Progress 01/01/21 to 12/31/24
Outputs
(N/A)
Impacts
What was accomplished under these goals?
Our focus this year was on investigating the diversity in Pep receptors (PEPRs) among different soybean germplasm. In order to activate plant immunity, Peps must interact with specific receptor kinases (PEPRs) on the cell surface. Peps typically have limited cross-species activity because of divergence of PEPRsacrossspecies. However, to our knowledge, the potential for intraspecific diversity in PEPR sequenceshas not previously been explored. If PEPRs vary among different soybean cultivars, this could potentially limit the efficacy of Pep treatments unless we specifically select for Peps that interact with conserved PEPRs. Therefore, for each of the 3 PEPRs found in the soybean genome, we have performed sequence comparisons across multiple sequenced soybean genomes. We have identified non-synonymous single nuceotide polymorphisms in all three PEPRs, as well as frame-shift mutations in one PEPR; PEPR2 has the greatest sequence diversity, whereas PEPR1b appears to be the most strongly conserved PEPR. This has important implications for the use of Pep treatments for pest management; and will guide future investigations into Pep-PEPR specificity.
Publications
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2025
Citation:
Fiona L. Goggin, Hillary Fischer, Jiamei Li, Reinier Gesto-Borroto, Argelia Lorence, Suxing Liu, and Alexander Bucksch, 2025. Exploring Plant Immunity to Vascular Herbivores. Invited talk, Nematodes and Aphids. Southern Association of Agricultural Scientists Annual Meeting, February 2025, Irving, TX.
- Type:
Peer Reviewed Journal Articles
Status:
Submitted
Year Published:
2025
Citation:
Alnasrawi, A, Sanadhya, P, Rojas, J.A., and Goggin, F.L. Optimizing Conditions for Ectopic Gene Expression in Bacillus subtilis and its Application as a Seed Treatment. Submitted.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2025
Citation:
Alnasrawi A., Payal Sanadhya P., Lei Zhang L., Gleason G., and Goggin F.L. 2024. Plant Elicitor Peptides and Rhizobacterial Delivery for Nematode Management. American Phytopathological Society Annual Meeting, Memphis, TN (Oral presentation).
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2025
Citation:
Li, J., Fischer, H.D. 1, Xu J., and Goggin F.L. 2024. Interactions Between Fatty Acid Metabolism and ROS Signaling in the Chloroplast Mediate Plant Responses to Biotic Stress. American Phytopathological Society Annual Meeting, Memphis, TN (Poster).
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2025
Citation:
Alnasrawi, A. (2024). The Impact of Ectopic Expression of a Plant Elicitor Peptide in Bacillus subtilis on Nematode Resistance in Soybean Through Seed Treatment. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/5449
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Progress 01/01/23 to 12/31/23
Outputs
Target Audience:Our target audience include senior and junior scientists in plant science, plant pathology, and molecular biology and genetics, as well as extension scientists and soybean growers. When possible, we also seek to communicate the relevance of our work to the general public and K12 students. Changes/Problems:One principal investigator, Alejandro Rojas, moved to Michigan State University part-way through the year. He intends to continue work on the project there, and funds have been transferred to support this. What opportunities for training and professional development has the project provided?As part of this project, the Goggin lab hosts 1 Ph.D. studentin the Cell and Molecular Biology Ph.D. program,and one full-time postdoctoral associate; the Rojas lab hosted one Ph.D. student in Plant Pathology with a part-time commitment to this work; and the Gleason lab housesone Ph.D. student in Plant Pathology with a part-time commitment to this work. The Goggin lab also trains two undergraduate researchers, one of whom obtained an undergraduate research fellowship from the university on the basis of this work. All of these students received training in experimental design and analysis as well as techniques relevant to their particular projects, such as digital plant phenotyping, protein purification, molecular cloning and gene expression analysis. One postdoctoral associate on the project has the opportunity to lead a training workshop on confocal microscopy. PI Goggin also organized a weekly scientific seminar series that benefited trainees on this project.The seminar series includes student lunches at which visiting speakers are invited to meet the graduate students and postdoctoral fellows and share career advice in an informal, social setting. Trainees also received guidance in scientific writing and presentation, and all participants participated in scientific conferences appropriate to their discipline. One undergraduate and the Ph.D. student in the Goggin lab also gained experience with grant writing; the PhD student obtained a Schlumburger Foundation Faculty for the Future grant to support her Ph.D. studies, and the undergraduate successfully competed for a research fellowship. How have the results been disseminated to communities of interest?To communicate our research findings to the scientific community, we submitted onemanuscript to a peer-reviewed journal in plant pathology, and gave 