|Van Berkum, Peter|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 5/27/1996
Publication Date: N/A
Interpretive Summary: Soil bacteria which form nitrogen-fixing symbioses with leguminous plants, collectively referred to as rhizobia, are important to agriculture because these partnerships extract inert gaseous nitrogen from the atmosphere for plant growth and seed production. Many important agricultural crops, including soybean and alfalfa, are legumes benefit from such symbioses. Because the plants are self-sufficient in nitrogen acquisition, the symbiosis is an essential part of low-input sustainable agriculture and fertilizer nitrogen applications are not required for crop production. Agrobacterium and Phyllobacterium are classified within the same family as the rhizobia based upon their phenotypic trait of producing hypertrophies on plants. Members of these two genera also are important to agriculture as potential plant pathogens and beneficial bacteria, repectively. The chapter outlines evolutionary relationships, narrates the limitations of approaches, and discusses the evidence for the different genera and species within the family Rhizobiaceae. The final conclusions are that estimates of the phylogenetic relationships are imprecise because of the limitations in current approaches and alternative speciation criteria are suggested.
Technical Abstract: This chapter reviews the molecular evolutionary relationships of bacteria which belong to the family Rhizobiaceae. Their genetic diversity and phylogenetic relationships are presented relative to the limitations of the approaches and methodologies in deriving the estimates. Conclusions include suggestions for alternative speciation criteria to be used in conjunction with the established approaches.