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Abstract Detail

Systematics Section / ASPT

Havananda, Tee [1], Maureira Butler, Ivan J. [2], Brummer, E. Charles [3], Doyle, Jeff J. [4].

The Medicago sativa species complex: views from mitochondrial and chloroplast DNA sequences on the relationships of diploid members.

Evolutionary relationships in the Medicago sativa species complex, which includes diploid and tetraploid taxa, remain unclear. Previous molecular systematic studies addressed taxonomic questions mainly at the generic level; hence not many members in the complex were studied. Even though subspecies sativa and falcata were included in many studies, especially for crop improvement, few wild accessions and other taxa have been included. The ability of diploids to freely interbreed, weak hybridization barriers between two ploidy levels, and tetrasomic inheritance in autotetraploids contribute to the complexity of the group. In order to describe the relationships among members, we initially analyzed chloroplast (cpDNA) and mitochondrial (mtDNA) DNA sequence data obtained from diploid accessions representing the diversity of the complex. Sequences of two intergenic spacers (rpl20-rps12 and trnG-trnS) were combined as our cpDNA sequence data, while one mitochondrial intergenic spacer (rps14-cob) and one gene (nad4) were combined as mtDNA sequence data. A large number of haplotypes were identified from both the cpDNA and mtDNA datasets. Phylogenetic trees and networks were obtained for each dataset. From cpDNA analysis, subspecies caerulea and falcata were distinguished from each other. However, a few accessions from the two subspecies were found to share chloroplast haplotypes. The distinction between these two main diploid taxa is less clear from the mtDNA analysis. Haplotypes were shared by accessions of these subspecies including the closely related M. prostrata. Incongruence between the two datasets was observed. This is likely due to the difference in the pattern of inheritance of cpDNA (biparentally largely paternal) and mtDNA (maternal) in Medicago. The relationships among diploid members will be proved useful in elucidating origins of tetraploids in the complex.

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1 - Cornell University, Plant Breeding, 248 Plant Science Building, Cornell University, Ithaca, NY, 14853, USA
2 - Agro Aquaculture Nutritional Genomic Center (CGNA), P.O. Box 58-D, Temuco, Chile
3 - University of Georgia, Crop and Soil Science, Center for Applied Genetic Technologies, 111 Riverbend Rd., Athens, GA, 30602, USA
4 - Cornell University, L.H. Bailey Hortorium and Department of Plant Biology, 228 Plant Science Building, Ithaca, New York, 14853, USA

chloroplast DNA
mitochondrial DNA

Presentation Type: Poster:Posters for Sections
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P59023
Abstract ID:2120

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