Submitted to: International Scholarly Research Network (ISRN)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2013
Publication Date: 4/1/2013
Citation: Abi-Ghanem, R., Smith, J.L., Vandemark, G.J. 2013. Diversity of Rhizobium leguminosarum from pea fields in Washington State. International Scholarly Research Network (ISRN). Volume 2013, Article ID 786030, 7 pages. Interpretive Summary: Global demand for food will increase as the world population grows to 8.3 billion by 2025. This demand will require increased production of fertilizer or plants that produce more of their own fertilizer. Rhizobium, which biologically fixes nitrogen on legume roots, was isolated from peas in Washington State and examined for their genetic diversity in fixing nitrogen. Plant biomass increased due to nitrogen fixation and also for the quantity of nitrogen fixed per variety. This study suggests that plant breeders and biological scientists could improve biological fixation of nitrogen in plants due to the wide diversity of strains of rhizobium found in local (regional) soils.
Technical Abstract: Rhizobia-mediated biological nitrogen (N) fixation in legumes contributes to yield potential in these crops and also provides residual fertilizer to subsequent cereals. Our objectives were to collect isolates of Rhizobium leguminosarum from several pea fields in Washington, examine genetic diversity among these isolates and several commercial isolates of R. leguminosarum, and compare genetically distinct isolates for their ability to fix N in a range of pea hosts. Seventy-nine isolates were collected from pea root from four noninoculated pea fields. Sequence-related amplified polymorphism (SRAP) markers generated by PCR were used to discriminate among isolates. Isolates fell into 17 clusters with robust bootstrap support values. Nearly half of the isolates fell into a single large cluster, but smaller clusters were also detected for isolates from all four field locations. The majority of commercial isolates fell into a distinct cluster. Four genetically distinct isolates were compared for their efficiency in fixing N in a greenhouse experiment. Host plant variety effects were significant for plant biomass due to N fixation and also for the quantity of N fixed per variety. Significant effects of R. leguminosarum isolates were observed for the quantity of N fixed per isolate, plant biomass, and the quantity of N per plant.