Researchers from the University of Arizona Department of Entomology in the College of Agriculture, Life and Environmental Sciences used genomics to investigate the genetic changes causing resistance to transgenic crops in field populations of the corn earworm, also known as cotton bollworm or Helicoverpa zea.
The researchers, led by Bruce Tabashnik, head of the Department of Entomology, discovered that in this pest, field-evolved resistance was not associated with any of the 20 genes that have been previously implicated in resistance to the pest-killing proteins in transgenic crops. The U of A researchers worked with colleagues from Texas A&M University who used bioassays to evaluate resistance by testing the insects from the field. The collaborating research teams analyzed 937 corn earworms from 17 sites in seven states across the southern United States, sampled from 2002 to 2020.
"We carefully examined 20 genes that affected how pests responded to Bt proteins in previous studies. Our evidence indicates changes in these genes are not causing resistance to Bt crops in wild populations of the corn earworm," said Andrew Legan, a U of A postdoctoral fellow and first author of the study. Legan added that they found resistance was associated with a cluster of genes that was duplicated in some resistant field populations. However, it remains a mystery as to how many of these genes contribute to resistance and how they confer resistance.
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