Investigation of Wild Oat (Avena ludoviciana) Biotypes Resistance to the Clodinafop propargyl, Pinoxaden Herbicides and their Mixture.

In order to evaluate the resistance of wild oat bitypes to clodinafop-propargyle, pinoxaden and their mixture (traxos), collected from Fars and Khoozestan provinces, pot and Petri dish bioassay studies were conducted on 8 suspected to resistance wild oat biotypes as well as one susceptible biotype at Iranian Research Institute of Plant Protection during 2008-2009. In pot bioassay experiments which were conducted as RCBD with four replications, wild oat plants were sprayed during 2-4 leaves stage using 0.25-16 times the recommended dose. Based on herbicide recommended rates (0.8, 0.45 and 1.5 l/ha for clodinafop-propargyle, pinoxaden and traxos, respectively), the applied doses were 0, 16, 32, 64, 128, 256, 512 and 1024 g ai ha^-1 for clodinafop-propargyle, 11.25, 22.5, 45, 90, 180, 360 and 720 g ai ha^-1 for pinoxaden and 16.87, 33.75, 67.5, 135, 270,540 and 1080 g ai ha^-1 for traxos. In Petri dish bioassay studies, after determination of discriminating dose for each herbicide (0.05, 0.03 and 0.01 mg ai/l for clodinafop-propargyle, pinoxaden and traxos respectively), dose response experiments using 0.25-16 times of the discriminating dose were conducted on germinated seeds. The results indicated that all biotypes was resistant to clodinafop propargyl and cross resistance to clodinafop-propargyle, pinoxaden and their mixture (traxos) in Khoozestan populations were confirmed. Greater than 37% of biotypes were controlled by pinoxaden or traxos herbicides and the resistance level  of all biotypes to traxos was lower than other herbicides.