Evaluation the fitness and competitive ability of wild mustard Sinapis arvensis susceptible and with multiple resistance to Tribenuron Methyl and 2,4-D+MCPA with wheat

This study was carried out to determine the resistance and relative fitness of susceptible and resistant mustard biotypes collected from wheat fields of the Gilane-gharb region in Kermanshah province. Weeds had a long history of exposure to common broadleaf herbicides during the last five years. The herbicides studied included thribenurone methyl (Granstar) and 2,4-D+ MCPA. The result of preliminary studies identified one biotype had multiple resistance to both herbicides Granstar and 2,4-D+ MCPA and one biotype had resistance to Granstar only. Fitness studies were performed in two parts in the greenhouse. In the first part, plant dry matter, leaf area and plant height change of resistant and susceptible biotypes were compared under no competition with wheat condition and in the second part, the growth of susceptible and resistant biotypes of wild mustard weed in competition with wheat. Dry weight and height were measured in both plants. According to the results, the susceptible biotype was superior to the resistance biotypes in terms of the studied traits under no competition with wheat and susceptible biotype had higher dry weight, height, and leaf area rather than the resistant biotypes. Similarly, the susceptible biotype was superior to resistant biotypes in terms of growth under competition condition and, wheat had less growth in competition with susceptible biotype rather than resistant ones. Overall, the results of this study indicated that the emergence of resistance reduced the fitness of resistant wild mustard compared to the sensitive biotype.