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Measuring Rates of Herbicide Metabolism in Dicot Weeds with an Excised Leaf Assay
Published on: September 7, 2015
Chloroplast membrane alterations in triazine-resistant Amaranthus retroflexus biotypes
C J Arntzen1, C L Ditto, P E Brewer
1U.S Department of Agriculture/SEA, University of Illinois, Urbana, Illinois 61801.
Summary
This study found that the chloroplast is the site of herbicide tolerance in redroot pigweed. Genetic modification of the target site explains resistance to herbicides like atrazine.
Area of Science:
- Plant Biology
- Biochemistry
- Agricultural Science
Background:
- Redroot pigweed (Amaranthus retroflexus L.) exhibits resistance to common herbicides.
- Understanding herbicide resistance mechanisms is crucial for effective weed management.
Purpose of the Study:
- To compare the effectiveness of diuron, atrazine, procyazine, and cyanazine on redroot pigweed growth.
- To elucidate the site and mechanism of selective herbicide tolerance in triazine-resistant biotypes.
Main Methods:
- Hydroponic culture to assess herbicide efficacy.
- Chloroplast assays measuring Photosystem II activity and chlorophyll fluorescence.
- Electrophoretic analysis of chloroplast membrane proteins.
Main Results:
- Atrazine showed a marked differential inhibition between resistant and susceptible biotypes, unlike diuron.
- Chloroplasts from resistant biotypes were partially resistant to procyazine and cyanazine, but susceptible to diuron.
- Resistant chloroplasts exhibited altered electron acceptor reoxidation rates and minor protein changes.
Conclusions:
- The chloroplast is the primary site of selective herbicide tolerance in triazine-resistant redroot pigweed.
- Herbicide resistance is likely due to a genetically controlled modification of the Photosystem II target site.
