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Abstract Detail



Genomics / Proteomics

Steele, Kelly [1], Mandakova, Terezia [2], Steier, Julia [3], Wojciechowski, Martin [3].

Genome Size Estimation in Medicago (Fabaceae): Independent Loss and Gain?

Genome size in flowering plants has been correlated with various aspects of life history, rarity and geographic distribution. To consider these and other hypotheses for the genus Medicago we obtained genome size estimates for more than 49 species (over half of the species in the genus) representing all major lineages using standard methods of flow cytometry performed on a FACSCalibur flow cytometer. Two primary internal standards were used, Glycine max "Polanka" with an estimated genome size of 2.5 picograms (pg) and Medicago truncatula Jemalong with an estimated genome size of 1.15 pg. Genome size ranged from just under 1.0 to 3.8 pg among diploid species with an average genome size of 1.79 (s.d. = 0.66). Five polyploid species were sampled, interestingly all have smaller genome sizes than that of the two diploid species with the largest genome sizes, M. carstiensis (3.8 pg) and M. suffruticosa (3.5 pg). Chromosome numbers were obtained from the same accessions as those used for genome size to confirm identification of morphologically similar 2n=14 versus 2n=16 species and to obtain new counts for early diverging taxa where previously published numbers, if even available, are quite unusual for the genus. Genome sizes were mapped onto a phylogeny based on analyses of DNA sequence data of four molecular markers (nuclear rDNA ITS, GA3oxidase, CNGC5 and the plastid trnK/matK) usually obtained from the same accessions as genome size, to examine patterns of genome size distribution. Genome size has a non-random distribution, with some clades being characterized by smaller genome sizes than others. Two separate derived clades of annual species are characterized by an average genome size smaller than that of their sister groups: one clade that includes M. polymorpha has an average genome size of 1.16 pg (s.d. = 0.06) and another clade that includes M. truncatula, has an average genome size of 1.19 pg (s.d. = 0.11), supporting the hypothesis of independent loss of genetic material in these two clades.


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1 - Arizona State University, School of Letters and Sciences, 6073 S. Backus Mall MC 2580, Mesa, AZ, 85212-6420, USA
2 - Masaryk University, Central European Institute of Technology (CEITEC), Brno, CZ-62500, Czech Republic
3 - Arizona State University, School of Life Sciences, Tempe, AZ, 85287-4501, USA

Keywords:
Medicago
genome size.

Presentation Type: Oral Paper:Papers for Topics
Session: 35
Location: Pines South/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 8:15 AM
Number: 35002
Abstract ID:803
Candidate for Awards:None


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