5 presentations at scientific conferences and universities. These results contribute to the larger, collaborative efforts of the agricultural research community to help growers fight crop pests andprotectagricultural productivity. Tocommunicate the value of USDA's investment in our research to the general public, and also to promote STEM education, we organized a hands-on outreach activity the Arkansas Lighthouse Summer Enrichment Academy (ALSEA). The Arkansas Lighthouse Academy (ALA) is a charter school with campuses in Jacksonville (K-12), Pine Bluff (K-8) and North Little Rock (K-5) that aims to overcome academic achievement gaps resulting from multi-generational income inequities. The ALSEA summer program is a partnership between ALA and the Dale Bumpers College of Agricultural, Food and Life Sciences. The program, which includes field trips to multiple departments within the college, aims to expose ALA students to the diversity of exciting educational and career opportunities in agricultural science, and to encourage ALA students to pursue higher education. On June 12, 2023, ENPL hosted ~27 ALSEA participants: fifteen 7th and 8th graders and seven educators from AR Lighthouse Charter Schools in Jacksonville, AR, and five University of Arkansas students who are serving as MANRRS (Minorities in Agriculture, Natural Resources, and Related Sciences) ambassadors and mentors to the ALSEA participants. Participants in the Entomology and Plant Pathology tour examined insects, nematodes, and plant pathogens under microscopes, and visited stations on insect diversity, insects in art, plant diseases, pollinator biology, and molecular biology. ALSEA students also had the opportunity to talk to faculty, graduate students, a postdoctoral scholar, and undergraduate interns about what it is like to study and work in the fields of Entomology and Plant Pathology. This event exposes junior high school students to agricultural science and seeks to increase the number and diversity of students who pursue education in our field. What do you plan to do during the next reporting period to accomplish the goals?The Goggin lab will complete confocal microscopy of nematode infection sites, complete bioinformatic analyses related to the project, and wrap up preparation of manuscripts for publication. An undergraduate student, Kallahan Minor, will also complete his Honors project. The Rojas lab will continue to perform greenhouse bioassays to measure the impacts of GmPep3 enrichmenton root pathogens and symbionts.
Impacts
What was accomplished under these goals?
This year we focused on optimizing conditions for ectopic expression of GmPep3 in Bacillus subtilis, and optimizing B. subtilis seed treatments for soybean. Identifying optimal conditions for ectopic expression in B. subtilis should be useful for a) producing vegetative cells for seed treatments; and b) growing B. subtilis in bioreactors for small or large-scale synthesis of GmPep3 or any other ectopic peptides whose expression is controlled by the B. subtilis aprE promoter. We tested different media (LB and 2xYT), temperatures (37C and 30C) and growth phases (log phase versus stationary phase) in all possible combinations, and measured the effects of these conditions on bacterial growth (as measured in colony forming units or CFUs) and on transcript abundance of our ectopic gene (GmPep3) per cell using absolute RT-qPCR. Our results indicated that total transcript yield, which is the product of cell numbers and transcripts per cell, were highest in the stationary phase grown on 2xYT at 30C. For larger scale peptide production in bioreactors, though, our results indicated that it may be beneficial to collect the bacteria in the log phase in order to yield more than one batch per day. We also explored means of increasing the retention of viable bacteria on the seeds over time in order to improve the shelf life of B. subtilis seed treatments. Specifically, we tested the benefits of using a binding agent, carboxymethylcellulose (CMC), to increase bacterial retention on seeds, and we also assessed the long-term viability of B. subtilis spores versus vegetative cells on the surface of soybean seeds. Whereas the binding agent provided limited benefit, use of spores extended the viability of B. subtilis seed treatments by at least three months. This information facilitates the use of rhizobacteria for crop protection.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2024
Citation:
Alnasrawi, A., Sanadhya, P., Zhang, L., Gleason, C., Goggin, F. 2024. The effects of Bacillus subtilis expressing a plant elicitor peptide on nematode infection on soybean. Phytopathology. DOI: 10.1094/PHYTO-03-24-0080-R
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Goggin, F.L., Gleason, C., Zhang, L., Rojas, A., and Rupe, J. 2023. Impacts of Plant Elicitor Peptides and Bacillus subtilis on nematode infection on soybean. USDA-NIFA Principal Investigator Workshop, Nov. 4, 2023. National Harbor, MD. Oral presentation.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Alnasrawi, A., Sanadhya, P., Zhang, L., Gleason, C., and Goggin, F.L. 2023. The effect of Bacillus subtilis expressing a plant elicitor peptide on nematode infection on soybean. Entomological Society of America Annual Meeting, Nov. 7, 2023. National Harbor, MD. Poster presentation.
