Abstract Detail

Systematics Section

Havananda, Tee [1], Sakiroglu, Muhammet [2], Brummer, E. Charles [3], Maureira Butler, Ivan J. [4], Doyle, Jeff J. [5].

Evolution of the Medicago sativa polyploid complex.

The Medicago sativa species complex includes several diploid (2n = 16) and tetraploid (2n = 32) taxa, including cultivated alfalfa. The two principal diploid taxa are “caerulea” (M. s. ssp. caerulea or M. caerulea) with purple-flowers and coiled pods, and “falcata” (M. s. ssp. falcata or M. falcata) with yellow-flowers and falcate pods. Alfalfa (M. s. ssp. sativa or M. sativa s.s.) is thought to be derived by autopolyploidy from “caerulea,” and yellow flowered tetraploids are thought to be autotetraploids derived from “falcata.” Hybridization has been observed within and between ploidy levels, resulting in morphologically distinctive diploid and polyploid taxa that are recognized taxonomically. To understand the evolutionary relationships among taxa in the complex, we surveyed sequence variation in two noncoding regions of predominantly paternally transmitted chloroplast DNA (cpDNA: rpl20-rps12 and trnS-trnG spacers) and in three regions of maternally transmitted mitochondrial DNA (mtDNA: nad4 intron, nad7 intron, and rpS14-cob spacer) in diploids. Results from cpDNA sequences supported the recognition of “caerulea” and “falcata” as differentiated taxa, despite the presence of some shared haplotypes, in agreement with morphological characters. In contrast, no significant evidence of mtDNA haplotype differentiation was observed. Chloroplast variation supported the hypothesis that alfalfa is an autopolyploid derived from “caerulea” and showed that there has been little gene flow between alfalfa and tetraploid “falcata.” Surprisingly, however, chloroplast haplotypes from tetraploid “falcata” are not closely related to those from diploid “falcata,” suggesting that the evolution of this tetraploid is not explained simply by autopolyploidy.

Broader Impacts:

1 - Cornell University, Plant Breeding & Genetics, 240 Emerson Hall, Ithaca, NY, 14853, USA
2 - Kafkas University , Department of Biology, Kars, 36100, Turkey
3 - University of Georgia, Crop and Soil Science, Center for Applied Genetic Technologies, 111 Riverbend Rd., Athens, GA, 30602, USA
4 - Agro Aquaculture Nutritional Genomic Center (CGNA), P.O. Box 58-D, Temuco, Chile
5 - Cornell University, Department of Plant Biology, L.H. Bailey Hortorium, 412 Mann Library Building, Ithaca,, New York, 14853-5908, USA

Keywords:
Medicago sativa
autopolyploidy
hybridization.

Presentation Type: Oral Paper:Papers for Sections
Session: 10
Location: Ballroom D/Convention Center
Date: Monday, August 2nd, 2010
Time: 4:00 PM
Number: 10012
Abstract ID:143