Selection and characterization of the inheritance of resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to chlorantraniliprole and cross‐resistance to other diamide insecticides

Abstract

BACKGROUND Understanding the genetic basis of insect resistance to insecticides can help to implement insecticide resistance management (IRM) strategies. In this study, we selected a strain of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) resistant to chlorantraniliprole using the F2 screen method, characterized the inheritance of resistance and evaluated patterns of cross‐resistance to other diamide insecticides. RESULTS The chlorantraniliprole‐resistant strain (Chlorant‐R) was selected from a field‐collected population with an estimated allele frequency of 0.1316. The estimated median lethal concentration (LC50) values were 0.011 and 2.610 µg a.i. cm–2 for the susceptible (Sus) and Chlorant‐R strains, respectively, resulting in a resistance ratio (RR) of 237‐fold. The LC50 values of the reciprocal crosses were 0.155 and 0.164 µg a.i. cm–2, indicating that resistance is autosomally inherited. Resistance was characterized as incompletely recessive and monogenic at concentrations close to the recommended field rates of chlorantraniliprole. Survival of the resistant strain and heterozygous larvae in maize plants treated at the field rate was ∼ 60 (similar to the susceptible strain on untreated maize) and 15%, respectively. The Chlorant‐R strain showed low cross‐resistance to cyantraniliprole (RR ∼ 27‐fold) and very high cross‐resistance to flubendiamide (RR > 42 000‐fold). CONCLUSIONS The frequency of chlorantraniliprole resistance allele was moderately high in a field‐collected population of S. frugiperda. The inheritance of chlorantraniliprole resistance was characterized as autosomal, incompletely recessive and monogenic. S. frugiperda showed cross‐resistance to other diamide insecticides. These results provide essential information for the implementation of IRM programs to preserve the useful life of diamide insecticides for controlling S. frugiperda in Brazil. © 2019 Society of Chemical Industry

Detection of a ryanodine receptor target‐site mutation in diamide insecticide resistant fall armyworm, Spodoptera frugiperda

“…A low frequency of resistance to chlorantraniliprole has been reported in Brazilian field populations of FAW collected in 2012, 2013 and 2014 . More recently, a F2 screen and subsequent laboratory selection resulted in a FAW strain, Chlorant‐R, showing high levels of diamide resistance . The genetics of resistance in this strain was characterized as monogenic, incompletely recessive, and it has been shown that some heterozygotes would survive field‐recommended rates of chlorantraniliprole, thus increasing the risk of rapid evolution of resistance .…”

“…Diamide resistant (Chlorant‐R) and susceptible (Sus) strains of S. frugiperda were maintained under controlled conditions (25 ± 1 °C, 70 ± 10% relative humidity (RH) and 14:10 h light/dark photoperiod). Strain Chlorant‐R was maintained under continuous selection pressure by chlorantraniliprole as described previously …”

“…Concentration–response bioassays were performed on third instar larvae of strains Sus and Chlorant‐R, using both chlorantraniliprole and flubendiamide. Artificial diet overlay assays were conducted in 24‐well plates as described previously . To evaluate the impact of metabolic resistance to diamide insecticides, 1 μL acetonic solutions of PBO, DEM and DEF were applied topically to third instar larvae 2 h prior to insecticide exposure.…”

“…Levels of diamide resistance much higher than those reported for FAW from Puerto Rico, were very recently described for a Brazilian field‐collected FAW strain, Chlorant‐R, resulting from an F2 screen and selection with chlorantraniliprole . The authors reported resistance ratios of > 230‐fold and > 42 000‐fold against chlorantraniliprole and flubendiamide, respectively.…”

“…The authors reported resistance ratios of > 230‐fold and > 42 000‐fold against chlorantraniliprole and flubendiamide, respectively. However, the molecular mechanism of resistance remained unknown, but genetic studies suggested monogenic resistance and an incompletely recessive mode of inheritance …”