Genetic Characterization and Diversity of Rhizobium Isolated From Root Nodules of Mid-Altitude Climbing Bean (Phaseolus vulgaris L.) Varieties
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Date
2018
Authors
Koskey, Gilbert
Mburu, Simon W.
Kimiti, Jacinta M.
Ombori, Omwoyo
Maingi, John M.
Njeru, Ezekiel M.
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Microbiology
Abstract
The increasing interest in the use of rhizobia as biofertilizers in smallholder agricultural
farming systems of the Sub-Saharan Africa has prompted the identification of a large
number of tropical rhizobia strains and led to studies on their diversity. Inoculants
containing diverse strains of rhizobia have been developed for use as biofertilizers to
promote soil fertility and symbiotic nitrogen fixation in legumes. In spite of this success,
there is paucity of data on rhizobia diversity and genetic variation associated with
the newly released and improved mid-altitude climbing (MAC) bean lines (Phaseolus
vulgaris L.). In this study, 41 rhizobia isolates were obtained from the root nodules of
MAC 13 and MAC 64 climbing beans grown in upper and lower midland agro-ecological
zones of Eastern Kenya. Eastern Kenya was chosen because of its high production
potential of diverse common bean cultivars. The rhizobia isolates were characterized
phenotypically on the basis of colony morphology, growth and biochemical features.
Rhizobia diversity from the different regions of Eastern Kenya was determined based on
the amplified ribosomal DNA restriction analysis (ARDRA) of PCR amplified 16S rRNA
genes using Msp I, EcoR I, and Hae III restriction enzymes. Notably, native rhizobia
isolates were morphologically diverse and grouped into nine different morphotypes.
Correspondingly, the analysis of molecular variance based on restriction digestion of
16S rRNA genes showed that the largest proportion of significant (p < 0.05) genetic
variation was distributed within the rhizobia population (97.5%) than among rhizobia
populations (1.5%) in the four agro-ecological zones. The high degree of morphological
and genotypic diversity of rhizobia within Eastern Kenya shows that the region harbors
novel rhizobia strains worth exploiting to obtain strains efficient in biological nitrogen
fixation with P. vulgaris L. Genetic sequence analysis of the isolates and testing for their
symbiotic properties should be carried out to ascertain their identity and functionality in
diverse environments.
Description
An Article Published Frontiers in Microbiology
Keywords
Rhizobium, Climbing beans, ARDRA, Genetic diversity, 16S rRNA genes
Citation
Koskey G, Mburu SW, Kimiti JM, Ombori O, Maingi JM and Njeru EM (2018) Genetic Characterization and Diversity of Rhizobium Isolated From Root Nodules of Mid-Altitude Climbing Bean (Phaseolus vulgaris L.) Varieties. Front. Microbiol. 9:968. doi: 10.3389/fmicb.2018.00968