Resistance of Winter Wild Oat (Avena ludoviciana) Populations to Pinoxaden in Fars Province

To evaluate the resistance of winter wild oat (Avena ludoviciana) biotypes to pinoxaden, Whole plant bioassay experiment was conducted at Department of Weed Science, Plant Protection Institute, in 2008. Twelve putative resistant and one susceptible populations that had been collected from wheat fields of Fars province were surveyed in a dose-response experiment. All populations were exposed to a range of pinoxaden dosages including 0.25 to 16 times the recommended dose (45 g a.i. ha-1). Results indicated that herbicide resistance was occurred in major of winter wild oat populations. The resistance index based on dry weight and plant survival was estimated in the range from 2.21 to 26.89 and 1.43 to 18.48, respectively. Four of 12 populations (F2, S2, S4 and ES4) showed high resistant to pinoxaden with resistance ratio >12 fold greater than the susceptible population. But the populations of M2 and ES indicated intense sensitivity to pinoxaden.