Association between resistance to Bt cotton and cadherin genotype in pink bollworm.
Two strains of pink bollworm, Pectinophora gossypiella (Saunders), each derived in 1997 from a different field population, were selected for resistance to Bacillus thuringiensis (Bt) toxin Cry1Ac in the laboratory. One strain (MOV97-R) originated from Mohave Valley in western Arizona; the other strain (SAF97-R) was from Safford in eastern Arizona. Relative to a susceptible laboratory strain, Cry1Ac resistance ratios were 1700 for MOV97-R and 520 for SAF97-R. For the two resistant strains, larval survival did not differ between non-Bt cotton and transgenic cotton producing CrylAc. In contrast, larval survival on Bt cotton was 0% for the two unselected parent strains from which the resistant strains were derived. Previously identified resistance (r) alleles of a cadherin gene (BtR) occurred in both resistant strains: r1 and r3 in MOV97-R, and r1 and r2 in SAF97-R. The frequency of individuals carrying two r alleles (rr) was 1.0 in the two resistant strains and 0.02 in each of the two unselected parent strains. Furthermore, in two hybrid strains with a mixture of susceptible (s) and r alleles at the BtR locus, all survivors on Bt cotton had two r alleles. The results show that resistance to Cry1Ac-producing Bt cotton is associated with recessive r alleles at the BtR locus in the strains of pink bollworm tested here. In conjunction with previous results from two other Bt-resistant strains of pink bollworm (APHIS-98R and AZP-R), results reported here identify the cadherin locus as the leading candidate for molecular monitoring of pink bollworm resistance to Bt cotton.
Tabashnik
Bruce E
BE
Department of Entomology, University of Arizona, Tucson, AZ 85721, USA.
Biggs
Robert W
RW
Higginson
Dawn M
DM
Henderson
Scottie
S
Unnithan
Devika C
DC
Unnithan
Gopalan C
GC
Ellers-Kirk
Christa
C
Sisterson
Mark S
MS
Dennehy
Timothy J
TJ
Carrière
Yves
Y
Morin
Shai
S
D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins / Q000235:genetics*; D015820:Cadherins / Q000235:genetics*; D004731:Endotoxins / Q000235:genetics*; D005838:Genotype; D003368:Gossypium / Q000235:genetics*; D006460:Hemolysin Proteins; D007305:Insecticide Resistance / Q000235:genetics*; D009036:Moths / Q000235:genetics*; D030821:Plants, Genetically Modified
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis