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10-Minute Presentation

Physiology, Biochemistry, and Toxicology

10-min: PBT, Toxicology

Mismatch between lab-selected and field-evolved Bt resistance in Helicoverpa zea

Tuesday, November 12, 2024
10:00 AM – 10:12 AM MST
Location: Phoenix Convention Center, 226 B, PCC
Oral Presentation
Transgenic crops producing crystalline (Cry) proteins from the bacterium Bacillus thuringiensis have been used extensively to control some major crop pests. However, many populations of the noctuid moth, Helicoverpa zea, one of the most important crop pests in the United States, have evolved practical resistance to several Cry proteins, including Cry1Ac. Although mutations in single genes that confer resistance to Cry proteins have been identified in lab-selected and gene-edited strains of H. zea and other pests, the genetic basis of field-evolved resistance to Cry proteins in H. zea has remained elusive. We used a population genomic approach to analyze the genetic basis of field-evolved resistance to Cry1Ac in H. zea in 27 samples derived from 17 sites in seven states of the southern United States. We found evidence for extensive gene flow among all populations studied. Field-evolved resistance was not associated with mutations in 19 single candidate genes previously associated with resistance to Cry proteins in H. zea or other lepidopterans. Instead, field-evolved resistance was associated with increased copy number of a cluster of trypsin genes. However, this increased trypsin copy number occurred in some susceptible samples but not in some resistant samples, implying that this increase alone was not consistently sufficient or necessary for resistance. Thus, we infer that mutations in other genes also contribute to field-evolved resistance to Cry1Ac in H. zea.