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The evolution of nitenpyram resistance has been confirmed to be related to overexpression of two key metabolic enzyme genes, CYP6ER1 and CarE1, in Nilaparvata lugens, a highly destructive rice pest that causes substantial economic losses and has developed insecticide resistance. As microRNAs (miRNAs) are important post‐transcriptional regulators of gene expression, whether they are involved in nitenpyram resistance is poorly understood in N. lugens. In this study, knockdown of key genes in the miRNA biogenesis pathway (Dicer1, Drosha, and Argonaute1) changed CYP6ER1 and CarE1 abundance, which confirmed the importance of miRNAs in nitenpyram resistance. Furthermore, global screening of miRNAs associated with nitenpyram resistance in N. lugens was performed, and a total of 42 known and 178 novel miRNAs were identified; of these, 57 were differentially expressed between the susceptible and resistant strains, and two (novel_85 and novel_191) were predicted to target CYP6ER1 and CarE1, respectively. Luciferase reporter assays demonstrated that novel_85 and novel_191 bind to the CYP6ER1 and CarE1 coding regions, respectively, and downregulate their expression. Moreover, modulating novel_85 and novel_191 expression by injection of miRNA inhibitors and mimics significantly altered N. lugens nitenpyram susceptibility. This is the first study to systematically screen and identify miRNAs associated with N. lugens nitenpyram resistance, and provides important information that can be used to develop new miRNA‐based targets in insecticide resistance management. [ABSTRACT FROM AUTHOR]

Carboxylesterases (CarEs) represent one of the major detoxification enzyme families involved in insecticide resistance. However, the function of specific CarE genes in insecticide resistance is still unclear in the insect Nilaparvata lugens (Stål), a notorious rice crop pest in Asia. In this study, a total of 29 putative CarE genes in N. lugens were identified, and they were divided into seven clades; further, the β‐esterase clade was significantly expanded. Tissue‐specific expression analysis found that 17 CarE genes were abundantly distributed in the midgut and fat body, while 12 CarE genes were highly expressed in the head. The expression of most CarE genes was significantly induced in response to the challenge of nitenpyram, triflumezopyrim, chlorpyrifos, isoprocarb and etofenprox. Among these, the expression levels of NlCarE2, NlCarE4, NlCarE9, NlCarE17 and NlCarE24 were increased by each insecticide. Real‐time quantitative polymerase chain reaction and RNA interference assays revealed the NlCarE1 gene to be a candidate gene mainly involved in nitenpyram resistance, while simultaneously silencing NlCarE1 and NlCarE19 produced a stronger effect than silencing either one individually, suggesting a cooperative relationship in resistance formation. These findings lay the foundation for further clarification of insecticide resistance mediated by CarE in N. lugens. [ABSTRACT FROM AUTHOR]

BACKGROUND Sulfoxaflor has been considered as a new tool for Nilaparvata lugens control in the field. In this study, a laboratory‐selected resistant strain and a susceptible strain were used to evaluate the inheritance and fitness costs of sulfoxaflor resistance in N. lugens. RESULTS: The resistant strain (SFX‐SEL) showed 123.63‐fold resistance compared with the susceptible strain (SS). Progenies of reciprocal crosses (F1RS and F1SR) showed similar concentration–mortality responses (LC50) to sulfoxaflor and also exhibited a similar degree of dominance; −0.16 for F1RS and −0.26 for F1SR. Significant differences between the observed and expected mortalities of F2 individuals suggested that sulfoxaflor resistance is associated with multiple genes. The resistant strain had a relative fitness of 0.75 with substantially decreased female adult period, oviposition days, total fecundity, egg hatchability and female adult survival rate, and prolonged pre‐adult period and total pre‐oviposition period. CONCLUSION: Sulfoxaflor resistance in N. lugens was inherited as autosomal, incompletely recessive and multigene. The development of resistance may have a significant fitness cost for the resistant population. Current research provides valuable information for researchers to establish management strategies to delay the development of sulfoxaflor resistance and control N. lugens sustainably in the field. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The brown planthopper, Nilaparvata lugens , is one of the most economically important rice crop pests in Asia, and has developed resistance to various insecticides from most chemical groups including neonicotinoid insecticides. At present, nitenpyram is the primary insecticide for N. lugens control in paddy fields. Thus, the susceptibility of N. lugens field populations to nitenpyram is of concern because of its extensive application. In the present study, the LC 50 values and the activities of the detoxifying enzymes of fifty-eight representative field populations of N. lugens were determined. The results showed that LC 50 values of field populations of N. lugens varied from 0.45 to 6.44 mg a. i./L, revealing that N. lugens has developed a moderate level of resistance (resistance ratio, RR = 2.4–33.9-fold) to nitenpyram. The activities of the detoxification enzymes including cytochrome P450 monooxygenase (r = 0.394, P = 0.002) and esterase (r = 0.274, P = 0.037), showed significant correlations with the log LC 50 values for the field populations of N. lugens . Moreover, piperonyl butoxide (PBO) showed obvious synergism (synergism ratio, SR = 1.6–2.1-fold) in the collected field populations. Obvious regional variation in nitenpyram susceptibility was detected among the field populations of N. lugens , suggesting that nitenpyram resistance has occurred in field populations of N. lugens in China, and the detoxification enzyme cytochrome P450 monooxygenase is more likely to a contributing factor to nitenpyram resistance. [ABSTRACT FROM AUTHOR]

Understanding the genetic basis of adaptive evolution following habitat expansion can have important implications for pest management. The pink rice borer (PRB), Sesamia inferens (Walker), is a destructive pest of rice that was historically restricted to regions south of 34° N latitude in China. However, with changes in global climate and farming practices, the distribution of this moth has progressively expanded, encompassing most regions in North China. Here, 3 highly differentiated subpopulations were discovered using high‐quality single‐nucleotide polymorphism and structural variant datasets across China, corresponding to northern, southern China regions, and the Yunnan‐Guizhou Plateau, with significant patterns of isolation by geographic and environmental distances. Our estimates of evolutionary history indicate asymmetric migration with varying population sizes across the 3 subpopulations. Selective sweep analyses estimated strong selection at insect cuticle glycine‐rich cuticular protein genes which are associated with enhanced desiccation adaptability in the northern group, and at the histone‐lysine‐N‐methyltransferase gene associated with range expansion and local adaptation in the Shandong population. Our findings have significant implications for the development of effective strategies to control this pest. [ABSTRACT FROM AUTHOR]