Diversity and abundance of arbuscular mycorrhizal fungi associated with acacia trees from different land use systems in Ethiopia

Abstract

Zerihun Belay, Mauritz Vestberg and Fassil Assefa

Root samples and rhizosphere soil of nine acacia species (Acacia abyssinica, Faidherbia albida, A. nilotica, A. senegal, A. seyal, A. sieberiana, A. saligna, A. tortilis and A. robusta) were collected from Bishoftu, Zeway and Addis Ababa sites with different land use types to assess their Arbuscular Mycorrhizal Fungal (AMF) diversity, spore density and root colonization. The percentage of root length colonized by AMF was estimated. Spores, spore clusters and sporocarps extracted from soil samples were counted and morphologically identified to species or specific morphotype. Roots of all acacia species were colonized from low to moderate or relatively high levels by AMF with the occurrence of arbuscules, vesicles and hyphae. Arbuscules were however not detected in roots of A. senegal. The highest AM fungal colonization was found in A. seyal (67.3%) from open grazing field (OGF) at Zeway followed by A. nilotica (44%), whereas the lowest AMF colonization of 12% was recorded in A. saligna at Bishoftu. Rhizosphere soils harbored AMF fungal spores ranging from 3.7 spores g-1 soil in A. nilotica to 15.0 spores g-1 in A. seyal from open grazing field (OGF) at Zeway. A total of 41 AMF species in 14 genera and 7 families of the Glomeromycota were identified. Nine species belonged to Acaulospora, 6 to Funneliformis, 4 each to Gigaspora, Glomus, and Rhizophagus, 3 each to Claroideoglomus, and Scutellospora, 2 each to Racocetra and Diversispora, and 1 each to Entrophospora, Sclerocystis, Paraglomus and Pacispora. Moreover, 2 unidentified morphotypes each of Glomus, and Acaulospora and 1 of Archaeospora were isolated. Based on relative abundance and isolation frequency of spores, C. claroideum, C. etunicatum, C. luteum, F. geosporus and G. aggregatum were the dominant species in the study. The study showed that the acacia species were characterized by relatively high AMF colonization and very high AMF diversity. AMF spore density and AM root colonization in acacia roots were influenced by soil factors such as available P and soil texture