Resistance of Wild Barley (Hordeum spontaneum L.) Populations Against Sulfosulfuron Herbicide in Different Fars Regions

In order to investigate the resistance of H. spontaneum L. against Sulfosulfuron herbicide, an experiment was conducted in five growing regions of this weed in Fars Province (Iran) in fallow farms that were naturally infected with H. spontaneum. Eight herbicide treatments including 0 (control), 0.25, 0.5, 1, 2, 4, 8 and 16 times the recommended dose (equivalent to 25 g ai.ha-1) in four replicates using the standard error of the mean treatments were compared. The results showed that the level of visual scoring (EWRC) was significantly influenced by Sulfosulfuron herbicide doses. The highest level of weed killing was under treatments of 200 and 400 g ai.ha-1 in all regions of this weed growth. The average survival of wild barley was 8% in different regions with the use of 400 g of herbicide. The dry weight response of H. spontaneum to different doses of Sulfosulfuron evaluated using the fitting of the log-logistic equation, and showed that by consuming up to 100 g of sulfosulfuron, the dry weight of wild barley had a severe reduction of 64%.The resistance degree of different regions biotypes to herbicides was variable considerably. Based on the GR50 ratio, Fasa region was the most resistant of biotype with a resistance degree of 1.22 and then Zarghan biotype was introduced with a resistance degree of 1.11. Eghlid and Jahrom (0.93 and 0.88) were intermediate degree too and Lar was identified as a sensitive biotype.