Inheritance of resistance to Bt toxin crylac in a field-derived strain of pink bollworm (Lepidoptera: Gelechiidae).
Laboratory selection with Cry1Ac, the Bacillus thuringiensis (Bt) toxin in transgenic cotton, initially produced 300-fold resistance in a field-derived strain of pink bollworm, Pectinophora gossypiella (Saunders), a major cotton pest. After additional selection increased resistance to 3,100-fold, we tested the offspring of various crosses to determine the mode of inheritance of resistance to Cry1Ac. The progeny of reciprocal F1 crosses (resistant male x susceptible female and vice versa) responded alike in bioassays, indicating autosomal inheritance. Consistent with earlier findings, resistance was recessive at a high concentration of Cry1Ac. However, the dominance of resistance increased as the concentration of Cry1Ac decreased. Analysis of survival and growth of progeny from backcrosses (F1 x resistant strain) suggest that resistance was controlled primarily by one or a few major loci. The progression of resistance from 300- to 3,100-fold rules out the simplest model with one locus and two alleles. Overall the patterns observed can be explained by either a single resistance gene with three or more alleles or by more than one resistance gene. The pink bollworm resistance to Cry1Ac described here fits "mode 1" resistance, the most common type of resistance to Cry1A toxins in Lepidoptera.
Tabashnik
Bruce E
BE
Department of Entomology, University of Arizona, Tucson 85721, USA. brucet@ag.arizona.edu
Liu
Yong-Biao
YB
Dennehy
Timothy J
TJ
Sims
Maria A
MA
Sisterson
Mark S
MS
Biggs
Robert W
RW
Carrière
Yves
Y
D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D004731:Endotoxins / Q000494:pharmacology*; D005260:Female; D003368:Gossypium; D006460:Hemolysin Proteins; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides / Q000494:pharmacology*; D008297:Male; D009036:Moths / Q000187:drug effects / Q000235:genetics*; D010572:Pest Control, Biological / Q000379:methods*; D030821:Plants, Genetically Modified
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis