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Bemisia tabaci is a threat to agriculture worldwide because of its potential to cause devastating damage to various crops. β-asarone is a bioactive pesticidal chemical originating from Acorus calamus (or "Sweet Flag") plants, and it displays significant lethal effects against insect pests. In this study, we established a baseline of susceptibility to β-asarone from China and patterns of cross-resistance to other popular insecticides. We found that all the 12 field-collected B. tabaci populations exhibited high susceptibility to β-asarone, and there was no cross-resistance detected for other tested insecticides. We subsequently evaluated the sublethal effects of β-asarone on physiology and biochemistry via LC25 treatment (4.7 mg/L). LC25 of β-asarone resulted in prolonged developmental duration and decreased survival rates in B. tabaci nymphs, pseudopupae, and adults. Significant reductions in oviposition duration, fecundity, and hatchability were also observed. Additionally, the metabolic enzyme activity and expression profiles of selected cytochrome P450 monooxygenase (P450) genes following the LC25 treatment of β-asarone suggest that enhanced detoxification via P450s could be involved in the observed sublethal effects. These findings demonstrate the strong toxicity and significant sublethal effects of β-asarone on B. tabaci and suggest that the induced overexpression of P450 genes could be associated with the response to β-asarone. [ABSTRACT FROM AUTHOR]

Abamectin, produced by the soil-dwelling actinomycete Streptomyces avermitilis, belongs to the macrocyclic lactones class of pesticides, has nematocidal, acaricidal, and insecticidal activity, and is highly effective when used against targeted species. Bemisia tabaci, the tobacco whitefly, is a highly destructive insect to agricultural production worldwide, and various insecticide-resistant strains have been identified in China. Here, we monitored levels of resistance to abamectin in twelve field-collected B. tabaci populations from northern China, and confirmed that, compared with the lab reference strain, six field populations exhibited strong abamectin resistance, while the other six exhibited low-to-medium resistance. Among these, the Xinzheng (XZ) population displayed about a 40-fold increased resistance to abamectin, and experienced significant cross-resistance to chlorpyrifos and imidacloprid. The abamectin resistance of XZ was found to be autosomal and incompletely dominant. Metabolic enzyme and synergism tests were conducted, and two metabolic enzymes, glutathione S-transferase and P450 monooxygenase, were found to be conducive to the field-developed abamectin resistance of the XZ population. The above results provide valuable information that can be used in identifying new pest control strategies and delaying the evolution of resistance to abamectin in field populations of whiteflies. [ABSTRACT FROM AUTHOR]

A growing number of studies have focused on the microRNA (miRNA) expression in Bemisia tabaci , one devastating agricultural insect pest of the tropical and subtropical areas for which the primary means of control are insecticides. In studying the genetic underpinnings of insecticide resistance, the choice of stable reference genes for normalizing data plays a key role to acquire unbiased expression profile results from quantitative real-time PCR (qPCR) analysis. Expression profiles of 11 selected reference genes were determined systematically in B. tabaci exposure to 11 insecticides. Furthermore, we assessed the stability of all the selected candidates in relation to other variables including sex, tissue type, and developmental stage. Candidate reference gene validation was conducted by analyzing the let-7-5p expression under various experimental treatments. Five programs BestKeeper, NormFinder, geNorm, △Ct, and RefFinder were applied to verify the accuracy of the selected candidates. Our results displayed that the best choices of the selected candidates for pymetrozine, sulfoxaflor, flonicamid, cyantraniliprole, afidopyropen, and deltamethrin treatment were miR-1-3p and miR-100-5p, U6 and miR-100-5p were best for chlorpyrifos and imidacloprid treatments, and U6 and miR-1-3p were best for flupyradifurone and β-cypermethrin treatments. The reference genes miR-624, miR-252, and miR-275 worked best in adult tissues, miR-100-5p and miR-1-3p worked best in either sex, and miR-624 and miR-11 were best to use across developmental stages. Not even one reference gene was found to be suitable for all experimental conditions. Our results contributed to the growing body of the literature on qPCR reference gene selection under various experimental conditions and facilitate further investigation on gene expression changes in B. tabaci , resulting from pesticide exposure. [ABSTRACT FROM AUTHOR]

Bemisia tabaci is one of notorious agricultural insect pests in China, and the strategies of management largely depend on application of insecticides. In order to assess levels of resistance in field populations of B. tabaci to six insecticides including abamectin, cyantraniliprole, pymetrozine, imidacloprid, chlorpyrifos and bifenthrin, we monitored the susceptibility to all tested insecticides in five field populations across China and the results indicated that field populations of B. tabaci have developed various levels of resistance to each chemical agent. Furthermore, para-type voltage gated sodium channel mutations (L925I and T929V) and acetylcholinesterase ace1 mutation (F331W) were confirmed, and expression levels of CYP6CM1, CYP4C64, GSTd7 and ABCG3 were detected for investigating mechanisms of imidacloprid resistance in the five field-collected populations. The results showed that, in all tested populations, frequencies of F331W were 100%, and the frequencies of the L925I and T929V were in the range of 28.5 to 47.0% and 11.0 to 53.5%, respectively. Moreover, CYP6CM1 and CYP4C64 were significantly overexpressed in two tested populations, respectively, and GSTd7 was significantly overexpressed in one population. No overexpression of ABCG3 was observed in all the populations. Above results provided valuable insight into the current status of insecticide resistance and could be contributed to design strategies of management for B. tabaci. Unlabelled Image • Low to high levels of resistance to six insecticides in Bemisia tabaci MED were determined. • Organophosphates resistance-associated mutation F331W in ace1 gene was fixed in all tested populations. • Pyrethroids resistance-associated mutations L925I and T929V in sodium channel gene were also determined. • Expression levels of CYP6CM1, CYP4C64, GSTd7 and ABCG3 in all field populations were determined, [ABSTRACT FROM AUTHOR]

Bemisia tabaci is one of the most destructive agricultural insect pests around the world, and it has developed high levels of resistance to most pesticides. Dimpropyridaz, a novel insecticide developed by BASF, displays excellent activity against piercing-sucking insect pests. In this study, baseline of susceptibility showed all tested field populations of B. tabaci are susceptible to dimpropyridaz. After continuous selection with dimpropyridaz in the lab, a B. tabaci strain (F12) developed 2.2-fold higher level of resistance compared with a susceptible MED-S strain, and the realized heritability (h 2) was estimated as 0.0518. The F12 strain displayed little cross-resistance to afidopyropen, cyantraniliprole, sulfoxaflor, or abamectin, and significantly increased activity of cytochrome P450 monooxygenase (P450). The fitness cost of dimpropyridaz resistance was evident in F12 strain, which had a relative fitness of 0.95 and significantly lower fecundity per female compared with MED-S strain. Taken together, B. tabaci displays high susceptibility to dimpropyridaz in the field, and low risk of developing resistance to dimpropyridaz under successive selection pressure. Little cross-resistance to popular insecticides was found, and fitness cost associated dimpropyridaz resistance was observed. Higher activity of cytochrome P450 in the F12 strain, may be involved in the process of detoxifying dimpropyridaz in whitefly. [Display omitted] • All tested field populations of Bemisia tabaci are highly susceptible to dimpropyridaz. • B. tabaci displays low risk to dimpropyridaz after continuous selections. • Dimpropyridaz showed little cross-resistance to the selected popular insecticides. • Cytochrome P450 monooxygenase could be involved in detoxification of dimpropyridaz. • Dimpropyridaz-resistance conferred fitness cost in the F12 strain of B. tabaci. [ABSTRACT FROM AUTHOR]

