Diversity of arbuscular mycorrhizal fungal communities in multi-species organic cover crops.

Scanty information is available on the impact of diversified cover crops on native arbuscular mycorrhizal fungi (AMF). To study the diversity and phylogenetic structure of AMF communities in multi-species and monospecific organic cover crops in Central Italy, we analysed 54 root systems of host plants from six experimental plots. In the multi-species cover crop treatment host plants included Vicia villosa Roth, Trifolium alexandrinum L., Trifolium incarnatum L., Avena sp. and Phacelia tanacetifolia Benth., while only V. villosa was present in the monospecific cover crop. We detected 376 AMF sequences, spanning the regions V3 and V4 of the nuclear SSU rRNA gene, using AML1 and AML2 primers. Based on 97% sequence similarity, 15 Glomeromycetes operational taxonomic units (OTUs) were found, encompassing seven different AMF genera. Four OTUs, representing 88% of sequences, were shared among all plant species. They referred to the genera Funneliformis, Claroideoglomus and Acaulospora. Three singletons found in V. villosa, Avena sp. and T. alexandrinum in the multi-species cover crop treatment, referred to Glomus, Diversispora and Archaeospora, respectively. Although each plant species hosted a similar number of sequence types either if grown alone, as V. villosa in the monospecific cover (7), or grown together (6-10), the total number of OTUs from the monospecific (7) was lower than from the multi-species cover crop (15). AMF community structure in the roots of V. villosa grown either as single cover crop species or together with the other four species, did not show any differences, as revealed by PERMANOVA analysis, which, by contrast, detected a significant difference (P=0.035) among AMF communities hosted by plants of multi-species crop treatment. Our data highlight the important role played by cover crop diversity in promoting AMF diversity, which is fundamental for biological soil fertility and the delivery of ecosystem services