Study on the Resistance of Problematic Grass Weed Species to Clodinafop Propargyl in Wheat in Iran

To evaluate the resistance of wild oat (Avena ludoviciana), annual ryegrass (Lolium rigidum) and littleseed canarygrass (Phalaris spp.) in wheat fields of Fars, Khouzestan, Golestan and Ilam Provinces of Iran to clodinafop-propargyl herbicide from ACCase inhibitors of aryloxyphenoxy propionate classes, 6 separate indoor experiments were conducted in the greenhouses of the Department of Weed Research in the Iranian Research Institute for Plant Protection. The experiments were conducted by using 19 populations of wild oat (including 15 questionably resistant populations and 4 susceptible populations), 14 littleseed canarygrass populations (including 10 suspected-resistant populations and 4 susceptible populations) and 9 annual ryegrass populations (including 8 questionably resistant populations and 1 susceptible mass) from Fars Province, 4 populations of wild oat (including 3 questionably resistant populations and 1 susceptible mass)from Lorestan Province, 17 littleseed canarygrass populations (including 16 probably resistant populations and 1 susceptible mass) from Khouzestan Province, and 12 littleseed canarygrass populations (including 11 questionably resistant populations and 1 susceptible mass) from Golestan Province. All the experiments were conducted separately in the form of a Randomized Complete Block Design (RCBD). A pot under no-herbicide application was also included as control. The remaining weeds number and dry weight percentage were calculated 30 days after herbicide application, and were then compared with their relative figures before herbicide application. A mass was recognized resistant only if it retained80% of its number and 50% of its dry weight, in comparisonto the control. On this basis, 4 resistant and 2 questionably resistant littleseed canarygrass populations, 6 resistant and 3 questionably resistant wild oat populations and 5 resistant and 3 questionably resistant Annual Ryegrass populations were identified in Fars Province. In Ilam Province, 2 resistant wild oat populations were identified. Overall, in this experiment 75 populations including 63 questionably resistant and 12 susceptible populations were evaluated. Amongst the 63 questionably resistant populations (including 37 littleseed canarygrass, 18 wild oat and 8 annual ryegrass populations), 28 totally resistant populations (including 12 littleseed canarygrass, 11 wild oat and 8 annual ryegrass populations) and 10 probably resistant (consisting of 4 littleseed canarygrass populations, 3 wild oat populations and 3 annual ryegrass populations) were detected. In other words, approximately 60% (44% resistant and 16% probably resistant) of all evaluated questionably resistant populations were identified as resistant and probably resistant.