Investigating cross-resistance of resistant-Phalaris minor to ACCase herbicides

Littleseed canarygrass (Phalaris minor) is one of the most important weeds in wheat and barley fields of Iran. Recently a biotype (SR3) of this weed has been detected in wheat fields of Fars province which has developed resistance to clodinafop-propargyl, fenoxaprop-P-ethyl and diclofop-methyl herbicides. In order to investigate the cross-resistance of SR3 biotype to cyclohexanedione and phenlypyrazolin herbicides, a dose-response assay was conducted at Gorgan University of Agricultural Sciences and Natural Resources during 2011. In the experiment, response of sensitive (ES) and resistant (SR3) biotypes were assayed by spraying the seedlings with 0, 0.25, 0.5, 1, 2, 4, 8, 16, and 32-fold of the recommended field dose of tralkoxydim, pinoxaden and sethoxydim herbicides. Results indicated that the ES biotype was 50% controlled with 140.26, 13.16 and 89.54 g ai ha-1 of tralkoxydim, pinoxaden and sethoxydim herbicides, respectively, while the amount of herbicides that controlled 50% of the SR3 biotype were 1863.32, 372.18 and 89.54 g ai ha-1, respectively. Resistance factor (RF) of SR3 biotype for tralkoxydim, pinoxaden and sethoxydim herbicides estimated as 13.28, 28.29 and 9.82, respectively. Results confirmed the cross-resistance in SR3 biotypes to APP, CHD and PPZ herbicides.