Characterization of <em>Bacillus thuringiensis </em>isolates active against <em>Spodoptera frugiperda </em>( Lepidoptera: Noctuidae)

Abstract

Bacillus thuringiensis is an entomopathogenic bacterium that, during sporulation, produces crystal proteins, coded by cry genes, which can act on crop pests such as Spodoptera frugiperda, abolishing its destructive effect. The objective of this work was to characterize some B. thuringiensis isolates by means of molecular and microbiological techniques and confirme their action by development of biassays, seeking the biological control of S. frugiperda larvae. Amplicons's size, plasmid profiles and antibiograms analyses were performed for identification and determination of the degree of genetic diversity using the subclasses of the gene cry1A (Aa, Ab, Ac e Ae). The molecular techniques suggest high genetic similarity among the studied isolates and the antibiograms performed show that all the isolates were sensitive to the antibiotics streptomycin, kanamycin, rifampicin, and erythromycin, exhibiting different MICs. The biassays demonstrated the entomopathogenic potential of the isolates and control strains controlling first instar S. frugiperda larvae.

Additional keywords: RAPD, plasmid profiles, antibiotics, cry genes.