Identification of Phalaris brachystachys Link. resistance to haloxyfop-R-methyl herbicide from fields of Golestan province

In order to investigate the resistance of Phalaris brachystachys Link. to haloxyfop-R-methyl herbicide, a test was conducted at Gorgan University of Agricultural Sciences and Natural Resources in 2017. Experimental treatments included 36 biotypes of P. brachystachys suspected resistance and one susceptible biotype which were collected from wheat fields in Golestan province. The experiments included determination of discriminating concentration, screening all biotypes with discriminating concentration, concentration-response and dose-response tests for resistant biotypes. In the seed bioassay, after determining the discriminating concentration and screening all biotypes, a range of herbicide concentrations were applied. In the dose-response test, the response of P. brachystachys biotypes in a range of doses from 0.25 to 8 times the recommended dose herbicide was investigated. The resistance factor obtained of whole plant assay was 2 to 4. Also, there was a high correlation between resistance factor obtained from whole plant and seed bioassay methods (87%). Checking the distribution map of resistant biotypes indicated that these biotypes were not uniform in the wheat fields of Golestan province.