Multiple Pro197ALS Substitutions Endow Resistance to ALS Inhibitors within and among Mayweed Chamomile Populations

Mayweed chamomile seeds were collected from six different fields across the Pacific Northwest. All populations (each collection site was considered a population) were suspected to have some level of acetolactate synthase (ALS) resistance. Greenhouse and laboratory studies were conducted to determine if these populations were resistant to three different classes of ALS inhibitors: sulfonylureas (SU), imidazolinones (IMI), and triazolopyrimidines (TP). A whole-plant dose–response andin vitroALS activity studies confirmed cross-resistance to thifensulfuron + tribenuron/chlorsulfuron (SU), imazethapyr (IMI), and cloransulam (TP); however, resistance varied by herbicide class and population. TwoALSisoforms of theALSgene (ALS1andALS2) were identified in mayweed chamomile; however, only mutations inALS1were responsible for resistance. No mutations were found inALS2. Sequence analysis of the partialALSgene identified four point mutations at position 197 (Pro197to Leu, Gln, Thr, or Ser) in the resistant populations. This study demonstrates genotypic variation associated with cross-resistance to ALS inhibitors within and between populations.

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Cross-Resistance of Eclipta (Eclipta prostrata) in China to ALS Inhibitors Due to a Pro-197-Ser Point Mutation

Weed Science ◽

10.1017/wsc.2017.16 ◽

2017 ◽

Vol 65 (5) ◽

pp. 547-556 ◽

Cited By ~ 5

Author(s):

Dan Li ◽

Xiangju Li ◽

Huilin Yu ◽

Jingjing Wang ◽

Hailan Cui

Keyword(s):

Gene Sequence ◽

Resistance Index ◽

Acetolactate Synthase ◽

Cross Resistance ◽

Eclipta Prostrata ◽

Whole Plant ◽

Plant Assays ◽

Als Inhibitors ◽

Als Inhibitor

Eclipta, widespread in tropical, subtropical, and temperate regions, is one of the main malignant broadleaf weeds and thrives in moist and dryland fields. Field rates of acetolactate synthase (ALS) inhibitors have failed to control eclipta in some farmlands in China. One ALS inhibitor–resistant population (R) collected from Jiangsu province in China was confirmed in the greenhouse in our preliminary work. Whole-plant assays revealed that this R population was highly resistant to four sulfonylureas (pyrazosulfuron-ethyl, 134-fold; bensulfuron-methyl, 172-fold; metsulfuron-methyl, 30-fold; and tribenuron-methyl, 195-fold), two triazolopyrimidines (pyroxsulam, 98-fold; penoxsulam, 30-fold), and one pyrimidinylthio-benzoate (bispyribac-sodium, 166-fold) and was moderately resistant to two imidazolinones (imazethapyr, 10-fold; imazapic, 19-fold). ALS enzyme-activity assays showed insensitivity of the ALS from the R population (resistance index values ranged from 12 to 293) to all of the above ALS inhibitors in vitro. Chromatograms fromALSgene sequence analysis detected a homozygous Pro-197-Ser amino acid substitution in the R population. These results confirmed that the Pro-197-Ser substitution results in broad-spectrum cross-resistance to ALS inhibitors in the eclipta R population. To our knowledge, this study is the first to report broad cross-resistance to ALS inhibitors in eclipta and to obtain the full-lengthALSgene sequence.

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Multiple ALS Mutations Confer Herbicide Resistance in Waterhemp (Amaranthus tuberculatus)

Weed Science ◽

10.1614/ws-06-213.1 ◽

2007 ◽

Vol 55 (5) ◽

pp. 421-428 ◽

Cited By ~ 53

Author(s):

William L. Patzoldt ◽

Patrick J. Tranel

Keyword(s):

