The response of weedy sunflower (Helianthus annuus L.) to nicosulfuron: an examination of vegetative parameters and acetolactate synthase activity

摘要

Paper description:Intensive use of nicosulfuron in maize fields can lead to development of herbicide resistance, which can result in variable responses of weedy sunflower populations.Effective doses of nicosulfuron and its effect on weedy sunflower acetolactate synthase (ALS) activity has not been reported.This research investigated effective doses of nicosulfuron on whole weedy sunflower plant and ALS enzyme activity.Weedy sunflower populations displayed very different responses to nicosulfuron, with the possibility of herbicide resistance development. This is the first examination of nicosulfuron effect on weedy sunflower ALS activity.: Genetic and morphological interpopulation variability of weed species is often responsible for variable responses to herbicides. As weedy sunflower, an invasive form of Helianthus annuus L., possesses high morphological and genetic variability, very different responses of its populations to herbicides can be expected. This species is one of the dominant weed species in row crops, including maize, in many European countries in which nicosulfuron is intensively used for weed control. There are little available data about the response of this sunflower form to nicosulfuron or of the interpopulation variability of its response to other herbicides. The responses of three weedy sunflower populations to nicosulfuron were studied in field dose-response experiments, and acetolactate synthase (ALS) enzyme activity at different herbicide concentrations was determined in vitro. Interpopulation variability in the response to nicosulfuron was confirmed. Populations WS2 and WS3 were more that 20-fold and 30-fold less susceptible to nicosulfuron, respectively, than population WS1, based on fresh weight, whereas the differences were not so prominent based on other parameters, including plant height, leaf area and ALS activity, and ranged from 2 to 12-fold.