Molecular characterization of Bacillus thuringiensis strains to control Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae) population

Abstract

The main objective of this study was to characterize the toxicity and genetic divergence of 18 Bacillus thuringiensis strains in the biological control of Spodoptera eridania. Bacterial suspensions were added to the S. eridania diet. Half of the selected B. thuringiensis strains caused high mortality seven days after infection. The genetic divergence of B. thuringiensis strains was assessed based on Enterobacterial Repetitive Intergenic Consensus (ERIC) and Repetitive Extragenic Palindromic (REP) sequences, and five phylogenetic groups were formed. Despite their genetic diversity B. thuringiensis strains did not show any correlation between the collection sites and toxicity to larvae. Some B. thuringiensis strains are highly toxic to S. eridania, thus highlighting the potential of their endotoxins as biopesticides.

Genetic diversity of Brazilian Bacillus thuringiensis isolates with toxicity against Aedes aegypti (Diptera: Culicidae)

“…Several studies have reported that ERIC markers are more informative than REP markers in discriminating Bt strains 32,26,9,35 , as was also verified in this research, suggesting that ERIClike sequences may be more widely distributed than REP-like sequences in Bt 26 . Among all the markers, GTG 5 was not as effective in discriminating between isolates of BtMA, indicating low genetic diversity.…”

“…The repetitive element palindromic-polymerase chain reaction (rep-PCR) technique has been used to investigate the interspecific and intraspecific genetic diversity of Bt isolates, allowing us to correlate them with the geographic regions of collection, the origin of the substrate, morphological, biochemical and genetic characteristics, and rates of mortality and toxicity against insect pests and vectors 32,50,21,19,35 .…”

“…Bacillus thuringiensis is a genetically diverse species, so its large number of strains can form several different profiles according to their genetic profile 48 . The high genetic variability of Bt may be related to both the influence of geographic and ecological factors 19,37,35 because this bacterium is isolated from several substrates and has a wide range of target hosts.…”

“…This low correlation was also verified by Huerta et al 21 when verifying subgroups of Bt formed according to the geographical origin and potential use against A. aegypti. Likewise, Da Silva and Valicente 9 and Machado et al 35 , comparing the genetic relationship of Bt isolates toxic to Spodoptera spp. and the collection sites of these isolates reported a low correlation.…”

“…Molecular typing has been used to identify and classify species belonging to the genus Bacillus, in addition to monitoring the evolution and phylogeny of the group 30,15,28,39 . Thus, the rep-PCR technique is widely used to investigate specific genetic relationships between Bt isolates 9,18,19,37,53,35 .…”