Phenotypic characteristics of root nodule Bacteria and Arbuscular Mycorrhizal Fungi infecting Acacia polyacantha growing in Ghibe wooded grasslands

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Addis Ababa University


Tree legume (Acacia polyacantha) was tested for their capacity to nodulate with indigenous root nodule bacteria in soil collected from Ghibe Valley. The five isolates were characterized by some biochemical and physiological tests. Based on specific growth rate and acid production, the isolates were assigned tentatively to Bradyrhizobium and Rhizobium. The infective propagules of Arbuscular mycorrhizal fungi (AMF) occurring on the study site was determined by spore count and most probable number (MPN). Average spore count of soil found out 58per 100g and a hundred gram of field soil contains 189.42 infective propagules. The dominant spore count encountered was Glomus like AMF (59.1%) and 40.9% of the rest spores were Gigaspora-Scutelospora type AMF. Response to inoculation with Bradyrhizobium, AMF, dual inoculation and fertilizer treatments of Acacia polyacantha studied in glasshouse condition submitted to 7 treatments. After 70 days, the plants were harvested and nodule number and dry mass, shoot height, dry weight, nitrogen and phosphorus content were determined. Results showed that A. polyacantha inoculated with both organisms recorded the highest nodule number, shoot dry weight, nitrogen and phosphorus content (p<0.001). Thus, the extent of rhizobium and mycorrhizal symbiosis in this tree species under green house condition can affect growth.