- Type:
Conference Papers and Presentations
Status:
Submitted
Year Published:
2023
Citation:
Alnasrawi, A., Sanadhya, P., Zhang, L., Gleason, C., and Goggin, F.L. 2023. Bacillus subtilis as a delivery system for bioactive peptides for nematode control on soybean. Arkansas Crop Protection Association Annual Meeting, Nov. 2023, Fayetteville, AR. Poster presentation.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Alnasrawi, A., Sanadhya, P., Zhang, L., Gleason, C., and Goggin, F.L. 2023. Optimizing a Bio-based Seed Treatment for Immune Activation in Soybean. Arkansas Bioscience Institute Annual Meeting, October 2023, Little Rock, AR. Poster presentation.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Alnasrawi, A., Sanadhya, P., Zhang, L., Gleason, C., and Goggin, F.L. 2023. The effect of Bacillus subtilis expressing a plant elicitor peptide on nematode infection on soybean. Agri-Food Innovation Summit, Nov. 2, 2023. Fayetteville, AR. Poster presentation
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Progress 01/01/22 to 12/31/22
Outputs
Target Audience:Our target audience include senior and junior scientists in plant science, plant pathology, and molecular biology and genetics, as well as extension scientists and soybean growers. When possible, we also seek to communicate the relevance of our work to the general public and K12 students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has provided research training opportunities for threegraduate students, four undergraduates, and threepostdoctoral trainees. As part of this project, the Goggin lab hosts 1 Ph.D. studentin the Cell and Molecular Biology Ph.D. program,one full-time and one part-time postdoctoral associate; the Rojas lab hosts one Ph.D. student in Plant Pathology; the Rupe lab hosts one part-time postdoctoral associate;and the Gleason lab housesone Ph.D. student in Plant Pathology with a part-time commitment to this work. The Goggin lab also trained one undergraduate researcher who completed her Honors thesis this year, along with one undergraduate hourly assistant and one summer intern from a local teaching college, and the Rojas lab supported one undergraduate hourly researcher. All of these students received training in experimental design and analysis as well as techniques relevant to their particular projects, such as digital plant phenotyping, protein purification, molecular cloning and gene expression analysis. PI Goggin also organized a training workshop on confocal microscopy and a weekly scientific seminar series that benefited four of the trainees on this project.The seminar series includes student lunches at which visiting speakers are invited to meet the graduate students and postdoctoral fellows and share career advice in an informal, social setting. Trainees also received guidance in scientific writing and presentation, and had the opportunity to participate in scientific conferences. The Honors student published her thesis in the university's undergraduate research journal, and the summer intern, two Ph.D. students, and one postdoctoral trainee presented their work at conferences. The Ph.D. student and postdoctoralassociatein the Goggin lab also gained experience with grant writing; the student obtained a Schlumburger Foundation Faculty for the Future grant to support her Ph.D. studies, and the postdoctoral associate obtained a minigrantthat funds access to shared-usage equipment oncampus. How have the results been disseminated to communities of interest?The reesearch team hasdisseminated the results of this project through one peer-reviewed journal article in Theoretical and Applied Genetics, one undergraduate research publication, and eightconference or seminar presentations. These presentations includeda keynote talk at Soy2022, a conference that brings together molecular biologists from throughout the US working on soybean improvement, and two presentations at theAmerican Phytopathological Society'sNational Soybean Nematode Conference. This research project was also the focus of an ArkansasDivision of Agriculture press release (https://news.uark.edu/articles/62664/how-genetics-amino-acids-bacteria-come-together-to-combat-soybean-nematode) that was picked up byother media outlets such as the Stuttgart Daily Leader and the Iowa Soybean Center. To communicate the relevance of our work to the general public, we also gave a presentation on molecular biology at the 2022 Arkansas Insect Festival, a biennialevent for K12 students and parents thattypically attracts~3,000 attendees. What do you plan to do during the next reporting period to accomplish the goals?Inthe coming year,the Gleason and Zhang labs will explorethe utility of alternativepromoters to increasepeptide expression inBacillus subtilis. The Rojas and Rupe labs will continue to optimize and perform greenhouse bioassays to measure the impacts of GmPep3 enrichment(delivered via transgenicrhizobia, seed treatments or soybean overexpression lines) on root pathogens and symbionts. The Goggin lab will continue to measure the effects of transgenicrhizobia, seed treatments orsoybean overexpression lines on plant growth, development, and resistance to root knot nematodesand soybean cyst nematodes. They will also perform bioinformatic analyses of Peps and their receptors in soybean, and explore the utility of hairy root transformation to test Pep activity in different geneticbackgrounds.
