Specificity and Sensitivity of a Rapid LAMP Assay for Early Detection of Emerald Ash Borer (Agrilus planipennis) in Europe

Buprestids are an emerging threat to broadleaf forests across the world. Species such as emerald ash borer (EAB, Agrilus planipennis) seriously threaten ash (Fraxinus spp.) in North America and Europe. As it continues spreading west from European Russia, native European ash populations will suffer dramatic losses. Due to their cryptic lifestyle of the egg and larval stages on developing bark and vascular tissue, buprestids and other wood borers can be difficult to detect. Early detection tools are vital to implement fast eradication measures, and prevent the establishment of invasive species populations. Detection methods using polymerase chain reaction (PCR) assays to target specific taxa can be extremely timely to obtain results especially since samples need to be transported to the laboratory first. However, loop-mediated isothermal amplification (LAMP) eDNA assays are highly specific and sensitive providing results within 30 min after sample extraction. In this study, we investigated the specificity and sensitivity of an EAB LAMP assay as an early detection tool in Europe. The assay was specific to EAB when tested against 12 European Agrilus spp., five buprestids, two Scolytinae, and five cerambycids (n = 24). The LAMP assay sensitivity amplified DNA from a concentration as low as 0.02 pg/mu L. These results demonstrate that the LAMP assay is a highly specific, sensitive tool that can be used to detect and monitor EAB in European forests and urban settings

Phylogeography of a host-specific insect: genetic structure of Ips typographus in Europe does not reflect past fragmentation of its host

The phylogeography of the bark beetle Ips typographus was assessed using five microsatellite markers. Twenty-eight populations were sampled throughout Europe on the host tree Picea abies. I. typographus showed very low levels of genetic diversity, and the study revealed a lack of genetic structure across Europe. No significant barrier to gene flow was found, even though P. abies has a fragmented distribution. A weak but significant effect of isolation by distance was found. These results suggest a high dispersal capacity of I. typographus, which leads to low genetic differentiation between populations. Its high dispersal capacity is likely to have prevented I. typographus from developing important local adaptations to its host, which would have influenced its genetic structure. The nuclear data was compared to previously published mitochondrial data that showed strong differentiation between Central-Northern European populations and Russian-Baltic populations, and a founder effect in Scandinavia, probably reflecting the postglacial history of I. typographus. Discrepancies between nuclear and mitochondrial markers could be due to the maternal inheritance of mitochondrial DNA, and to sex-biased dispersal in I. typographus. The overall low genetic diversity observed on both markers on a large geographical scale is discusse

From Plant Exploitation to Mutualism

International audiencePhytophagous insects have developed mechanisms of various complexity levels to utilize plants in spite of the barriers that plants have built to resist aggressions. Plant exploitation, the simplest level, is the use of plant defence chemicals for the benefit of insects. It is illustrated by the use of plant toxins for defence against predators. The energetic cost of that defence strategy is discussed according to the toxicity of the chemicals and the necessity of protecting the herbivore, and the modes of action on predators are presented. Furthermore, manipulation of the plant can reorient the plant metabolism to satisfy insect needs. Drastic remodelling of the host plant can occur, from ultrastructure to anatomy levels, with alteration of both its nutritional quality and secondary metabolism. The mechanisms involved are being investigated. Outcomes concern optimization of the nutritional value of the host plant and protection from adverse abiotic and biotic (natural enemies, competition) conditions. Cooperation with conspecifics or microorganisms often interferes. At the highest level of complexity, mutualism is the result of a compromise between insect and plant where each partner benefits from the association. Pollination is a typical example. Pollinators vary from generalists to specialists and belong to a community of insect linked to a community of plants. In the fig–fig wasp mutualism, the various mechanisms involved in situations of monoecy and dioecy are discussed, as well as the existence of coadaptations and cospeciations. The chapter ends with a presentation of research perspectives for improving crop productivity

Effects of fertilisation on amino acid mobilisation by a plant-manipulating insect

National audience1. Phytophagous insects frequently manipulate their host-plant to improve their immediate environment. This generally implies substantial modifications of host metabolism, and sometimes an alteration of nitrogen allocation within the host-plant. However, the outcome of plant manipulation on amino acid or protein content can be modulated by environmental factors and host-plant traits. 2. It was investigated whether the pseudogall induced by the aphid Phloeomyzus passerinii (Signoret) (Aphididae: Phloeomyzinae) in the bark of its host-plant affects the amino acid content in bark tissues, and whether the strength of the modification is modulated by the fertilisation regime and/or the resistance level of the host-plant. The development of aphid colonies on a resistant and a susceptible poplar genotype, under three fertilisation regimes, was studied. After the development of colonies, the free and protein-bound amino acid content of the infested bark were quantified.3. Fertilisation enhanced poplar growth and increased the free amino acid content of bark tissues. Infestation also triggered accumulations of both free and protein-bound amino acids in the feeding sites, but in the susceptible genotype only. The increase in amino acid content was more pronounced when fertilisation was low, and fertilisation did not enhance aphid development.4. In conclusion, infestation by P. passerinii triggers an accumulation of amino acids, but the effect is influenced by both the fertilisation regime and the resistance level of the host-plant. This suggests that P. passerinii could affect the allocation of nutrients within trees during outbreaks