Resistance to acetyl‐CoA carboxylase (ACCase)‐inhibiting herbicides in Lolium multiflorum Lam. populations of Argentina

• Published in: Pest management science 2024-12, Vol.80 (12), p.6600-6606
• Main Authors: Depetris, Mara B., Muñiz Padilla, Esteban, Ayala, Fabián, Tuesca, Daniel, Breccia, Gabriela
• Format: Article
• Language: English
• Subjects: ACCase; Acetyl-CoA Carboxylase - antagonists & inhibitors; Acetyl-CoA Carboxylase - genetics; Acetyl-CoA Carboxylase - metabolism; Argentina; Asparagine; clethodim; haloxyfop; Herbicide resistance; Herbicide Resistance - genetics; Herbicides; Herbicides - pharmacology; High resistance; Isoleucine; Italian ryegrass; Lolium - drug effects; Lolium - enzymology; Lolium - genetics; Lolium multiflorum; Lolium perenne; Mutation; pinoxaden; Plant Proteins - antagonists & inhibitors; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Weeds - drug effects; Plant Weeds - enzymology; Plant Weeds - genetics; Population studies; Populations; Resistance factors; Weeds
• ISSN: 1526-498X; 1526-4998; 1526-4998
• DOI: 10.1002/ps.8399

BACKGROUND Italian ryegrass (Lolium multiflorum Lam.) is one of the most troublesome grass weeds in Argentina. The extensive and repetitive use of acetyl‐CoA carboxylase (ACCase)‐inhibiting herbicides has induced resistance in this weed species. The objectives of this study were to quantify the resistance levels to ACCase‐inhibiting herbicides in two resistant populations and to identify the target‐site mutations associated with their resistance. RESULTS Two resistant Italian ryegrass populations, Roldán and H2, were studied. Roldán was a suspected haloxyfop‐resistant population, located in a wheat field from Santa Fe province with a history of ACCase‐inhibiting herbicide use. The H2 population was obtained from the susceptible Hernandarias population (H0) after two cycles of selection with the herbicide quizalofop‐ethyl. Whole‐plant dose–response assays revealed that the resistant populations exhibited a high resistance to haloxyfop, with resistance factors (RF) exceeding 97‐fold. Additionally, both populations showed a moderate resistance to pinoxaden (RF > 7), while maintaining susceptibility to clethodim. Partial chloroplastic ACCase sequences revealed isoleucine‐to‐asparagine substitution at position 2041 (Ile‐2041‐Asn) in both resistant populations. CONCLUSION This work provides a better understanding of cross‐resistance to ACCase‐inhibiting herbicides in L. multiflorum populations and represents the first report of the target‐site mutation Ile‐2041‐Asn conferring resistance in populations from Argentina. © 2024 Society of Chemical Industry. Two Argentinian populations of Italian ryegrass exhibited high resistance to haloxyfop, moderate resistance to pinoxaden, and susceptibility to clethodim. Partial ACCase sequencing identified an isoleucine‐to‐asparagine substitution at position 2041 in both resistant populations.