Table of Contents
ISRN Soil Science
Volume 2013, Article ID 786030, 7 pages
Research Article

Diversity of Rhizobium leguminosarum from Pea Fields in Washington State

1Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164-6420, USA
2Land Management and Water Conservation Research Unit, USDA-ARS and Washington State University, Pullman, WA 99164-6421, USA
3Grain Legume Genetics Physiology Research, USDA-ARS and Washington State University, Pullman, WA 99164-6421, USA

Received 19 December 2012; Accepted 13 January 2013

Academic Editors: G. Benckiser, J. A. Entry, H. K. Pant, and A. P. Schwab

Copyright © 2013 Rita Abi-Ghanem et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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.