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Title: Effects of Land Use Changes on Arbuscular Mycorrhizal Fungi Abundance and Diversity in Selected Agro-Ecological Zones of Ethiopia: Implications for Sustainable Agro-Ecosystems
???metadata.dc.contributor.*???: Dr. Fassil Assefa
Belay, Zerihun
Keywords: Abundance;diversity;Arbuscular mycorrhiza! fungi (AMF);Claroideoglomus;Glomus;Fwmeliformis;land use change;Rift valley;Showa Robit
Issue Date: May-2015
Publisher: Addis Ababa University
Abstract: Arbuscular ihycorrhizal fungi (AMF) are ubiquitous soil organisms that form the symbioscs with majority of terrestrial plants including most of the agricultural crops. These fungi help plants in mineral and water uptake, and alleviation of abiotic and biotic stresses. They are particularly important in tropical ecosystems that are characterized by low soil fertility. The density and diversity of AMF are the major contributors to the maintenance of plant biodiversity, productivity, and ecosystem stability and function. AMF are also important in the reclamation and restoration of degraded ecosystems and in horticultural systems. However, AMF communitystructure and function arc affected by changes induced by severe deforestation and land degradation that, in turn, affect the soil physical and chemical characteristics, fertility and stability. The land use and land cover change from forests and grasslands into settlements and agricultural systems for several decades in Ethiopia is supposed to drastically change plant diversity that directly influences the community structure of AMF. This necessitates the exploration of the AMF-land use change associationwithin selected agroecosystems in the country. 'The main questions of this work, therefore, were; 1) Have different land use systems impacted the community composition and abundance of AMF species? and 2) If so, what is the community shift of AMF in terms of plant type and cropping systems in the changing land use and land cover of the ecosystem? 3) Is AMF species diversity and abundance influenced by the plant species composition or soil factors? For this purpose abundance and diversity of AMF were studied in different land use systems in relation to vegetation types, soil physical and chemical properties, and different disturbances in humid lowland ecosystem at Showa Robit, Central Ethiopia, and dry acacia grassland ecosystem, Rift Valley, Ethiopia. From the dry acacia grassland ecosystem, root samples and rhizosphcre 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 Bishofhi, Zeway with different land use types to assess AMF diversity, spore density and root colonization. The highest AM fungal colonization was found in A. seyal (67.3%) from open grazing field (OGF) at Zeway, whereas the lowest AMFcolonization of 12% was recorded from A. saligna at Bishoftu. The AMF spore count from the rhizospherc of the different trees was within the range of 3.7 spores gas 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 familes were identified. Apart from the common AMF genera of Glomus, Clarohleoglonms, Funneliformis, other rare genera such as Racocetra, Diversispora, Archaeospora, Entrophosphora and Sclerocystis were also recorded. Claroideogloinus claroideum, C. etunicatum, C. luleum, Funneliformis geosporum and Glomus aggregation were the dominant species. The study showed that the acacia species were characterized by relatively high AMF colonization and very high AMF diversity From the study of the humid lowland ecosystem at Showa Robit, the indigenous AM fungal populations in soil and in trap cultures were evaluated from different land use types. Accordingly, seven land use types were selected, that include low-input arable systems, either having a mixture of crops (Arable1) or monocropped with sorghum (Arable2) or maize (Arable3). Arable4 was a relatively high-input system with monocropped sorghum. The others were; fruit cropping area (FC) managed with composts and plant residues, a natural forest (NF) and an acacia plantation (AP). The parameters studied were; AMF spore abundance, species richness, diversity indices and Mycorrhizal Inoculum Potential (MIP). The result showed a significantly higher number of spores from PC, Arable1 and Arable3 (5.8-6.1 spores 4g soil) than the land use types characterized by the lowest spore numbers (Arable 4, NF, AP) (2.8-3.9 spores 'g soil) in field soil while AP, PC, and Arablc2 had the highest numbers (9.8- 11.1 4g soil) and Arabled and NF were lowest number of spores (2.5-3.8 '!g soil) in trap cultures. The data showed slightly different pattern of mycorrhizal infectivity potential with Arable1 (53.7%) and FC (52.6%), having significantly higher HC (%) compared to the other land use types that fell within percentage colonization of 19.9- 25.8 %. A total of 38 and 28 morphospecies of AMF in 15 genera were identified in field soil and trap culture soil, respectively. The data showed that trap culturing increased spore number but caused a loss of AMF species richness. Higher species richness and MTP were obtained in FC and Arable1 compared to the other systems. The groups were categorized into Dominant, Common and Rare genera. Claroideoglomus and Funnelifonnis were found to be dominant that were distributed across all land use types in both trap culture and field soil. The results clearly showed that manuring and diversification of crops under low-input agricultural system enhances AMF diversity In the final component of the study, mycorrhizal fungi association of six fruit plant species [Mangiferci indica (mango), Musa acuminate (banana), Carica papaya (papaya,), Citrus Union (lemon), Persea americana (avocado), and Psidium guajava (guava)] was investigated. The result showed that fruit crops fell into higher spore density group of (7.2-8.8 spores g4 of soil) and low spore density group (3.7-5.3 spores g'1 of soil). Accordingly, mango, avocado, banana, and lemon were from the high density spore group; whereas, papaya, and guava fell into the low spore density group at P <0.05. The AM colonization also showed that mango and lemon fell into high mycorrhization (71.7%), and guava under low mycorrhization group (27.3%). A total of 32 morphospecics into 12 genera were characterized from all the fruit crops. The highest AMF species richness was in mango (18 species) followed by banana (16 species) and guava (14 species). The species Claroideoglomus claroideum and Glomus aggregation were the dominant species (“ generalists” ) among the fruit trees. Generally, the spore abundance and the species diversity of AMF identified from the selected agro-ecological zones of Ethiopia were relatively large compared to the previous works. The study also showed more diversity of AMF species was identified in dry acacia grassland ecosystem than in humid lowland ecosystem. However, future studies should be focused on the genera Claroideoglomus, Glomus and Fwmeliformis so as to develop AMF inocula for enhancing productivity of the different cropping system. Understanding the role of AMF over a broad range of land use systems is essential to establish seedling of woody plants for land rehabilitation and effective management for sustainable production through AMF technology
Description: A Thesis Submitted to The Department of Microbial, Cellular and Molecular Biology Presented in Fulfillment of the Degree of Doctor of Philosophy (Microbial, Cellular and Molecular Biology)
Appears in Collections:Thesis- Microbial, Cellular and Molecular Biology

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