Fitness costs of adaptive chlorantraniliprole resistance in the
Spodoptera exigua (Lepidoptera: Noctuidae)
The beet armyworm, Spodoptera exigua, is a multifeeding insect pest,
which has developed high resistance to chlorantraniliprole, a
benzoylurea insecticide that targets on the ryanodine receptors (RyRs).
However, few studies have been conducted on the highly resistant strain.
Here, the resistant strain (SE-Sel) and sensitive strain (SE-Sus) were
obtained by bidirectional screening for 6 generations. The potential
oviposition and oviposition rate of the SE-Sel strain were dramatically
lower than those of the SE-Sus strain, on the contrary the weights of
prepupae and preadult were significantly increased. And the expression
levels of vitellogenin (SeVg) and its receptor (SeVgR) in the SE-Sel
strain were consistently lower than those in the SE-Sus strain. The
RyRI4765M mutation and the upregulation of detoxification genes, such as
SeABCOK, SeGST15, SeGSTZ2, SeCarEs1, CYP6AEW and SeCYP6AB10, contributed
to the evolution of resistance to chlorantraniliprole. The RyRI4765M
mutation could affect neuropeptide activation, and it conduced to the
upregulated expression of the neuropeptide SeNPF and its receptor,
SeNPFR, which could inhibit courtship behavior and reduce oviposition.
And the neuropeptide SeNPF could influence the expression of juvenile
hormone-binding protein and juvenile hormone diol kinase, and it led to
the downregulated expression of SeVg. Therefore, these results indicate
that the fitness cost accompanied by chlorantraniliprole resistance in
S. exigua is related to the wicked evolution of RyR.