Spore-based arbuscular mycorrhizal fungal community in an olive cultivation area in southern Brazil

Arbuscular mycorrhizal fungi (AMF), belonging to the phylum Glomeromycota, establish symbiotic associations with approximately 90% of terrestrial plant species and play a key role in nutrient acquisition, tolerance to abiotic stresses, and agroecosystem functioning. Although olive cultivation has expanded in southern Brazil, information on native AMF communities associated with this crop remains scarce. This study characterized the AMF community associated with the rhizosphere of the olive cultivars Arbequina, Coratina, and Picual cultivated in Rio Grande do Sul, Brazil. Soil sampling was conducted in February 2025, during the summer dry season, when trees were in a vegetative growth, were not flowering or fruiting. Because AMF sporulation may vary according to host phenology and seasonal environmental conditions, the present survey reflects fungal communities under vegetative growth during the dry season. Spores were extracted by wet sieving and identified based on morphological characteristics. Six species belonging to five genera: Acaulospora koskei, Glomus ambisporum, Diversispora globifera, Gigaspora decipiens, Gigaspora rosea, and Scutellospora calospora. G. ambisporum was dominant in all cultivars. Differences among cultivars were observed for G. decipiens, D. globifera, and G. rosea. Cultivar identity explained 56.2% of the total compositional variation. Coratina showed lower evenness due to the dominance of G. ambisporum. SIMPER analysis indicated that G. ambisporum and G. decipiens accounted for 59.7% of the dissimilarity between Arbequina and Coratina. This study represents the first inventory of AMF associated with olive rhizospheres in southern Brazil and provides a basis for selecting native isolates for future inoculant development.