R Paul Schreiner,* David Janos, and Tian Tian
*USDA-ARS-HCRL, 3420 NW Orchard Ave., Corvallis, OR 97330 (paul.schreiner@ars.usda.gov)

Grapevines rely on arbuscular mycorrhizal fungi (AMF) to obtain ample phosphorus (P) from soils with moderate to low P, like the red-hill soils in western Oregon. Prior research using DNA sequencing indicated that six to 11 species of AMF colonized the roots of Pinot noir within a given vineyard. However, little is known about how different species of AMF function in vineyard ecosystems. We investigated the efficacy of five native AMF species representing five genera to promote growth and nutrient uptake of Pinot noir in a red-hill soil under well-watered and drought conditions. Rooted cuttings were grown in the presence of five different AMF or without AMF, and with or without moderate drought stress. After eight and 16 weeks, whole vines were destructively harvested and biomass and nutrient uptake were determined. Results showed that four of the five AMF colonized roots well, increased root and shoot biomass, and predominantly increased P uptake. However, a Claroideoglomus isolate was superior in promoting shoot growth and P movement to shoots. The ability to enhance vine growth and P uptake was not related to the extent of arbuscules in roots, suggesting that some P exchange may occur via hyphae. Water limitation reduced P uptake in this soil as a main effect across all AMF treatments, indicating that water stress reduced the capacity for P uptake by all AMF species studied here in a similar fashion.

Funding Support: USDA-ARS