Canadian Journal of Microbiology - Revue Canadienne de Microbiologie (2009) 55, 536-543

Galina Kalmykova, Ljudmila Burtseva, Ross Milne and Kees van Frankenhuyzen (2009)
Activity of spores and extracellular proteins from six Cry⁺ strains and a Cry^- strain of Bacillus thuringiensis subsp. kurstaki against the western spruce budworm, Choristoneura occidentalis (Lepidoptera: Tortricidae)
Canadian Journal of Microbiology - Revue Canadienne de Microbiologie 55 (5), 536-543
Abstract: We characterized insecticidal activity of previously untested strains of Bacillus thuringiensis kurstaki belonging to two crystal serovars (K-1 and K-73) against the western spruce budworm (Choristoneura occidentalis Freeman 1967). By testing various components, we demonstrated that spores play a critical role in the pathogenesis of each strain. Spore-free crystals caused low mortality and purified spores were generally not toxic. The addition of spores to purified protoxin increased toxicity several hundred-fold, regardless of the parental strain from which the spores or protoxins were derived. The crystal and spore components did not account for full insecticidal activity of whole sporulated cultures owing to the toxicity of soluble proteins that are secreted during cell growth. We observed a marked difference in toxicity of secreted proteins between the K-1 and K-73 type strains, with the K-1 preparations causing much higher mortality, mass reduction, and inhibition of pupation. There was a consistent correlation between relative toxicity of secreted protein preparations and the presence and quantity of the Vip3A protein, suggesting that this protein contributes to the virulence of B. thuringiensis subsp. kurstaki in western spruce budworm larvae. However, other virulence factors have to be invoked to explain the synergizing effect of spores from both K-1 and K-73 strains on Cry protein toxicity.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Kees van Frankenhuyzen

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Choristoneura freemani
Bacillus thuringiensis var. kurstaki (entomopathogen)	Choristoneura freemani