Location: Global Change and Photosynthesis Research
2023 Annual Report
Objectives
Objective 1: Determine the structure and functions of microbial communities in cropping systems that include chemical and non-chemical weed control tactics, and elucidate their interactions with herbicide resistant weeds, and response to various weed management tactics under climate change.
1.1 Characterize the microbial community structure associated with the rhizosphere of problematic weed species in Midwest cropping systems.
1.2 Characterize the microbial community structure associated with herbicide resistant weeds.
Objective 2: Develop alternative cropping systems that include the integration of new chemical and non-chemical tactics for managing weeds for Midwest specialty crops production and improve the knowledge or understanding of influences of the climate variability on crop and weed management outcomes.
2.1 Determine the scope of the problem of weeds and their management in processing vegetable legumes, specifically snap bean.
2.2 Quantify snap bean cultivar variability in herbicide tolerance and traits important to weed competitiveness.
2.3 Model effectiveness of preemergence herbicides across variation in rainfall and soil temperature.
2.4 Determine the relationships among weed control and weather variability on corn yield loss due to weeds.
2.5 Investigate the role of sweet corn postharvest weed seed control in reducing weed seedbank inputs.
Approach
Many of the pressing weed issues in the nation's cropping systems have resulted from the simplification of weed management systems through over-reliance on specific herbicides, causing economic losses of tens of billions of dollars annually. Weeds have adapted to this selection pressure through evolution of herbicide resistances. Moreover, emerging chemical 'solutions' to manage herbicide resistant weeds in agronomic crops offers no benefit to specialty crop production systems because herbicide tolerant cultivars are either not available or largely unaccepted, yet these crops face greater sensitivity to weed competition, off-target herbicide injury, and adverse weather. Our research aims to develop strategies that may help to reduce the risk that weeds pose to food production in the face of climate change. We will utilize an array of experimental approaches at various spatial and temporal scales, all aimed at building resilience in weed management systems to reduce weed fitness and enhance crop performance. Study systems will range in spatial scale from plant-microbe rhizosphere dynamics to weed community assemblages of specialty crop fields in multiple states. The temporal scale of our study systems will range from days, for microbial research, to decades, for long-term weed management trials. Our experimental approaches are diverse, including microbial ecology, weed ecology, genetics, modeling, and agronomic research using both empirical hypothesis testing and observational analyses. The knowledge gained through this research addresses specific agricultural problems of national importance including those associated with pest management, food security, and grower profitability.
Progress Report
In support of Objective 1, research continued to collect qualitative characteristics of microbial communities specific to the rhizosphere compartments associated with eight annual weed species important to Midwest agricultural ecosystems. Specific progress includes:
Significant variation in plant root architecture between weed species has necessitated the development of species-specific methodologies that allow consistent and reliable standard procedures for obtaining quality samples for molecular analyses from plant rhizoplanes and the gradient of rhizosphere soil taken increasingly distant from the root surfaces. For example, we found that analysis of giant ragweed and common ragweed required significant modifications to procedures for dissection of rhizosphere zones specific to the species. Microbial molecular analyses particularly in soil require care in sample collection to enable reliable specimens for comparative analyses between plants with a critical need to achieve high statistical robustness at the level of microbial gene analyses. These protocols are being compiled into a journal manuscript to provide a detailed guide to conducting similar comparative studies in the rhizospheres of a variety of weed species and will be novel in its information.
Finding specific microbial populations within individual zones of the weed rhizosphere led to questioning of the functional significance of these populations in relationship to plant growth and success. Over the years, we have built a functional database of microbial genes found in agricultural soils that are relevant to plant nitrogen (N)-nutritional needs and have now expanded genetic characterization of weed rhizosphere microbial communities to include N-cycling genes. We added a microbial-encoded functional gene, phnJ, thought to encode carbon-phosphorus (C-P) lyase, and involved in one mechanism of glyphosate degradation.
Additional herbicide degradation genes are being evaluated for their relevance to the rhizospheres of amaranths, ragweed and weedy grass species as gene targets to identify potential mechanisms of plant-microbe relationships that confer resistance or tolerance to herbicides in use. These will be key targets in further controlled chamber and field experiments designed for the upcoming season.
In support of Objective 2, research continued improving knowledge of climate variability on crop/weed outcomes and developing alternative cropping systems that include integrating new chemical and non-chemical tactics for managing weeds in Midwest specialty crops. Specific progress includes:
Weed scientists from the Pacific Northwest, Midwest, and Mid-Atlantic conducted surveys of lima bean and snap bean production fields. Weed data have been compiled with soil data and field management records. To date, 93 and 346 fields of lima bean and snap bean, respectively, have been surveyed. Preliminary results, identification of the most problematic weeds in snap bean, have been presented at meetings of the North Central Weed Science Society and Weed Science Society of America (WSSA).
The SNap Bean Association Panel (SNAP), a genotyped diversity panel with 377 entries, was used to determine tolerance to several herbicides including metribuzin, flumioxazin, lactofen, and saflufenacil under field conditions. To confirm single-year results, trials on lactofen and saflufenacil are being repeated in 2023. Two peer-reviewed publications on this topic have been published; one concerning sulfentrazone tolerance (Frontiers in Agronomy) and another concerning pyroxasulfone. Results show how sulfentrazone tolerance in snap bean could be improved by introducing alleles conditioning herbicide tolerance, and that pyroxasulfone is too injurious for herbicide registration.
