Evaluation of Resistance to Diclofop-Methyl, Clodinafop Propargyl Herbicides in Phalaris minor Populations from Iran. Javid Gherekhloo1, Mohammad Rashed Mohassel1, Mehdi Nassiri Mahallati1, Eskandar Zand2, Ali Ghanbari1, Rafael De Prado3, Maria Osuna Ruiz4; 1Ferdowsi University of Mashhad, Mashhad, Khorasan Razavi, Iran; 2Plant Protection Research Institute, Tehran, Iran; 3Universidad de Cordoba, Cordoba, Spain; 4Finca La Orden, Badajoz, Spain Diclofop-methyl and clodinafop propargyl are two Aryloxyphenoxy propionate herbicides which are commonly used post emergence to control grass weeds such as Avena spp and Phalaris spp in wheat fields of Iran. In recent years, we received many reports about poor control of Phalaris minor in wheat fields by aryloxyphenoxy propionate herbicides from two provinces of Iran where these graminicides had been applied for several years. Forty-four populations of little seed canary grass, sampled from wheat fields of Fars and Golestan provinces, were studied under controlled conditions in greenhouse and laboratory to confirm resistance to ACCase herbicides. Pre-screening experiment was done in greenhouse and the seedlings were sprayed with recommended dose of diclofop methyl. From this experiment, 9 populations including 8 potentially resistant and one susceptible were selected, and a dose response experiment with 9 doses was conducted to determine the resistance factor. The populations showed different resistance levels and these results suggest that the resistance in these biotypes are may be because of different mechanisms. Selected populations were also subjected to clodinafop propargyl in a dose-response assay. Results showed three populations have cross-resistance to clodinafop propargyl. Bioassay in Petridish confirmed the results of dose-response in greenhouse. But the resistant factors were higher than greenhouse assay for all populations and the two applied herbicides.

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