Mechanism and pattern of resistance to some ACCase inhibitors in winter wild oat (Avena sterilis subsp. ludoviciana (Durieu) Gillet & Magne) biotypes collected within canola fields

Due to the reports regarding unsuccessful control of Avena sterilis subsp. ludoviciana (Durieu) Gillet & Magne by haloxyfop-R-methyl in canola fields, the following study was conducted to investigate the resistance of this weed to haloxyfop-R-methyl. Five out of 22 accessions were resistant to haloxyfop-R-methyl. These biotypes were then subjected to various rates of clodinafop propargyl, sethoxydim, pinoxaden and mesosulfuron methyl + iodosulfuron-methyl herbicides and their cross-resistance to clodinafop propargyl and sethoxydim was confirmed. However, no resistance was observed to pinoxaden and mesosulfuron-methyl + iodosulfuron-methyl herbicides. Indirect study of metabolism by P450 using 1aminobenzotriazole and piperonyl butoxide showed that this enzyme had no contribution to occurrence of resistance in the studied biotypes. Allele-specific PCR results indicated that Ile-2041-Asn mutation is responsible for resistance of A. sterilis subsp. ludoviciana biotypes, which was confirmed by sequencing of the samples. Since pinoxaden negatively affects canola, the growers face a serious limitation in their choice for chemical management and thus, implementation of integrated weed management such as introduction of row crops such as faba bean in crop rotation and increasing the diversity of herbicide mode of action by cultivation of crops such as sugar beet in crop rotation may prove helpful. In fields under canola-wheat rotation, it is also possible to use pinoxaden in wheat. Also, trifluralin, cycloxydim and clethodim herbicides may be tested on A. sterilis subsp. ludoviciana. This was the first case of A. sterilis subsp. ludoviciana resistance to ACCase inhibitors in canola fields.