by SDS-PAGE showed the same protein banding pattern for most of the strains