Implications of a phylogeographic approach for the selection of Ceutorhynchus assimilis as a potential biological control agent for Lepidium draba

Authors: LESIEUR, VINCENT - Montpellier Supagro – International Center For High Education In Agricultural Sciences; MARTIN, JEAN-FRANCOIS - Montpellier Supagro – International Center For High Education In Agricultural Sciences; HINZ, HARIET - Commonwealth Agricultural Bureau International (CABI) - Switzerland; FUMANAL, BORIS - Clermont Universite, Universite D'Auvergne, Unite De Nutrition Humaine; SOBHIAN, ROUHOLLAH - Retired Non ARS Employee; BON, MARIE-CLAUDE - European Biological Control Laboratory (EBCL)

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2018
Publication Date: 5/8/2018
Citation: Lesieur, V., Martin, J., Hinz, H., Fumanal, B., Sobhian, R., Bon, M. 2018. Implications of a phylogeographic approach for the selection of Ceutorhynchus assimilis as a potential biological control agent for Lepidium draba. Biological Control. 123(43-52). /doi.org/10.1016/j.biocontrol.2018.05.001.
DOI: https://doi.org/10.1016/j.biocontrol.2018.05.001

Interpretive Summary: Hoary cress (Lepidium draba) is a perennial mustard indigenous to Eurasia that was introduced accidentally to North America in the mid- to late 1800s. In North America, it is recorded from the east to the west coast, but it is considered particularly problematic throughout the west, where it is declared as noxious in 16 states and three Canadian provinces. Hoary cress is a very difficult weed to control, and has been targeted for classical biological control. So far, only one or two herbivores appear to be specific enough to be considered as biological control agents. Preliminary research identified some populations of the root-galling weevil Ceutorhynchus assimilis which are highly specific to hoary cress. However, the host-specific weevils look the same as those from populations which are not specific to hoary cress and also attack some crop species. We developed a DNA-based method to distinguish host-specific weevils from the generalist weevils. Analysis of weevil populations from various sites in Europe indicate that host-specific populations occur from northern Spain to northern Italy. This weevil biotype will be evaluated to determine if it is safe to use for biocontrol of hoary cress.

Technical Abstract: The root-galling weevil, Ceutorhynchus assimilis Paykull (Coleoptera: Curculionidae), has been selected as a candidate to control hoary cress, Lepidium draba L. (Brassicaceae), a highly invasive weed in western North America. This weevil originally had been described as being oligophagous, attacking various mustard species, including some crops. However, preliminary data indicated that there is a host race of C. assimilis that is specific to L. draba. We therefore explored the phylogeographic structure of the weevil's populations by sampling five different host plant species including L. draba in 12 European countries. To explore the genetic diversity of C. assimilis, we sequenced the 3' end of the mitochondrial COI region. Analysis revealed three distinct evolutionary lineages, one of which, the Lepidium host race, was only found on L. draba and appears to occur in a restricted area, ranging between northern Spain and northern Italy. The results allow us to target sites for collection of the Lepidium host race and justify the prioritization of this host race as a candidate for the biological control of L. draba.