Combined analysis of supernatant-based feeding bioassays and PCR as a first-tier screening strategy for Vip -derived activities in Bacillus thuringiensis strains effective against tropical fall armyworm.
OBJECTIVE
To assess whether feeding bioassays using culture-supernatant proteins could be combined with PCR into a first-tier screening strategy for Vip3A-like genes efficient against tropical Spodoptera frugiperda.


RESULTS
Out of 12 Bacillus thuringiensis strains studied, the total protein concentrated from the culture supernatant of only the strain HD125 yielded a significantly increased armyworm mortality and an intense band of the predicted size for VIP3A protein in SDS-PAGE. However, PCR and sequencing data indicated Vip-like genes are ubiquitous in tropical B. thuringiensis isolates. Interestingly, the HD125 strain was also the only one displaying a single-band amplification pattern and the highest sequence identity to the reported Vip3A(a) gene.


CONCLUSIONS
Results suggest the insecticidal effectiveness of putative VIPs in B. thuringiensis isolates can be preliminarily estimated by the use of supernatant-derived total protein in feeding experiments, though only in a limited manner.


CONCLUSIONS
A simple and cost-effective first-tier screening strategy for VIP-derived activities in B. thuringiensis collections can be developed by combining PCR and feeding bioassays. Moreover, the employed primers showed to be useful as a tool for strains differentiation at DNA level, and for characterization and isolation of Vip-like genes in tropical B. thuringiensis germplasm.
Loguercio
L L
LL
Department of Biological Sciences, UESC-State University of Santa Cruz, Ilhéus, Brazil. leandro@uesc.br
Barreto
M L
ML
Rocha
T L
TL
Santos
C G
CG
Teixeira
F F
FF
Paiva
E
E
D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001681:Biological Assay / Q000379:methods*; D005247:Feeding Behavior; D005820:Genetic Testing; D010572:Pest Control, Biological; D016133:Polymerase Chain Reaction; D018411:Spodoptera / Q000382:microbiology*
D001426:Bacterial Proteins; C447139:Vip3A protein, Bacillus thuringiensis