Bemisia tabaci is a formidable insect pest worldwide, and exhibits significant resistance to various insecticides. Flupyradifurone is one novel butenolide insecticide and has emerged as a new weapon against B. tabaci , but field-evolved resistance to this insecticide has become a widespread concern. To unravel the mechanisms of field-evolved flupyradifurone resistance, we conducted a comprehensive investigation into susceptibility of twenty-one field populations within the Beijing-Tianjin-Hebei Region of China. Alarmingly, thirteen of these populations displayed varying degrees of resistance, ranging from low to medium levels, and building upon our prior findings, we meticulously cloned and characterized the CYP6CX4 gene in B. tabaci. Our investigations unequivocally confirmed the association between CYP6CX4 overexpression and flupyradifurone resistance in three of the thirteen resistant strains via RNA interference. To further validate our findings, we introduced CYP6CX4 overexpression into a transgenic Drosophila melanogaster line, resulting in a significant development of resistance to flupyradifurone in D. melanogaster. Additionally, homology modeling and molecular docking analyses showed the stable binding of flupyradifurone to CYP6CX4 , with binding free energy of −6.72 kcal mol−1. Collectively, our findings indicate that the induction of CYP6CX4 exerts one important role in detoxification of flupyradifurone, thereby promoting development of resistance in B. tabaci. [ABSTRACT FROM AUTHOR]

Bemisia tabaci , sweetpotato whitefly, is one notorious insect pest on a series of crops worldwide, and many populations show high resistance to various insecticides. The cyantraniliprole-resistant strain of B. tabaci SX-R (138.4-fold) was obtained by selections with an outdoor-collected cyantraniliprole resistant population. By crossing and repeated backcrossing to a susceptible MED-S strain, the trait of cyantraniliprole resistance from SX-R was moved into MED-S to establish one near-isogenic line (CYAN-R). MED-S and CYAN-R were utilized to build patterns of cross-resistance, CYAN-R strain exhibited 63.317-fold resistance to cyantraniliprole, but no cross-resistance to several other successfully commercialized chemical agents. After that significant inhibition of cyantraniliprole resistance by piperonyl butoxide (PBO) and increased cytochrome P450 (3.4-fold) were observed in CYAN-R strain, indicating putative involvement of P450 in detoxification. Furthermore, five published detoxification-related P450 genes in B. tabaci , CYP4C64, CYP6CM1, CYP6CX1, CYP6CX4, and CYP6DZ7 were selected and expression levels of them were measured for exploring mechanisms of cyantraniliprole resistance. Compare with MED-S, no significant overexpression of the five P450 genes was observed in the CYAN-R strain. Above results could be conductive to study on mechanism of cyantraniliprole resistance and will be very helpful for the management of whitefly. Unlabelled Image • One near-isogenic cyantraniliprole resistant strain CYAN-R was established. • No cross-resistance of all tested chemicals was observed in CYAN-R strain. • Piperonyl butoxide exerted significant synergism in CYAN-R strain. • Enhanced P450 monooxygenases is involved in the resistance in CYAN-R strain. • Five resistance-related P450s are not related with cyantraniliprole resistance. [ABSTRACT FROM AUTHOR]

Combinatorial delivery of different double-stranded RNAs (dsRNAs) can result in competitive inhibition in insect pests and remains one of the obstacles in the way of future applications of the RNA interference (RNAi)-based pest control. In this study, we attempted to discover the basic competition characteristics between dsRNAs and provided insight into the solutions of competitive inhibition. RNAi sensitive insect species Tribolium castaneum were treated, and competitions between dsRNA fragments influencing the effectiveness of RNAi response could be measured. A chimeric dsRNA strategy for conjugating different dsRNA fragments into a single molecule and a nanoparticle carbon quantum dots-mediated dsRNA delivery were confirmed as efficient methods to knock down multiple target genes simultaneously. Furthermore, in vitro assays were conducted for determining the accumulation speed of serially diluted and incubated dsRNA in the midgut tissues. Our data showed that the accumulation of dsRNAs of different treated amounts was 0.25 μg ≈ 0.5 μg > 1 μg ≥ 2 μg > 4 μg, indicating that accumulation speed would be affected by treated dsRNA. Overall, our results strongly suggest that endocytic components influencing cellular uptake might be oversaturated when an excess amount of dsRNAs were treated, thereby causing competitive inhibition of target genes. [Display omitted] • Competitions between dsRNA fragments in T. castaneum , can influence RNAi response. • Conjugated chimeric dsRNAs can decrease competitive inhibition. • Nanoparticle CQD-mediated dsRNA delivery decreased competitive inhibition. • Competitions between dsRNAs mainly occur at the level of dsRNA uptake due to oversaturation of endocytic components. [ABSTRACT FROM AUTHOR]