Impacts
What was accomplished under these goals?
In Objective 1, we proposed to develop a bacterial system for synthesizing the matureGmPep3 peptidein vitro. Using a Bacillus subtilis strain that the Zhang lab transformed to express codon-optimized GmPep3, the Goggin lab used RT-qPCR to confirm that expression of the GmPEP3 gene is comparable to expression of the kanamycin selection marker, and exceeds expression of a housekeeping control on the B. subtilis chromosome. Preliminary Western blot results from the Gleason lab also confirm expression of the His-tagged GmPep3. To optimize methods for seed treatments, the Goggin lab also tested the time frame over which Bacillus subtilis remains viable when applied as a seed treatment. Without amendments, bacterial viability declined rapidly after the seed was dried, dropping to zero within a week of application. However, we determined that amending the seed treatment with a common cellulose-derived emulsifier prevented this decrease in bacterial viability; amended seeds had similar colony-forming units (CFUs) of B. subtilis at four weeks after treatment (the longest time point tested) as at 30 minutes after treatment. Thus, we have identified an amendment that can dramatically extend the shelf life of B. subtilis seed treatments. For Objective 2, we proposed to characterize the impacts of PEPs on soil-borne microbes of importance to plant health. Preliminary results from laboratory assays in the Rojas lab indicate that the peptide is not directly toxic to soil-borne pathogens. Greenhouse assays are underway to test whether Bacillus-mediated Pep delivery to plants influences susceptibility to Rhizoctonia solani (AG4). For Objectives 1 and 3, bioassays are underway to measure the impacts of bacterial GmPep3 delivery or GmProPep3 overexpression on plant growth, development, photosynthetic activity, and nematode resistance in comparison to controls. These bioassays will help us assess the relative benefits of these approaches for management of root knot and soybean cyst nematode (Objective 1), and will also generate phenotypic data that can help address Objective 3 (to measure the effects of PEPs on plant growth). Image-based phenotyping assays in the Goggin lab suggest that seed treatments with GmPep3, B. subtilis, and B subtilis expressing GmPep3 do not impact root growth and architecture in soybean seedings. Greenhouse phenotyping of transgenic plants overexpressing GmProPep3 also so far have not detected costs to plant growth. In fact, preliminary results suggest that bacterial delivery of GmPep3 or overexpression of GmProPep3 can promote more rapid plant growth early in development. In summary, in year 2 we have made significant progress on all three objectives.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Jackson, S. , Goggin, F. L2. (2022). Root Phenotyping of Peptide-treated Glycine max. Inquiry: The University of Arkansas Undergraduate Research Journal, 21(2). https://scholarworks.uark.edu/inquiry/vol21/iss2/1
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Goggin, F.L. Arkansas Bioscience Institute Annual Conference, "Plant Elicitor Peptides and Bacillus subtilis for nematode management on soybean," Fayetteville, AR, United States. (October 2022). Keynote Talk.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Goggin, F.L., Molecular and Cellular Biology of the Soybean Soy2022, "Impacts of Plant Elicitor Peptides and Bacillus subtilis on nematode infection on soybean," Iowa State University, Virtual Conference. (August 2022). Invited talk.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Goggin, F.L., Department of Entomology Invited Seminar, "To suck or not to suck: mechanisms of plant defense against aphids and nematodes," Virginia Tech University, Blacksburgh, VA, United States. (July 2022). Invited seminar.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Sanadhya, P., Alnasrawi, A., Zhang, L., Gleason, C., Goggin, F., National Soybean Nematode Conference, American Phytopathological Society, "Dissecting the role of Gmpep3, a plant elicitor peptide from soybean in modulating the plant response to pathogenic nematodes," Savannah, GA, United States. (December 2022).