Linkage mapping an indoxacarb resistance locus in Helicoverpa armigera (Lepidoptera: Noctuidae) by genotype-by-sequencing.

Background: A major challenge to sustainable agricultural pest control is the rapid evolution of insecticide resistance. This is caused by mechanisms that reduce insecticide efficacy. Understanding the genetic mechanisms of resistance is essential for DNA-based monitoring of resistance in field populations. One such insecticide is indoxacarb, an important selective control option for Helicoverpa armigera in a range of crops including grain, horticulture and cotton. Recently, a strain of H. armigera (GY7-39) resistant to indoxacarb (198-fold) was isolated from field-collected moth.

Results: To identify the indoxacarb resistance locus, GY7-39 was backcrossed for six generations to susceptible strain New GR. In each generation, only resistant males were used to cross back to New GR. Genotype-by-sequencing was carried out on 95 H. armigera samples. In total, 13 203 tags with 8697 unique locations on the H. armigera genome were obtained. The indoxacarb resistance locus in strain GY7-39 was mapped to a 2.6 Mbp region on chromosome 16. In this region, two closely linked loci (IndoR1 and IndoR2) were found to be associated with indoxacarb resistant GY7-39.

Conclusions: We mapped indoxacarb resistance in GY7-39 to two closely linked loci IndoR1 and IndoR2 in a narrowed 2.6 Mbp region of H. armigera chromosome 16. The results provide essential background data for future genetic investigations including fine mapping of the indoxacarb resistance gene and the eventual development of an effective DNA-based diagnostic to support resistance management. © 2019 Society of Chemical Industry.