Location: Characterization and Interventions for Foodborne Pathogens
2018 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
Progress was made on Objective 1A, Increase propagule density of inoculum produced when the indigenous Arbuscular mycorrhizal (AM) fungus community is used as starter inoculum. An experiment was conducted in 2017 utilizing soil collected from habitats at the Rodale Institute farm. Soil from the pasture produced higher levels of AM fungi than it did the previous year (300 propagules cm-3 vs. 140 in 2016). Soil from fields used to produce small grain the prior year also produced satisfactory levels of inoculum. Progress was also made on Objective 2B, Measure the flow of Carbon (C), Nitrogen (N), and Phosphorus (P) among component organisms in the tripartite symbiosis of legumes. Legumes live in symbiosis with both AM fungi (supplying P) and Rhizobia (supplying N), with the plant supplying carbon in both instances. Physiological experiments conducted with a legume grown in compartmented chambers, separating the symbioses, showed that when N or P were externally applied chemically, the plant supplied carbon (sugar) preferentially to the organism supplying the nutrient that was in the most limited supply. This result helps us further understand the working of the symbiosis in order to put it to use for the sustainability of agriculture.
Accomplishments