Ongoing cover crop research includes developing a probabilistic assessment of cereal rye cover crop impacts on regional crop yield and soil carbon. The research, providing the most complete estimate of uncertainty in the benefits of a cereal rye cover crop in Illinois, is now published. A new field experiment was initiated, whereby researchers are parameterizing a waterhemp emergence model driven by a latitudinal gradient (Texas to Wisconsin) of cover crop and tillage practices.
With new headquarters-provided postdoc funding, researchers in Urbana, Illinois, are building a relational database of historic, multi-institutional herbicide evaluations. Once completed, this dataset will be used to develop new knowledge about crop/weed management and environmental variability in corn-soybean production systems. To date, researchers have compiled and harmonized 9,304 trials, totaling 7.4 million observations, from 16 institutions. The first product is a manuscript showing rapid agronomic weed adaptation to glyphosate across North America since the introduction of glyphosate-tolerant crops in the mid-1990’s. The manuscript is currently in review.
In parallel research, a sweet corn dataset collected on 16,040 fields across a 27-year period was used to unravel the significance of local weather anomalies on sweet corn yield. The work showed the negative impact of extreme heat during flowering on sweet corn, especially under rainfed conditions in the Midwest. The publication of this research underscores the critical importance of prioritizing crop adaptation strategies to sustain production of this highly popular crop. This and related work served as the impetus for a WSSA-funded symposium on the intersection of climate change and weed science on crop management during the 2023 annual meeting.
Off-target movement of synthetic auxin herbicides in the Midwest remains a threat to sensitive crops and plants. Researchers in Urbana, Illinois, are exploring the use of remote sensing platforms to quantify the spatiotemporal extent of the problem.
Finally, an experiment from the previous project (5012-12220-009-000D) is completed. Estimates of local eradication costs for invasive Miscanthus populations throughout the Eastern and Midwestern United States have now been published). Results show the cost to eradicate documented Miscanthus populations in the United States ranges from $10 to $37 million.
Accomplishments
1. Sweet corn yield decreased in response to high temperatures during flowering. The impact of climate change on vegetable crops, which are more sensitive to environmental stressors than staple cereal crops and are essential to human health, has received little study. ARS researchers in Urbana, Illinois, used a sweet corn dataset collected on 16,040 fields across a 27-year period to unravel the significance of local weather anomalies on sweet corn yield. High temperatures (>86 degrees F) during flowering resulted in significant yield losses in sweet corn which were exacerbated under rainfed conditions. This result is cause for concern given predictions of increased frequency of hotter and drier mid-season growing conditions in much of the U.S. Corn Belt. The research underscores the critical importance of prioritizing crop adaptation strategies to high temperature to sustain production of this highly popular crop.
2. Snap bean tolerance to herbicides effective on waterhemp is investigated. Waterhemp is a growing threat to U.S. snap bean production because it contaminates the harvested product and few tools are available for controlling this weed. Pyroxasulfone and sulfentrazone control waterhemp before the weed emerges, but the two herbicides are not registered for use with snap bean due to concern of crop injury. ARS researchers in Urbana, Illinois, with university collaborators, determined snap bean tolerance to pyroxasulfone and sulfentrazone using a panel of 277 entries representing the diversity of snap beans grown in the U.S. over the last century. A handful of entries were tolerant to pyroxasulfone across variable environments, but the margin of crop safety is insufficient for registration of pyroxasulfone on snap bean crops. In contrast, tolerance to sulfentrazone was associated with multiple genomic regions conditioning larger seed size, oxidative stress tolerance, and herbicide metabolism. This new knowledge identifies specific genomic targets that the snap bean seed industry can use to improve sulfentrazone tolerance in sensitive lines, which may facilitate registration of the herbicide, as well as improve environmental stress tolerance in new cultivars.
Review Publications
Dhaliwal, D., Williams, M. 2022. Evidence of sweet corn yield losses from rising temperatures. Scientific Reports. 12. Article 18218. https://doi.org/10.1038/s41598-022-23237-2.
Rai, T., Lee, N., Williams, M., Davis, A., Villamil, M., Dokoohaki, H. 2023. Probabilistic assessment of cereal rye cover crop impacts on regional crop yield and soil carbon. Agriculture. 13(1). Article 176. https://doi.org/10.3390/agriculture13010176.
Chen, M., Conroy, J.L., Geyman, E.C., Sanford, R.A., Chee Sanford, J.C., Connor, L.M. 2022. Stable carbon isotope values of syndepositional carbonate spherules and micrite record spatial and temporal changes in photosynthesis intensity. Geobiology. 20(5):667-689. https://doi.org/10.1111/gbi.12509.
Lowry, C., Matlaga, D., West, N.M., Williams II, M.M., Davis, A. 2022. Estimating local eradication costs for invasive Miscanthus populations throughout the eastern and midwestern United States. Invasive Plant Science and Management. 15(3):115-121. https://doi.org/10.1017/inp.2022.20.
Williams II, M.M., Saballos, A., Peachey, R. 2023. Snap bean response to pyroxasulfone in a diversity panel. Weed Technology. 37(1):84-88. https://doi.org/10.1017/wet.2023.12.
Chen, M., Conroy, J.L., Sanford, R.A., Wyman-Feravich, D.A., Chee Sanford, J.C., Connor, L.M. 2023. Tropical lacustrine sediment microbial community response to an extreme El Niño event. Nature Scientific Reports. 13. Article 6868. https://doi.org/10.1038/s41598-023-33280-2.
Williams II, M.M., Dhaliwal, D., Hausman, N.E. 2023. No evidence sowing date influences optimum plant density of sweet corn grown in the Midwestern United States. HortScience. 58(3):301-306. https://doi.org/10.21273/HORTSCI16933-22.
