Survey of target site mutations linked with insecticide resistance in Italian populations of Aphis gossypii.

Background: Aphis gossypii is a worldwide agricultural pest that causes high levels of economic losses by feeding and transmitting virus diseases. It is usually controlled by chemical insecticides, but this could lead to the selection of resistant populations. Several single nucleotide polymorphisms (SNPs) have been identified associated with insecticide resistance.

Transposon-mediated insertional mutagenesis unmasks recessive insecticide resistance in the aphid .

The evolution of resistance to insecticides threatens the sustainable control of many of the world's most damaging insect crop pests and disease vectors. To effectively combat resistance, it is important to understand its underlying genetic architecture, including the type and number of genetic variants affecting resistance and their interactions with each other and the environment. While significant progress has been made in characterizing the individual genes or mutations leading to resistance, our understanding of how genetic variants interact to influence its phenotypic expression remains poor.

Slug Monitoring and Impacts on the Ground Beetle Community in the Frame of Sustainable Pest Control in Conventional and Conservation Agroecosystems.

In conservation agriculture, slugs are considered significant pests and their monitoring is a key option in the integrated pest management framework. Together with molluscicide applications, predators such as ground beetles can offer a tool for slug control in the field. Through the evaluation of slug and ground beetle monitoring strategies, this work compared their presence in conventional and conservation agricultural plots.

Analysis of the extent of synteny and conservation in the gene order in aphids: A first glimpse from the Aphis glycines genome.

In the last decade several insect genomes have been sequenced, but for most the chromosomal mapping of the identified scaffolds/annotated genes is not available. The lack of this information makes it difficult to analyse various genetic aspects, including the presence of genome rearrangements and the extent of synteny within and across species. We mapped five multigenic DNA families (major and minor rDNAs, histone gene cluster, esterases and carotenoid desaturases) and seven scaffolds corresponding to 9 Mb of the soybean aphid, Aphis glycines, genome and identified loci spanning the four soybean aphid chromosomes.

Biochemical evaluation of interactions between synergistic molecules and phase I enzymes involved in insecticide resistance in B- and Q-type Bemisia tabaci (Hemiptera: Aleyrodidae).

Background: Metabolic resistance is an important consideration in the whitefly Bemisia tabaci, where an esterase-based mechanism has been attributed to pyrethroid resistance and over-expression of the cytochrome P450, CYP6CM1, has been correlated to resistance to imidacloprid and other neonicotinoids.

Results: In vitro interactions between putative synergists and CYP6CM1, B and Q-type esterases were investigated, and structure-activity relationship analyses allowed the identification of chemical structures capable of acting as inhibitors of esterase and oxidase activities. Specifically, methylenedioxyphenyl (MDP) moieties with a polyether chain were preferable for optimum inhibition of B-type esterase, whilst corresponding dihydrobenzofuran structures were potent for the Q-esterase variation.

Use of the synergist piperonyl butoxide can slow the development of alpha-cypermethrin resistance in the whitefly Bemisia tabaci.

The development of insecticide resistance in insect pests of crops is a growing threat to sustainable food production, and strategies that slow the development of resistance are therefore urgently required. The insecticide synergist piperonyl butoxide (PBO) inhibits certain insect detoxification systems and so may delay the evolution of metabolic resistance. In the current study we characterized resistance development in the silverleaf whitefly, Bemisia tabaci, after selection with either a neonicotinoid (thiacloprid) or pyrethroid (alpha-cypermethrin) insecticide alone or in combination with PBO.

Qualitative Sybr Green real-time detection of single nucleotide polymorphisms responsible for target-site resistance in insect pests: the example of Myzus persicae and Musca domestica.

Chemical insecticides have been widely used to control insect pests, leading to the selection of resistant populations. To date, several single nucleotide polymorphisms (SNPs) have already been associated with insecticide resistance, causing reduced sensitivity to many classes of products. Monitoring and detection of target-site resistance is currently one of the most important factors for insect pest management strategies.

