Sweet potato whitefly (Bemisia tabaci) are classified in the order Hemiptera, family Aleyrodidae. B. tabaci is a sucking pest which causes damage to host plants by feeding and transmission of numerous plant viruses. The Middle East–Asia Minor 1 (MEAM1) and Mediterranean (MED) complexes (previously known as B biotype and Q biotype) are considered the most invasive species with a broad host range of plants. Ketoenols, tetronic and tetramic acid derivates, are used for sucking pest control. They are classified as group 23 of the IRAC MoA classification. They are act as inhibitors of acetyl-CoA carboxylase (ACC), a key enzyme for lipid biosynthesis across taxa. The mechanisms of resistance in different arthropod species to ketoenols have been linked to mutations in the ACC CT domain and enhanced detoxification by overexpression of cytochrome P450 monooxygenase,glutathione S-transferase and uridine diphosphate glycosyltransferase genes. The aim of this study was to eva‎luate the resistance in several B. tabaci populations to ketoenols. For this purpose, five B. tabaci populations populations were collected from different regions of Isfahan, Yazd, Bandarabas province, and the sensitivity of the populations to spirotetramat was determined by toxicity bioassays using a leaf dip method. The LC50 values of populations were estimated between 14.12 (Bandarabas) and 785.56 (Dehaghan) mg active ingredient (a.i.) L−1. The population of Dehaghan had a resistance ratio of 55-fold. To elucidate the resistance mechanisms, the effects of pretreatment with three synergists, pipronil butoxide (PBO), triphenilphosphat (TPP) and di ethyl maleat (DEM), were investigated. In the susceptible and resistant populations. To investigate the role of detoxification enzymes, also, the activity of cytochrome P450 monooxygenases, esterases and glutathione S-transferases (GST) were determined. The results showed a higher P450 activity and esterases in the resistant populations respectively. Resistance to spirotetramat was also detected by using sequencing techniques. By partial sequencing of the acetyl-CoA carboxylase and based on the amino acid sequences and the resulting chromatogram, the A2083V substitution, substitution of the amino acid valin instead of alanin (GTC/GCC), was observed in the 2083 part of CT domain of the acetyl-CoA carboxylase in two resistance population (Dehaghan and Sin). The cross-resistance levels in these populations were also assessed against spiropidion and spiromesife. Spirotetramat resistant population of Dehaghan exhibited a high cross resistance to spiromesifen and low level cross resistance to spiropidion. Distinct cross resistance levels have been found among the ketoenol compounds.

جهانگير خواجه علي , نفيسه پورجواد

مجيد طالبي

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