Location: Crop Production Systems Research
2024 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 have resulted in significant additive or synergistic effects on the control of weeds. Studies of herbicides and a fungal bioherbicide (Fusarium lateritium) showed that combinations of 2,4-DB [ 4-(2, 4-dichlorophenoxy)butanoic acid] and the fungus resulted in synergistic interactions that improved control of the weed, velvetleaf (Abutilon theophrasti). Results were summarized and a manuscript was published.
A series of five phosphonate compounds (related to the phosphonate herbicide, glyphosate) were examined for phytotoxicity and effects on secondary plant metabolism using soybean (Glycine max) seedlings as a model species. One compound (phosphono-acetic acid) reduced growth and elevated extractable activity of a key enzyme [phenylalanine ammonia-lyase (PAL)] similar to effects caused by glyphosate. Two compounds (phosphono-formic acid and N-phosphono-acetyl-L-aspartic acid) were phytotoxic, but lowered extractable PAL activity and two other phosphonates (2-amino-4-phosphonobutyric acid and 3-phosphonopropionic acid) were not phytotoxic and had no effect PAL activity levels. Laboratory experiments have been completed, results are summarized, and a manuscript is in preparation.
Studies on the antioxidant capacity of two (red-pigmented and green-pigmented) glyphosate-resistant Palmer amaranth (Amaranthus palmeri) biotypes exhibiting different pigment profiles were completed. The levels of ethanol-soluble phenolic compounds and flavonoids were higher in leaf tissues than in petiole or stem tissues of both biotypes and these constituents were slightly higher in the green-pigmented biotype. Generally, leaf bioassays indicated both biotypes were sensitive to low concentrations of the herbicides (acifluorfen and methyl viologen) but exhibited some resistance to atrazine. Results were summarized and a manuscript is being reviewed in a peer-reviewed journal.
Gibberellic acid (GA) is a plant growth regulator that 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 critical enzyme, phenylalanine ammonia-lyase activity (PAL), and GA plus glyphosate treatments resulted in additive increases in PAL activity. GA increased stem elongation and caused marginal reversal of glyphosate’s inhibition of stem growth. Results were summarized and a manuscript was published.
Laboratory and field experiments on the control of glyphosate-resistant horseweed (Conyza canadensis) with a fungal bioherbicide (Albifimbria verrucaria) showed that spray applications of mycelial formulations of the bioherbicide infected both glyphosate-resistant and -susceptible C. canadensis plants at various growth stages. Results demonstrated the potential of this fungus as a bioherbicidal agent against this troublesome weed that has become resistant to various herbicides. Data were summarized and a manuscript was published.
A fungal bioherbicide (Alternaria cassiae) previously shown to control the weed sicklepod (Senna obtusifolia) in soybeans, was tested for control of this weed during cotton (Gossipium hirsutum) production. Experiments utilized several concentrations of the fungus and weed control in soybean was included for comparison. The severe reduction in control of sicklepod 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 production. Results have been summarized and a manuscript has been prepared.
Accomplishments
1. Effects of phosphonate compounds structurally related to glyphosate on plant growth and secondary metabolism. ARS researchers at Stoneville, Mississippi, completed laboratory studies that showed phosphono-acetic acid reduced growth and elevated a key enzyme, phenylalanine ammonia-lyase (PAL), activity in soybean seedlings during a 72-hr time course. Growth inhibition was significant, much like that caused by glyphosate, but the effect on elevating PAL activity was lower than that caused by glyphosate. Two compounds (phosphono-formic acid and N-phosphono-acetyl-L-aspartic acid) reduced root elongation, dry weight accumulation and extractable PAL activity, while other compounds (2-amino-4-phosphonobutyric acid and 3-phosphonopropionic acid) had little effect on growth or PAL activity. These results are important in discerning the impact of chemical structure on growth, phytotoxicity and biological activity of compounds related to glyphosate in plants.
Review Publications
Hoagland, R.E., Boyette, C.D. 2024. Interaction of gibberellic acid and glyphosate on growth and phenolic metabolism in soybean seedlings. Agronomy. 14(4). Article 14040684. https://doi.org/10.3390/agronomy14040684.
Young, S.L., Anderson, J.V., Baerson, S.R., Bajsa Hirschel, J.N., Blumenthal, D.M., Boyd, C.S., Boyette, C.D., Brennan, E.B., Cantrell, C.L., Chao, W.S., Chee Sanford, J.C., Clements, D.D., Dray Jr, F.A., Duke, S.O., Porter, K.M., Fletcher, R.S., Fulcher, M.R., Gaskin, J., Grewell, B.J., Hamerlynck, E.P., Hoagland, R.E., Horvath, D.P., Law, E.P., Madsen, J., Martin, D.E., Mattox, C.M., Mirsky, S.B., Molin, W.T., Moran, P.J., Mueller, R.C., Nandula, V.K., Newingham, B.A., Pan, Z., Porensky, L.M., Pratt, P.D., Price, A.J., Rector, B.G., Reddy, K.N., Sheley, R.L., Smith, L., Smith, M., Snyder, K.A., Tancos, M.A., West, N.M., Wheeler, G.S., Williams, M., Wolf, J.E., Wonkka, C.L., Wright, A.A., Xi, J., Ziska, L.H. 2023. Agricultural Research Service weed science research: past, present, and future. Weed Science. 71(4):312-327. https://doi.org/10.1017/wsc.2023.31.
Boyette, C.D., Hoagland, R.E., Stetina, K.C. 2024. Interaction of a bioherbicidal fungus and a phenoxy herbicide for controlling velvetleaf (abutilon theophrasti). Biocontrol Science and Technology. 34(4):323-335. https://doi.org/10.1080/09583157.2024.2324396.