First Detection and Characterization of Cross- and Multiple Resistance to Acetyl-CoA Carboxylase (ACCase)- and Acetolactate Synthase (ALS)-Inhibiting Herbicides in Black-Grass ( Alopecurus myosuroides ) and Italian Ryegrass ( Lolium multiflorum ) Populations from Ireland

Vijaya Bhaskar Alwarnaidu Vijayarajan, Patrick D Forristal, Sarah K Cook, David Schilder, Jimmy Staples, Michael Hennessy and Susanne Barth
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Vijaya Bhaskar Alwarnaidu Vijayarajan: Crop Research Centre Oak Park, Teagasc, R93 XE12 Carlow, Ireland
Patrick D Forristal: Crop Research Centre Oak Park, Teagasc, R93 XE12 Carlow, Ireland
Sarah K Cook: Crop Protection Department, Weed Biology, ADAS Boxworth, Boxworth CB23 4NN, UK
David Schilder: Crop Research Centre Oak Park, Teagasc, R93 XE12 Carlow, Ireland
Jimmy Staples: Crop Research Centre Oak Park, Teagasc, R93 XE12 Carlow, Ireland
Michael Hennessy: Crop Research Centre Oak Park, Teagasc, R93 XE12 Carlow, Ireland
Susanne Barth: Crop Research Centre Oak Park, Teagasc, R93 XE12 Carlow, Ireland

Agriculture, 2021, vol. 11, issue 12, 1-15

Abstract: Understanding the resistance spectrum and underlying genetic mechanisms is critical for managing herbicide-resistant populations. In this study, resistance to acetyl CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors was investigated in four suspected resistant populations of Alopecurus myosuroides (ALOMY-001 to ALOMY-004) and Lolium multiflorum (LOLMU-001 to LOLMU-004), collected from cereal production fields in Ireland. Glasshouse assays with three ALOMY-active herbicides [propaquizafop, cycloxydim (ACCase) and mesosulfuron + iodosulfuron (ALS)] or five LOLMU-active herbicides [pinoxaden, propaquizafop, cycloxydim (ACCase) and mesosulfuron + iodosulfuron, pyroxsulam (ALS)], and target-site resistance mechanism studies, based on pyrosequencing, were carried out in each of those populations. For A. myosuroides , Ile-1781-Leu ACCase mutation contributed to propaquizafop and cycloxydim resistance (shoot dry weight GR 50 resistance factor (RF) = 7.5–35.5) in all ALOMY populations, and the independent Pro-197-Thr or Pro-197-Ser ALS mutation contributed to mesosulfuron + iodosulfuron resistance (RF = 3.6–6.6), in ALOMY-002 to ALOMY-004. Most of the analyzed plants for these mutations were homo/heterozygous combinations or only heterozygous. For L. multiflorum, phenotypic resistance to mesosulfuron + iodosulfuron (RF = 11.9–14.6) and pyroxsulam (RF = 2.3–3.1) was noted in all LOLMU populations, but the Pro-197-Gln or Pro-197-Leu ALS mutation (mostly in homozygous status) was identified in LOLMU-001, LOLMU-002 and LOLMU-004 only. Additionally, despite no known ACCase mutations in any LOLMU populations, LOLMU-002 survived pinoxaden and propaquizafop application (RF = 3.4 or 1.3), and LOLMU-003 survived pinoxaden (RF = 2.3), suggesting the possibility of non-target-site resistance mechanisms for ACCase and/or ALS resistance in these populations. Different resistance levels, as evidenced by a reduction in growth as dose increased above field rates in ALOMY and LOLMU, were due to variations in mutation rate and the level of heterozygosity, resulting in an overall resistance rating of low to moderate. This is the first study confirming cross- and multiple resistance to ACCase- and ALS-inhibiting herbicides, highlighting that resistance monitoring in A. myosuroides and L. multiflorum in Ireland is critical, and the adoption of integrated weed management strategies (chemical and non-chemical/cultural strategies) is essential.

Keywords: ACCase; ALS; A. myosuroides; L. multiflorum; herbicide resistance; target-site resistance (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2021
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