Isolation and Assessment of the Symbiotic Efficiency of Faba bean (Vicia faba L.) Nodulating Rhizobial Isolates from Eastern Hararghe Highlands of Ethiopia

Mulugeta Mekonnen¹* and Ameha Kebede²

¹Ethiopian Institute of Agricultural Research, Holeta Agricultural Research Center, Addis Ababa, Ethiopia.

²Department of Biology, Faculty of Natural and Computational Science, Haramaya University, Haramaya, Ethiopia.

Corresponding Author’s Email: Mmulebiotec@gmail.com

DOI : http://dx.doi.org/10.12944/CARJ.9.2.04

Abstract:

This particular work was devoted to isolate and assess the symbiotic efficiency of faba bean (Vicia faba L.)-nodulating rhizobia isolate at few faba bean growing areas of the eastern Hararghe highlands of Ethiopia. Overall 50 rhizobia isolates were obtained from soil samples of three Woredas (districts) of the eastern Hararghe highlands using the host trap method. Out of these 50 isolates, 40 were presumptively identified as rhizobia. Among these 40 rhizobia isolates, only 31 were successful to nodulate faba bean, and authenticated as true faba bean nodulating rhizobia. Concerning the symbiotic efficiency, about 52%, 35%, and 13% of the rhizobial isolates were found to be highly effective, effective, and lowly-effective, respectively. The correlation data on the sand experiment displayed that nodule dry weight was associated positively and significantly (r = 0.494, p<0.05) with shoot dry weight while shoot dry weight was associated positively and significantly (r=0.41, p<0.05) with plant total nitrogen. Positive correlations were also observed concerning shoot dry weight and dry weight of nodules (r = 0.7, p<0.05) on unsterilized soil. Among the observed rhizobium isolates, EHHFR (4A, 6A) showed the highest symbiotic efficiency above 110%, tolerated NaCl concentration ranging from 2% to 6% and 2% to 8%, respectively, and a pH range of 4.5 to 8 and 5 to 8, respectively. Thus, based on their symbiotic efficiency at the greenhouse level and relative tolerance to extreme conditions these faba bean nodulating rhizobia isolates were recommended to be used as nominees for the future development of faba bean rhizobial inoculants after being tested on field conditions.

Keywords:

Biological Nitrogen Fixation (BNF); Faba Bean; Inoculant; Rhizobia; Strain; Symbiotic Efficiency

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