Herbicide Resistance Mechanisms in Lolium rigidum Populations: Target-Site Mutations and Metabolic Detoxification

Abstract

Herbicide resistance in weed populations has become a major challenge to sustainable crop production, reducing the effectiveness of widely used chemical weed control strategies. The present study investigated the herbicide resistance mechanisms in Lolium rigidum populations with particular emphasis on target-site mutations and metabolic detoxification processes. Resistant and susceptible populations were collected from agricultural fields with a long history of herbicide application and evaluated through physiological, biochemical, and molecular analyses. Herbicide response assays demonstrated significant differences in survival and growth between resistant and susceptible populations following treatment with commonly used herbicides. Molecular characterization identified specific target-site mutations in genes associated with herbicide mode of action, indicating reduced herbicide binding efficiency in resistant plants. In addition to target-site resistance, enhanced metabolic detoxification mechanisms were observed through increased activity of detoxifying enzymes including cytochrome P450 monooxygenases, glutathione S-transferases, and other metabolic pathways involved in herbicide degradation. Resistant populations exhibited the ability to rapidly metabolize and detoxify herbicidal compounds before they reached toxic concentrations within plant tissues. The coexistence of multiple resistance mechanisms contributed to high levels of resistance and cross-resistance to different herbicide groups. Environmental selection pressure resulting from repeated herbicide use was identified as a major factor driving resistance evolution in L. rigidum populations. The findings provide valuable insights into the molecular and biochemical basis of herbicide resistance and emphasize the need for integrated weed management strategies incorporating crop rotation, herbicide diversification, and non-chemical control methods to delay further resistance development and sustain effective weed control in agricultural systems.