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

Abstract

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.

Empowering Australian insecticide resistance research with genetic information: the road ahead

“…2017), narrowing the list of candidates to a cluster of P450 genes using genome‐wide association analyses (Chen et al . 2020). Similarly, recent evolution resistance in Bemisia tabaci to derivatives of tetramic and tetronic acid (Lueke et al .…”

“…Additionally, linkage mapping indicates that P450 genes in the CYP6AE family likely play a role in resistance to the oxadiazine (Group 22A), indoxacarb (Chen et al . 2020), in H. armigera .…”

Relative fitness and stability of resistance in a near‐isogenic strain of indoxacarb resistant Helicoverpa armigera (Lepidoptera: Noctuidae)

“…Esterases and glutathione‐S‐transferase (GST) are thought to have a role in indoxacarb resistance in P. xylostella 53,54 and Spodoptera exigua (Hübner) 55 while indoxacarb resistance is associated with enhanced metabolism by P450 monooxygenases in Spodoptera litura (Fabricius) 56 , Choristoneura rosaceana (Harris) 57 , Musca domestica (L.) 58 and H. armigera 10,39 . The putative mechanism of indoxacarb resistance in a precursor strain of GY7‐39BC4 was associated with the CYP6AE gene cluster 11 which is consistent with findings from inhibition experiments 10 and from CYP6AE gene cluster knockout experiments which restored susceptibility to indoxacarb in H. armigera 59 . The lack of a fitness cost in GY7‐39BC4 suggests either the detoxification of indoxacarb is not energetically costly or there is involvement of fitness modifiers that ameliorate the cost of resistance 60…”

“…However, use of selective products such as indoxacarb for control of H. armigera has increased over the past decade due to expansion of the Australian pulse industry 6,62 and the cotton IRMS is not sufficiently effective for managing resistance risk in insecticides utilized to target H. armigera in other commodities 63 . Moreover, because of high levels of genetic dominance and probable metabolic mechanism of indoxacarb resistance in H. armigera 10,11 it is likely that resistance will develop rapidly under certain conditions of selection.…”

“…However, reduced levels of susceptibility have been recorded at certain times of the year and in certain locations 9 . High levels of genetic dominance and a probable metabolic mechanism of indoxacarb resistance in H. armigera 10,11 suggest there is a high risk that resistance will develop rapidly under certain conditions of selection.…”