Journal of Economic Entomology (1998) 91, 1032-1037

Y.-B. Liu and B.E. Tabashnik (1998)
Elimination of a recessive allele conferring resistance to Bacillus thuringiensis from a heterogeneous strain of diamondback moth (Lepidoptera : Plutellidae)
Journal of Economic Entomology 91 (5), 1032-1037
Abstract: We devised and tested a procedure for eliminating a recessive allele conferring resistance to Bacillus thuringiensis subsp. kurstaki from a laboratory strain of diamondback moth, Plutella xylostella (L.), composed of resistant and susceptible individuals. We established a homozygous susceptible strain (LAB-PS) from a heterogeneous strain (LAB-P) as follows: We obtained F₁ progeny from 7 single-pair families from the heterogeneous strain. Hybrid F₂ progeny were produced in 7 mass crosses, each of which involved 10 female F₁ progeny from a single-pair family and 10 males from a resistant strain (NO-QA). The hybrid F₂ progeny were tested in bioassays with a liquid formulation of B. thuringiensis toxin Cry1Ab at a diagnostic concentration that kills susceptible homozygotes and heterozygotes, but not resistant homozygotes. If the resistance allele occurred in either of the 2 parents that produced a particular F₁ family, the hybrid F₂ progeny derived from that family were expected to contain at least 25% homozygous resistant individuals that would survive exposure to the diagnostic concentration of Cry1Ab. Conversely, 0% survival of a set of hybrid F₂ progeny in the diagnostic bioassay would indicate that the single-pair family from which it was derived was homozygous susceptible. We found 0% survival in 1 set of hybrid F₂ progeny and used the F₁ single-pair family from which this set was derived to establish a homozygous susceptible strain. Subsequent bioassays showed that diagnostic concentrations of Cry1Ab or Cry1Aa killed 100% of larvae tested from this strain. The LC₅₀ of Cry1Ab at 5 d for the susceptible strain was 7-fold lower than that for the heterogeneous strain. The procedure can be adapted for other insects and other traits, such as resistance to other insecticides.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Yong-Biao Liu, Bruce E. Tabashnik

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
pesticide resistance of pest
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

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