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

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Monday 28 November 2011
Concurrent Session 3 – Taxonomy & Evolution
1530 - 1650
Authors: Tadashi Yokoyama 1 , Chandra Prasad Risal 2 , Naoko Ohkama-Ohtsu 1 , Salem Djedidi 3 &
Hitoshi Sekimoto 4
1 Institute of Agriculture, Tokyo Univ. of Agri. and Tech., Saiwai-cho 3-5-8, Fuchu, Tokyo
183-8509, Japan
2 Soil Management Directorate, Dept. of Agriculture, Hariharbhawan 552-0314, Nepal
3 Faculty of Agriculture, Tokyo Univ. of Agri. and Tech., Tokyo 183-8509, Japan
4 Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan
Presentation Title: Genetic diversity of native soybean and mungbean bradyrhizobia from different
topographical regions along the southern slopes of the Himalayan Mountains in Nepal
Presentation Time: 1630 - 1650
Soybean-nodulating bradyrhizobia are genetically diverse and are classified into different species. In this study,
the genetic diversity of native soybean and mungbean bradyrhizobia isolated from different topographical regions
along the southern slopes of the Himalayan Mountains in Nepal was explored. Soil samples were collected from
three different topographical regions with contrasting climates. Local Glycine max cv. Cobb and Vigna radiata cv.
Kalyan were used as trap plants to isolate bradyrhizobia. All the Nepalese soybean and mungbean isolates
characterized in this study were slow growers and were assigned to the Bradyrhizobium genus based on their
molecular characterization. We found that 46% of the isolates from soybean analyzed in the present study were
phylogenetically related to B. elkanii, 21% were related to B. japonicum, and 8% were related to B.
yuanmingense. Phylogenetic analyses also revealed three novel lineages comprising 25% of the analyzed
population. Similarly, we found 50% of the isolates from the mungbean were phylogenetically related to B.
yuanmingense, 13% were related to B. japonicum, 8% were related to B. elkanii, and 29% were found with novel
phylogenetic origin. Furthermore, we found that most mungbean rhizobial genotypes were conserved across
agro-ecological regions of Nepal. All the strains from tropical Terai region belonged to B. yuanmingense or a
novel lineage of B. yuanmingense, and dominance of B. japonicum related strains observed in the Hill region.
Our results indicate that there is higher genetic diversity of Bradyrhizobium strains in the temperate and subtropical
region than in the tropical region. Though nifD genes are considered as high homology genes,
considerable nifD gene sequence divergence of Nepalese strains with known reference strains were noticed.
We, for the first time, analyzed nifD genes from B. yuanmingense in this study. We found nifD genes in B.
yuanmingense isolated from soybean and mungbean are far different from other Bradyrhizobium species.
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