Analysing natural diversity of arbuscular mycorrhizal fungi in olive tree ( Olea europaea L.) plantations and assessment of the effectiveness of native fungal isolates as inoculants for commercial cultivars of olive plantlets

Abstract

The natural diversity of arbuscular mycorrhizal (AM) fungi in the root-associated soil from long-term established olive tree plantations was analysed. Four distinguishable native AM species, namely, G. intraradices (BEG 123), G. mosseae (BEG 124), G. clarum (BEG 125) and G. viscosum (BEG 126), were morphologically identified. These strains were also genetically characterised by PCR amplification and sequence analysis of a portion of their SSU rRNA. Phylogenetic analysis of these sequences shows that the new sequences of G. mosseae, G. intraradices and G. viscosum cluster with those of the same species found in the database. However, the new sequence of G. clarum fell in a different clade. The effectiveness of these native AM fungi as inoculants for two target varieties of olive (Arbequina and Leccino), currently used in many Mediterranean areas, was assessed. Two AM isolates from our own culture collection, namely G. intraradices and G. mosseae, were also used as reference inocula. G. intraradices and G. viscosum isolated from the target agro-system were the most effective fungi to improve the development of both olive varieties. This study supports the need to explore and exploit the natural diversity of AM fungi as a starting point to formulate inoculants to be applied during the commercial nursery production of olive varieties.