Lolium rigidum Gaud. biotypes from Greece with Resistance to Glyphosate and other Herbicides

Monoculture and extensive use of glyphosate, ACCase and ALS inhibitors can greatly increase the risks of reduced efficacy of these herbicides on several weeds.In our study, seed samples of five Lolium rigidum accessions were collected from wheat fields and olive orchards in 2012 and 2013.Most of the sites were known as having poor L. rigidum control and pot experiments were conducted in order to evaluate the sensitivity of the biotypes to glyphosate, clodinafop and chlorsulfuron.Data analysis confirmed significant differences in biomass reduction of the several biotypes in response to the herbicides.In particular, one biotype was found to be resistant to glyphosate, one to clodinafop and two to chlorsulfuron, while several biotypes had an intermediate response.These findings confirm that the reported unsatisfactory control of rigid ryegrass could be attributed to herbicide resistance and therefore rotational use of herbicides and several non-chemical methods are required.