Progress 10/01/04 to 09/30/06
Outputs
Progress Report 4d Progress report. This report serves to document research under a specific cooperative agreement between ARS and the Institut National de Recherche Scientifique et Technique (INRST), BP95, 2050 Hammam Lif, Tunisia. Funds were provided by the American Society for Microbiology and UNESCO for a grant entitled Clonal complex of alfalfa-nodulating rhizobia in an arid Tunisian habitat. Additional details of the research can be found in the report for the parent project 1275-21000-220-00D (National Rhizobium Germplasm Resource Collection, Genetic Resource Management, Systematics, and Bioinformatics). The objective of this project was to use comparative genomics to describe distinctions between the clonal complex of rhizobia of nodulation-restricted Medicago laciniata with non- restricted M. truncatula. An approach based on Multi-Locus Sequence Typing (MLST) was used to determine variation in the chromosomes of rhizobia originating from the two hosts grown
in a single soil from an arid region in Tunisia. The collaborator sent 148 cultures, 74 from each legume species. These rhizobia were divided into 26 different allelic profiles (chromosomes). Of these 26, 4 and 18 allelic profiles were unique to M. laciniata and M. truncatula, respectively, while 4 originated from both hosts. Therefore, more diversity was associated with rhizobia originating from M. truncatula than M. laciniata. Specificity of nodulation for M. laciniata is determined by the nodC allele present in the rhizobial genome. The nodC genes and gene products of the rhizobia originating from M. laciniata were significantly different to those of M. truncatula. Four different nodC alleles were present among the M. laciniata isolates, while there were 5 among the M. truncatula isolates. Therefore, the symbiosis genes among rhizobia of Medicago have a history of recombination, which explains why 4 of the 26 allelic profiles were common to both host species.
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Progress 10/01/04 to 09/30/05
Outputs
4d Progress report. This report serves to document research under a specific cooperative agreement with the Institut National de Recherche Scientifique et Technique (INRST), BP95, 2050 Hammam Lif, Tunisia. Funds are being provided by the American Society for Microbiology and UNESCO for a grant entitled "Clonal complex of alafalfa-nodulating rhizobia in an arid Tunisian habitat" and supports the objectives of project 1275-21000-149- 00D. The objective of this project is to use comparative genomics to describe distinctions between the clonal complex of rhizobia of nodulation-restricted Medicago laciniata with non-restricted M. truncatula. An approach based on Multi-Locus Sequence Typing (MLST) will be used to determine chromosomal types of 200 rhizobial isolates originating from the two hosts grown in soil from an arid region in Tunisia. The collaborator has sent 52 cultures and 148 need to be obtained. Analyses have begun and results are still very preliminary. It
would appear that the chromosmal types of the rhizobia from the two legume hosts overlap, but some are unique to each host. More diversity seems to be associated with rhizobia originating from M. truncatula.
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