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The olfactory system of insects is crucial in modulating behaviors such as host seeking, mating, and oviposition. Odorant-binding proteins (OBPs) are involved in semiochemical recognition. OBPs recognize and bind odorants and transport them to odorant receptors located in olfactory neurons. Harmonia axyridis (Coleoptera: Coccinellidae) is a widely used predacious biological control agent for many agricultural and forestry pests. This study identified 19 OBPs in H. axyridis based on the antennal and whole-body transcriptomes of adults and obtained all the full-length open reading frames, including 11 ‘Classic’ OBPs, 7 ‘Minus-C’ OBPs and 1 ‘Plus-C’ OBP. They encoded 125 to 241 amino acid proteins with molecular weights ranging from 13.75 to 27.75 kDa and isoelectric points ranging from 4.15 to 8.80. Phylogenetic analyses were used to study the relationships between H. axyridis OBPs and OBPs from other species of Coleoptera. Quantitative real-time PCR (qPCR) analysis showed that HaxyOBP2, 3, 5, 8, 10, 12, 13, 14, and 15 were highly expressed in antennae of both adult females and males. Moreover, HaxyOBP2, 3, 5, 12, and 15 were more abundantly expressed in antennae than other body parts, while HaxyOBP13 and HaxyOBP14 were expressed predominantly, and at similar levels, in the head and antennae. The other OBP genes were highly expressed in non-olfactory tissues including the thorax, abdomen, legs, and wings. These results provide valuable information for further study of H. axyridis olfaction, which may ultimately enhance its use as a biocontrol agent.

Cyantraniliprole is a novel anthranilic diamide insecticide with significant efficacy against Bemisia tabaci, an important pest insect worldwide. In this study, we conducted reversion and selection work and genetic analysis, and determined cross-resistance spectrum and synergism of cyantraniliprole resistance based on the reported population, SX population, of B. tabaci collected from Shanxi Province, China. Compared with a susceptible strain (MED-S), SX population, the field-evolved cyantraniliprole-resistant population exhibited 26.4-fold higher resistance to cyantraniliprole. In SX, a sharp decline of cyantraniliprole resistance was shown in the absence of selection. Another tested strain, SX-R, was established from SX population after successive selection with cyantraniliprole and recently developed 138.4-fold high resistance to cyantraniliprole. SX-R had no cross-resistance to abamectin, imidacloprid, thiamethoxam, sulfoxaflor, or bifenthrin. Genetic analysis illustrated that cyantraniliprole resistance in SX-R was autosomally inherited and incompletely dominant. Additionally, piperonyl butoxide (PBO) significantly inhibited cyantraniliprole resistance in the SX-R strain. In conclusion, the selection of SX with cyantraniliprole led to high resistance to cyantraniliprole which is incompletely dominant and no cross-resistance to several common types of insecticides. Enhanced oxidative metabolism is possibly involved in the resistance of SX-R, yet target-site resistance could not be excluded.

The Bemisia tabaci (Gennadius) cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide. In China, the B. tabaci Mediterranean (MED) (or biotype Q) species is threatening agricultural production all over the country as resistance to commonly used insecticides has increased. This situation highlights the need for alternative pest control measures. Cyantraniliprole, a novel anthranilic diamide insecticide, has been widely employed to control Hemipteran pests. To monitor the levels of resistance to cyantraniliprole in B. tabaci field populations in China, bioassays were conducted for 18 field samples from nine provinces over two years. Compared with median lethal concentration (LC50) for the MED susceptible strain, all field samples had significantly higher resistance to cyantraniliprole. Furthermore, resistance factors (RFs) increased significantly in samples from Shanxi (from 5.62 in 2015 to 25.81 in 2016), Hunan (3.30 in 2015 to 20.97 in 2016) and Hubei (from 9.81 in 2015 to 23.91 in 2016) provinces. This study indicates a considerable decrease in the efficacy of cyantraniliprole against B. tabaci and establishes a baseline of susceptibility that could serve as a reference for future monitoring and management of B. tabaci resistance to cyantraniliprole.