Browsing by Author "Mulugeta, Endashaw"

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    Phenotypic and Symbiotic Properties of Rhizobia on Some Acacia Species from Silti Zone, Lanfuro Woreda Southern Ethiopia
    (Addis Ababa University, 2017-08-03) Mulugeta, Endashaw; Assefa, Mulugeta (PhD)
    Acacia is a multipurpose leguminous woody plant widely distributed in a wide range of habitats because of its ability to fix nitrogen and improve soil fertility. However, effectiveness in nitrogen fixation is variable, due to different factors. In this study, eleven isolates of root nodule bacteria from four Acacia species were isolated and evaluated for their effectiveness in nitrogen fixation under greenhouse conditions. The isolates were characterized based on their morphological, physiological and symbiotic characteristics. Accordingly, most of the isolates (80%) collected from Acacia abyssinica, Acacia negrii and Acacia seyal were fast growing rhizobia, whereas root nodule bacteria from Acacia albdia were slow growers. The isolates showed variations in morphological and physiological characteristics and most of them were tolerant to high concentration of NaCl (5-6%) and grew over a wider temperature ranges of (40C-450C) and they were capable of utilizing various types of carbohydrates. Three isolates of AURAaby21, AURAaby24 (both from A. abyssinica) and AURAsey41 (from Acacia seyal) were phosphate solubilizes. The symbiotic effectiveness of the isolates showed significant (P≤ 0.05) variation in mean shoot dry weight compared to their respective N+ and Ncontrol groups. The isolates induced nodulation with average nodule number of 34 NN/plant (Acacia albdia) and 52 NN/plant with Acacia seyal, average nodule dry weight of 0.051 mg/plant (Acacia negrii) and 0.041 mg/p (Acacia abyssinica). The Seedlings accumulated shoot dry weight of 0.3 g/plant (A. abyssinica) to 0.43 g/plant (Acacia negrii). Accordingly, more than 70% of the isolates i.e. AURAal 11 (Acacia albdia), AURAaby22 (A. abyssinica), AURAneg31 (Acacia negrii) and AURAsey41 (Acacia seyal) induced highly effective, whereas, AURAaby21, AURAaby24 (both from Acacia .abyssinica), AURAneg32 (Acacia negrii) and AURAsey42 (Acacia seyal) induced effective nitrogen fixation on their respective host. Some acacia spp. nodulated only with fast growing rhizobia, while other acacia spp. nodulated only with slow growing rhizobia. In most case, acacia spp. that nodulated with both fast and slow growing can only develop an effective symbiotic with one type of symbiont.