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

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Title Isolation and characterization of diazotrophic microsymbionts from root nodules of mucuna
bracteata
Authors Salwani Shaffie ,Amir Ghazali, and Nazalan Najimudin
Poster Board Number 21
School of Biological Sciences, Universiti Sains Malaysia
An increasing number of bacteria that can nodulate and fix N2 in legumes which do not belong to the genus of
Rhizobium or Bradyrhizobium was identified. This study was conducted to determine indigenous microsymbiont
strains which could further promote symbiotic N2-fixation activities for Mucuna bracteata (an important
leguminous cover crop) and to verify the identity of the isolates based on nitrogenase enzyme assay, nifH gene
isolation and partial 16S rDNA sequence analysis. Our findings indicated that the isolated microsymbionts could
nodulate and promote N2-fixation activity in M. bracteata. The isolates also contributed to enhanced plant growth
in terms of leaf protein and chlorophyll content and higher plants and nodule biomass. Additionally, the nifH gene
fragments were successfully amplified for all of the isolates. The 16S rDNA sequencing results suggested that
bacteria which were able to form N2-fixing symbioses with root known as rhizobia is not only from the α-class of
proteobacteria but also from β-class of proteobacteria (Burkholderia sp. and Achromobacter sp., 99-100% of
similarity) and γ-class of proteobacteria (Stenotrophomonas sp., 99% of similarity). The findings indicate the
diversity of potentially-beneficial diazotrophic microsymbionts active in this emerging legume species.
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