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Multiple ATP-binding cassette transporters genes are involved in thiamethoxam resistance in Aphis gossypii glover

ATP-binding cassette (ABC) transporters represent the largest known group of efflux pumps, utilizing ATP to translocate a broad spectrum of substrates across lipid membranes, which play an important role in phase III of the detoxification process. The presence of ABC transporters and their potential association with insecticide resistance have not been investigated in Aphis gossypii, one of the most economically important agricultural pests worldwide. In this study, the ABC transporter inhibitor-verapamil significantly increased thiamethoxam toxicity against resistant cotton aphids, suggesting that ABCs are involved in thiamethoxam resistance. ABC transporter genes were identified using the A. gossypii genome database and transcriptome data. A total of 69 ABC transporters were identified and grouped into seven subfamilies (A-G), including 4 ABCAs, 5 ABCBs, 25 ABCCs, 2 ABCDs, 1 ABCE, 4 ABCFs and 30 ABCGs. Of these ABC transporters, 53 were predicted to be functional, 19 were full transporters, 30 were half-transporters and 4 had two NBDs. Subfamilies C and G accounted for 77% (32 and 45%, respectively) of the genes. The transcripts of 20 of 26 ABCs based on the transcriptome were upregulated, and ABCA1, ABCA2, ABCB1, ABCB4, ABCB8, ABCD1, ABCD2, ABCE1, ABCF1, ABCF3, ABCG7, ABCG15, ABCG17, ABCG24, ABCG27, ABCG30, MRP1, MRP7, MRP14 and MRP21 transcripts were significantly increased in the thiamethoxan resistant strain compared to the susceptible strain with qRT-PCR. The suppression of overexpressed ABCs (ABCA2, ABCD1, ABCD2, ABCE1 and ABCG15) significantly increased the thiamethoxam sensitivity of resistant aphids. These results suggest that ABC transporters might be involved in thiamethoxam resistance in A. gossypii and will facilitate further work to validate the functional roles of these ABCs in thiamethoxam resistance. These results are useful for understanding the multiple resistance mechanisms of thiamethoxam and the management of insecticide-resistant cotton aphids.

Effect of sublethal doses of some insecticides and their role on detoxication enzymes and protein-content of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

The indiscriminating and intensive use of insecticides to control the cotton leafworm (CLW), Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), usually induces high levels of resistance. The insecticides are the principal method for controlling this pest because of its critical role in reducing insects when the economic threshold (ETL); therefore, the effectiveness of these insecticides should be maintained. So, the target of the present work was directed to focus on studying the change in the activities of some important enzymes as a result of sublethal treatment concentrations (viz. LC25 values) of tested new insecticides (profenofos, cyfluthrin, emamectin benzoate, lufenuron, and spinetoram). The expected results could offer better understanding and more specific information about the resistance development in field populations of CLW because resistance is a significant challenge to pest control workers and these results may contribute to making the right decision at the right time.

Insecticide Resistance and Detoxification Enzymes Activity in Nilaparvata lugens Stål Against Neonicotinoids

The Nilaparvata lugens (Stål) is one of the most destructive pests of rice crops in Asian. To assess the resistance of imidacloprid, thiamethoxam, clothianidin, and nitenpyram, N. lugens exposed to each pesticide up to 15 generations. Results showed that the resistance of N. lugens increased significantly against imidacloprid, thiamethoxam, clothianidin, and nitenpyram (neonicotinoids) under selection pressure. There was a 118.07-fold increase in resistance against imidacloprid, 90.37-fold against thiamethoxam, 217.81-fold against clothianidin, and 34.09-fold against nitenpyram in 15th generation as compared to F0. Based on fold increase, imidacloprid and clothianidin subjected for enzymatic analysis and results showed that enzyme activity involves resistance development against neonicotinoids. Cytochrome P450, esterase, and GST had significantly higher activity as the generation passes under the selection pressure of imidacloprid and clothianidin. There was a significant correlation existed between GST, and esterase activity, when compared to LC50 of imidacloprid. GST, esterase and P450 showed a significant correlation with LC50 of clothianidin. The results showed that detoxification enzymes play an important role in insecticide detoxification. When the mixture of imidacloprid and clothianidin tested results showed that the mortality exerted was similar to control when imidacloprid and clothianidin resistant populations were exposed.

