Identifying short-spike canarygrass (Phalaris brachystachys) accessions resistante to ACCase-inhibiting herbicides using seed bioassay technique

In order to investigate the resistance of short spike canarygrass (Phalaris brachystachys) biotypes to acetyl coenzyme A carboxylase inhibiting herbicides wheat fields of Golestan province, 43 suspected resistance were collected from a different area in 2018. The susceptible biotype was also collected from regions with no chemical control record. The study was carried out in three steps including determination of discriminating concentration for susceptible biotype, screening P. brachystachys biotypes with the discriminating concentrations, and concentration-response experiment for suspected resistant biotypes at Gorgan University of Agricultural Sciences and Natural Resources in 2018. According to the seed bioassay test, the discriminating concentration of sensitive biotype for clodinafop propargyl, diclofop methyl, haloxyfop-r-methyl, cycloxydim and pinoxaden were 0.02, 1.36, 0.03, 0.06 and 0.08 mg a.i.L-1, respectively. In the screening test using the discriminating concentration, 36 (84%), 36 (84%), 19 (44%), 23 (53%), 21 (48%) out of 43 biotypes were identified as suspected resistant to clodinafop propargyl, diclofop methyl, haloxyfop-R-methyl, cycloxydim and pinoxaden, respectively. In general, the results showed that the studied biotypes had different patterns in terms of resistance to different groups of ACCase-inhibiting herbicides. The results of the concentration-response test also showed that among 43 suspected resistance suspected of resistance, 19 biotypes were resistant to all five herbicides.