Diversity of Bacillus thuringiensis strains from Colombia with insecticidal activity against Spodoptera frugiperda (Lepidoptera:Noctuidae).
OBJECTIVE
To identify and characterize Bacillus thuringiensis strains highly toxic to Spodoptera frugiperda, and to explore the genetic diversity of such strains.


RESULTS
The insecticidal activity of 1100 strains of B. thuringiensis from Colombian soil samples was assayed against first instar S. frugiperda larvae, and 32 active strains were found. After a second bioassay evaluation, the eight most potent strains were selected for further characterization, which included crystal protein profiles determined by polyacrylamide gel electrophoresis, plasmid profile, plasmid restriction patterns, cry gene composition, qualitative determination of beta-exotoxin production, random amplified polymorphic DNA, serotyping, and toxicity to S. frugiperda. All Colombian strains contained cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C and cry1D genes. However, PCR profiles of the Colombian strains suggested the presence of variants of the cry1 genes. Serotyping indicated that these strains belong to the kurstaki, thuringiensis, canadiensis and indiana subspecies. Interestingly, three strains belonging to different serotypes and subspecies were found in the same soil sample, and toxicity ranged between 11 and 976 ng cm(-2) of diet.


CONCLUSIONS
It has been shown that B. thuringiensis strains belonging to different serotypes and displaying variable potency to S. frugiperda larvae can be found in the same soil sample.


CONCLUSIONS
The results obtained indicate that some of the B. thuringiensis strains studied could be of interest for further development for S. frugiperda control programmes.
Arango
J A
JA
Biotechnology and Biological Control Unit, Corporación para Investigaciones Biológicas, Medellín, Colombia.
Romero
M
M
Orduz
S
S
D000818:Animals; D001413:Bacillus thuringiensis / Q000145:classification* / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000633:toxicity*; D001427:Bacterial Toxins; D003105:Colombia; D004269:DNA, Bacterial / Q000032:analysis; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics / Q000633:toxicity*; D014644:Genetic Variation; D006460:Hemolysin Proteins; D010572:Pest Control, Biological; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D019105:Random Amplified Polymorphic DNA Technique; D018411:Spodoptera / Q000187:drug effects*
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis