Pollen- and Seed-Mediated Gene Flow in Kochia (Kochia scoparia)

Efficient natural dispersal of herbicide-resistance alleles via seed and pollen can markedly accelerate the incidence of herbicide-resistant weed populations across an agroecoregion. Studies were conducted in western Canada in 2014 and 2015 to investigate pollen- and seed-mediated gene flow in kochia. Pollen-mediated gene flow (PMGF) from glyphosate-resistant (GR) to non-GR kochia was quantified in a field trial (hub and spoke design) at Saskatoon, Saskatchewan. Seed-mediated gene flow of acetolactate synthase (ALS) inhibitor-resistant kochia as a function of tumbleweed speed and distance was estimated in cereal stubble fields at Lethbridge, Alberta and Scott, Saskatchewan. Regression analysis indicated that outcrossing from GR to adjacent non-GR kochia ranged from 5.3 to 7.5%, declining exponentially to 0.1 to 0.4% at 96 m distance. However, PMGF was significantly influenced by prevailing wind direction during pollination (maximum of 11 to 17% outcrossing down-wind). Seed dropped by tumbleweeds varied with distance and plant speed, approaching 90% or more (ca. 100,000 seeds or more) at distances of up to 1,000 m and plant speeds of up to 300 cm s–1. This study highlights the efficient proximal (pollen) and distal (seed) gene movement of this important GR weed.

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Occurrence and Molecular Characterization of Acetolactate Synthase (ALS) Inhibitor–Resistant Kochia (Kochia scoparia) in Western Canada

Weed Technology ◽

10.1614/wt-d-10-00067.1 ◽

2011 ◽

Vol 25 (1) ◽

pp. 170-175 ◽

Cited By ~ 19

Author(s):

Hugh J. Beckie ◽

Suzanne I. Warwick ◽

Connie A. Sauder ◽

Chris Lozinski ◽

Scott Shirriff

Keyword(s):

Molecular Characterization ◽

Sequence Data ◽

Acetolactate Synthase ◽

Western Canada ◽

Kochia Scoparia ◽

Mean Frequency ◽

Auxin Resistance ◽

The Mean ◽

Als Inhibitor

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.

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Response of glyphosate-resistant kochia (Kochia scoparia L. Schrad.) to alternative herbicides

Canadian Journal of Plant Science ◽

10.4141/cjps-2014-179 ◽

2014 ◽

Vol 94 (8) ◽

pp. 1407-1411 ◽

Cited By ~ 2

Author(s):

Nikki Burton ◽

Scott W. Shirriff ◽

Hugh J. Beckie

Keyword(s):

Acetolactate Synthase ◽

Shoot Biomass ◽

Western Canada ◽

Weed Species ◽

Kochia Scoparia ◽

Oilseed Crops ◽

Greenhouse Study ◽

Herbicide Treatments ◽

Chemical Fallow ◽

Als Inhibitor

Burton, N., Shirriff, S. W. and Beckie, H. J. 2014. Response of glyphosate-resistant kochia (Kochia scoparia L. Schrad.) to alternative herbicides. Can. J. Plant Sci. 94: 1407–1411. A greenhouse study was conducted to examine the response of glyphosate-resistant (GR) plus acetolactate synthase (ALS) inhibitor-resistant kochia to five post-emergence herbicide treatments commonly used to control the weed species in chemical fallow, cereals, or oilseed crops in western Canada. The treatments, which were applied to two GR kochia biotypes and one non-GR (susceptible) biotype, included the labeled rate of dicamba, dicamba/fluroxypyr, dicamba/diflufenzopyr, MCPA/bromoxynil, and glufosinate. Both GR and non-GR biotypes responded similarly to each of the herbicide treatments. Although both GR biotypes were sensitive to the herbicides, MCPA/bromoxynil was the most effective treatment in reducing shoot biomass 3 wk after application (99%), followed by glufosinate (91%) then the dicamba mixtures (82%). Dicamba alone only suppressed kochia biomass (76% reduction).

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Herbicide strategies for managing glyphosate-resistant and susceptible kochia (Bassia scoparia) in spring wheat

Canadian Journal of Plant Science ◽

10.1139/cjps-2020-0303 ◽

2021 ◽

Author(s):

Alysha T Torbiak ◽

Robert Blackshaw ◽

Randall N Brandt ◽

Bill Hamman ◽

Charles M. Geddes

Keyword(s):

Spring Wheat ◽

Acetolactate Synthase ◽

Management Program ◽

Integrated Weed Management ◽

Western Canada ◽

Management Options ◽

Visible Injury ◽

Herbicide Resistant ◽

Als Inhibitor ◽

Biomass Reduction

Kochia [<i>Bassia scoparia</i> (L.) A.J. Scott] is a summer-annual tumbleweed that is tolerant of heat, drought and salinity, and capable of causing large yield losses in spring wheat (<i>Triticum aestivum</i> L). Increased incidence of glyphosate and acetolactate synthase (ALS) inhibitor-resistant kochia in Western Canada warrants investigation of alternative herbicides to manage these biotypes. Herbicides applied pre- or post-emergence in spring wheat were evaluated based on crop tolerance and control of ALS inhibitor-resistant kochia accessions with and without the glyphosate resistance trait in five environments near Lethbridge and Coalhurst, Alberta, from 2013-2015. The most effective and consistent treatments for kochia management included sulfentrazone applied pre-emergence, and fluroxypyr/bromoxynil/2,4-D or pyrasulfotole/bromoxynil applied post-emergence. All of these treatments resulted in ≥ 90% visible control in all environments and ≥ 90% kochia biomass reduction compared with the untreated control in Lethbridge 2014 and 2015. MCPA/dichlorprop-p/mecoprop-p, dicamba/2,4-D/mecoprop-p, and dicamba/fluroxypyr resulted in acceptable control among environments (≥ 80% visible control in all environments and ≥ 80% kochia biomass reduction in Lethbridge 2014 and 2015); however the latter two options caused unacceptable (> 10%) wheat visible injury in Coalhurst 2014. Recent confirmations of auxinic herbicide-resistant kochia in Western Canada – due, in part, to use of synthetic auxins to manage glyphosate-resistant kochia in small-grain cereals – will limit kochia management options. When implemented with non-chemical tools as part of an integrated weed management program, alternative herbicide modes of action like protoporphyrinogen oxidase inhibitors before and photosystem II or 4-hydroxyphenylpyruvate dioxygenase inhibitor(s) within spring wheat could mitigate selection for multiple herbicide-resistant kochia.

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Investigating the resistance levels and mechanisms to penoxsulam and cyhalofop-butyl in barnyardgrass (Echinochloa crus-galli) from Ningxia province, China

Weed Science ◽

10.1017/wsc.2021.37 ◽

2021 ◽

pp. 1-25

Author(s):

Qian Yang ◽

Xia Yang ◽

Zichang Zhang ◽

Jieping Wang ◽

Weiguo Fu ◽

...

Keyword(s):

Herbicide Resistance ◽

Molecular Mechanisms ◽

Acetolactate Synthase ◽

Rice Fields ◽

Target Site ◽

Herbicide Resistant ◽

Susceptible Populations ◽

High Level ◽

Als Inhibitor ◽

Encoding Genes

Abstract Barnyardgrass (Echinochloa crus-galli) is a noxious grass weed which infests rice fields and causes huge crop yield losses. In this study, we collected twelve E. crus-galli populations from rice ﬁelds of Ningxia province in China and investigated the resistance levels to acetolactate synthase (ALS) inhibitor penoxsulam and acetyl-CoA carboxylase (ACCase) inhibitor cyhalofop-butyl. The results showed that eight populations exhibited resistance to penoxsulam and four populations evolved resistance to cyhalofop-butyl. Moreover, all of the four cyhalofop-butyl-resistant populations (NX3, NX4, NX6 and NX7) displayed multiple-herbicide-resistance (MHR) to both penoxsulam and cyhalofop-butyl. The alternative herbicides bispyribac-sodium, metamifop and fenoxaprop-P-ethyl cannot effectively control the MHR plants. To characterize the molecular mechanisms of resistance, we ampliﬁed and sequenced the target-site encoding genes in resistant and susceptible populations. Partial sequences of three ALS genes and six ACCase genes were examined. A Trp-574-Leu mutation was detected in EcALS1 and EcALS3 in two high-level (65.84- and 59.30-fold) penoxsulam-resistant populations NX2 and NX10, respectively. In addition, one copy (EcACC4) of ACCase genes encodes a truncated aberrant protein due to a frameshift mutation in E. crus-galli populations. None of amino acid substitutions that are known to confer herbicide resistance were detected in ALS and ACCase genes of MHR populations. Our study reveals the widespread of multiple-herbicide resistant E. crus-galli populations at Ningxia province of China that exhibit resistance to several ALS and ACCase inhibitors. Non-target-site based mechanisms are likely to be involved in E. crus-galli resistance to the herbicides, at least in four MHR populations.

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Pollen-Mediated Gene Flow of Sulfonylurea-Resistant Kochia (Kochia scoparia)

Weed Science ◽

10.1017/s0043174500080887 ◽

1995 ◽

Vol 43 (1) ◽

pp. 95-102 ◽

Cited By ~ 60

Author(s):

George P. Stallings ◽

Donald C. Thill ◽

Carol A. Mallory-Smith ◽

Bahman Shafii

Keyword(s):

Gene Flow ◽

Soil Temperature ◽

Wind Direction ◽

Spring Barley ◽

Growing Season ◽

Sulfonylurea Herbicide ◽

Kochia Scoparia ◽

Herbicide Resistant ◽

Resistant Trait ◽

Plot Design

The movement of sulfonylurea herbicide-resistant (R) kochia pollen was investigated in a spring barley field near Moscow, ID, using a Nelder plot design in 1991 and 1992. Each 61 m diameter plot had 16 rays spaced 22.5° apart and contained 211 kochia plants. There were 12 susceptible (S) plants and one R plant along each ray. The R and S plants were 1.5 m and 3.0 to 30.5 m from the center of the plot, respectively. Wind direction and speed in the 16 vectors, air and soil temperature, and rainfall were monitored continuously. Mature kochia seed was collected from individual plants, planted in the greenhouse, and sprayed with chlorsulfuron to test for resistant F1progeny. Results from the 2-yr study showed outcrossing of R pollen onto S plants at rates up to 13.1% per plant 1.5 m from the R plants and declining to 1.4% per plant or less 29 m from the R plants. At least 35% of the total R x S crosses occurred in the direction of prevailing southeastward winds. Predicted percentages of R x S crosses per plant ranged from 0.16 to 1.29 at 1.5 m, and 0.00 to 0.06% at 29 m. Thus, resistant kochia pollen can spread the sulfonylurea-resistant trait at least 30 m during each growing season.

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

Weed Science ◽

10.1614/ws-d-12-00140.1 ◽

2013 ◽

Vol 61 (2) ◽

pp. 310-318 ◽

Cited By ~ 50

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.

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Growth Characterization of Kochia (Kochia scoparia) with Substitutions at Pro197or Trp574Conferring Resistance to Acetolactate Synthase–Inhibiting Herbicides

Weed Science ◽

10.1614/ws-d-12-00116.1 ◽

2013 ◽

Vol 61 (2) ◽

pp. 267-276 ◽

Cited By ~ 15

Author(s):

Anne Légère ◽

F. Craig Stevenson ◽

Hugh J. Beckie ◽

Suzanne I. Warwick ◽

Eric N. Johnson ◽

...

Keyword(s):

Acetolactate Synthase ◽

Dry Weight ◽

Variable Response ◽

Kochia Scoparia ◽

Replacement Series ◽

Mixed Stands ◽

Population Total ◽

Factors Affecting ◽

Herbicide Resistant ◽

Growth Characterization

Over 90% of Canadian kochia populations are resistant to acetolactate synthase (ALS)– inhibiting herbicides. We questioned whether the target site–based resistance could affect plant growth and competitiveness. Homozygous F2herbicide-resistant (HR) kochia plants with an amino acid substitution at Trp574(sources: Alberta [AB], Saskatchewan [SK], and Manitoba [MB]), or Pro197(MB, AB with two populations) were grown in replacement series with homozygous F2herbicide-susceptible (HS) plants from the corresponding heterogeneous population (total: six populations). In pure stands, growth of HR plants from AB and SK was similar to that of HS plants, regardless of mutation; conversely, MB2-HR plants (Trp574Leu) developed more slowly and were taller than MB2-HS plants. Final dry weight of HR plants in pure stands was similar across all six populations, whereas that for HS plants in pure stands and HR–HS plants in mixed stands (50–50%) varied with population. Results for AB and SK populations suggest little impact of either ALS mutation on kochia growth, whereas those for MB lines would suggest an unidentified factor (or factors) affecting the HS, HR, or both biotypes. The variable response within and between lines, and across HS biotypes highlights the importance of including populations of various origins and multiple susceptible controls in HR biotype studies.

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

Weed Technology ◽

10.1614/wt-d-11-00075.1 ◽

2012 ◽

Vol 26 (1) ◽

pp. 151-155 ◽

Cited By ~ 11

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.

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Negative Cross-Resistance of Acetolactate Synthase Inhibitor–Resistant Kochia (Kochia scoparia) to Protoporphyrinogen Oxidase– and Hydroxyphenylpyruvate Dioxygenase–Inhibiting Herbicides

Weed Technology ◽

10.1614/wt-d-12-00020.1 ◽

2012 ◽

Vol 26 (3) ◽

pp. 570-574 ◽

Cited By ~ 3

Author(s):

Hugh J. Beckie ◽

Eric N. Johnson ◽

Anne Légère

Keyword(s):

Growth And Development ◽

Null Hypothesis ◽

Acetolactate Synthase ◽

Pleiotropic Effect ◽

Cross Resistance ◽

Kochia Scoparia ◽

Protoporphyrinogen Oxidase ◽

Synthase Inhibitor ◽

Sites Of Action ◽

Als Inhibitor

This greenhouse experiment examined the response of homozygous susceptible and acetolactate synthase (ALS) inhibitor–resistant plants from six Canadian kochia accessions with the Pro197 or Trp574 mutation to six alternative herbicides of different sites of action. The null hypothesis was ALS-inhibitor–resistant and –susceptible plants from within and across accessions would respond similarly to herbicides of different sites of action. This hypothesis was accepted for all accessions except that of MBK2 with the Trp574 mutation. Resistant plants of that accession were 80, 60, and 50% more sensitive than susceptible plants to pyrasulfotole, mesotrione (hydroxyphenylpyruvate dioxygenase [HPPD] inhibitors), and carfentrazone (protoporphyrinogen oxidase [PPO] inhibitor), respectively. However, no differential dose response between resistant and susceptible plants of this kochia accession to bromoxynil, fluroxypyr, or glyphosate was observed. A previous study had found marked differences in growth and development between resistant and susceptible plants of this accession, but not of the other accessions examined in this experiment. Negative cross-resistance exhibited by resistant plants of accession MBK2 to PPO and HPPD inhibitors in this experiment may be a pleiotropic effect related to the Trp574 mutation.

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Resistance to post-emergent herbicides is becoming common for grass weeds on New Zealand wheat and barley farms

PLoS ONE ◽

10.1371/journal.pone.0258685 ◽

2021 ◽

Vol 16 (10) ◽

pp. e0258685

Author(s):

Christopher E. Buddenhagen ◽

Trevor K. James ◽

Zachary Ngow ◽

Deborah L. Hackell ◽

M. Phil Rolston ◽

...

Keyword(s):

New Zealand ◽

Ad Hoc ◽

Acetolactate Synthase ◽

Stellaria Media ◽

Herbicide Resistant ◽

The North ◽

Mother Plants ◽

Als Inhibitors ◽

Als Inhibitor ◽

North And South

To estimate the prevalence of herbicide-resistant weeds, 87 wheat and barley farms were randomly surveyed in the Canterbury region of New Zealand. Over 600 weed seed samples from up to 10 mother plants per taxon depending on abundance, were collected immediately prior to harvest (two fields per farm). Some samples provided by agronomists were tested on an ad-hoc basis. Over 40,000 seedlings were grown to the 2–4 leaf stage in glasshouse conditions and sprayed with high priority herbicides for grasses from the three modes-of-action acetyl-CoA carboxylase (ACCase)-inhibitors haloxyfop, fenoxaprop, clodinafop, pinoxaden, clethodim, acetolactate synthase (ALS)-inhibitors iodosulfuron, pyroxsulam, nicosulfuron, and the 5-enolpyruvyl shikimate 3-phosphate synthase (EPSPS)-inhibitor glyphosate. The highest manufacturer recommended label rates were applied for the products registered for use in New Zealand, often higher than the discriminatory rates used in studies elsewhere. Published studies of resistance were rare in New Zealand but we found weeds survived herbicide applications on 42 of the 87 (48%) randomly surveyed farms, while susceptible reference populations died. Resistance was found for ALS-inhibitors on 35 farms (40%) and to ACCase-inhibitors on 20 (23%) farms. The number of farms with resistant weeds (denominator is 87 farms) are reported for ACCase-inhibitors, ALS-inhibitors, and glyphosate respectively as: Avena fatua (9%, 1%, 0% of farms), Bromus catharticus (0%, 2%, 0%), Lolium spp. (17%, 28%, 0%), Phalaris minor (1%, 6%, 0%), and Vulpia bromoides (0%, not tested, 0%). Not all farms had the weeds present, five had no obvious weeds prior to harvest. This survey revealed New Zealand’s first documented cases of resistance in P. minor (fenoxaprop, clodinafop, iodosulfuron) and B. catharticus (pyroxsulam). Twelve of the 87 randomly sampled farms (14%) had ALS-inhibitor chlorsulfuron-resistant sow thistles, mostly Sonchus asper but also S. oleraceus. Resistance was confirmed in industry-supplied samples of the grasses Digitaria sanguinalis (nicosulfuron, two maize farms), P. minor (iodosulfuron, one farm), and Lolium spp. (cases included glyphosate, haloxyfop, pinoxaden, iodosulfuron, and pyroxsulam, 9 farms). Industry also supplied Stellaria media samples that were resistant to chlorsulfuron and flumetsulam (ALS-inhibitors) sourced from clover and ryegrass fields from the North and South Island.

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