Glyphosate- and Acetolactate Synthase Inhibitor–Resistant Kochia (Kochia scoparia) in Western Canada

Weed Science ◽  
2013 ◽  
Vol 61 (2) ◽  
pp. 310-318 ◽  
Author(s):  
Hugh J. Beckie ◽  
Robert E. Blackshaw ◽  
Ryan Low ◽  
Linda M. Hall ◽  
Connie A. Sauder ◽  
...  
Keyword(s):  
Dose Response ◽  
Best Management Practices ◽  
Management Practices ◽  
Acetolactate Synthase ◽  
Glyphosate Resistance ◽  
Western Canada ◽  
Wild Oat ◽  
Green Foxtail ◽  
Inhibitor Resistance ◽  
Als Inhibitor

In summer, 2011, we investigated suspected glyphosate-resistant (GR) kochia in three chem-fallow fields (designated F1, F2, F3, each farmed by a different grower) in southern Alberta. This study characterizes glyphosate resistance in those populations, based on data from dose–response experiments. In a greenhouse experiment, the three populations exhibited a resistance factor ranging from 4 to 6 based on shoot biomass response (GR50ratios), or 5 to 7 based on survival response (LD50ratios). Similar results were found in a field dose–response experiment at Lethbridge, AB, in spring 2012 using the F2 kochia population. In fall 2011, we surveyed 46 fields within a 20-km radius of the three chem-fallow fields for GR kochia. In the greenhouse, populations were screened with glyphosate at 900 g ae ha−1. Seven populations were confirmed as GR, the farthest site located about 13 km from the three originally confirmed populations. An additional GR population more than 100 km away was later confirmed. Populations were screened for acetolactate synthase (ALS)–inhibitor (thifensulfuron : tribenuron) and dicamba resistance in the greenhouse, with molecular characterization of ALS-inhibitor resistance in the F1, F2, and F3 populations. All GR populations were resistant to the ALS-inhibiting herbicide, but susceptible to dicamba. ALS-inhibitor resistance in kochia was conferred by Pro197, Asp376, or Trp574amino acid substitutions. Based upon a simple empirical model with a parameter for selection pressure, calculated from weed relative abundance and glyphosate efficacy, and a parameter for seedbank longevity, kochia, wild oat, and green foxtail were the top three weeds, respectively, predicted at risk of selection for glyphosate resistance in the semiarid Grassland region of the Canadian prairies; wild oat, green foxtail, and cleavers species were predicted at greatest risk in the subhumid Parkland region. This study confirms the first occurrence of a GR weed in western Canada. Future research on GR kochia will include monitoring, biology and ecology, fitness, mechanism of resistance, and best management practices.

Management Practices Influencing Herbicide Resistance in Wild Oat

2004 ◽  
Vol 18 (3) ◽  
pp. 853-859 ◽  
Author(s):  
Hugh J. Beckie ◽  
Linda M. Hall ◽  
Scott Meers ◽  
James J. Laslo ◽  
F. Craig Stevenson
Keyword(s):  
Herbicide Resistance ◽  
Management Practices ◽  
Conservation Tillage ◽  
Acetolactate Synthase ◽  
Grass Species ◽  
Wild Oat ◽  
Forage Crops ◽  
Oat Seeds ◽  
Inhibitor Resistance ◽  
Als Inhibitor

A 3-yr study was conducted in Wheatland County, Alberta to determine if agronomic practices of growers influenced the occurrence of herbicide resistance in wild oat. Wild oat seeds were collected in 33 fields in 1997 and in 31 fields in each of 1998 and 1999 (one field per grower). Seedlings were screened for resistance to two acetyl-CoA carboxylase (ACCase) inhibitors, imazamethabenz, an acetolactate synthase (ALS) inhibitor, and triallate, a thiocarbamate herbicide. A questionnaire on herbicide resistance awareness and management practices was completed by each grower. Both ACCase and ALS inhibitor resistance in wild oat were linked to a lack of crop rotation diversity. In addition, ALS inhibitor–resistant wild oat was associated with conservation-tillage systems and recent use of herbicides with that mode of action. Results of this study suggest that timely tillage and inclusion of fall-seeded and perennial forage crops in rotations will effectively slow the selection of resistance in this grass species.

Acetolactate Synthase Inhibitor–Resistant False Cleavers (Galium spurium) in Western Canada

2012 ◽  
Vol 26 (1) ◽  
pp. 151-155 ◽  
Author(s):  
Hugh J. Beckie ◽  
Suzanne I. Warwick ◽  
Connie A. Sauder ◽  
Gina M. Kelln ◽  
Chris Lozinski
Keyword(s):  
Point Mutations ◽  
Low Frequency ◽  
Acetolactate Synthase ◽  
Western Canada ◽  
Resistance Factors ◽  
Als Inhibitors ◽  
Synthase Inhibitor ◽  
Inhibitor Resistance ◽  
Als Inhibitor ◽  
Galium Spurium

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 theALSgene including sites known to conferALSresistance 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. TheseALStarget-site mutations have not been documented previously in this species.

scholarly journals Risk Assessment of Glyphosate Resistance in Western Canada

2011 ◽  
Vol 25 (1) ◽  
pp. 159-164 ◽  
Author(s):  
Hugh J. Beckie ◽  
K. Neil Harker ◽  
Linda M. Hall ◽  
Frederick A. Holm ◽  
Robert H. Gulden
Keyword(s):  
Best Management Practices ◽  
Management Practices ◽  
Cropping Systems ◽  
Resistance Management ◽  
Decision Support Tool ◽  
Glyphosate Resistance ◽  
Western Canada ◽  
Support Tool ◽  
Resistance Evolution ◽  
Risk Rating

With increasing incidence of glyphosate-resistant weeds worldwide, greater farmer awareness of the importance of glyphosate stewardship and proactive glyphosate-resistance management is needed. A Web-based decision-support tool (http://www.weedtool.com) comprising 10 questions has been developed primarily for farmers in western Canada to assess the relative risk of selection for glyphosate-resistant weeds on a field-by-field basis. We describe the rationale for the questions and how a response to a particular question influences the risk rating. Practices with the greatest risk weighting in western Canadian cropping systems are lack of crop-rotation diversity (growing mainly oilseeds) and a high frequency of glyphosate-resistant crops in the rotation. Three case scenarios are outlined—low, moderate, and high risk of glyphosate-resistance evolution. Based on the overall risk rating, three best-management practices are recommended to reduce the risk of glyphosate resistance in weeds.

Glyphosate and acetolactate synthase inhibitor resistance in Russian thistle (Salsola tragus L.) in Alberta

2019 ◽  
Vol 99 (3) ◽  
pp. 384-387
Author(s):  
Hugh J. Beckie ◽  
Linda M. Hall ◽  
Scott W. Shirriff ◽  
Elise Martin ◽  
Julia Y. Leeson
Keyword(s):  
Acetolactate Synthase ◽  
Glyphosate Resistance ◽  
Synthase Inhibitor ◽  
Inhibitor Resistance ◽  
Als Inhibitor

A survey was conducted in Alberta in 2017 to determine the distribution and abundance of acetolactate synthase (ALS) inhibitor and glyphosate resistance in Russian thistle. Of 45 populations tested, 31 (62%) were ALS inhibitor resistant. No populations exhibited resistance to glyphosate. This survey serves as a baseline to monitor future incidence of resistance in this weed.

In vitro and whole-plant magnitude and cross-resistance characterization of two imidazolinone-resistant sugarbeet (Beta vulgaris) somatic cell selections

Weed Science ◽  
1998 ◽  
Vol 46 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Terry R. Wright ◽  
Donald Penner
Keyword(s):  
Somatic Cell ◽  
Shoot Culture ◽  
Acetolactate Synthase ◽  
Cross Resistance ◽  
Shoot Cultures ◽  
Als Inhibitors ◽  
Whole Plants ◽  
Inhibitor Resistance ◽  
Als Inhibitor

Acetolactate synthase (ALS)-inhibiting herbicide carryover in soil can severely affect sugarbeets grown in the year(s) following application. Two newly developed imidazolinone-resistant (IMI-R) sugarbeet somatic cell selections (Sir-13 and 93R30B) were examined for magnitude of resistance and extent of cross-resistance to other classes of ALS inhibitors and compared to a previously developed sulfonylurea-resistant (SU-R) selection, Sur. In vitro shoot culture tests indicated Sir-13 resistance was specific to imidazolinone (IMI) herbicides at approximately a 100-fold resistance compared to the sensitive control sugarbeet. Sur was 10,000-fold resistant to the sulfonylurea (SU) herbicide, chlorsulfuron, and 40-fold resistant to the triazolopyrimidine sulfonanilide (TP) herbicide, flumetsulam, but not cross-resistant to the IMI herbicides. 93R30B was selected for IMI-R from a plant homozygous for the SU-R allele,Sur, and displayed similar in vitro SU-R and TP-R as Sur, but also displayed a very high resistance to various IMI herbicides (400- to 3,600-fold). Compared to the sensitive control, Sir-13 was 300- and > 250-fold more resistant to imazethapyr and imazamox residues in soil, respectively. Response by whole plants to postemergence herbicide applications was similar to that observed in shoot cultures. Sir-13 exhibited > 100-fold resistance to imazethapyr as well as imazamox, and 93R30B showed > 250-fold resistance to both herbicides. 93R30B showed great enough resistance to imazamox to merit consideration of imazamox for use as a herbicide in these sugarbeets. Sir-13 showed a two- to threefold higher level of resistance in the homozygous vs. heterozygous state, indicating that like most ALS-inhibitor resistance traits, it was semidominantly inherited.

Acetolactate Synthase Resistance in a Common Waterhemp (Amaranthus rudis) Population

1997 ◽  
Vol 11 (1) ◽  
pp. 13-18 ◽  
Author(s):  
John R. R. Hinz ◽  
Micheal D. K. Owen
Keyword(s):  
Plant Material ◽  
Resistance Mechanism ◽  
Acetolactate Synthase ◽  
Grain Amaranth ◽  
Common Waterhemp ◽  
Resistant Species ◽  
Whole Plant ◽  
Amaranthus Rudis ◽  
Inhibitor Resistance ◽  
Als Inhibitor

Research was initiated to determine (a) whether a common waterhemp population was resistant to acetolactate synthase (ALS) inhibiting herbicides, (b) the percentage of the population that was ALS-inhibitor resistant, (c) the resistance mechanism, and (d) the effectiveness of a whole plant assay to detect ALS-inhibitor resistance. ALS-inhibitor resistance was confirmed in a common waterhemp population near Davis City, IA. The Davis City common waterhemp population was cross resistant to both imidazolinone and sulfonylurea herbicides, but not to lactofen. Approximately 10% of the Davis City common waterhemp population was sensitive to a rate of imazaquin 4 times the normal field rate. Davis City common waterhemp isolated ALS was much less sensitive to imazaquin and primisulfuron inhibition than was grain amaranth or an ALS-sensitive common waterhemp isolated ALS. Imazaquin I50values were 366.4 and 3.4 μM for ALS isolated from Davis City common waterhemp and grain amaranth, respectively. Primisulfuron I50values were 3.6 and 0.007 μM for ALS isolated from Davis City common waterhemp and grain amaranth, respectively. A whole plant ALS assay was developed that allowed for much more rapid detection of an ALS-resistant species and used less plant material than a conventional ALS assay.