Leaf Disc ◽

Acetolactate Synthase ◽

Cross Resistance ◽

Whole Plant ◽

Amaranthus Tuberculatus ◽

Susceptible Control ◽

Als Inhibitors ◽

Als Inhibitor ◽

Disc Assay

In a survey of herbicide responses among Illinois waterhemp half-sib populations, several were observed with differential responses to imazethapyr and thifensulfuron, two acetolactate synthase (ALS)–inhibiting herbicides. Plants from two waterhemp populations were verified resistant to imazethapyr, but susceptible to chlorimuron, using a nondestructive leaf-disc assay. Sequencing of the ALS gene revealed that imazethapyr-resistant waterhemp plants from both populations had inferred amino acid substitutions at position 653 of ALS. Depending on the population, the serine at position 653 of ALS was substituted with either asparagine (S653N) or threonine (S653T). Waterhemp lines were derived from each population to create uniformly imidazolinone-resistant (IR) waterhemp biotypes, designated IR-62 and IR-101. ALS-inhibitor responses of each IR biotype were compared with a previously identified ALS inhibitor–resistant biotype with a tryptophan to leucine substitution at position 574 (W574L) and an herbicide-susceptible control. Whole-plant dose–response experiments with waterhemp biotypes containing W574L, S653N, or S653T mutations indicated that each biotype was resistant to imazethapyr, but only the biotype with a W574L mutation was resistant to thifensulfuron. In vitro ALS-activity assays revealed unique patterns of cross-resistance among protein extracts derived from each biotype in response to imazethapyr, thifensulfuron, cloransulam, and pyrithiobac. In conclusion, three different forms of target-site–based resistance to ALS inhibitors have been identified in waterhemp.

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

Weed Science ◽

10.1017/s0043174500090123 ◽

1998 ◽

Vol 46 (1) ◽

pp. 24-29 ◽

Cited By ~ 8

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.

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Target site–based penoxsulam resistance in barnyardgrass (Echinochloa crus-galli) from China

Weed Science ◽

10.1017/wsc.2019.5 ◽

2019 ◽

Vol 67 (3) ◽

pp. 281-287 ◽

Cited By ~ 1

Author(s):

Jiapeng Fang ◽

Tingting Liu ◽

Yuhua Zhang ◽

Jun Li ◽

Liyao Dong

Keyword(s):

Amino Acid ◽

Amino Acid Sequence ◽

Acetolactate Synthase ◽

Target Site ◽

Cross Resistance ◽

Predicted Amino Acid Sequence ◽

Sequence Analyses ◽

Als Inhibitors ◽

Higher Sensitivity

AbstractBarnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is acknowledged to be the most troublesome weed in rice fields in Anhui and Jiangsu provinces of China. It cannot be effectively controlled using certain acetolactate synthase (ALS)-inhibiting herbicides, including penoxsulam. Echinochloa crus-galli samples with suspected resistance to penoxsulam were collected to identify the target site–based mechanism underlying this resistance. Populations AXXZ-2 and JNRG-2 showed 33- and 7.3-fold resistance to penoxsulam, respectively, compared with the susceptible JLGY-3 population. Cross-resistance to other ALS inhibitors was reported in AXXZ-2 but not in JNRG-2, and occasionally showed higher sensitivity than JLGY-3. In vitro ALS activity assays revealed that penoxsulam concentrations required to inhibit 50% of ALS activity were 11 and 5.2 times greater in AXXZ-2 and JNRG-2, respectively, than in JLGY-3. DNA and predicted amino acid sequence analyses of ALS revealed Ala-205-Val and Ala-122-Gly substitutions in AXXZ-2 and JNRG-2, respectively. Our results indicate that these substitutions in ALS are at least partially responsible for resistance to penoxsulam.

