Symbiotic and Phenotypic Characterization of Rhizobia Nodulating Fenugreek (Trigonella Foenum-Graecum L.) from North and East Shewa, Ethiopia.
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Date
2013-03-20
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Addis Ababa University
Abstract
Fenugreek (Trigonella foenum-graecum L.) is among spices produced in different high land areas of Ethiopia. It grows in a wide range of altitudes and fixes nitrogen with rhizobia and performs well in less fertility soils. However, the effectiveness in nitrogen fixation varies depending upon the host varieties, type of strain and different environmental characters. It is, therefore, necessary to evaluate the efficiency of different isolates from different sampling areas. Thus, 18 fenugreek rhizobial isolates (11from North and 7 from East Shewa) were isolated and characterized based on their morphological, cultural, and physiological properties. These isolates were re-inoculated on sand culture using “chala” variety of fenugreek to authenticate nodulation and determine their symbiotic effectiveness. All but 2 isolates were authenticated as root nodule bacteria with their capacity to infect and nodulate their host. Inoculation of Fenugreek by the isolates showed significant differences in percent effectiveness (45%-84%). Most of the isolates displayed fast doubling time (1.8-3.3hrs) and colonies diameter of (2-5 mm) and all but 2 changed the BTB-YEMA media to yellow which showed that they are acid producers and fast growing rhizobia.. The preliminary screening of the isolates for symbiotic effectiveness on sand culture showed that isolates AAUFR-26 and AAUFR-30 of North Shewa were highly effective whereas, 67% were found to be effective. Isolates from North Shewa responded better in shoot dry weight than isolates from East Shewa indicating that some soil-related factors such as pH affect symbiotic effectiveness. Isolates were also exhibited different characterstics for their tolerance to different eco-physiological features such as pH, temperature, salt concentration, intrinsic antibiotic resistance and utilization of different carbon and nitrogen sources. These results showed the presence of wide eco-physiological diversity between isolates. Plants inoculated with different isolates displayed differences with respect to nodule number, nodule dry weight and shoot dry weight. The numerical analysis of isolates based on 60 phenotypic features showed the presence of diversity among isolates and also statistical analysis indicates their diversity towards symbiotic effectiveness.
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Fenugreek, Rhizobia, Nitrogen Fixation, Nodulation, Phenotypic Diversity