So, what's the problem
The western corn rootworm, Diabrotica virgifera virgifera, is one of the most destructive pests of maize in North America and Europe. This leaf beetle has one generation a year with eggs that overwinter in the soil. These hatch after the maize has germinated in spring, and the larvae feed on maize roots, often causing entire plants to bend (lodge) and topple. Adult beetles can reduce yields through intensive silk feeding, which interferes with maize pollination.
The pest has been managed through crop rotation, granular soil insecticides, insecticide seed coatings, and/ or by planting transgenic maize which produces Bacillus thuringiensis toxins which act as insecticides. But the western corn rootworm has been shown to be able to develop resistance against nearly all control measures. Moreover, some soil insecticides are being phased out owing to their high toxicity, and others, such as the neonicotinoids, appear to be problematic to bees. Novel control measures are needed, preferably with multiple-ways-of acting on the insect which are environmentally friendly.
What is this project doing?
The project, officially called Utilisation de la DiversitE microbienne pour idenTifier des activités insEcTICides contre la larve de la chrysomèle du maïs (Diabrotica virgifera virgifera) (DIETETIC), is supported by the French Groupement National Interproffessionel des Semences et plants (GNIS), a service provider for farmers. The three-year project is being implemented by a consortium of five French partners (three science-based SMEs, two research institutions), as well as CABI.
We aim to identify new technologies to protect maize from corn rootworm larvae. We are using a bioinformatics-based candidate gene search approach followed by high-throughput screening to investigate a diversity of microbes (mainly bacteria), and identify those producing proteins with insecticidal effects on rootworms. The long-term goal is to develop biopesticidal or biotechnological control options against this major invader.
- Isolate and identify novel microbial strains from field surveys that may protect maize roots from corn rootworm larvae
- Perform bacterial strain sequencing to select candidate genes with insecticidal potential
- Screen bacterial strains and their toxic proteins on rootworms to assess biocontrol/ biotechnological potential including the evaluation of non-target effects
Proof of concept experiments from existing collections of microbials and a literature search using a data-based bioinformatic approach has identified the project’s first bacterial species/ strains likely to possess insect toxin-related genes – some already known, some novel. We have also carried out a survey of rootworm-infested fields in central Europe to obtain samples of microbial species/ strains in the maize rhizosphere – the roots and surrounding soil. So far, genomes from the microbial collections and the rhizosphere survey are being sequenced by project partners. Promising proteins are screened in vitro in part by CABI harnessing its expertise developed in Hungary with this pest.