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Resistance to Bensulfuron-Methyl in Water Plantain (Alisma plantago-aquatica) Populations from Chilean Paddy Fields

Weed Technology ◽

10.1614/wt-08-078.1 ◽

2008 ◽

Vol 22 (4) ◽

pp. 602-608 ◽

Cited By ~ 2

Author(s):

Rodrigo Figueroa ◽

Marlene Gebauer ◽

Albert Fischer ◽

Marcelo Kogan

Keyword(s):

Weed Management ◽

Wide Spectrum ◽

Acetolactate Synthase ◽

Rice Fields ◽

Integrated Weed Management ◽

Cross Resistance ◽

Content Type ◽

Als Inhibitors

Bensulfuron-methyl (BSM) has been one of the most widely used herbicides in Chilean rice fields because it controls a wide spectrum of weeds and does not require field drainage for application. However, failures of BSM to control water plantain in rice fields have been noted since 2002. We assessed BSM effects on suspected resistant (CU1 and CU2) and susceptible (AN1) water plantain accessions collected in Chilean rice fields during 2004 and 2005. BSM rates resulting in 50% growth reduction (GR50) of CU2 and CU1 plants were 12- and 33-fold higher than for AN1 plants, respectively. Acetolactate synthase (ALS) activity assays in vitro suggested resistance in CU1 and CU2 was due to an ALS enzyme with reduced BSM sensitivity compared to the AN1 biotype. Resistance indices (RI), or ratios of the resistant to susceptibleI50values (BSM rate to inhibit ALS-enzyme activity by 50%), were 266 (CU2/AN1) and > 38,462 (CU1/AN1). This agreed with in vivo ALS activity assays whereRIwere 224 (CU2/AN1) and > 8,533 (CU1/AN1). Resistance levels detected in whole-plant or in vivo ALS activity assays were orders of magnitude lower than those detected in in vitro ALS activity studies suggesting nontarget site mechanisms may have mitigated BSM toxicity. However, a consistent ranking of BSM sensitivity levels (AN1 > CU2 > CU1) throughout all three types of assays suggests resistance is primarily endowed by low target site sensitivity. We conclude that susceptible and resistant water plantain biotypes coexist in Chilean paddies, and the use of integrated weed management involving herbicides with a different mode of action would be imperative to prevent further evolution of resistance to BSM and possibly cross-resistance to other ALS inhibitors. In vitro ALS-enzyme assays provided the best discrimination of resistance levels between biotypes.

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Corn (Zea mays) acetolactate synthase sensitivity to four classes of ALS-inhibiting herbicides

Weed Science ◽

10.1017/s004317450009010x ◽

1998 ◽

Vol 46 (1) ◽

pp. 8-12 ◽

Cited By ~ 20

Author(s):

Terry R. Wright ◽

Donald Penner

Keyword(s):

Plant Protection ◽

Enzyme Level ◽

Acetolactate Synthase ◽

Application Rate ◽

Field Application ◽

Cross Resistance ◽

Commercial Development ◽

Whole Plant ◽

Imidazolinone Herbicides

In vitro acetolactate synthase (ALS) activity from three commercial imidazolinone-resistant corn hybrids (ICI 8692 IT, Pioneer 3751 IR, and Ciba 4393 IMR) was compared to imidazolinone-sensitive isogenic hybrid controls for sensitivity to 11 herbicides representing four classes of ALS-inhibiting herbicide chemistry. Acetolactate synthase activity from Pioneer IR and Ciba IMR was cross-resistant to all four classes of ALS inhibitors, ranging from 48- to 5,000-fold. The ICI IT hybrid displayed only four- to eightfold resistance to the six imidazolinone herbicides and the pyrimidinylthiobenzoate herbicide, pyrithiobac, but no cross-resistance to the sulfonylurea and triazolopyrimidine sulfonanilide herbicides. The four- to eightfold enzyme resistance to imidazolinone herbicides provides whole-plant resistance; however, the sevenfold enzyme resistance to pyrithiobac was insufficient to afford whole-plant protection to a field application rate of the herbicide. A second imidazolinone-specific resistance allele,XI-12, currently under commercial development, was examined for the level of dominance at the enzyme level. In the heterozygous state, imazethapyr resistance was fivefold, compared to 250-fold in the homozygous condition, indicatingXI-12is a semidominant trait. No cross-resistance to nicosulfuron or primisulfuron was observed in the heterozygousXI-12hybrid extracts nor to nicosulfuron in theXI-12homozygote; however, a fivefold resistance to primisulfuron was detected in theXI-12homozygote.