The interactions of piperonyl butoxide and analogues with the metabolic enzymes FE4 and CYP6CY3 of the green peach aphid Myzus persicae (Hemiptera: Aphididae).

Background: Piperonyl butoxide (PBO) is a well-known insecticide synergist capable of interacting with phase 1 metabolic enzymes, specifically esterases and cytochrome P450s. In this study, structure-activity relationship analyses were used to characterise the interaction of around 30 analogues of PBO with the esterase FE4 and the P450 CYP6CY3 from insecticide-resistant Myzus persicae (Sulzer), in order to predict the synthesis of more potent inhibitors.

Results: Enzyme inhibition studies were performed against esterase and oxidase activities and, together with in silico modelling, key activity determinants of the analogues were identified and optimised.

Presence and impact of allelic variations of two alternative s-kdr mutations, M918T and M918L, in the voltage-gated sodium channel of the green peach aphid Myzus persicae.

Background: Pyrethroids have been widely employed in order to control several agricultural pests, including Myzus persicae. Target-site resistance is the main mechanism that confers insensitivity to this class of compounds, and the most common amino acid substitutions are kdr (L1014F) and s-kdr (M918T), but recently another mutation in the s-kdr locus (M918L) has been described in French and Korean populations of M. persicae.

Detecting the presence of target-site resistance to neonicotinoids and pyrethroids in Italian populations of Myzus persicae.

Background: Myzus persicae is a key pest of peach, which in commercial orchards is mainly controlled by chemical treatments. Neonicotinoids represent the main control strategy, but resistance monitoring programmes in Southern Europe have shown the widespread presence of populations highly resistant to this insecticide class in peach orchards. Moreover, in Italy reports of neonicotinoid application failures are increasing.

A1-3 chromosomal translocations in Italian populations of the peach potato aphid Myzus persicae (Sulzer) not linked to esterase-based insecticide resistance.

Esterase-based resistance in the peach-potato aphid, Myzus persicae (Sulzer), is generally due to one of two alternative amplified carboxylesterase genes, E4 or FE4 (fast E4). The E4 amplified form is distributed worldwide and it is correlated with a particular translocation between autosomes 1 and 3, whereas the FE4 form, which has hitherto not been found to be associated with chromosomal rearrangements, is typical of the Mediterranean regions. In this study, we present for the first time cytogenetic and molecular data on some M.

Karyotype variations in Italian populations of the peach-potato aphid Myzus persicae (Hemiptera: Aphididae).

In this study, we present cytogenetic data regarding 66 Myzus persicae strains collected in different regions of Italy. Together with the most common 2n = 12 karyotype, the results showed different chromosomal rearrangements: 2n = 12 with A1-3 reciprocal translocation, 2n = 13 with A1-3 reciprocal translocation and A3 fission, 2n = 13 with A3 fission, 2n = 13 with A4 fission, 2n = 14 with X and A3 fissions. A 2n = 12-13 chromosomal mosaicism has also been observed.

Recombinant production of eight human cytosolic aminotransferases and assessment of their potential involvement in glyoxylate metabolism.

PH1 (primary hyperoxaluria type 1) is a severe inborn disorder of glyoxylate metabolism caused by a functional deficiency of the peroxisomal enzyme AGXT (alanine-glyoxylate aminotransferase), which converts glyoxylate into glycine using L-alanine as the amino-group donor. Even though pre-genomic studies indicate that other human transaminases can convert glyoxylate into glycine, in PH1 patients these enzymes are apparently unable to compensate for the lack of AGXT, perhaps due to their limited levels of expression, their localization in an inappropriate cell compartment or the scarcity of the required amino-group donor. In the present paper, we describe the cloning of eight human cytosolic aminotransferases, their recombinant expression as His6-tagged proteins and a comparative study on their ability to transaminate glyoxylate, using any standard amino acid as an amino-group donor.