Location: Crop Production Systems Research
2025 Annual Report
Objectives
1. Determine differences in seed biology and fitness characteristics, such as competitiveness, photosynthetic capacity, responses to stress, and other growth- related factors of herbicide-susceptible versus herbicide-resistant weed biotypes.
1A. Determine differences in fitness characteristics, such as competitiveness, photosynthetic capacity, and responses to stress factors in herbicide-susceptible versus herbicide-resistant weed biotypes.
1B. Determine differences in fitness characteristics, such as competitiveness and responses to stress factors in herbicide-susceptible versus herbicide-resistant weed biotypes.
1C. Determine differences in fitness characteristics, photosynthetic capacity, and responses to stress factors in herbicide-susceptible versus herbicide-resistant weed biotypes.
1D. Comparison of whole-plant physiological processes of herbicide resistant weed populations with corresponding susceptible populations.
1E. Comparison and characterization of pigment contents and antioxidant capacities of red and green biotypes of glyphosate-resistant Palmer amaranth plants and their responses to selected herbicides and a bioherbicide.
2. Discover and characterize patterns of herbicide resistance in weed populations, elucidate underlying physiological, biochemical, and molecular mechanisms for use in identifying unique biological features that define their “weediness”, and explore their utility for developing control strategies.
2A. Discover and characterize patterns of herbicide resistance in weed populations.
2B. Elucidate underlying physiological, biochemical, molecular mechanisms of resistance to herbicides in weed populations where the level and nature of resistance is known.
2C. Discover and develop new approaches to weed control based on development of molecular herbicides specifically targeting our most troublesome weeds.
3. Identify key additive and/or synergistic interactions of combinations of chemicals, natural products and/or plant pathogens with herbicides to manage or control herbicide resistant weeds.
4. Evaluate for efficacy novel herbicide drift management and application techniques, emerging commercial herbicide or herbicide resistant crop technologies, and weed control methods such as microwave and steam.
4A. Evaluation of a novel fluorescent compound for measuring herbicide drift.
4B. Evaluation of unmanned aerial vehicle (UAV) technology for detection and management of herbicide-resistant weed populations and herbicide drift issues.
4C. Evaluation of emerging commercial herbicide and or herbicide resistant crop technologies.
4D. Evaluate the efficacy of microwave weed control methods.
Approach
The overall project goal is to discover basic and practical knowledge of the occurrence, distribution, mechanism of resistance and management of weeds that are difficult to control or that have evolved resistance to one or to multiple herbicides. This broad-scope approach will lead to more effective weed control methods and novel weed control management practices. The development of new weed management tools, aided by knowledge of resistance mechanisms and weed biology will advance the development of sustainable practices for early detection and management of weeds and facilitate the development of strategies to provide more efficacious weed control via integrated use of chemical, mechanical, biological and cultural methods.
Through basic analyses, assays and bioassays of whole plants and plant tissues from laboratory, greenhouse and field experiments will determine major differences in resistant versus susceptible weed biotypes. Subsequent biochemical, genetic, proteomic, immunochemical and radiological studies will identify and characterize specific site differences in herbicide resistant and sensitive weed biotypes within species. Experiments on the development of novel mechanical weed control methods and weed control using bioherbicides will provide important results that could substantially lower the amount of herbicide usage. The knowledge generated from these experiments will provide a greater understanding of the biochemistry, physiology and genetics of resistance mechanisms and provide insight for recommendations that will promote efficacious and sustainable weed control coupled with more efficient and economic crop production with reduced herbicide usage and impact on the environment.
Progress Report
Combinations of certain herbicides and bioherbicides has resulted in important additive or synergistic effects on the control of weeds. Studies of phenoxy herbicides and a fungal bioherbicide (Fusarium lateritium) showed that combinations of 2,4-DB and the fungus resulted in synergistic interactions for the control of the weed, velvetleaf (Abutilon theophrasti Medik.). Results were summarized and a manuscript was published.
A series of phosphonate compounds related to the herbicide glyphosate were examined for phytotoxicity and effects on secondary plant metabolism using soybean seedlings as a model plant. Laboratory experiments have been completed and results are being summarized in a manuscript.
Results from studies on the antioxidant capacity of two (red-pigmented and green-pigmented) glyphosate - resistant Palmer amaranth biotypes exhibiting different betalain pigment profiles. Results on antioxidant/reducing potential, oxidative enzyme activity and tolerance/susceptibility to certain herbicides were summarized and a manuscript is in journal review.
The plant growth regulator, gibberellic acid (GA), has various uses in agriculture and horticulture. Laboratory studies of the effects of combinations of GA and the herbicide glyphosate on growth and secondary metabolism in soybean plants indicated both GA and glyphosate increased the activity of a key enzyme, phenylalanine ammonia-lyase activity (PAL) and GA plus glyphosate treatments resulted in additive increases in PAL activity.
GA increased hypocotyl and epicotyl elongation and caused marginal reversal of glyphosate inhibition of elongation of these organs. Results were summarized and a manuscript was published in 2024.
Results of laboratory and field experiments on the control of glyphosate-resistant horseweed (Conyza canadensis) with a fungal bioherbicide (Albifimbria verrucaria) were summarized and a manuscript was published. The bioherbicidal fungus was found to be efficacious against glyphosate-resistant and – susceptible horseweed when applied as a mycelial formulation under greenhouse and field conditions. Although rosette leaf-stage plants were more susceptible, the fungus provided >95% control of bolting plants under greenhouse conditions. Field tests using plants in the bolting/inflorescence stage showed less efficacy (~80 to 85% control). Results indicate that this fungus can infect and kill horseweed, demonstrating its bioherbicidal potential on this important weed.
A fungal bioherbicide, Alternaria cassiae, previously shown to control sicklepod in soybeans was tested for control of this weed during cotton production. Experiments utilized several concentrations of the fungus, and control in soybean was included for comparison. The severe reduction in weed control in cotton was attributed to the detrimental effects on the fungus caused by the chemical regime used in the production of cotton compared to that used in soybean. Results have been summarized and a manuscript is in preparation.
Accomplishments