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Subject

Mycorrhizae

Description

Microscopic hyphae and spores of AM fungi in the cortex of a grapevine root.

Arbuscular mycorrhizal (AM) fungi are soil microbes that live in vine roots. The combination of the fungus and the vine is a mycorrhiza – a symbiotic relationship with mutual benefits. The vine provides the fungus with its sole source of carbon and the fungus provides the vine with soil-derived nutrients, namely phosphorus. Mycorrhizae play essential roles in grapevine nutrition, as evidenced by their beneficial effects on vine growth, phosphorus nutrition, and water relations. The fungal filaments – hyphae (pronounced ‘high-fee’) – that extend into the soil make up the majority of the fungal biomass. The length of these external hyphae is typically one to two orders of magnitude higher than that of roots. As such, they significantly increase the absorptive surface area of the root system and enhance the ability of grapevines to utilize nutrients from the soil solution.

The nutrient deficiencies grapevines develop in the absence of mycorrhizae, as can occur after soil fumigation, make it clear that adopting practices to encourage mycorrhizae is worth the effort. In the field, AM fungi naturally colonize grapevines. Sources of AM fungi include roots of field-propagated nursery stock (e.g. dormant benchgrafts and rootings), cover crops, and weeds, and wind-blown spores from other vineyards, orchards, and row crops. Based on the fact that mycorrhizal roots are a better source of AM fungal inoculum than are spores, an easy way to encourage mycorrhizae is to plant a cover crop.

People

Kendra Baumgartner
Dr. R. Paul Schreiner, Research Plant Physiologist, USDA-ARS, Corvallis

Links

Mycorrhiza Literature Exchange

Adobe/Macromedia Breeze Presenter modules provide on-demand viewing of previously recorded PowerPoint presentations with streaming video and audio on the Web. They feature high-quality still images with synchronized audio and video; automatic playback or manual navigation; and a keyword search of slide text and notes. As Flash movies they are platform independent, but they do require Flash Player 6 or higher, which is currently installed on most computers. These modules were produced by UC Davis IET Mediaworks. The speaker and presentation may be viewed in video on the following links:

“MYCORRHIZAL FUNGI” - Dr. Kendra Beumgartner USDA-ARS research plant pathologist, UC Davis. Presented at Recent Advances in Viticulture and Enology (RAVE) March 16, 2006, UC Davis.

Publications

Baumgartner, K. 2003. Why and how - Encouraging beneficial AM fungi in vineyard soil (PDF). Practical Winery and Vineyard (January/February):57-60.

Baumgartner, K., Smith, R., and Bettiga, L. 2005. Weed control practices and cover crop management affect mycorrhizal colonization of grapevine roots and arbuscular mycorrhizal fungal spore populations in a California vineyard. Mycorrhiza 15:111-119.

Cheng, X, Baumgartner K. 2004. Arbuscular mycorrhizal fungi-mediated nitrogen transfer from vineyard cover crops to grapevines. Biology and Fertility of Soils 40:406-412.

Cheng, X., and Baumgartner, K. 2004. Survey of arbuscular mycorrhizal fungal communities in Northern California vineyards and mycorrhizal colonization potential of grapevine nursery stock. HortScience 39:1702-1706.

Cheng, X., and Baumgartner, K. 2005. Overlap of Grapevine and Cover-Crop Roots Enhances Interactions among Grapevines, Cover Crops, and Arbuscular Mycorrhizal Fungi (PDF). Pages 171-174 In: Proceedings of the Soil Environment and Vine Mineral Nutrition Symposium. American Society of Enology and Viticulture, 29-30 June 2004, San Diego, CA.

Cheng, X., and Baumgartner, K. 2006. Effects of mycorrhizal roots and extraradical hyphae on ¹⁵N uptake from vineyard cover crop litter and the soil microbial community. Soil Biology and Biochemistry 38:2665-2675.

Baumgartner, K. 2006. The Role of Beneficial Mycorrhizal Fungi in Grapevine Nutrition (PDF). American Society of Enology and Viticulture Technical Update 1:3.

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