Monitoring the resistance status of canarygrass (Phalaris minor ) accessions to some commonly used herbicides in wheat fields of five provinces in Iran

The spread of weed resistance to herbicides is expanding in Iran; therefore, monitoring of resistance to the most commonly used herbicides and evaluation of cross-resistance to the herbicides were carried out on 38 canarygrass accessions collected from wheat fields in five provinces (Golestan, Fars, Khuzestan, Ardabil and Tehran provinces) of Iran. The whole plant screening test was conducted with four replications in the greenhouse of Iranian Research Institute of Plant Protection in 2019. Plants at the two- to -three leaves stage were exposed to the recommended field dose of herbicides. Four weeks after spraying, the percentage of fresh and dry weights and plants survival were measured. Of the 38 accessions, 13 (34%), eight (21%), two (5%) and one (about 2.5%) accessions were classified to being high resistant and suspected resistant to mesosulfuron+iodosulfuron+mefenpyr-diethyl (Atlantis), clodinafop-propargyl (Topik), pinoxaden (Axial), and mesosulfuron+iodosulfuron+difloficane+mefenpyr- diethyl (Othello), respectively. Overall, mesosulfuron+iodosulfuron+diflufenican+mefenpyr- diethyl and pinoxaden showed higher efficiency on the accessions than the other two herbicides. Cross-resistance to clodinafop-propargyl and pinoxaden herbicides was observed in two accessions (GM1 from Golestan, PA1 from Ardabil). One accession (AL1) from Golestan province showed resistance to mesosulfuron+iodosulfuron+mefenpyr-diethyl and mesosulfuron+iodosulfuron+diflufenican+mefenpyr- diethyl. Resistance to ACCase inhibitors in the accessions collected from Khuzestan province and the cross-resistance in the accessions collected from Golestan and Ardabil provinces showed the rapid development of herbicide resistance problem in Iran, especially in the mentioned provinces. Therefore, it is necessary to pay more attention to the prevention, delay and management of canarygrass herbicide-resistant accessions.