Association of PCR and feeding bioassays as a large-scale method to screen tropical Bacillus thuringiensis isolates for a cry constitution with higher insecticidal effect against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae.
OBJECTIVE
To verify whether the presence of any of the cry1C, 1D, 1E and 1F genes could be associated with high toxicity against fall armyworm.


RESULTS
A sample of 60 strains from a large collection of tropical Bacillus thuringiensis (B.t.) isolates was subjected to feeding bioassays and gene-specific PCR. Positive amplification of cry-specific fragments, so confirmed by sequencing, revealed that cry1C was ubiquitous and distributed among high and low mortality classes, cry1D was underrepresented and showed no clear association to high toxicity, and cry1F was not detected. The presence of cry1E significantly correlated to high levels of insecticidal activity, as estimated by linear regression analysis.


CONCLUSIONS
The PCR amplification of cry1E-specific fragments alone appears to be sufficient to identify B.t. strains with high mortality levels against tropical armyworm.


CONCLUSIONS
The approach presented is promising as a simple and efficient method for first-tier, marker-assisted screening of environment-specific B.t. germplasm effective in controlling a single target pest.
Loguercio
L L
LL
Department of Biological Sciences, UESC - State University of Santa Cruz, Ilhéus, Brazil. leandro@uesc.br
Santos
C G
CG
Barreto
M R
MR
Guimaraes
C T
CT
Paiva
E
E
D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry* / Q000302:isolation & purification; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins; D001681:Biological Assay; D004731:Endotoxins / Q000494:pharmacology*; D006460:Hemolysin Proteins; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D007915:Lepidoptera / Q000187:drug effects; D010572:Pest Control, Biological; D016133:Polymerase Chain Reaction / Q000379:methods*; D018411:Spodoptera / Q000187:drug effects
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis