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Title: GENETIC DIVERSITY AMONG RHIZOBIA ISOLATED FROM SOILS OF THE AMERICAS

Author
item WANG, ENTAO - MEXICO
item Van Berkum, Peter
item MARTINEZ-ROMERO, ESPERANZA - MEXICO

Submitted to: International Congress of Genetics Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The Legume-Rhizobium nitrogen-fixing symboses are important in global nitrogen economy and in the sustainability of agriculture and forestry. We isolated rhizobia from nodules of Amorpha fruticosa, Sesbania herbacea, and Leucaena leucocephala growing in the USA and Mexico and characterized them by restriction fragment length polymorphism (RFLP) of PCR-amplified 16S rRNA genes, 16S rRNA gene sequencing, multilocus enzyme electrophoresis (MLEE), DNA hybridization, electrophoretic mobilities of plasmids, and RFLP analysis of the symbiotic gene loci. These isolates were genetically and phylogenetically diverse. Among the isolates of A. fruticosa, originating from the USA, and among those of S. herbacea, originating from Mexico, genetic diversity was limited. Distinct groups were identified based upon which we proposed the separate species Mesorhizobium amorphae and Rhizobium huautlense, respectively. The diversity was greater among isolates of L. leucocephala originating from Mexico. We observed twelve 16S PCR-RFLP patterns, which were characteristic of species within the genera Mesorhizobium, Rhizobium, and Sinorhizobium. However, several patterns were distint from those obtained with the reference strains of the species. Analysis of the data obtained with MLEE and PCR-RFLP resulted in corresponding groupings. There were common plasmids within each PCR-RFLP group, but between each of the PCR-RFLP groups different plasmid patterns were observed. Based on the MLEE analyses we concluded a clonal genetic structure within each of the groups indicating possibly that the isolates of Leucaena do not share common gene pools.