• Agriculture and Agri-Food Canada
• Herbicide Resistance

Objective

To develop a rapid, soilless assay for wild oat resistance to pinoxaden and for wild oat and green foxtail resistance to clethodim (ACC-inhibiting herbicides). To evaluate rapid soil assays for testing grass and broadleaf weed resistance to ALS-inhibiting (Group 2) herbicides.

Outcome

Shoot length inhibition and presence of seedlings with shoot tips exhibiting chlorophyll (with or without emerged first leaf) at 1 µM clethodim and 16 µM pinoxaden reliably identified HR and susceptible (HS) wild oat and green foxtail seedlings in an agar dish bioassay. The developed soil pouch bioassay enabled HR biotypes to be distinguished from HS biotypes, and was successfully applied for determination of percentage of HR plants in wild mustard populations. Root length bioassay for wild oat did not allow differentiation of HR from HS biotypes, as all of the examined biotypes were found to be tolerant to flucarbazone, pyroxsulam and metsulfuron, but sensitive to imazamox/imazethapyr. Preliminary studies with cleavers showed that root length inhibition of an HS biotype increased significantly whereas it remained unchanged for an HR biotype in response to addition of all four ALS-inhibiting herbicides to the model soil.

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