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Alnasrawi, A., Sanadhya, P., Zhang, L., Gleason, C., Goggin, F., National Soybean Nematode Conference, American Phytopathological Society, "The effect of Bacillus subtilis expressing a plant elicitor peptide on nematode infection on soybean," Savannah, GA, United States. (December 2022).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Alnasrawi, A., Sanadhya, P., Gleason, C., Zhang, L., Goggin, F.L., Entomological Society of America Annual Meeting, "Utility of plant elicitor peptides and rhizobacterial treatments to activate host plant defenses," Vancouver, Canada. (November 2022).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Chrisman, J. (Undergraduate Intern), Sanadhya, P., Alnasrawi, A., Goggin, F.L., Arkansas Idea Network of Biomedical Research Excellence (INBRE) Conference, "The study of the effect of Bacillus expressing plant elicitor peptides on germination and growth parameters in soybean plants," Fayetteville, AR, United States. (October 2022). Poster presentation.
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Lin, F., Vierira, C., Da Silva, M., Rojas, A., Rupe, J., Plopper, D., Chen, P., Wang, D., Nguyen, H. (2022). Breeding for disease resistance in soybean: a global perspective. Theoretical and Applied Genetics, 135, 3773-3872.
https://doi.org/10.1007/s00122-022-04101-3
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Roa, J., Fan, Q., Spurlock, T., Faske, T., Roberts, T., Rojas, J. A., Plant Health 2022, "Effect of cover crop rotation on rhizospheric and soil microbial community in a corn-soybean rotation system," American Phytopathological Society. (August 2022).
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Progress 01/01/21 to 12/31/21
Outputs
Target Audience:Our target audience include senior and junior scientists in plant science, plant pathology, and molecular biology and genetics, as well as extension scientists and soybean growers. When possible, we also seek to communicate the relevance of our work to the general public and K12 students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has provided research training opportunities for two graduate students (1 in the Entomology M.S. program and 1 in the Cell and Molecular Biology Ph.D. program), three undergraduates, one visiting scientist who will begin a Ph.D. in Plant Pathology in year 2, and three postdoctoral associates with partial assignments to this project. Participants are developing new skill sets in image-based plant phenotyping and 16S microbiome analysis, and one of the undergraduates on the project is completing an Honors thesis on the basis of this research. All participants also present their research in group lab meetings to gain experience with presentations; this will help prepare trainees to present their work at scientific conferences in years 2 and 3 of the project. How have the results been disseminated to communities of interest?A. Rojas presented work associated with this project to the Arkansas Soybean Board. The board recognized the value of the project and has agreed to provide supplemental support for a graduate student on the project. Other opportunities to present this work have been somewhat limited due to COVID, but we expect to present the project at national conferences in years 2 and 3. What do you plan to do during the next reporting period to accomplish the goals?In year 2 we will continue ongoing experiments to characterize nematode infection and plant growth in transgenic lines overexpressing GmPEP3, as well as on plants receiving a seed treatment of synthetic GmPEP3 or Bacillus subtilis expressing GmPEP3. Our treatment groups will also be assayed with other soil-borne pathogens: Macrophomina phaseolina, Pythium ultimum and Rhizoctonia solani (AG4), and Fusarium virguliforme. Soil samples collected in year 1 will be processed to test for effects of peptide treatment on the soil microbiome, quantifying soilborne pathogens and determine effects on microbes associated to roots (Nitrogen fixers). Results of these experiments will guide further assays to explore the effects of both GmPEP3 and B. subtilis treatment on root colonization of beneficial and pathogenic microbes on soybean under controlled conditions using pasteurized soil and soil collected from fields.
Impacts
What was accomplished under these goals?
