Final Report: June 2023
Principal Investigator: Tanya Cheeke, Washington State University, Richland
Cooperators: Dr. Michelle Moyer, WSU; Sarah Del Moro, crop consultant
Summary: In an effort to optimize the impact of mycorrhizal inoculations on wine grape production in Washington and validate the efficacy of mycorrhizal inoculants available to growers, this research pursued two objectives: 1) Determine whether inoculation with arbuscular mycorrhizal fungi (AMF) improves grapevine growth and foliar nutrient content under different phosphorus conditions; and 2) Evaluate the impact of different mycorrhizal inoculant products compared to locally-collected soil inoculants on wine grape growth and foliar nutrient content.
For the first objective, dormant cuttings of Merlot and Chardonnay were rooted in autoclaved field soil with the following four treatments of no AMF or phosphorus fertilizer, AMF inoculant only, phosphorus fertilizer only and both AMF and phosphorus fertilizer. The potted vines were grown in a greenhouse for five months. Merlot vines had a stronger growth response to the AMF than Chardonnay, especially in the pots with no added phosphorus. This study provides evidence of grapevine cultivar-specific responses to AMF in a greenhouse, which may be useful when planning nursery management strategies. In the second objective, three commercially available inoculant products were compared to two locally-collected mycorrhizal inoculants from vineyard soil and remnant steppe soil on Merlot vines grown in pots containing live field soil. Live field soil was used to represent the abiotic and biotic factors that young vines might encounter in a new vineyard planting. The addition of the inoculant products from the five tested sources did not improve the growth of the young potted vines, nor did it increase mycorrhizal root colonization compared to vines grown in the field soil. This suggests that the soil into which new vineyards may be planted may already contain enough viable mycorrhizal propagules to provide sufficient colonization of roots and benefits for wine grape growth.
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