Multiple resistance to flumetsulam and MCPA in two clones of Ranunculus acris

• Published in: New Zealand journal of agricultural research Vol. 65; no. 4-5; pp. 415 - 429
• Main Authors: Jackman, Sarah, Bourdôt, Graeme W., Noble, Alasdair, Lamoureaux, Shona L., Ghanizadeh, Hossein
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 03.09.2022; Taylor & Francis Ltd
• Subjects: Acetolactate synthase; Acid resistance; ALS inhibitor resistance; Carboxylic acids; Cloning; Exposure; Genetics; Glyphosate; Herbicide; Herbicide resistance; Herbicides; Inhibitors; pasture weeds; Ranunculus acris; Seedlings
• ISSN: 0028-8233; 1175-8775
• DOI: 10.1080/00288233.2020.1779755

Herbicide dose-responses of seedling progenies of Ranunculus acris populations varying in herbicide exposure history indicate that this weed has evolved multiple resistance to phenoxycarboxylic acid and acetolactate synthase (ALS)-inhibitor herbicides. To test the hypothesis that this 'multiple-resistance' can occur in the same plant, we conducted an experiment where 11 clones of R. acris, varying in parental population exposure to these two mode-of-action herbicides, were treated with full- and half-label doses of MCPA and flumetsulam. Aminopyralid and glyphosate (pyridine carboxylic acid and 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase-inhibitor mode-of-actions respectively), both with label recommendations for R. acris, were included for comparison. Two clones, both from the same field population exposed historically to MCPA and to flumetsulam, and with anecdotal records of field control failures, were unaffected by flumetsulam and many plants survived treatment with MCPA, providing conclusive evidence for multiple herbicide resistance to these two herbicides in the same R. acris individuals. By contrast, there was no evidence among the 11 clones for resistance to either aminopyralid or glyphosate (86-100% mortality in all clones). The herbicide-resistant and -susceptible clones of R. acris provide a unique opportunity to investigate the biochemical mechanism(s) and genetics of phenoxycarboxylic acid and ALS-inhibitor resistance in this species.