Location: Sustainable Biofuels and Co-products Research
2022 Annual Report
Objectives
Objective 1: Determine the impact of management practices on AMF community dynamics and AMF colonization efficiency of crops, and the resulting impact on crop yield and quality.
Sub-objective 1.A: Determine optimal AMF inoculum composition for production of sweet corn and winter squash under organic and conventional management practices.
Sub-objective 1.B: Identify the impact of soil microbial dynamics caused by farm management practices on outcomes of AMF inoculations.
Objective 2: Determine the physiological and transcriptional responses of AMF to phytochemical signals and environmental conditions promoting spore germination and growth.
Sub-objective 2.A: Evaluate whether abietic acid and dehydroabietic acid are signals that activate carbon uptake by AM fungi.
Sub-objective 2.B: Evaluate whether hypoxia is a physiologic condition that activates carbon uptake by AM fungi, either acting alone or in combination with signals derived from root exudates.
Approach
For Obj. 1A, a greenhouse trial will be conducted to evaluate the infectivity
potential of nine different AMF species on sweet corn and winter squash seedlings. Seedlings will be harvested at 10 and 30 days after germination for analysis of root colonization and biomass measurements. Colonization will be measured by root staining/microscopy and molecular methods. Biomass measurements and mineral nutrient content will be analyzed.
For Obj. 1B, the three top-performing AMF isolates from 1A will be selected for
field trials. Field trials will be conducted within the Rodale Institute’s Vegetable Systems Trial (VST). Tillage systems consist of two organic and two conventional systems, and within each pair one utilizes plastic mulch for weed suppression and the other utilizes a cover crop. Mycorrhizal yield response will be evaluated. The field trial will be repeated a second year, and the results will be used to design a larger field study.
For Obj. 2A, spores of R. irregularis will be used in immobilized cell cultre in
phytagel M medium with 13C labelled glucose, AA, DHA,and Myr-K media amendments.
Growth and sporulation will be monitored. Lipid uptake will be assessed by
fluorescence microscopy, and uptake of carbohydrates will be measured by NMR. Based on biomass yield and uptake/labeling of 13C, an RNA-Seq experiment will be designed to capture genes differentially expressed in response to the amendments.
For Obj. 2B, spore germination and hyphal growth responses of two AMF species,
Gigaspora gigantea and R. irregularis, will be evaluated in response to partially
purified root exudates and reduced oxygen conditions (hypoxia). Carbohydrate and
lipid uptake will be measured by NMR and fluorescence microscopy as in 2A.
Progress Report
For Goal 1.A, a controlled Arbuscular Mycorrhizal Fungi (AMF) inoculation study was conducted using seedlings of two crops, sweet corn and butternut squash, in a greenhouse setting using nine individual single-species AMF inocula and one mixed-species native soil AMF community, as well as non-mycorrhizal control. Mycorrhizal colonization was assessed at two time points (15- and 30-days post-germination), root and shoot biomass were measured, and leaf mineral nutrient uptake was analyzed. Two of the nine AMF species plus the mixed native community were selected as treatments for a two-year field trial within the Rodale Institute’s Vegetable Systems Trial. Funding to Rodale for this project has been awarded from Pennsylvania Department of Agriculture Specialty Crop Block Grant with ARS as a collaborator, “Impact of Management Practices on Soil Mycorrhizal Fungi and Nutrient Uptake in Vegetable Crops,” ARIS Log No. 66605. Additionally, the findings have been used to prepare a manuscript “Impact of AMF inoculation on nutrient uptake and growth of sweet corn (Zea mays) and butternut squash (Cucurbita moschata) seedlings.”
For Goal 2.A and Hypothesis 2.B, biological materials have been cultured and prepared (spores and root exudates) and other supplies are on hand. It is anticipated the milestones will be fully met within the 12-month period ending 11/2022.
Nutritional quality of crops improved through fungal inoculation. Conducted controlled inoculation studies of individual- and mixed-species Arbuscular Mycorrhizal (AM) fungus inoculum on different crops to identify individual species or combinations of species of fungi which colonize roots most efficiently, enhance mineral nutrient acquisition from the soil, and promote favorable increases to yield and/or nutritional content. These controlled trials (in pots) enable the characterization of species-specific plant-fungal interactions and allow screening of ~10 species of AM fungi prior to selection of crop-specific inoculum formulations to be tested in field trials, some of which are already underway or are commencing this year. Controlled inoculation trials of beans, asparagus, wheat, and oats have confirmed a suspected but previously unproven role of AM fungi in the bioaccumulation of the nutraceutical antioxidant ergothioneine in plants. Ergothioneine, which is synthesized only by fungi and certain bacteria, is acquired by humans through dietary sources, and has gained attention as a molecule associated with the prevention inflammatory disorders and slowing the aging process in humans. Supplemental inoculation of wheat and oats with AM fungi in native soil (which already contains some AM fungi) doubled the grain ergothioneine content, and in sterile media, inoculation of black beans dramatically increased the ergothioneine content of seeds by >100-fold. Taken together, the controlled and field inoculation trials aid in the development of crop-specific formulations of individual- or mixed-species AM fungi inoculum as a biofertilizer which provides favorable increases to yield and enhances the nutritional quality of crops.
Accomplishments
