Resistance Mechanisms to ALS-Inhibiting Herbicides in Papaver rhoeas Populations from Intensively Farmed Cereal Fields

Abstract

The evolution of herbicide resistance in weed populations poses a significant threat to cereal crop productivity, particularly in intensively managed agroecosystems. The present study investigates resistance mechanisms to acetolactate synthase (ALS)-inhibiting herbicides in Papaver rhoeas populations collected from intensively farmed cereal fields. Seed samples were gathered from multiple locations with a history of repeated ALS-inhibitor applications, and dose–response assays were conducted to determine resistance levels. Results revealed substantial variation in herbicide sensitivity among populations, with several exhibiting high levels of resistance compared to susceptible controls. Physiological assays indicated reduced herbicide efficacy in resistant biotypes, characterized by enhanced survival and normal growth following application of ALS-inhibiting compounds. Molecular analysis identified target-site mutations in the ALS gene in certain populations, suggesting altered enzyme binding as a primary resistance mechanism. In addition, evidence of non-target-site resistance mechanisms, including enhanced herbicide metabolism and reduced translocation, was observed in highly resistant populations. Biochemical assays further supported increased detoxification activity in resistant biotypes. The coexistence of multiple resistance mechanisms indicates a complex evolutionary response driven by repeated herbicide selection pressure in intensive cereal systems. The study also highlights the role of agronomic practices, such as continuous cereal monocropping and reliance on a limited herbicide mode of action, in accelerating resistance development. Overall, P. rhoeas populations exhibit both target-site and non-target-site resistance mechanisms to ALS-inhibiting herbicides, emphasizing the need for integrated weed management strategies. These findings contribute to a better understanding of resistance evolution and support the implementation of diversified control measures to manage herbicide-resistant weed populations in cereal agroecosystems.