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Acetolactate synthase activity in Euphorbia heterophylla resistant to ALS- and protox- inhibiting herbicides

Planta Daninha ◽

10.1590/s0100-83582013000400013 ◽

2013 ◽

Vol 31 (4) ◽

pp. 867-874 ◽

Cited By ~ 6

Author(s):

E. Xavier ◽

M.C. Oliveira ◽

M.M. Trezzi ◽

R.A. Vidal ◽

F. Diesel ◽

...

Keyword(s):

Acetolactate Synthase ◽

Inhibitory Effect ◽

Cross Resistance ◽

Multiple Resistance ◽

Vitro Assay ◽

Susceptible Population ◽

Resistance Factors ◽

Als Inhibitors ◽

High Inhibitory Effect

The objective of this study was to determine the activity of the enzyme acetolactate synthase in biotypes of wild poinsettia (Euphorbia heterophylla) with multiple resistance to ALS- and Protox- inhibitors in the presence and absence of imazapyr, imazethapyr and nicosulfuron. We conducted in vitro assay of ALS enzyme extracted from plants of Vitorino, Bom Sucesso do Sul and Medianeira biotypes (with multiple resistance) and a susceptible population in the absence and presence of imazapyr, imazethapyr and nicosulfuron. In the absence of herbicides, biotypes with multiple resistance showed higher affinity for the substrate of the enzyme compared with the susceptible population. The herbicides imazapyr, imazethapyr and nicosulfuron had little effect on the enzyme activity of ALS-resistant biotypes and, conversely, high inhibitory effect on ALS of the susceptible population. Resistance factors were very high, greater than 438, 963 and 474 for Vitorino, Bom Sucesso do Sul and Medianeira biotypes, respectively. The resistance to ALS inhibitors is due to the insensitivity of ALS to herbicides of both imidazolinone and sulfonylurea groups, characterizing a cross-resistance.

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The Evidence for Reduced Glyphosate Efficacy on Acetolactate Synthase–Inhibiting Herbicide-Resistant Yellow Nutsedge (Cyperus esculentus)

Weed Science ◽

10.1614/ws-d-15-00182.1 ◽

2016 ◽

Vol 64 (3) ◽

pp. 389-398

Author(s):

Parsa Tehranchian ◽

Jason K. Norsworthy ◽

Matheus Palhano ◽

Nicholas E. Korres ◽

Scott McElroy ◽

...

Keyword(s):

Amino Acid ◽

Production Systems ◽

Acetolactate Synthase ◽

Dry Weight ◽

Cross Resistance ◽

Purple Nutsedge ◽

Yellow Nutsedge ◽

Epsps Gene ◽

Treated Leaf ◽

Als Inhibitors

A yellow nutsedge biotype (Res) from an Arkansas rice field has evolved resistance to acetolactate synthase (ALS)-inhibiting herbicides. TheResbiotype previously exhibited cross-resistance to ALS inhibitors from four chemical families (imidazolinone, pyrimidinyl benzoate, sulfonylurea, and triazolopyrimidine). Experiments were conducted to evaluate alternative herbicides (i.e., glyphosate, bentazon, propanil, quinclorac, and 2,4-D) currently labeled in Arkansas rice–soybean production systems. Based on the percentage of aboveground dry weight reduction, control of the yellow nutsedge biotypes with the labeled rate of bentazon, propanil, quinclorac, and 2,4-D was < 44%. Glyphosate (867 g ae ha−1) resulted in 68 and > 94% control of theResand susceptible yellow nutsedge biotypes, respectively, at 28 d after treatment. Dose-response studies were conducted to estimate the efficacy of glyphosate on theResbiotype, three susceptible yellow nutsedge biotypes, and purple nutsedge. Based on the dry weights, theResbiotype was ≥ 5- and ≥ 1.3-fold less responsive to glyphosate compared to the susceptible biotypes and purple nutsedge, respectively. Differences in absorption and translocation of radiolabeled glyphosate were observed among the yellow nutsedge biotypes and purple nutsedge. The susceptible biotype had less14C-glyphosate radioactivity in the tissues above the treated leaf and greater radioactivity in tissues below the treated leaf compared to theResbiotype and purple nutsedge. Reduced translocation of glyphosate in tissues below the treated leaf of theResbiotype could be a reason for the lower glyphosate efficacy in theResbiotype. No amino acid substitution that would correspond to glyphosate resistance was found in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene of theResbiotype. However, an amino acid (serine) addition was detected in the EPSPS gene of theResbiotype; albeit, it is not believed that this addition contributes to lower efficacy of glyphosate in this biotype.

