Diversity of Arbuscular Mycorrhizal Fungi in olive orchard soils in arid regions of Southern Tunisia

Arbuscular Mycorrhizal Fungi (AMF) play a fundamental role in the development and survival of plant species in arid regions. The objectives of the present research were (1) to characterize the native AMF communities in olive orchard soils collected from arid regions of southern Tunisia and (2) to study the AMF-host specificity hypothesis. AMF spores were extracted from soil-root samples collected from orchards planted with two indigenous olive cultivars (Chemlali and Zarrazi) and located at three sites (Matmata, Zarzis and Tataouine) along an aridity gradient. First, the abundance of AMF spores was determined; then the AMF spores were grouped into several morpho-types and molecularly characterized by 18S rDNA nested-PCR approach. AMF abundance and diversity varied among cultivars and sites. Olive orchard soil of Zarzis site had the highest spore density (140 spores/100g soil), while the Tataouine site had the lowest density (100 spore/100 g soil). Pooled data of morpho-typing and sequence-driven analyses allowed the identification of 10 AMF taxa with the dominance of Glomeraceae family, represented by Glomus, Rhizophagus and Funneliformis genera, followed by Diversisporaceae family. The less arid site (Matmata) exhibited the highest AMF diversity, while the most arid-site (Tataouine) showed the lowest one. The cultivar Zarrazi displayed a higher ability to associate with AMF than Chemlali. For all analyzed sequences, five AMF taxa were associated with Chemlali and eight were associated with Zarrazi.