Characteristic of resistance to dichlorvos and biochemical mechanisms in the greenhouse strains of Frankliniella occidentalis (Thysanoptera: Thripidae)

The western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is an invasive pest in greenhouse with high potential to cause damage to crops. There are a limited number of effective insecticides to manage this pest and several cases of chemical control failures have been reported in Iran which can be due to resistance to insecticides. To evaluate the status of insecticide resistance and possible resistance mechanisms, eight Iranian strains of F. occidentalis, collected from Tehran, Markazi, Alborz, Qazvin, Isfahan, Yazd (M and B) and Kerman provinces, were assayed against dichlorvos as a recommended insecticide for chemical control of thrips. Compared with the susceptible strain (Isfahan), two strains collected from Yazd had the lowest susceptibility to dichlorvos (Resistance Factor = 2.14 and 2.04 fold). Bioassay by synergists and enzyme assays demonstrated interfering of carboxyl esterase and glutathion S- transferase in Yazd M strain. The esterase inhibitor, triphenyl phosphite (TPP), and Glutathione S-transferase inhibitor, diethyl maleate (DEM), synergized the toxicity of dichlorvos in the Yazd M strain, (Synergistic Ratio = 5.28 and 1.79 fold, respectively). Also, carboxylesterase (for α- naphtyl acetate and ß- naphtyl acetate) and glutathion S- transferases activities in this population were 1.69, 7.31 and 0.97 fold higher than in the Isfahan strain. Furthermore, dichlorvos resistance did not significantly diminish after several months. Based on our results, we suggest that dichlorvos should be removed from the control program of this pest.

Laboratory selection, cross‐resistance, and estimations of realized heritability of indoxacarb resistance in Phenacoccus solenopsis (Homoptera: Pseudococcidae)

Cotton mealybug Phenacoccus solenopsis is a pest of cotton, vegetables, ornamentals, and medicinal plants. In many parts of the world P. solenopsis has been managed by integration of cultural, mechanical, biological and chemical methods, but in Pakistan the use of insecticide sprays has resulted in the development of resistance to some insecticides. In this study indoxacarb resistance was investigated by selecting a P. solenopsis population under laboratory conditions for many generations. The cross‐resistance potential of indoxacarb resistance with other chemistries and the realized heritability of indoxacarb resistance were also evaluated. A field population of P. solenopsis selected with indoxacarb for 27 generations had a 25 623.17‐fold resistance level. The highly indoxacarb resistant population showed very high cross‐resistance to spinosad and very low cross‐resistance to bifenthrin and chlorpyrifos. The mean estimated h2 of resistance to indoxacarb was only 0.04. The number of generations predicted for the development of ten‐fold indoxacarb resistance at a constant h2 = 0.04 against selection intensities of 10% and 95% were 346 and 36 (slope = 3.18), 237 and 25 (slope = 2.18) and 128 and 13 (slope = 1.18). However, at a constant slope = 1.18 and selection intensities of 10% and 95%, the same increase in indoxacarb resistance occurred after 128 and 13 (h2 = 0.04), 103 and 11 (h2 = 0.05), and 86 and 9 (h2 = 0.06) generations. This study revealed that P. solenopsis has a very high resistance to indoxacarb as a result of laboratory selection. Thus, resistance to this insecticide in the field may also occur. Indoxacarb resistance can be minimized by rotating it with bifenthrin and/or chlorpyrifos due to its very low cross‐resistance to these insecticides and by avoiding its rotation with Spinosad, which has very high cross‐resistance.

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Desenvolvido por Allge Pesquisa e Desenvolvimento