Incidence of the Endophyte Neotyphodium occultans in annual ryegrass in Southern New South Wales

Annual ryegrass (Lolium rigidum Gaudin) is a major weed of economical and agricultural importance in winter cropping areas in southern Australia. A shift in farming practices over the past 30 years from a focus on cultivation to one of minimum or no-tillage systems with a heavy dependence on herbicides for weed control has led to the evolution of herbicide resistance in many annual ryegrass populations. This has resulted in a loss of diversity in the chemical modes of action left available to control this weed. Studies in other grass/endophyte associations have determined that endophytes have a significant effect on the morphology and physiology of the host plant (Hesse et al., 2003). Whilst there is an abundance of research on perennial ryegrass (Lolium perenne L.) and its symbiotic relationship with the endophyte Neotyphodium lolii, little is known about the relationship of annual ryegrass and N. occultans. This paper reports the incidence of N. occultans in populations of annual ryegrass across southern Australia to provide a benchmark for further studies of this relationship. Endophyte was found in all populations studied but the level of infection varied with an average infestation of 53%.