Effects of Elevated CO2 Concentration on Host Adaptability and Chlorantraniliprole Susceptibility in Spodoptera frugiperda

Abstract

Elevated atmospheric carbon dioxide concentrations (eCO2) can affect both herbivorous insects and their host plants. The fall armyworm (FAW), Spodoptera frugiperda, is a highly polyphagous agricultural pest that may attack more than 350 host plant species and has developed resistance to both conventional and novel-action insecticides. However, the effects of eCO2 on host adaptability and insecticide resistance of FAW are unclear. We hypothesized that eCO2 might affect insecticide resistance of FAW by affecting its host plants. To test this hypothesis, we investigated the effect of eCO2 on (1) FAW’s susceptibility to chlorantraniliprole after feeding on wheat, (2) FAW’s population performance traits (including the growth and reproduction), and (3) changes in gene expression in the FAW by transcriptome sequencing. The toxicity of chlorantraniliprole against the FAW under eCO2 (800 µL/L) stress showed that the LC50 values were 2.40, 2.06, and 1.46 times the values at the ambient CO2 concentration (400 µL/L, aCO2) for the three generations, respectively. Under eCO2, the life span of pupae and adults and the total number of generations were significantly shorter than the FAW under aCO2. Compared to the aCO2 treatment, the weights of the 3rd and 4th instar larvae and pupae of FAW under eCO2 were significantly heavier. Transcriptome sequencing results showed that more than 79 detoxification enzyme genes in FAW were upregulated under eCO2 treatment, including 40 P450, 5 CarE, 17 ABC, and 7 UGT genes. Our results showed that eCO2 increased the population performance of FAW on wheat and reduced its susceptibility to chlorantraniliprole by inducing the expression of detoxification enzyme genes. This study has important implications for assessing the damage of FAW in the future under the environment of increasing atmospheric CO2 concentration.