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Identification of mutations in the para sodium channel of Bemisia tabaci from Crete, associated with resistance to pyrethroids |
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| Authors: | Emmanouil Roditakis John Vontas |
| Institution: | a Laboratory of Entomology and Agricultural Zoology, Plant Protection Institute of Heraklion, National Agricultural Research Foundation, Heraklion (N.AG.RE.F.), 71003 Heraklio, Greece b Laboratory of Plant Biotechnology, Institute of Horticulture and Floriculture, National Agricultural Research Foundation, Heraklion (N.AG.RE.F.), 71003 Heraklio, Greece c Laboratory of Pesticide Science, Agricultural University of Athens, Iera Odos 75, Athens 11855, Greece |
| Abstract: | We investigated the mechanisms of resistance to α-cypermethrin in a Q biotype, highly resistant Bemisia tabaci strain (GRMAL-RP) isolated from Crete. Cytochrome P450-dependent monoxygenase activity with the substrate ethoxycoumarin, and carboxylesterase activity with the substrates α-naphthyl-acetate, β-naphthyl-acetate, and para-nitrophenol acetate were substantially elevated in the GRMAL-RP, compared to the susceptible SUD-S strain, while glutathione-S-transferase activity with the substrate 1-chloro-2,4-dinitrobenzene was not different. The metabolic inhibitors piperonyl butoxide and S,S,S-tributyl phosphorotrithioate synergised cypermethrin toxicity in the GRMAL-RP strain, however, mortality was still lower than that of the susceptible strain, indicating the presence of an additional resistance mechanism. Analysis of the sequence of the IIS4-IIS6 region of the para sodium channel gene of the GRMAL-RP strain revealed two amino acid replacements compared to that of the SUD-S susceptible strain. One is the leucine to isoleucine substitution at position 925 (L925I) previously implicated in B. tabaci pyrethroid resistance and the other is a novel kdr resistant mutation for B. tabaci, a threonine to valine substitution at position 929 (T929V). Genotype analysis showed that the L925I and T929V were present in all GRMAL-RP males tested, at an approximately 1:1 frequency, but never in combination in the same haplotype. |
| Keywords: | Pyrethroids Cytochrome P450s Carboxylesterases kdr mutations Genotype Bemisia |
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