Cohort of arbuscular mycorrhizal fungi (AMF) in Vitis vinifera, a typical mediterranean fruit crop

In wine grape production mineral fertilizer and cover crops are combined to optmize the soil nutrient content. A low fertilizer input can be applied, since grapevine roots are colonized by arbuscular mycorrhizal fungi (AMF) under field conditions. The root symbiotic fungi that form arbuscular mycorrhizae (phylum Glomeromycota) are among the most important soil organisms. They are the oldest group of organisms living in symbiosis with land plants (Redecker et al., 2000; Bonfante, Genre, 2008). AMF facilitate mineral nutrient uptake from the soil in exchange for plant-assimilated carbon and promote water-stress tolerance and resistance to certain diseases (Smith, Read, 2008). The inoculation of vine rootstock with AMF can result in increased growth (Schubert et al., 1988), enhanced nutrient uptake (Schreiner, 2007) and improved drought tolerance e.g., in 'Cabernet sauvignon' grafted onto various rootstocks (Nikolaou et al., 2003). Increased root colonization by AMF in response to a lower soil water content implies that AMF may play a significant role in the response of vines to water stress (Schreiner et al., 2007). However, little is known about the species composition of AMF communities associated to grapevine roots in vineyards. Previuos studies, based on the identification of AMF spores, reported the genus Glomus as being the most represented in vineyards (Karagiannidis et al., 1997). However, the spores were not able to mirror the AMF community present in the soil due to the seasonality and their different production rate. Recently, the use of a molecular approach has allowed this gap in knowledge to be overcome (Schreiner, Mihara, 2009; Balestrini et al., 2010). Balestrini et al. (2010) have carried out an investigation on AMF communities in vineyards by means of the analysis of partial rRNA gene sequences. Two vineyard soils, with different physical-chemical features, were compared and the results have shown that the soil characteristics can play an important role and shape the AMF assemblage structure and composition, thus confirming previous studies (Schreiner, Mihara, 2009; Lumini et al., 2010). The aim of this study is to characterize the AMF community in association with grapevine roots in a Piedmont vineyard and to analyze the relationship between AMF communities outside and inside roots.