Confirmation of Glyphosate-Resistant Horseweed (Conyza canadensis) in Montana Cereal Production and Response to POST Herbicides

2017 ◽  
Vol 31 (6) ◽  
pp. 799-810 ◽  
Author(s):  
Vipan Kumar ◽  
Prashant Jha ◽  
Amit J. Jhala
Keyword(s):  
Great Plains ◽  
Dose Response ◽  
Best Management Practices ◽  
Management Practices ◽  
Dry Weight ◽  
Shoot Dry Weight ◽  
Greenhouse Study ◽  
Whole Plant ◽  
Cereal Production ◽  
Sites Of Action

In recent years, horseweed has become an increasing problem in Montana. To confirm and characterize the level of glyphosate resistance, seeds were collected from putative glyphosate-resistant (GR) horseweed (GR-MT) plants in a wheat–fallow field in McCone County, MT. Known GR (GR-NE) and glyphosate-susceptible (GS-NE) horseweed accessions from Lincoln, NE, were included for comparison in dose–response and shikimate accumulation studies. Whole-plant glyphosate dose–response experiments conducted at the early- (5- to 8-cm diameter) and late- (12- to 15-cm diameter) rosette stages of horseweed indicated that GR-MT accessions had a 2.5- to 4.0-fold level of resistance to glyphosate relative to the GS-NE accession, on the basis of shoot dry weight (GR50values). The level of resistance was 3.1- to 7.9-fold on the basis of visually assessed injury estimates (I50values). At the whole-plant level, about 2.1- to 4.5-fold higher shikimate accumulation was observed in the GS-NE accession compared with the GR-MT and GR-NE accessions over a 10-d period after glyphosate was applied at 1,260 g ae ha−1. In a separate greenhouse study, all three horseweed accessions were also screened with alternate POST herbicides registered for use in wheat–fallow rotations. The majority of the tested herbicides provided ≥90% injury at the field-use rates for all three horseweed accessions 3 wk after treatment. This is the first published report on the occurrence of GR horseweed in Montana cereal production. Increased awareness and adoption of best management practices, including the use of diversified (based on multiple sites of action) herbicide programs highlighted in this study, would aid in mitigating the further spread of GR horseweed in the cereal production fields of the U.S. Great Plains.

scholarly journals ALS–Resistant Annual Sedge (Cyperus compressus) Confirmed in Turfgrass

Weed Science ◽  
2016 ◽  
Vol 64 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Patrick E. McCullough ◽  
Jialin Yu ◽  
J. Scott McElroy ◽  
S. Chen ◽  
H. Zhang ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Acetolactate Synthase ◽  
Shoot Biomass ◽  
Resistance Level ◽  
Physiological Basis ◽  
History Of ◽  
Leaf Tissues ◽  
Als Inhibitors ◽  
Inhibitor Resistance ◽  
Als Inhibitor

Acetolactate synthase (ALS) inhibitors are widely used for POST control of sedges in turfgrass. A suspected resistant (R) biotype of annual sedge was collected from a bermudagrass turf in Georgia with a history of exclusive use of halosulfuron. Research was conducted to evaluate the resistance level of this biotype to halosulfuron, efficacy of ALS-inhibiting herbicides and other mechanisms of action for control, and the molecular and physiological basis for resistance. In greenhouse experiments, the halosulfuron rate required to reduce shoot biomass 50% in comparison with the nontreated at 8 wk after treatment (WAT) were 8 and > 1,120 g ai ha−1for the S (susceptible) and R biotypes, respectively. Imazapic, sulfosulfuron, and trifloxysulfuron reduced biomass of the S biotype greater than 60% at 8 WAT, but biomass was reduced less than 20% for the R biotype. Glufosinate, glyphosate, MSMA, and sulfentrazone reduced shoot biomass of the R biotype by 93, 86, 97, and 45%, respectively. In laboratory experiments, the halosulfuron concentration required to inhibit ALS activity by 50% in excised leaf tissues was 5.8 and > 1,000 μM for the S and R biotypes, respectively. Gene sequencing of the R biotype revealed a Pro-197-Ser substitution that confers resistance to ALS inhibitors. This is the first report of ALS-inhibitor resistance in annual sedge and herbicide resistance in a sedge species from a turfgrass system.

