Genetic variability in Tetranychus urticae (Acari : Tetranychidae) from Greece : insecticide resistance and isozymes

Etude de la résistance au méthyl-parathion, au méthidathion et au méthomyl chez une population de #Tetranychus urticae$ Koch originaire de Grèce. A la CL 50 le taux de résistance est hautement variable avec le méthidathion (5 à 63 fois) et avec le méthomyl (6 à 34 fois). Les courbes de mortalité avec le méthyl-parathion présentent un plateau net à une mortalité d'environ 20% et le taux de résistance est d'environ 50 fois à CL 50, dans tous les échantillons. Par utilisation de la focalisation isoélectrique sur des membranes d'acétate de cellulose, les études électrophorétiques de 5 loci codant les estérases (Est-1 et Est-2), l'isomérase gluco-phosphate (Gpi), l'enzyme malique (Me) et la phosphoglucomutase (Pgm), indiquent les différences génétiques importantes parmi les échantillons. (Résumé d'auteur

Ryanodine receptor point mutations confer diamide insecticide resistance in tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae).

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Insect ryanodine receptors (RyR) are the molecular target-site for the recently introduced diamide insecticides. Diamides are particularly active on Lepidoptera pests, including tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). High levels of diamide resistance were recently described in some European populations of T. absoluta, however, the mechanisms of resistance remained unknown. In this study the molecular basis of diamide resistance was investigated in a diamide resistant strain from Italy (IT-GELA-SD4), and additional resistant field populations collected in Greece, Spain and Brazil. The genetics of resistance was investigated by reciprocally crossing strain IT-GELA-SD4 with a susceptible strain and revealed an autosomal incompletely recessive mode of inheritance. To investigate the possible role of target-site mutations as known from diamondback moth (Plutella xylostella), we sequenced respective domains of the RyR gene of T. absoluta. Genotyping of individuals of IT-GELA-SD4 and field-collected strains showing different levels of diamide resistance revealed the presence of G4903E and I4746M RyR target-site mutations. These amino acid substitutions correspond to those recently described for diamide resistant diamondback moth, i.e. G4946E and I4790M. We also detected two novel mutations, G4903V and I4746T, in some of the resistant T. absoluta strains. Radioligand binding studies with thoracic membrane preparations of the IT-GELA-SD4 strain provided functional evidence that these mutations alter the affinity of the RyR to diamides. In combination with previous work on P. xylostella our study highlights the importance of position G4903 (G4946 in P. xylostella) of the insect RyR in defining sensitivity to diamides. The discovery of diamide resistance mutations in T. absoluta populations of diverse geographic origin has serious implications for the efficacy of diamides under applied conditions. The implementation of appropriate resistance management strategies is strongly advised to delay the further spread of resistance.The work of Hellenic Agricultural Organisation - 'Demeter' was partially supported by an ARIMnet2 StomP grand to A.T and E.R. This work was also partially funded from a fellowship granted to H.A.A.S. (CNPq - PQ - Proc 308461/2013-4). The Universidad Politécnica de Cartagena group would like to thank for partial financial support the Ministerio de Economía y Competitividad of Spain and FEDER (AGL2011-25164). Lidia García-Vidal holds a grant from the MECD (FPU13/01528). The Tuta absoluta strain from Gela, Sicily was collected under the frame a resistance monitoring program established among the Hellenic Agricultural Organisation - 'Demeter' and DuPont De Nemurs (data published in 2015). Finally, the Hellenic Agricultural Organisation - 'Demeter' would like to thank Fytochem S.A., Neo Mirtos, Ierapetra for supplies of plant material

Identification and functional characterization of a novel acetyl-CoA carboxylase mutation associated with ketoenol resistance in Bemisia tabaci

