The Diversity of Arbuscular Mycorrhizal Fungi Amplified from Grapevine Roots (Vitis vinifera L.) in Oregon Vineyards is Seasonally Stable and Influenced by Soil and Vine Age

Authors: Schreiner, Roger - Paul; Mihara, Keiko

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2009
Publication Date: 9/2/2009
Citation: Schreiner, R.P., Mihara, K.L. 2009. The diversity of arbuscular mycorrhizal fungi amplified from grapevine roots (Vitis vinifera L.) in Oregon vineyards is seasonally stable and influenced by soil and vine age. Mycologia. 101:599-611.

Interpretive Summary: The types of beneficial, arbuscular mycorrhizal fungi (AMF) present as spores in soil and in the roots of 'Pinot noir' grapevines from a variety of vineyards in Oregon were identified. Spores were identified based on microscopic characters (classical method) and fungi in roots were identified by amplifying fungal DNA from roots using PCR. The fungi identified as spores in soil did not match those fungi in grape roots. AMF identified from the roots of vines from 10 vineyards were almost exclusively (>99%) fungi from the genus Glomus, while spores in soil also represented fungi from three other genera. Four fungi were found in roots at every vineyard we examined and accounted for 81% of all root clones evaluated. Only one of these four common fungi is a known species, Glomus intraradices. The types of AMF in 'Pinot noir' roots did not change over the growing season, but they were affected by soil type and by vine age. Some fungi were more commonly found in red-hill soils and some were more numerous in valley soils, and these differences were related to higher fertility in the valley soils. The diversity of fungi in grape roots declined as vines aged beyond about 20 years. Taken together, these findings indicate that; (1) the types of AMF engaged in symbiosis in roots cannot be predicted by the types of AMF spores found in soil (this is important because we use spores to ultimately identify and culture these fungi), (2) grapevines selectively associate with certain AMF out of the whole vineyard AMF community, (3) the small number of AMF that dominate the symbiosis with grape roots in western Oregon vineyards do not change over the growing season, and (4) some AMF may be better adapted to the lower fertility red-hill soils, but these same fungi are present in roots in valley soils.

Technical Abstract: The diversity of arbuscular mycorrhizal fungi (AMF) associated with the roots of grapevines in 10 commercial Oregon vineyards was assessed by examining spores in soil and by amplifying mycorrhizal DNA from ‘Pinot noir’ root extracts. Seventeen spore morphotypes were found in the soil beneath the vines, including seven species in the Acaulosporaceae. Scutellospora calospora was found in soil from nine vineyards, Glomus mosseae and Glomus intraradices were each found in soil from eight vineyards, and Acualospora elegans and a small clear Glomus sp. were each found in soil from seven vineyards. Cloned PCR products using AM1 and NS31 primers gave a total of 18 phylotypes from grape roots, and these were dominated by Glomus spp. (> 99%). A few clones representing a single phylotype within the Gigasporaceae and a single clone within the Archaeosporaceae clade were identified from grape roots. However, no clones representing fungi within the Acaulosporaceae were found in roots. Four Glomus phylotypes (including G. intraradices) were found in grape roots from all the sites, and these four fungi accounted for 81% of all clones. The AMF phylotypes amplified from ‘Pinot noir’ roots did not change over the growing season, although an analysis comparing age-matched, samples from red-hill versus valley floor soils indicated the abundance of six phylotypes varied with soil type. The presence of three phylotypes was affected by vine age and the total number of phylotypes (richness) appeared to decline as vine age increased beyond 20 years. PCA analysis supported the hypothesis that the AMF community is different in red-hill soils than in the valley soils, and indicated certain phylotypes may be associated with lower soil and vine nutrient status. However, the changes in the AMF community in grape roots from site to site were subtle, since most root samples were dominated by the same three or four phylotypes. A separate analysis using primers to amplify AMF from the Archaeosporaceae/Paraglomeraceae showed most root samples were also colonized by at least one Paraglomus or Archaeospora phylotype.