Influence of plant cover on the long-term dynamics of an arbuscular mycorrhizal fungal SynCom in a semi-arid Mediterranean environment.

The influence of the plant cover on the composition of an arbuscular mycorrhizal (AM) fungal synthetic community (SynCom) was studied in a time-course experiment. A mesocosm system was designed to mimic the environmental conditions of a semi-arid Mediterranean ecosystem, allowing the assessment of changes in AM fungal establishment, persistence, and sporulation within the SynCom. The mesocosm system included soil, AM fungi and plant species characteristic of the target region from Southern Spain. Retama sphaerocarpa, Lavandula latifolia, Thymus mastichina and Rosmarinus officinalis were selected and cultivated either in monoculture or in pairwise combinations, covering all possible dual associations. The initial AM SynCom was composed of six species (Rhizophagus clarus, Septoglomus constrictum, Funneliformis coronatum, R. intraradices, F. mosseae and S. viscosum), all isolated from southern Spain. Changes in the AM SynCom, both colonizing plant roots and the spores in the rhizosphere, were monitored every three months over three years. Fungi colonizing roots were identified through nested PCR-TTGE of the SSU rDNA, while AM fungal spores were quantified based on morphotype. Results indicate that plant species composition exerted only a limited influence on the AM fungal community structure, whereas pronounced species-specific differences in establishment, persistence, and sporulation shaped community trajectories over time. Septoglomus constrictum showed increasing spore abundance and specific density across all plant cover types, while other species (R. clarus, F. coronatum) became undetectable in the spore pool or maintained a low spore density (F. mosseae, S. viscosum). Qualitative root-detection patterns were generally consistent with rhizospheric sporulation trends, although the pooled PCR-TTGE approach did not allow quantitative comparison between intraradical occurrence and spore abundance. Overall, these results suggest that S. constrictum showed the most consistent persistence and sporulation under semi-arid Mediterranean conditions, identifying it as a candidate for further validation in AM fungal consortia intended for semi-arid Mediterranean environments, particularly for further testing in restoration-oriented applications under increasing aridity.