Molecular detection and quantification of slug parasitic nematodes from the soil and their hosts

Authors: JAFFUEL, GEOFFREY - NEUCHATEL UNIVERSITY - SWITZERLAND; PUZA, VLADIMIR - INSTITUTE FOR ENTOMOLOGY - CZECH REPUBLIC; HUG, ANNA-SOFIA - AGROSCOPE; MEULI, RETO GUILIO - AGROSCOPE; NERMUT, JAJIRI - INSTITUTE FOR ENTOMOLOGY - CZECH REPUBLIC; TURLINGS, TED - NEUCHATEL UNIVERSITY - SWITZERLAND; DESURMONT, GAYLORD - EUROPEAN BIOLOGICAL CONTROL LABORATORY (EBCL); CAMPOS-HERRERA, RAQUEL - UNIVERSITY OF LA RIOJA

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2018
Publication Date: 11/28/2018
Citation: Jaffuel, G., Puza, V., Hug, A., Meuli, R., Nermut, J., Turlings, T., Desurmont, G., Campos-Herrera, R. 2018. Molecular detection and quantification of slug parasitic nematodes from the soil and their hosts. Journal of Invertebrate Pathology. 160:18-25. https://doi.org/10.1016/j.jip.2018.11.005.
DOI: https://doi.org/10.1016/j.jip.2018.11.005

Interpretive Summary: Terrestrial mollusks (slugs and snails) are pests of various crops worldwide, and they are notoriously difficult to control using conventional methods (mechanical or chemical control). Several species of nematodes (worm-like creatures that live in the soil) are known to be lethal parasites of snails and slugs, but their diversity and abundance in the soil are not well known. Here, an extensive survey of Swiss soils was conducted to investigate the abundance of several slug-killing nematode species using molecular techniques (DNA analyses). The same technique was used to test a method to detect nematodes inside slugs directly in order to improve the detection of nematode-infected slugs. Results showed that the molecular techniques used were effective to detect nematode DNA in soil samples and in slug tissues. The abundance and diversity of slug-killing nematodes in Swiss soils was overall very low. This study improves our understanding of the prevalence and potential of nematodes as biological control agents of snails and slugs.

Technical Abstract: y difficult to control. Many species of nematodes are able to parasitize land snails and slugs, but few of them are lethal to their host. Species and/or populations of mollusc-parasitic nematodes (MPNs) that are able to kill their hosts are promising for biological control purposes. For instance, the species Phasmarhabditis hermaphrodita can be highly lethal to the slug Deroceras reticulatum. Recently, the discovery of new species of the genus Phasmarhabditis in Europe and the association between Alloionema spp. and slugs are expanding the possibilities of control for this group. However, very little is known about the distribution and ecology of these species. In order to fill gaps in our knowledge of this assemblage of species, we developed new primers and probes for 5 species of the genus Phasmarhabditis and one species of the genus Alloionema and surveyed their presence in soil samples coming from natural and agricultural areas in Switzerland. We also developed a method which allows the detection and quantification P. hermaphrodita associated to their slug host in a laboratory experiment. The new molecular tools were optimized to limit cross-amplification with close-related species and allow quantitative assays. By using these tools, we detected mollusc-parasitic nematodes in 7.5% of sampled sites. We were able to detect the presence of P. hermaphrodita inside slug hosts, with more in the susceptible species of Deroceras sp. as compared to the resistant Arion sp. These primers/probe sets provide a novel and quick tool to identify MPNs from soil samples and infected slugs without the necessity of culturing and retrieving all nematode life stages, bringing new opportunities to unravel the ecology and behavior of the nematode-slug complex.