In Objective 1, we proposed to develop a bacterial system for synthesizing the mature peptide (GmPEP3) in vitro. To this end, the Zhang lab has transformed Bacillus subtilis with a codon-optimized construct encoding the mature GmPEP3 peptide. The Goggin lab has confirmed the transformation by sequencing, is optimizing assays to quantify peptide excretion by the bacteria, and is currently performing greenhouse bioassays to test the effects of this transgenic B. subtilis on soybean growth and nematode infection. In Objective 1, we also proposed to characterize transgenic soybean lines with enhanced expression of a soybean propeptide (GmPROPEP3). Towards this goal, the Goggin lab has used qPCR to identify independent lines with single transgene insertions, and have performed PCR genotyping and segregation analyses to select for seed lots that are homozygous for the transgene. To date we have developed homozygous seed lots for two independent events with single transgene insertions, and greenhouse bioassays are underway to measure plant growth, development, photosynthetic activity, and nematode resistance in these lines in comparison to plants that received peptide seed treatments or control treatments. Work is also underway to select homozygous materials for at least one additional single insertion line. Selecting for single insertions will help reduce the likelihood of gene silencing in subsequent generations and selecting for homozygous lines facilitates bioassays by eliminating the need for prior genetic screening. Moreover, the use of single-insertion homozygous lines eliminates variation in gene dosage that could cause excessive within-treatment variation. The bioassays underway will help us assess the relative benefits of the transgene for nematode management, and will also generate phenotypic data that can help address Objective 3 (to measure the effects of PEPs on plant growth). In Objective 3 we proposed to measure the costs and benefits of activatingPEP-mediated immunity on plant growth and productivity in the presence and absence of nematode infestation. The Goggin lab is optimizing an image-based root phenotyping protocol to characterize root growth and architecture in soybean seedings, and is currently applying this approach to assess the effects of GmPEP3 seed treatment on early root development. To address both Objective 3 and Objective 2 (to characterize the impacts of activatingPEP-mediated immunity on the balance of beneficial and pathogenic microbial guilds in soil communities), we have also initiated a large greenhouse microplot experiment testing plant health and soil microbial composition. The experiment included three variables with two levels each (1 µM GmPEP3 seed treatment or carrier control treatment: pasteurized or unpasteurized field-collected soil; and inoculation with 5,000 or root knot nematode infective juveniles or mock inoculation with water) which were combined in a full factorial design to give a total of 8 treatment groups. Pots without plants containing pasteurized and unpasteurized soil were also included to monitor soilborne pathogens in fallow soil. The experiment was performed using sandy loam soil collected from the Vegetable Research Station at Kibler, AR, and the soil was tested prior to use to confirm the absence of phytoparasitic nematodes. Plants were grown to maturity (R5-R6) and plant height, development, above and belowground biomass, seed production, and nematode infection levels were monitored by the Goggin laboratory to assess the potentially interacting influences of peptide treatment, nematode infection, and naturally occurring microbial communities on soybean productivity. The Rojas lab collected soil samples at planting to monitor baseline of soilborne pathogens, and then sampled all plots again at physiological stage R5-R6, collecting roots and rhizosphere soil to monitor pathogens at maturity and harvesting. Samples are being processed to establish microbial communities. Protocols for DNA extraction from soil and root samples were standardized to evaluate samples from this experiment. In addition, the Rojas lab has been working to establish a collection of rhizospheric microbes including diazotrophs and rhizobia for inoculation experiments to determine the impact of PEPs on root colonization symbiotic and free-living organisms associated with nitrogen fixation. For Objective 2, we also proposed to characterize the impacts of PEP enhancement on soil-borne microbes of importance to plant health. In year 1, the Rojas lab initiated seed plate assays based on the method developed by Da Silva et al. (2019) to evaluate the activity of GmPEP3 seed treatments (1 and 2 µM) on distinct soil-borne pathogens as compared with water controls and standard pesticide seed treatments for the pathogens evaluated. We are currently testing different soil-borne pathogens: Macrophomina phaseolina, Pythium ultimum and Rhizoctonia solani (AG4), comparing PEP treatments to traditional seed treatment for each pathogen (M. phaseolina - fludioxonil, Rhizoctonia spp - sedaxane, and Pythium ultimum - mefenoxam). Imbibition with peptide was evaluated at saturation and overnight (2 hrs and 24 hrs respectively). The imbibition at 24 hrs resulted in better germination overall, and this treatment will be used for future assays. In summary, in year 1 we have generated all the protocols and materials (transgenic lines and genetically modified bacteria) planned for this year, and have made significant progress on all three objectives.
Publications
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