The role of fungal endophyte infection in the evolution of Lolium multiflorum resistance to diclofop-methyl

Diclofop-methyl resistance was evaluated in populations of Italian ryegrass (Lolium multiflorum Lam.) infected and uninfected with fungal endophyte (N eotyphodium). Survival was tested in susceptible populations using herbicid e screening. The results served as inputs to a model for investigating the role of endophyte infection in the evolution of L. multiflorum resistance t o herbicide. The tolerance of infected plants varied depending on the origi n of the population and the herbicide dose. Only in some populations and at some diclofop-methyl doses did plants infected with these endophytes have higher survivorship than endophyte-free plants. The model demonstrated that endophytes might indeed play an important role in the evolution of herbici de-resistant weeds, delaying the appearance of herbicide resistance.