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Abstract Detail



Recent Topics Posters

Dorman, Hanna [1], Wallace, Lisa [2].

Rhizboial Diversity Associated with Chamaecrista fasciculata (Fabaceae) in Mississippi.

Legume-rhizobium symbioses are suggested to exhibit high degrees of specificity determined by molecular signaling between bacteria and their plant hosts.  However, recent studies on variation in these relationships indicate that specificity and the functionality of these symbioses can vary geographically within a plant species and among rhizobial strains. Given these findings, symbiotic relationships could have a substantial effect on the evolution and ecology of both partners.  In this study, we present preliminary findings on the diversity of rhizobia associated with Chamaecrista fasciculata in Mississippi, which represents the southern extent of its range. Chamaecrista fasciculata has been found to be symbiotic with Bradyrhizobium elkanii and may associate with other Bradyrhizobium species in the northern part of its range.  Given the wide range of C. fasciculata throughout the eastern United States and its occurrence in varying soil types, we hypothesized that there could be other compatible rhizobia functioning in root nodules and that rhizobia would vary geographically due to plant genotypic differences and/or soil characteristics.  Root samples were collected from 8 populations in the historical Black Belt Prairie near Starkville, MS. These locations are characterized by different soil types and are made up of different plant communities. . Rhizobial DNA was isolated from root nodules and a portion of the 16s-23s rDNA intergenic spacer (IGS) was amplified by PCR and sequenced.  For several individuals we also characterized intra-plant rhizobia diversity. The data set contained 27 sequences and exhibited high levels of diversity (π= 0.089; Watterson’s θ= 0.059). Phylogenetic analysis indicated clustering of the recovered sequences with sequences of B. elkanii and B. japonicum available in GenBank. Additionally, the samples cluster based on geography with those in chalky soils primarily associated with B. japonicum and those in other prairie soils with B. elkanii.  Identical sequences of rhizobia from different nodules of the same plant were rarely found, although they typically were found to be the same species of Bradyrhizobium.  These results suggest that the specificity exhibited by C. fasciculata is not rhizobium species-specific. Studies to characterize rhizobia diversity across a wider sampling of soil types in Mississippi are underway.  Additionally, we plan to study the functional significance of rhizobial diversity in this wide-ranging species, which is increasingly considered a model species for studying rhizobia-legume symbioses and for use in agriculture. 

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1 - Mississippi State University , Biology, p.o. gy, Mississippi State, MS, 39762, USA
2 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA

Keywords:
Rhizobial symbiosis
Chamaecrista fasciculata
Bradyrhizobium
Rhizobial diversity
phylogenetic relationship.

Presentation Type: Recent Topics Poster
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PRT034
Abstract ID:1329
Candidate for Awards:None


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