Changes in the composition of native root arbuscular mycorrhizal fungal communities during a short-term cover crop-maize succession

Arbuscular mycorrhizal fungi (AMF) establish mutualistic associations with the most important agricultural food and feed crops, sustaining plant growth, nutrient uptake and tolerance of biotic and abiotic stresses. Scanty information is available on the role played by crop identity and diversity as a driving force shaping AMF species communities in the field, in particular in low-input and organic farming, where crop rotation and the use of cover crops are common practices. Here, using a molecular approach, we investigated whether plant communities established in low and high diversity cover crop treatments affect the composition of native AMF root communities of subsequent maize in a Mediterranean organic agroecosystem. A total of 16 AMF sequence types were detected, with Acaulospora cavernata as the most abundant phylotype, accounting for 37.4 % of the sequences, followed by Funneliformis mosseae, Claroideoglomus lamellosum and Rhizoglomus intraradices. Sequences matching to Funneliformis caledonium, Diversispora aurantia, Diversispora epigaea and Archaeospora schenckii corresponded to less than 2.0 % of the total. The most abundant sequences retrieved in plants from cover crop treatments were represented by A. cavernata, while sequences in maize roots were related to F. mosseae, R. intraradices and Glomus sp. Such data show for the first time a change in the composition of native AMF communities colonizing maize roots, which was independent of the identity and diversity of the preceding crop. Our findings suggest that host preference may represent a strong driver of AMF community dynamics in agroecosystems, differentially boosting or depressing AMF species, possibly in relation to their functional significance.