Resistance of rye grass (Lolium rigidium L.) biotypes to clodinafob propargil herbicide in Fars province

In order to investigate the resistance of ryegrass to clodinafop propargil، greenhouse trials were carried out during 2007. Treatments included 7 ryegrass biotypes suspected to resistant to clodinafop propargil and a susceptible biotype collected from Fars province. Greenhouse trials included two distinct section، screening tests and dose response. Screening test was conducted for 7 biotypes as a completely randomized design with 4 replications using recommended dose of clodinafop propargil (64 g ai/ha). Dose response was also conducted using 9 dose of clodinafob propargil (0-32 time of recommended dose). Screening test was conducted performing EWRC visual rating، number of survived plant after herbicide application (NO) and dry weight of shoot biomass survived plant after herbicide application (DM). Number (DRN) and dry weight (DRD) of survived ryegrass after herbicide application were also measured in dose response test. Results indicated that RF2، RF4، RF6 and RF1 showed highest resistance to clodinafob propargil and all of the EWRC، NO، DM، DRN and DRD indices confirmed it properly. It is concluded that screen test using recommended dose could be advised as the powerful method of preliminary determination of resistant biotypes. It is also suggested to use fresh weight to standard check index as well as DRN and DRD due to different results in dose response test.