Molecular characterization and crystal morphology of indigenous entomophatogenic Bacillus strains against Spodoptera frugiperda

Abstract

Introduction: Bacillus thuringiensis (Bt) are the microorganisms most widely used in biological control of insect pest. These bacteria produce entomophatogenic crystals (Cry) during sporulation showing different morphologies according to Bt strains. Objectives: To determine the morphology of crystals produced by threenative Bt strains active against larvae of Spodoptera frugiperda (Sf) and to characterize the microorganisms molecularly. Materials and methods: Crystals were studied by scanning electron microscopy. Sporulated cells were removed from the agarized medium, washed and placed on a micro slide. The 16S rDNA gene was amplified from genomic DNA by PCR. Results and conclusions: Morphological observations showed that the three strains contained bipyramidal crystals of two different sizes. This feature may resemble those against lepidopteran targets. The 16S rDNA analysis identifies the isolations as B. thuringiensis subspecies. The sequences were deposited in the Gene Bank, access Nº: RT EF638795, LSM EF638796 an LQ EF638798. These results complement the knowledge on these native pathogenic strains with promissory characteristics for Sf biological control. Acknowledgments: PICTO-UNT 761, PIP 6062 and CIUNT 26/ D308.