Identification and Evaluation of Wild Mustard (Sinapis arvensis L.) Populations Resistant to Mesosulfuron-Methyl+ Iodosulfuron-Methyl-Sodium+ Diflufenican in Wheat Fields of Ramhormoz, Iran

The overreliance on herbicides and their continuous use has led to the selection of resistant populations, which is considered a fundamental and serious problem in agricultural systems today. The continuous use of acetolactate synthase-inhibiting herbicides over the years in wheat fields of Khuzestan Province has also caused resistance in weeds in these fields and imposed costs on farmers in this province. For this purpose, based on the agricultural land map and farm history, after visiting wheat fields in Ramhormoz County, Khuzestan Province, seeds of 22 suspected ALS-resistant wild mustard populations were collected from wheat fields. In addition, a population from a location in the same region with no history of ALS herbicide application was collected as a susceptible population. The experiment was conducted in two parts: screening and dose-response, which involved, respectively, the application of the recommended dose of the herbicide mesosulfuron-methyl + iodosulfuron-methyl-sodium + diflufenican (Othello, OD 6%, 96 g a.i. ha^-1) and a range of doses of 0, 24, 48, 96, 192, 384, and 768 g a.i. ha^-1 in the autumn and winter of 2024 at the Agricultural Sciences and Natural Resources University of Khuzestan. Based on the two Adkins and Moss ranking indices, 4 and 15 wild mustard populations were classified into the suspected resistant (PR) and resistant (RR) groups to the Othello herbicide, respectively. The resistance index to the Othello herbicide for wild mustard populations was estimated to be between 1.45-4.80 based on the fresh weight index and between 3.95-7.52 based on the percentage of plant survival after herbicide application. Considering the increasing prevalence of Othello-resistant weed populations in this province, management programs for herbicide-resistant weeds, including crop rotation and judicious herbicide application, should be pursued more rigorously than before.