Phylogeny and distribution of arbuscular mycorrhizal fungi associated with Vachellia tortilis ssp. raddiana in relation to soil properties under arid ecosystems of Tunisia

It is of interest to investigate the diversity of arbuscular mycorrhizal fungi (AMF) associated with Vachellia tortillis ssp. raddiana to provide insights into the contribution of soil properties in shaping the AMF community composition and to define new strains for the production of inoculants under arid climate. A total of 230 symbiotic AMF clones associated with native V. tortilis roots growing in arid Tunisian soils were analyzed using nested PCR, cloning, and sequencing of the rDNA 18S region. The differential effects of soil properties on the diversity and community composition and distribution were also carried out. Phylogenetic analyses of four representative clones' libraries grouped them into nine AMF operational taxonomic units (OTUs) among the Glomeraceae family. Two OTUs (OTU4 and OTU7) were separated from any AMF reference sequence and may constitute new species within the Glomeraceae. The distribution pattern under soil properties showed that high available phosphorus content in the soil and electric conductivity decrease AMF diversity and that the remaining soil parameters are correlated with the AMF community composition. Specific soil properties associated with the diverse relative distribution of AMF species, described for the first time in this work, may serve as a model for studying how spatially distributed AMF in a wide range of habitats may be utilized by a pioneering plant with a situation that is frequently occurring at reclaimed sites or in ameliorated soils when a new vegetation cover such as Vachellia sp. needs to be established.