Arbuscular Mycorrhizal Fungal Communities Associated with Vitis vinifera Vines under Different Frequencies of Irrigation

Abstract

The effects of irrigating daily or every three days on arbuscular mycorrhizal fungal communities associated with grapevine roots were determined in vineyard blocks of Merlot and Syrah on 3309 rootstock. After exposure to treatments for four growing seasons, root samples were analyzed for changes in AM fungal colonization, species richness, and community composition. AM fungal colonization was higher in response to irrigating every three days compared with daily irrigation, indicating a treatment effect on the physiology of the fungal communities. Using a pyrosequencing approach, no difference in AM fungal community composition was found in response to irrigation frequency. Species richness, identity and dispersion were consistent across the two treatments. A difference in AM fungal communities between the two varietal blocks was associated with differences in soil chemistry and plant physiological traits. In particular, soil carbon and extractable copper levels along with vine vigor and photosynthesis were correlated with community variation. This indicates environmental factors other than irrigation frequency influence the fungal community structure in vineyards.