Resistance of sunflower hybrids to imazamox and tribenuron-methyl

The response of the imazamox resistant and susceptible sunflower hybrids Rimi and S to imazamox and of tribenuron-methyl resistant and susceptible hybrids Rsu and S to tribenuron-methyl was investigated both in a whole-plant bioassay and in field experiments. Plants were treated post-emergence with imazamox/tribenuron-methyl at four true leaves (grown in pots) and at four–six true leaves (grown in field). Visual injury estimation and vegetative parameters (plant height, fresh weight, dry weight, leaf area) were recorded. ALS (acetolactate synthase) enzyme activity in different herbicide concentrations was determined in vitro. Pronounced differences were noted between Rimi and S hybrids and between Rsu and S hybrids in the vegetative parameters and ALS activity. Namely, Rimi hybrid was 9–64-fold more resistant than S for vegetative parameters and about 3000-fold for ALS activity, while Rsu hybrid was 14–56-fold more resistant than S for vegetative parameters, and about 2600-fold for ALS activity.

► Responses of the sunflower hybrids to imazamox and tribenuron-methyl were studied.
► Rimi resistance level to imazamox was 9–64 for vegetative parameters.
► For ALS activity level of resistance of Rimi hybrid was 3000.
► Rsu resistance level to tribenuron-methyl was 14–56 for vegetative parameters.
► Level of resistance of Rsu hybrid was 2600 based on ALS activity.