Location: Characterization and Interventions for Foodborne Pathogens
2017 Annual Report
Objectives
1: Increase efficiency of AM fungus inoculum production and utilization to enhance vegetable production and reduce inputs.
1A. On-farm production and utilization of AM fungus inoculum to enhance vegetable crop yields and reduce inputs.
o Increase propagule density of inoculum produced when the indigenous community is used as starter inoculum. (Douds)
o Demonstrate use of AM fungus inoculum produced on-farm for eggplant production.
1B. Examine the use of black plastic mulch upon indigenous AM fungus activity and evaluate relative to opportunities to utilize AM fungus inoculum. (Douds)
2: Determine the effects of arbuscular mycorrhizal fungus species on improving crop physiological responses that enhance nutrient uptake, increase production of polyphenols, and enhance plant resistance to insect pests and diseases.
2A. Quantify the impact of AM fungus colonization upon production of polyphenols of known health benefit in different crops.
2B. Enhance the utilization of the AM symbiosis through studies of basic physiology and nutrient uptake.
o Measure the flow of C, N, and P between plants of varying photosynthetic rates via common, interconnected AM fungus networks and correlate to expression of plant P and NH4 transporter genes.
o Determine the impact of newly-identified root exudate signal molecules (abietic acid and dehydroabietic acid) on carbon uptake and lipid synthesis by germinating spores of AM fungi via NMR spectroscopy.
o Determine the impact of semi-purified root exudate signals in combination with low oxygen concentrations upon AM fungus germination and growth.
3: Develop management practices that minimize the potential negative effects of off-site transport of pathogenic bacteria in integrated crop/livestock production systems.
3A. Inactivate pathogenic bacteria, originating from animal manure, moving in surface water as a result of heavy rainfalls, before they can enter farm irrigation ponds by using erosion control socks amended with fast pyrolysis biochar.
Approach
Arbuscular mycorrhizal [AM] fungi are obligate symbiotic soil fungi that form a mutualistic symbiosis with the majority of crop plants. Better utilization of this symbiosis will enable farmers to increase or maintain yields while reducing synthetic chemical inputs. Earlier, we developed a method for the on-farm production of inoculum of AM fungi using bahiagrass as the host plant. This method will be refined for the production of AM fungi indigenous to the farm and its usefulness demonstrated for the production of eggplant. The obligate symbiotic nature of these fungi require that a host plant be present during the production of inoculum for use by farmers. Large scale production of pure inoculum of these fungi (i.e. growth of the fungi by themselves, in the absence of a plant) is possible if the physiological limitations that require colonization of a host plant could be overcome. We will attempt to overcome these constraints by growing the fungi in the presence of a combination of environmental factors (root exudate signals, high CO2, and low oxygen) more representative of the environment in which they naturally grow rather than typical laboratory conditions. Other studies will examine the impact of AM fungus colonization upon mineral nutrient uptake and the production of human health-promoting compounds in plants. Farms with integrated livestock and crop production are faced with regulatory pressures designed to minimize the risk of contamination of produce with bacteria originating in animal manure. We will explore the idea that erosion control socks containing biochar, previously shown to reduce the population of pathogenic bacteria in soil by 100 fold, could be used to intercept rainwater runoff from pastures and inactivate bacteria before they contaminate the water in an irrigation pond.
Progress Report
This project, “Production, utilization, and importance of arbuscular mycorrhizal fungi in sustainable vegetable production” completed the OSQR Peer Review Process and was approved on October 14, 2016. Progress was made on all objectives, all of which fall under National Program 212 Research Components: 1. Management and stewardship of soil resources and 3. Reducing environmental risk of agricultural operations. Problem Statement 1B: Agricultural management for resilient soil, Problem Statement 1C: Enhancing Soil Biodiversity and Functions, Problem Statement 3A: Reducing pathogens and antibiotic resistance.
Arbuscular mycorrhizal (AM) fungi are soil fungi which form a symbiosis with the majority of crop plants, assisting roots in nutrient uptake, drought tolerance, and disease resistance. Better utilization of this symbiosis in agriculture through the contributions of this project should result in decreased synthetic chemical input and increased profits and sustainability. A number of field experiments were conducted to demonstrate the ability of AM fungus inoculum produced on-farm to enhance yield of crops in real-world situations. Experiments with eggplant concluded in autumn 2016 and showed increases in yield of AM fungus inoculated vs. non-inoculated plants of 6 to 18% (or 1 to 1.5 fruit per plant). Also completed was one replicate of a large scale experiment to determine which farm habitat is best for collection of field soil as starter inoculum for the on-farm production of indigenous isolates of AM fungi. Results indicated that a field previously used to produce a row crop subsequently planted to an overwintering small grain produced the most potent inoculum. The replicate of this experiment is underway. Biochemical studies were expanded to investigate levels of different polyphenols of (human) nutritional quality in plants (e.g., leeks, pepper, corn, tomato, lettuce) as a result of AM symbiosis. Mechanistic studies with collaborators at South Dakota State University examined how mineral nutrient flow to a given plant is governed by the relative photosynthetic strength of that plant compared to the others.
Accomplishments
1. Use of fungus inoculum increased yield in eggplants. The Grand Challenge of ARS is to increase crop yields with reduced input of resources. One option is the intentional use of naturally-occurring symbioses between soil microorganisms and plant roots such as the one formed by arbuscular mycorrhizal [AM] fungi. ARS researchers at Wyndmoor, Pennsylvania conducted two years of experimentation at conventional vegetable farms which showed increases in yield of eggplant fruit of 6-18% by weight. Fungus Inocula were produced on-farm at a cost of less than a penny per plant. This result demonstrates the great potential for the use of AM fungi to increase the yield of vegetables without increased inputs.
Review Publications
Liu, Y., McKeever, L., Malik, N.S. 2017. Assessment of the antimobial activity of olive leaf extract against foodborne bacterial pathogens. Frontiers in Microbiology. doi: 10.3389/fmicb.2017.00113.
Chaiyasen, A., Douds, D.D., Gavinlertvatana, P., Lumyong, S. 2017. Diversity of arbuscular mycorrhizal fungi in Tectona grandis Linn.f. plantations and their effects on growth of micropropagated plantlets. New Forests. doi: 10.1007/s11056-017-9584-6.
Douds, D.D., Carr, E., Shenk, J., Ganser, S. 2017. Positive yield response of eggplant (Solanum melongena L.) to inoculation with AM fungi produced on-farm. Scientia Horticulturae. doi: 10.1016/j.scientia.2017.05.017.
Malik, N.S., Nunez, A., McKeever, L., Kunta, M., Douds, D.D., Needleman, D.S. 2016. Mycorrhizal fungi collected from the rhizospheres around different olive cultivars vary in their ability to improve growth and polyphenol levels in leeks. Journal of Agricultural Science. 8:1-10.
Malik, N.S., Nunez, A., McKeever, L. 2015. Mycorrhizal symbiosis produces changes in specific flavonoids in leaves of pepper plant (Capsicum annum L.). Subtropical Agriculture and Environments. 66:16-22.
Douds, D.D., Lee, J., McKeever, L., Ziegler-Ulsh, C., Ganser, S. 2016. Utilization of inoculum of AM fungi produced on-farm for the production of Solanum lycopersicum: a summary of 7 years of field trials on a conventional vegetable farm with high soil phosphorus. Scientia Horticulturae. 207:89-96.
