An <scp>ALA<sub>122</sub>THR</scp> substitution in the <scp>AHAS</scp>/<scp>ALS</scp> gene confers imazamox‐resistance in <scp><i>Aegilops cylindrica</i></scp>

Rodríguez, Jeanette; Hauvermale, Amber L.; Carter, Arron H.; Zuger, Rachel J.; Burke, Ian C.

doi:10.1002/ps.6498

Cited by 5 publications

(2 citation statements)

References 27 publications

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“…Target-site mutations of Pro197 and Ser653 conferring imazamox resistance in downy brome ( Bromus tectorum L.) populations from Oregon and Montana, respectively, have previously been documented (Kumar et al 2017; Park and Mallory-Smith 2004). Similarly, an Ala 122 Thr point mutation in the ALS gene has been reported to confer a high-level resistance to imazamox in a jointed goatgrass ( Aegilops cylindrical L.) population from Washington (Rodriguez et al 2021). The absence of any known target-site mutations in the ALS genes of IMI-R shattercane from northwestern Kansas warrants further investigation on the possibility of non-target site resistance mechanisms.…”

Section: Resultsmentioning

confidence: 98%

Characterization of imazamox-resistant shattercane (Sorghum bicolor L.) populations from Kansas

Kumar,

Liu,

Chauhan

et al. 2023

Weed Technol

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Shattercane is a problematic summer annual grass weed species in regions that produce grain sorghum. Three shattercane populations (DC8, GH4, and PL8) collected from sorghum fields from northwestern Kansas survived the field-use rate (52 g ha−1) of postemergence-applied imazamox. The main objectives of this research were to 1) confirm and characterize the level of resistance to imazamox in putative imazamox-resistant (IMI-R) shattercane populations, 2) investigate the underlying mechanism of resistance, and 3) determine the effectiveness of postemergence herbicides for controlling IMI-R populations. A previously known imazamox susceptible (SUS) shattercane population from Rooks County, KS, was used. All three putative populations exhibited a 4.1-fold to 6.0-fold resistance to imazamox compared with the SUS population. The ALS gene sequences from all IMI-R populations did not reveal any known target-site resistance mutations. A pretreatment with malathion, which inhibits cytochrome P450, followed by imazamox at various doses, reversed the resistance phenotype of the PL8 population. In a separate greenhouse study, postemergence treatments with nicosulfuron, quizalofop, clethodim, and glyphosate resulted in ≥96% injury to all IMI-R populations. The lack of known ALS target-site mutations and the reversal of resistance phenotype by malathion suggest the possibility of metabolism-based resistance to imazamox in PL8 shattercane population.

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Section: Resultsmentioning

confidence: 98%

Characterization of imazamox-resistant shattercane (Sorghum bicolor L.) populations from Kansas

Kumar,

Liu,

Chauhan

et al. 2023

Weed Technol

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“…However, it has been ascertained that the long-term use of the same MOA herbicides is one of the greatest risk factors for rapid resistance evolution (Norsworthy et al 2012). Unsurprisingly, resistance to mesosulfuron-methyl has occurred in diverse arable weeds in recent years, such as jointed goatgrass ( Aegilops cylindrica Host) (Rodriguez et al 2021), B. sterilis (Sen et al 2021), and Italian ryegrass [ Lolium perenne L. ssp. multiflorum (Lam.)…”

Section: Resultsmentioning

confidence: 99%

Molecular mechanism of resistance to mesosulfuron-methyl in shortawn foxtail (Alopecurus aequalis) from China

