The spread of herbicide resistant annual ryegrass pollen

Lolium rigidum Gaud. (annual ryegrass) is a major agricultural weed commonly found throughout the southern Australian wheatbelt. It is an obligate outcrossing wind pollinated grass species. Populations of this weed have developed resistance to many different herbicides including glyphosate. The current concern relating to the observance of glyphosate resistance in the fi eld has raised issues relating to the gene fl ow of resistant to susceptible L. rigidum plants within populations. Gene fl ow through pollen dispersal aids the spread of resistance by the fertilisation of susceptible plants with pollen carrying genes for herbicide resistance (Maxwell and Mortimer 1994). Thus, a fi eld study was conducted during 2001 at Roseworthy, South Australia to determine whether pollen from resistant L. rigidum plants could disperse, remain viable and The spread of herbicide resistant annual ryegrass pollen