IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Title Diversity and phylogeny of Bradyrhizobium spp. Isolated from shrub and tree legumes in
Ethiopia
Authors Aregu Amsalu Aserse 1,2 , Leena.A.Räsänen 1 ,Fassil Assefa 2 , Asfaw Hailemariam 3 and
Kristina Lindström 1
Poster Board Number 30
1 University of Helsinki, Department of Food and Environmental Sciences,
2 Addis Ababa University, Cellular, Microbial and Molecular Biology Program Unit
3 National Soil Testing Centre,
In Eastern Africa including Ethiopia, crop production has been affected by recurrent drought, deforestation and
losses of soil fertility. Soil fertility is the major constraint and nitrogen is considered as one of the most limiting
nutrients in the region. Nitrogen-fixing shrubs and tree legumes, such as Crotalaria, Erythrina and Indigofera
species have been used in agroforestry systems (home-gardens, fallows and land reclamation) to improve the
availability of nitrogen in the soil. Soybean is an exotic crop legume in Ethiopia and its symbionts capable of
forming nitrogen-fixing nodules do not exist in the soil. Inoculation of soybean has not always been successful.
Therefore, effective rhizobial strains that are adapted to their local environments are required. Interestingly,
indigenous rhizobial strains, which nodulate leguminous shrubs and trees have been found to infect soybean as
well. However, knowledge on the symbionts of different leguminous plants in Ethiopia is scarce. Therefore, the
aim of this study was to explore the diversity and phylogeny of indigenous Bradyrhizobium strains isolated from
Crotalaria incana, Erythrina brucei, Indigofera arrecta and Gycine max. Fifty-five strains were isolated from
nodules collected at 29 sites located mainly in southwestern Ethiopia. The diversity of the bacterial collection was
studied using amplified fragment length polymorphism (AFLP) fingerprinting. The strains were preliminary
identified by comparing the partial sequences of the 16S rRNA gene against a nucleotide database. For further
phylogenetic studies, the housekeeping genes recA, rpoB and glnII were sequenced. Phylogenetic trees of these
genes as well as phylogenies of the symbiotic genes nodA and nifH will be presented together with strains
symbiotic capacity and plant growth promoting activities.
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