Efficacy of Fall- and Spring-Applied Pyroxasulfone For Herbicide-Resistant Weeds in Field Pea

2014 ◽  
Vol 28 (2) ◽  
pp. 351-360 ◽  
Author(s):  
Breanne D. Tidemann ◽  
Linda M. Hall ◽  
Eric N. Johnson ◽  
Hugh J. Beckie ◽  
Ken L. Sapsford ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Matter Content ◽  
Acetolactate Synthase ◽  
Field Trials ◽  
Matter Content ◽  
Field Pea ◽  
Wild Oat ◽  
Herbicide Activity ◽  
Als Inhibitor

Field trials were initiated in fall 2011 to determine the potential of pyroxasulfone to control acetolactate synthase (ALS) inhibitor-resistant weeds in field pea. Pyroxasulfone was applied in split-plot trials at five locations in western Canada using fall and PRE spring applications of 0 to 400 g ai ha−1. Trial locations were chosen with a range of soil organic matter content: 2.9, 4.3, 5.5, 10.5, and 10.6% at Scott, Kernen, Kinsella, Melfort, and Ellerslie, respectively. The herbicide dose required to reduce biomass by 50% (ED50) in false cleavers ranged between 53 and 395 g ha−1at Scott and Ellerslie, respectively. Wild oat ED50s varied between 0.54 g ha−1at Scott in the fall and 410 g ai ha−1in the spring at Melfort. ED50s for wild oat and false cleavers varied by 7.4- and 746-fold, respectively, depending primarily on the organic matter content at the trial location. The effect of application timing was not consistent. Significant yield reductions and pea injury occurred at 150 and 100 g ha−1and higher at Kernen and Scott, respectively. Low organic matter and high precipitation levels at these locations indicates increased herbicide activity under these conditions. Pyroxasulfone may allow control of ALS inhibitor-resistant false cleavers and wild oat; however, locations with high soil organic matter will require higher rates than those with low organic matter for similar control levels.

Comparison of ALS inhibitor resistance and allelic interactions in shattercane accessions

Weed Science ◽  
1999 ◽  
Vol 47 (3) ◽  
pp. 275-281 ◽  
Author(s):  
Chad D. Lee ◽  
Alex R. Martin ◽  
Fred W. Roeth ◽  
Blaine E. Johnson ◽  
Donald J. Lee
Keyword(s):  
Sorghum Bicolor ◽  
Acetolactate Synthase ◽  
Cross Resistance ◽  
Wild Type ◽  
Forage Sorghum ◽  
South Central ◽  
Inhibitor Resistance ◽  
Als Inhibitor

Reports of unacceptable shattercane (Sorghum bicolor) control with acetolactate synthase (ALS)-inhibiting herbicides prompted the investigation of 29 fields in central and south-central Nebraska for ALS-resistant (ALSr) shattercane. These fields were located in three distinct geographical areas designated C, G, and P. Shattercane from 13 fields spanning all three areas was resistant to 80 g ai ha−1(2 X field rate) primisulfuron. Accessions C and G were more resistant than accession P to primisulfuron and nicosulfuron. Accessions C and G were susceptible to imazethapyr, whereas accession P was resistant. The ALS resistance was associated with alterations in the ALS enzyme. Primisulfuron I50values for ALS from ROX (forage sorghum), C, G, and P were 7, 8,510, 8,870, and 714 nM, respectively; nicosulfuron I50values were 647, 4,110, 4,070, and 1,460 nM, respectively; and imazethapyr I50values were 5,440, 13,100, 11,800, and 51,700 nM, respectively. Based on cross-resistance and enzyme sensitivities, at least two biotypes are represented in the three accessions of ALSr shattercane. Shattercane individuals from accessions C, G, and P were intercrossed to determine if the ALSr genes in each of the accessions were at independent loci. All the F2populations were resistant to 80 g ai ha−1primisulfuron, suggesting that the ALSr alleles in the three accessions are at the same locus or possibly linked loci. When the C, G, and P accessions were crossed with the wild type (WT), comparisons between the F1, susceptible, and resistant populations showed that primisulfuron resistance was expressed as a dominant, partially dominant, and additive trait for the C, G, and P accessions, respectively. The differences in ALSr allelic interactions indicate that primisulfuron resistance developed independently in each of the three accessions.

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