DNA screening reveals pink bollworm resistance to Bt cotton remains rare after a decade of exposure.
Transgenic crops producing toxins from the bacterium Bacillus thuringiensis (Bt) kill insect pests and can reduce reliance on insecticide sprays. Although Bt cotton (Gossypium hirsutum L.) and Bt corn (Zea mays L.) covered 26 million ha worldwide in 2005, their success could be cut short by evolution of pest resistance. Monitoring the early phases of pest resistance to Bt crops is crucial, but it has been extremely difficult because bioassays usually cannot detect heterozygotes harboring one allele for resistance. We report here monitoring of resistance to Bt cotton with DNA-based screening, which detects single resistance alleles in heterozygotes. We used polymerase chain reaction primers that specifically amplify three mutant alleles of a cadherin gene linked with resistance to Bt cotton in pink bollworm, Pectinophora gossypiella (Saunders), a major pest. We screened DNA of 5,571 insects derived from 59 cotton fields in Arizona, California, and Texas during 2001-2005. No resistance alleles were detected despite a decade of exposure to Bt cotton. In conjunction with data from bioassays and field efficacy tests, the results reported here contradict predictions of rapid pest resistance to Bt crops.
Tabashnik
Bruce E
BE
Department of Entomology, University of Arizona, Tucson, AZ 85721, USA. brucet@ag.arizona.edu
Fabrick
Jeffrey A
JA
Henderson
Scottie
S
Biggs
Robert W
RW
Yafuso
Christine M
CM
Nyboer
Megan E
ME
Manhardt
Nancy M
NM
Coughlin
Laura A
LA
Sollome
James
J
Carrière
Yves
Y
Dennehy
Timothy J
TJ
Morin
Shai
S
D000483:Alleles; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D005787:Gene Frequency; D017344:Genes, Insect; D003368:Gossypium / Q000469:parasitology*; D006460:Hemolysin Proteins; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides; D008297:Male; D009036:Moths / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015206:Southwestern United States
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis