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1 January 2012 Acetolactate Synthase Inhibitor–Resistant False Cleavers (Galium spurium) in Western Canada
Hugh J. Beckie, Suzanne I. Warwick, Connie A. Sauder, Gina M. Kelln, Chris Lozinski
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Cleavers species (false cleavers and catchweed bedstraw) are among the top 10 most abundant weeds across the prairie region of western Canada, and are increasing in relative abundance at the fastest rate since the 1970s. In 2008, two false cleavers populations from Tisdale and Choiceland, Saskatchewan, were suspected of acetolactate synthase (ALS) –inhibitor resistance. Dose-response experiments were conducted with the use of imazethapyr and florasulam, both ALS inhibitors, as well as fluroxypyr, a synthetic auxin. Additionally, a 1,954–base-pair region of the ALS gene including sites known to confer ALS resistance were sequenced. Both populations were highly resistant to imazethapyr (resistance factors greater than 100), one population (Tisdale) was highly resistant to florasulam (Choiceland population susceptible, although a second, larger screening of 200 individuals indicated low frequency [2%] florasulam resistance), and both populations were susceptible to fluroxypyr. All sequenced Tisdale individuals screened with imazethapyr posessed the Trp574Leu mutation. In contrast, three point mutations were found for Choiceland individuals sequenced: Ser653Asn, Trp574Leu, and Asp376Glu. These ALS target-site mutations have not been documented previously in this species.

Nomenclature: Florasulam; fluroxypyr; imazethapyr; catchweed bedstraw, Galium aparine L.; false cleavers, Galium spurium L. GALSP.

Weed Science Society of America
Hugh J. Beckie, Suzanne I. Warwick, Connie A. Sauder, Gina M. Kelln, and Chris Lozinski "Acetolactate Synthase Inhibitor–Resistant False Cleavers (Galium spurium) in Western Canada," Weed Technology 26(1), 151-155, (1 January 2012).
Received: 3 June 2011; Accepted: 1 September 2011; Published: 1 January 2012

ALS gene sequencing
ALS-inhibitor resistance
Herbicide resistance
target-site mutation
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