Entomopathogenic nematodes (EPNs) are involved in biological control operations and their use represents about 20% of the bio-pesticide market. They are mainly effective against Lepidoptera and Coleoptera. Our knowledge of these beneficials for the defence of agricultural production is about 80 years old.

These nematodes carry bacteria in their digestive tract capable of multiplying and killing insects by septicaemia within 24-48 h. Since 1999, the DGIMI unit has housed a collection of living NEPs of the genera Steinernema and Heterorhabditis.

In 2008, 40 strains of EPNs from INRA Guadeloupe (H. Mauléon) were transferred to the DGIMI unit. Since then, this collection has been regularly enriched with new isolates following surveys carried out internally in France or via our network of international nematologist colleagues (Czech Republic, Lebanon, South Africa, USA, Ireland, Italy, Belgium, ......) (see also Axis 1. Taxonomy and valorisation). Each new strain is characterized by a molecular approach at genus and species level. Over the years, the unit has built up a unique collection rich in biological diversity.

Today, the collection contains about 150 isolates with a majority belonging to the genus Steinernema and in which 14 different species are represented among more than 100 species described in the literature. The Asian and South African countries have contributed significantly to the increase in diversity in the genus Steinernema. The genus Heterorhabditis is less represented and we only have 4 species alive out of about 20 described species.

The viability and pathogenicity of the strains are maintained by natural infestation on insects at a regular frequency (3 to 6 months depending on the species or isolates). The quiescent larval stages (IJs for infective juveniles) are collected and stored at 9°C for Steinernema and 15°C for Heterorhabditis in Ringer's liquid.

The diversity of species in the collection is a major asset for research projects. Our missions are to conserve living strains and to valorize their use as bio-pesticides. Gnotoxenic work is carried out in order to study the functionality of the associated symbiont and also of the recently described FAM (frequently associated microbiota) bacteria associated with nematodes (Ogier et al, 2020). 

Since 2016, the collection has been associated with the environment pillar of the Agronomic Resource Centre for Research www.brc4env.fr (Mougin et al, 2018).

Bibliography

Mougin, C., Artige, E., Marchand, F., Mondy, S., Ratié, C., Sellier, N., Castagnone, P., Coeur D'Acier, A., Esmenjaud, D., Faivre-Primot, C., Granjon, L., Hamelet, V., Lange, F., Pages, S., Rimet, F., Ris, N., Salle, G. 2018. BRC4Env, a network of biological resource centres for research in environmental and agricultural sciences. Environ Sci Pollut Res Int, 25, 33849–33857. DOI : 10.1007/s11356-018-1973-7.

Ogier, J.C., Pagès, S., Frayssinet, M., Gaudriault, S. 2020. Entomopathogenic nematode-associated microbiota: from monoxenic paradigm to pathobiome. Microbiome, 8, 25. DOI : 10.1186/s40168-020-00800-5.