Toxicity of a Bacillus thuringiensis israelensis-like strain against Spodoptera frugiperda

Bacillus thuringiensis (Bt) Berliner is a promising agent for microbial control of agriculturally and medically important insects. This study aimed at searching for Bt strains encoding Cry proteins that act more efficiently against fall armyworm. Thirty Bt strains were isolated from soil samples in Pernambuco State and evaluated through bioassays. Among these, strain I4A7 was the most efficient against the fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), and thus it was characterized by biochemical sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and molecular (polymerase chain reaction (PCR) and sequencing reaction) methods. The protein pattern of this strain on a SDS-PAGE was similar to that of B. thuringiensis israelensis (Bti). Moreover, I4A7 cry DNA sequence showed high identity (99-100%) to genes cry4Aa, 4Ba, 10Aa, 11Aa, cyt1Aa and cyt2B from Bti. The toxicity of the newly isolated Bti-like strain upon S. frugiperda should be considered as this strain might be used in combination with other Bt strains, such as B. thuringiensis var. kurstaki (Btk).