This is the final version. Available from Elsevier / Academic Press via the DOI in this record. Insecticides of the tetronic/tetramic acid family (cyclic ketoenols) are widely used to control sucking pests such as whiteflies, aphids and mites. They act as inhibitors of acetyl-CoA carboxylase (ACC), a key enzyme for lipid biosynthesis across taxa. While it is well documented that plant ACCs targeted by herbicides have developed resistance associated with mutations at the carboxyltransferase (CT) domain, resistance to ketoenols in invertebrate pests has been previously associated either with metabolic resistance or with non-validated candidate mutations in different ACC domains. A recent study revealed high levels of spiromesifen and spirotetramat resistance in Spanish field populations of the whitefly Bemisia tabaci that was not thought to be associated with metabolic resistance. We confirm the presence of high resistance levels (up to >640-fold) against ketoenol insecticides in both Spanish and Australian B. tabaci strains of the MED and MEAM1 species, respectively. RNAseq analysis revealed the presence of an ACC variant bearing a mutation that results in an amino acid substitution, A2083V, in a highly conserved region of the CT domain. F1 progeny resulting from reciprocal crosses between susceptible and resistant lines are almost fully resistant, suggesting an autosomal dominant mode of inheritance. In order to functionally investigate the contribution of this mutation and other candidate mutations previously reported in resistance phenotypes, we used CRISPR/Cas9 to generate genome modified Drosophila lines. Toxicity bioassays using multiple transgenic fly lines confirmed that A2083V causes high levels of resistance to commercial ketoenols. We therefore developed a pyrosequencing-based diagnostic assay to map the spread of the resistance alleles in field-collected samples from Spain. Our screening confirmed the presence of target-site resistance in numerous field-populations collected in Sevilla, Murcia and Almeria. This emphasizes the importance of implementing appropriate resistance management strategies to prevent or slow the spread of resistance through global whitefly populations.European Union Horizon 2020Australian cotton research and development corporatio

Recent emergence and worldwide spread of the red tomato spider mite, [i]Tetranychus evansi[/i]: genetic variation and multiple cryptic invasions

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699Plant biosecurity is increasingly challenged by emerging crop pests. The spider mite Tetranychus evansi has recently emerged as a new threat to solanaceous crops in Africa and the Mediterranean basin, with invasions characterized by a high reproductive output and an ability to withstand a wide range of temperatures. Mitochondrial (868 bp of COI) and nuclear (1,137 bp of ITS) loci were analyzed in T. evansi samples spanning the current geographical distribution to study the earliest stages of the invasive process. The two sets of markers separate the samples into two main clades that are only present together in South America and Southern Europe. The highest COI diversity was found in South America, consistent with the hypothesis of a South American origin of T. evansi. Among the invaded areas, the Mediterranean region displayed a high level of genetic diversity similar to that present in South America, that is likely the result of multiple colonization events. The invasions of Africa and Asia by T. evansi are characterized by a low genetic variation associated with distinct introductions. Genetic data demonstrate two different patterns of invasions: (1) populations in the Mediterranean basin that are a result of multiple cryptic introductions and (2) emerging invasions of Africa and Asia, each likely the result of propagules from one or limited sources. The recent invasions of T. evansi illustrate not only the importance of human activities in the spread of agricultural pests, but also the limits of international quarantine procedures, particularly for cryptic invasion

Spider mite web mediates anti-predator behaviour

Herbivores suffer significant mortality from predation and are therefore subject to natural selection on traits promoting predator avoidance and resistance. They can employ an array of strategies to reduce predation, for example through changes in behaviour, morphology and life history. So far, the anti-predator response studied most intensively in spider mites has been the avoidance of patches with high predation risk. Less attention has been given to the dense web produced by spider mites, which is a complex structure of silken threads that is thought to hinder predators. Here, we investigate the effects of the web produced by the red spider mite, Tetranychus evansi Baker & Pritchard, on its interactions with the predatory mite, Phytoseiulus longipes Evans. We tested whether female spider mites recognize predator cues and whether these can induce the spider mites to produce denser web. We found that the prey did not produce denser web in response to such cues, but laid more eggs suspended in the web, away from the leaf surface. These suspended eggs suffered less from predation by P. longipes than eggs that were laid on the leaf surface under the web. Thus, by altering their oviposition behaviour in response to predator cues, females of T. evansi protect their offspring

First record of the invasive mite Tetranychus evansi (Acari: Tetranychidae) Baker and Pritchard in Greece

E-mail Addresses: [email protected] audienceThe red spider mite Tetranychus evansi (Acari : Tetranychidae) Baker and Pritchard was recorded for the first time in Greece, in the area of Tympaki (south-central Crete) on Solanum nigrum. T evansi is a pest of crops of the family Solanaceae, which are grown extensively in Crete. The species identification was based on both morphological and molecular data. The second internal transcribed spacer was PCR amplified and sequenced in samples from Crete. Sequences were compared with the sequence of T evansi from Brazil and with the ITS2 sequences (retrieved from GenBank) of the two closely related tetranychid species most commonly found in Greece, Tetranychus turkestani and Tetranychus urticae.Author Keywords: internal transcribed spacer (ITS2); red spider mite; Solanaceae; Solanum nigrum; Tetranychidae; Tetranychus turkestani; Tetranychus urtica