Weed resistance monitoring has been routinely conducted in the Northern Great Plains of Canada (Prairies) since the mid-1990s. Most recently, random surveys were conducted in Alberta in 2001, Manitoba in 2002, and Saskatchewan in 2003 totaling nearly 800 fields. In addition, nearly 1,300 weed seed samples were submitted by growers across the Prairies between 1996 and 2006 for resistance testing. Collected or submitted samples were screened for group 1 [acetyl-CoA carboxylase (ACCase) inhibitor] and/or group 2 [acetolactate synthase (ALS) inhibitor] resistance. Twenty percent of 565 sampled fields had an herbicide-resistant (HR) wild oat biotype. Most populations exhibited broad cross-resistance across various classes of group 1 or group 2 herbicides. In Manitoba, 22% of 59 fields had group 1–HR green foxtail. Group 2–HR biotypes of kochia were documented in Saskatchewan, common chickweed and spiny sowthistle in Alberta, and green foxtail and redroot pigweed in Manitoba. Across the Prairies, HR weeds are estimated to occur in fields covering an area of nearly 5 million ha. Of 1,067 wild oat seed samples submitted by growers and industry for testing between 1996 and 2006, 725 were group 1 HR, 34 group 2 HR, and 55 groups 1 and 2 HR. Of 80 submitted green foxtail samples, 26 were confirmed group 1 HR; most populations originated from southern Manitoba where the weed is most abundant. Similar to the field surveys, various group 2–HR biotypes were confirmed among submitted samples: kochia, wild mustard, field pennycress,Galiumspp., common chickweed, and common hempnettle. Information from grower questionnaires indicates patterns of herbicide usage are related to location, changing with cropping system. Two herbicide modes of action most prone to select resistance, groups 1 and 2, continue to be widely and repeatedly used. There is little evidence that growers are aware of the level of resistance within their fields, but a majority have adopted herbicide rotations to proactively or reactively manage HR weeds.

A late-summer survey of herbicide-resistant (HR) weeds was conducted in Alberta in 2007, Manitoba in 2008, and Saskatchewan in 2009, totaling 1,000 randomly selected annually cropped fields. In addition, we screened 1,091 weed seed samples (each sample from one field) submitted by Prairie growers between 2007 and 2011. Of 677 fields where wild oat samples were collected, 298 (44%) had an HR biotype. Group 1 (acetyl CoA carboxylase inhibitor)-HR wild oat was confirmed in 275 fields (41%), up from 15% in previous baseline surveys (2001 to 2003). Group 2 (acetolactate synthase)-HR wild oat was found in 12% of fields (vs. 8% in 2001 to 2003). Group 8 (triallate, difenzoquat)-HR wild oat was identified in only 8% of fields (not tested in 2001 to 2003); the frequency of occurrence of group 1+2-HR wild oat was similar (8%, vs. 3% in 2001 to 2003). Group 1-HR green foxtail was found in 27% of 209 fields sampled for the weed (vs. 6% in 2001 to 2003). Group 2-HR spiny sowthistle was confirmed in all Alberta fields sampled (vs. 67% in 2001); common chickweed was found mainly in Alberta in 40% of fields (vs. 17% in 2001). Group 2-HR weed biotypes not previously detected in the baseline surveys included false cleavers mainly in Alberta (17% of fields) and Saskatchewan (21%), Powell amaranth in Manitoba (16% of fields), wild mustard (three populations in Saskatchewan and Manitoba), and wild buckwheat (one population in Alberta). No sampled weed populations across the Prairies were found to be resistant to herbicides from group 4 (synthetic auxins), group 9 (glyphosate), or group 10 (glufosinate). Based on the proportion of total field area at each site infested with HR weeds, it is estimated that 7.7 million ha (29% of annually cropped land) are infested with HR weeds (eight-fold increase from 2001 to 2003), in a total field area of 9.9 million ha (37%)—over a two-fold increase. Of 816 cases of HR wild oat identified from submitted samples, 69% were group 1-HR, 15% group 2-HR, and 16% group 1+2-HR. Additionally, there were 10 populations of group 1-HR green foxtail in Saskatchewan or Manitoba, and six populations of group 1-HR Persian darnel in southern Alberta and Saskatchewan. Various group 2-HR broadleaf weeds were identified, including 17 wild mustard populations mainly from Saskatchewan and 39 cleavers populations across the three Prairie provinces. Herbicide-use data from 2006 to 2010 indicated continued reliance on group 1 herbicides in cereal crops and group 2 herbicides in pulse crops.

A survey of 109 fields was conducted across western Canada in spring 2007 to determine the extent of ALS-inhibitor and dicamba (synthetic auxin) resistance in kochia. Weed seedlings were collected from fields in three provinces of western Canada and transplanted into the greenhouse. Seeds were harvested from selfed plants, and the F1progeny were screened for resistance to the ALS-inhibitor mixture thifensulfuron–tribenuron or dicamba. All kochia populations were susceptible to dicamba. ALS inhibitor–resistant kochia was found in 85% of the fields surveyed in western Canada: 80 of 95 fields in Alberta, six of seven fields in Saskatchewan, and all seven fields in Manitoba. For the 93 ALS inhibitor–resistant populations, the mean frequency (±SE) of parental plants classified as resistant was 61 ± 3%. Most of the resistant populations (87%) were heterogeneous and contained both resistant and susceptible individuals.ALSsequence data (Pro197and Asp376mutations) and genotyping data (Trp574mutation) obtained for 87 kochia parental (i.e., field-collected) plants confirmed the presence of all three target-site mutations as well as two mutational combinations (Pro197+ Trp574, Asp376+ Trp574) in resistant individuals.

Ford, G. 2015. Glyphosate-resistant kochia (Kochia scoparia L. Schrad.) in Saskatchewan and Manitoba. Can. J. Plant Sci. 95: 345Á349. Previous surveys have documented the occurrence of glyphosate-resistant (GR) kochia in Alberta in 2011 and 2012. To determine the incidence of GR kochia in Saskatchewan and Manitoba, a stratified-randomized survey of 342 sites (one population per site) in southern and central regions of Saskatchewan and a similar survey of 283 sites in southern Manitoba was conducted in the fall of 2013. Mature plants were collected, seed threshed, and progeny screened by spraying with a discriminating glyphosate dose of 900 g ae ha Á1 under greenhouse conditions. Screening confirmed 17 GR kochia populations in nine municipalities in west-central or central Saskatchewan, but only two GR populations from different municipalities in the Red River Valley of Manitoba. While the majority of GR kochia populations in Saskatchewan originated in chemicalfallow fields, some populations were found in cropped fields (wheat, Triticum aestivum L.; lentil, Lens culinaris Medik.; GR canola, Brassica napus L.) and non-cropped areas (oil well, roadside ditch). In Manitoba, the two populations occurred in fields cropped to GR corn (Zea mays L.) and soybean (Glycine max L. Merr.). Agronomic and economic impact of this GR weed biotype is compounded because of consistent multiple resistance to acetolactate synthase-inhibiting herbicides. However, GR kochia is susceptible to dicamba, an increasingly important auxinic herbicide used for control of this multiple-resistant weed biotype. Pour e´tablir l'incidence de cette adventice GR en Saskatchewan et au Manitoba, les auteurs ont proce´deá`u ne enqueˆte ale´atoire stratifie´e a`342 sites (un peuplement par site) dans le sud et le centre de la Saskatchewan, puis ont effectue´une enqueˆte similaire a`283 sites dans le sud du Manitoba, a`l'automne 2013. Ils ont recueilli des plants matures, en ont re´colte´les graines et ont pre´se´lectionne´la proge´niture en la pulve´risant avec 900 g de glyphosate par hectare, en serre, aux fins de discrimination. La pre´se´lection a confirme´la pre´sence de 17 peuplements de kochie GR dans neuf municipalite´s du centre-ouest ou du centre de la Saskatchewan, mais seulement deux populations GR dans des municipalite´s diffe´rentes de la valle´e de la rivie`re Rouge, au Manitoba. Bien que la majorite´des peuplements de kochie GR de la Saskatchewan aient e´te´observe´s dans des jache`res chimiques, quelques-uns ont e´te´retrouve´s dans des cultures (ble´, Triticum aestivum L.; lentille, Lens culinaris Medik.; canola GR, Brassica napus L.) et sur des terrains en friche (puits de pe´trole, fosse´d'une route). Au Manitoba, les deux populations ont e´te´de´couvertes dans des champs de maı¨s GR (Zea mays L.) et de soja (Glycine max L. Merr.). L'impact agronomique et e´conomique de cette adventice GR est complexe, car la kochie pre´sente une re´sistance multiple aux herbicides qui inhibent l'ace´tolactate synthase. Ne´anmoins, la kochie GR est sen...

RESEARCHN umerous biological, environmental, and crop management factors and their interactions infl uence the frequency and distance of pollen-mediated gene fl ow (PMGF) between donor and receptor fi elds, including type of vector (wind and/or insect), genotype or cultivar, fertility (e.g., male-fertile or -sterile receptor plants), pollen viability and longevity, synchrony of fl owering or pollen production, wind speed and direction, air turbulence or convective air currents, temperature, humidity, and area and plant density of donor and receptor populations (Beckie and Hall, 2008). At a landscape or regional scale, additional factors infl uencing PMGF are topography, vegetation, distribution and abundance of volunteer and feral populations, and number, shape, and spatial arrangement of pollen donor and receptor fi elds.The frequency of PMGF generally declines rapidly with increasing distance from the donor fi eld, often described by a leptokurtic curve, that is, higher probability distribution in the tail than predicted by a normal distribution. The length and shape of the asymptote tail depends on the species, environment, and limits of transgene or phenotypic detection and can be the result ABSTRACT Crop intraspecifi c pollen-mediated gene fl ow (PMGF) can be scale dependent. In 2004-the fi rst year imidazolinone (IMI)-resistant spring wheat (Triticum aestivum L.) was commercially available-a study was conducted in western Canada to examine PMGF in commercial fi elds. At each of two sites located 4 km apart in the semiarid grassland region of Saskatchewan, PMGF was measured from a 16-ha (400 × 400 m) fi eld of IMI-resistant wheat (cultivar CDC Imagine) to an adjacent fi eld of conventional (non-IMI-resistant) wheat (cultivar AC Barrie) with the same dimensions. Wheat grain samples of AC Barrie were collected at varying distances to 400 m along fi ve equally-spaced transects oriented perpendicular to the common border with CDC Imagine. A total of 2000 seedlings per sample were screened for resistance to imazamox at 200 μM in a 7-d soilless bioassay. Putative resistant hybrids were confi rmed by polymerase chain reaction (PCR) analysis. Averaged across transects and sites, PMGF was 0.2% at the common border and declined exponentially with increasing distance; the maximum distance that PMGF was detected was 80 m from the donor fi eld. Higher levels of PMGF were generally observed in this study compared with that of previous studies in western Canada. Results of this study provide a more complete assessment of PMGF in this crop under western Canadian climatic conditions. Together with previous studies, frequency and distance of PMGF can guide grower stewardship practices for identify preservation in wheat cultivars possessing different traits.