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Evaluation of the phytotoxicity of 2,4-diacetylphloroglucinol and Pseudomonas brassicacearum Q8r1-96 on different wheat cultivars

Phytopathology ◽

10.1094/phyto-07-20-0315-r ◽

2021 ◽

Author(s):

Mingming Yang ◽

Linda S Thomashow ◽

David M Weller

Keyword(s):

Seed Germination ◽

Pacific Northwest ◽

Root Colonization ◽

The United States ◽

Wheat Cultivars ◽

The Pacific ◽

Root Necrosis ◽

Growth Promoting ◽

Pseudomonas Brassicacearum

Pseudomonas brassicacearum Q8r1-96 and other 2,4-diacetylphloroglucinol (DAPG)-producing pseudomonads of the Pseudomonas fluorescens complex possess both biocontrol and growth-promoting properties and play an important role in suppression of take-all of wheat in the Pacific Northwest (PNW) of the United States. However, P. brassicacearum can also reduce seed germination and cause root necrosis on some wheat cultivars. We evaluated the effect of Q8r1-96 and DAPG on the germination of 69 wheat cultivars that have been or currently are grown in the PNW. Cultivars varied widely in their ability to tolerate P. brassicacearum or DAPG. The frequency of germination of the cultivars ranged from 0 to 0.87 and from 0.47 to 0.90 when treated with Q8r1-96 and DAPG, respectively. There was a significant positive correlation between the frequency of germination of cultivars treated with Q8r1-96 in assays conducted in vitro and in the greenhouse. The correlation was greater for spring than for winter cultivars. In contrast, the effect of Q8r1-96 on seed germination was not correlated with that of DAPG alone, suggesting that DAPG is not the only factor responsible for the phytotoxicity of Q8r1-96. Three wheat cultivars with the greatest tolerance and three cultivars with the least tolerance to Q8r1-96 were tested for their ability to support root colonization by strain Q8r1-96. Cultivars with the greatest tolerance supported significantly greater populations of strain Q8r1-96 than those with the least tolerance to the bacteria. Our results show that wheat cultivars differ widely in their interaction with P. brassicacearum and the biocontrol antibiotic DAPG.

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Common Cocklebur (Xanthium strumarium) Resistance to Selected ALS-Inhibiting Herbicides

Weed Technology ◽

10.1017/s0890037x00042901 ◽

1997 ◽

Vol 11 (2) ◽

pp. 241-247 ◽

Cited By ~ 16

Author(s):

Christy L. Sprague ◽

Edward W. Stoller ◽

Loyd M. Wax

Keyword(s):

Acetolactate Synthase ◽

Cross Resistance ◽

Xanthium Strumarium ◽

Laboratory Studies ◽

Whole Plant ◽

Plant Level

Five biotypes of common cocklebur that were not controlled with acetolactate synthase (ALS)-inhibiting herbicides were tested in greenhouse and laboratory studies to determine the magnitude of resistance and cross-resistance to four ALS-inhibiting herbicides. In vivo inhibition of ALS was also evaluated. Based on phytotoxicity, all five ALS-resistant biotypes of common cocklebur were > 390 times more resistant than the susceptible biotype to imazethapyr. However, only four of these biotypes were also resistant to another imidazolinone, imazaquin. Two biotypes were cross-resistant to the sulfonylurea, chlorimuron, and the triazolopyrimidine sulfonanilide, NAF-75. One biotype demonstrated intermediate susceptibility to imazaquin, chlorimuron, and NAF-75. In all cases, the resistance exhibited at the whole plant level was associated with an insensitive ALS.

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