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United States Department of Agriculture

Agricultural Research Service

Research Project: Development of Rhizobium and Bradyrhizobium Germplasm, Determining Host Plant-Microbe Symbiotic Interactions, And…the Rhizobium Collection

Location: Soybean Genomics and Improvement

Project Number: 1245-21000-269-00
Project Type: Appropriated

Start Date: May 09, 2013
End Date: May 08, 2018

Objective:
Manage the USDA-ARS Rhizobium Germplasm Resource Collection which is maintained in Beltsville, Maryland and is a part of the Germplasm Resources Information Network (GRIN) within the National Microbial Germplasm Program (NMGP). The Collection is a service-oriented program with a major objective of distributing characterized germplasm of rhizobia to stakeholders in industry for use in inoculants and for research at State, Federal and University laboratories. The second part of the project is research-oriented with the focus on soybean, the most important leguminous grain crop for U.S. agriculture. The purpose of the study is to investigate the soybean host genotype and its influence on the genotypes of the rhizobia that infect and establish in the nodules on the roots. This part of the project is the only one of its kind and is made possible by the development by ARS of a method for determining the rhizobial genotype in each individual nodule. The specific objectives of the project are: Objective 1: Preserve, curate and provide long-term back-up of germplasm in the USDA-ARS Rhizobium Germplasm Resource Collection and assess the needs of the agri-business and research community in order to define gaps in the collection followed by the acquisition of new Rhizobium accessions. Objective 2: Determine the influence of soybean cultivar on the Bradyrhizobium multilocus chromosomal genotypes that occupy soybean nodules.

Approach:
Rhizobial cultures will be managed by their preservation, quality control and disbursement to ARS customers upon request. Technical information about rhizobia, their isolation, culturing and symbiosis and advice will be given. New rhizobial cultures will be isolated from soil samples. Emphasis will be placed on preparing and sending cultures for long-term backup at the USDA, ARS, National Center for Genetic Resources Preservation, Fort Collins, CO. The goal is to send the most important rhizobia accessions for the grain legumes and forages. Research will be conducted to determine the impact of soybean genotype, location and year on the genotype of Bradyrhizobium that forms nitrogen-fixing nodules in typical U.S. soybean production fields. The soybean genotypes will consist of a diverse set of genotypes including the major ancestral cultivars that form the genetic base of U.S. soybeans, elite cultivars, and a highly diverse sets of Glycine max landraces and G. soja (wild soybean) genotypes selected based upon the genetic analysis of the USDA Soybean Germplasm Collection with 50,000 single nucleotide polymorphism (SNP) DNA markers. Nodules will be harvested from these field-grown plants and analyzed to determine the strain of B. japonicum or B. elkanii that form nodules. The resulting nodule occupancy data will be used to determine if differences among the genotypes are present for % nodule occupancy by B. japonicum genotypes and/or % occupancy by B. elkanii genotypes.

Last Modified: 4/20/2014
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