Study on diclofop-methyl resistance in wild oat (Avena ludoviciana): A comparison between the whole plant and the seed bioassays

In order to investigate the resistance of wild oat populations to diclofop-methyl a greenhouse and laboratory experiments were carried out during 2006. The collected wild oat biotypes have already shown several cases of resistance to diclofop-methyl in different locations in Iran. Greenhouse experiments included screening tests and dose response experiments where as, seed bioassay experiment included ID50 determination and dose response experiments. The treatments consisted of wild oat populations included FR1, FR2, FR3, FR4, collected from Fars province, MR1, MR2, MR3, collected from Markazi province, KR1, KR2, KR3, collected from Khuzestan province and S, collected from a location which had never been treated previously with any graminicide. Results indicated that KR1, KR2 and KR3 populations showed resistance to diclofop-methyl according to whole plant and seed bioassay trials. Resistance ratios tested populations were different and ratios that obtained at seed bioassay were lower than those obtained at whole plant assay. It is also concluded that the seed bioassay could be used as a simple, comparatively rapid, inexpensive and accurate method for identifying wild oat populations resistant to Acetyl CoA carboxylase inhibitors.