|Van Berkum, Peter|
Submitted to: North American Conference on Symbiotic Nitrogen Fixation
Publication Type: Abstract Only
Publication Acceptance Date: 11/21/2000
Publication Date: N/A
Technical Abstract: The USDA, ARS National Rhizobium Germplasm Collection contained 143 accessions of slow-growing soybean strains at the time Date and Decker (1965, Can. J. Microbiol. 11,1-8.) identified 17 distinct serological groups. Eleven strains appeared to have no serological affinity with the 17 serogroups. Our objectives were to determine whether these strains were diverse and to examine their phylogenetic placement. Nine strains formed nitrogen-fixing symbioses with soybean indicating that these accessions were not contaminants. We concluded from results of Amplified Fragment Length Polymorphism (AFLP) analysis, using three selective primers with 8 strains, that they were genetically dissimilar. Nine strains were examined for their fatty acid composition using Fatty Acid Methyl Ester derivatives (FAME). The FAME results with 5 strains and serotype strains of B. elkanii were similar, while results with each of the remaining two pairs were either similar to the type strain of B. japonicum (USDA 6) or to USDA 110. Evolutionary history of 8 strains was reconstructed from sequence divergence of a combination of the complete 16S rRNA gene, the Internally Transcribed Space region and about 400 bases of the 5' end of the 23S rRNA gene. Placement of 5 strains was nested within B. elkanii, of two was with USDA 110, and with the other was with USDA 6. We concluded that soybean isolates that cannot be placed within one of the 17 established serogroups are phenotypically and genetically as diverse as the serotype strains.