Tang

Wang

et al. 2023

Weed Sci

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Shortawn foxtail (Alopecurus aequalis Sobol.) is an obligate wetland plant that is widely distributed throughout Europe, temperate Asia, and North America. In China, it is widespread in the middle and lower reaches of the Yangtze River as a noxious weed in winter cropping fields with a rice (Oryza sativa L.) rotation. The acetolactate synthase (ALS)-inhibiting herbicide mesosulfuron-methyl has been widely used to control annual grass and broadleaf weeds, including A. aequalis, in wheat fields, leading to the selection of herbicide-resistant weeds. In this study, an A. aequalis population AHFT-4 survived mesosulfuron-methyl at its field-recommended rate (9 g ai ha-1) was collected in Anhui Province. Single-dose testing confirmed that suspected AHFT-4 had evolved resistance to mesosulfuron-methyl. Target gene sequencing revealed a resistance mutation of Pro-197-Ala in ALS1 of the resistant plants, and a derived cleaved amplified polymorphic sequence (dCAPS) marker was developed to specifically detect the mutation. Relative expression assay showed no significant difference in ALS expression between AHFT-4 and a susceptible population without or with mesosulfuron-methyl treatment. Whole-plant dose-response bioassays indicated that AHFT-4 had evolved broad-spectrum cross-resistance to ALS-inhibiting herbicides of all five chemical families tested, with GR50 resistance index (RI) values ranging from 21 to 206. However, it remained susceptible to the photosystem II inhibitor isoproturon. Pre-treatment with the cytochrome P450 inhibitor malathion or the glutathione S-transferase inhibitor 4-chloro-7-nitrobenzoxadiazole (NDB-Cl) had no significant effects on the resistance of AHFT-4 to mesosulfuron-methyl. To our knowledge, this study reports for the first time the ALS gene Pro-197-Ala substitution conferring broad-spectrum cross-resistance to ALS-inhibiting herbicides in A. aequalis.

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Survey of ACCase and ALS resistance in winter annual grasses identifies target‐site and nontarget‐site imazamox resistance in Secale cereale

Soni

Westra

Allegretta³

et al. 2022

Pest Management Science

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Background Early detection of herbicide resistance in weeds is crucial for successful implementation of integrated weed management. We conducted a herbicide resistance survey of the winter annual grasses feral rye (Secale cereale), downy brome (Bromus tectorum), and jointed goatgrass (Aegilops cylindrica) from Colorado winter wheat production areas for resistance to imazamox and quizalofop. Results All samples were susceptible to quizalofop. All downy brome and jointed goatgrass samples were susceptible to imazamox. Out of 314 field collected samples, we identified three feral rye populations (named A, B, and C) that were imazamox resistant. Populations B and C had a target‐site mechanism with mutations in the Ser653 residue of the acetolactate synthase (ALS) gene to Asn in B and to Thr in C. Both populations B and C had greatly reduced ALS in vitro enzyme inhibition by imazamox. ALS feral rye protein modeling showed that steric interactions induced by the amino acid substitutions at Ser653 impaired imazamox binding. Individuals from population A had no mutations in the ALS gene. The ALS enzyme from population A was equally sensitive to imazamox as to known susceptible feral rye populations. Imazamox was degraded two times faster in population A compared with a susceptible control. An oxidized imazamox metabolite formed faster in population A and this detoxification reaction was inhibited by malathion. Conclusion Population A has a nontarget‐site mechanism of enhanced imazamox metabolism that may be conferred by cytochrome P450 enzymes. This is the first report of both target‐site and metabolism‐based imazamox resistance in feral rye. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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An ALA₁₂₂THR substitution in the AHAS/ALS gene confers imazamox‐resistance in Aegilops cylindrica

Cited by 5 publications

References 27 publications

Characterization of imazamox-resistant shattercane (Sorghum bicolor L.) populations from Kansas

Characterization of imazamox-resistant shattercane (Sorghum bicolor L.) populations from Kansas

Molecular mechanism of resistance to mesosulfuron-methyl in shortawn foxtail (Alopecurus aequalis) from China

Survey of ACCase and ALS resistance in winter annual grasses identifies target‐site and nontarget‐site imazamox resistance in Secale cereale

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An ALA122THR substitution in the AHAS/ALS gene confers imazamox‐resistance in Aegilops cylindrica

Cited by 5 publications

References 27 publications

Characterization of imazamox-resistant shattercane (Sorghum bicolor L.) populations from Kansas

Characterization of imazamox-resistant shattercane (Sorghum bicolor L.) populations from Kansas

Molecular mechanism of resistance to mesosulfuron-methyl in shortawn foxtail (Alopecurus aequalis) from China

Survey of ACCase and ALS resistance in winter annual grasses identifies target‐site and nontarget‐site imazamox resistance in Secale cereale

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An ALA₁₂₂THR substitution in the AHAS/ALS gene confers imazamox‐resistance in Aegilops cylindrica