Abstract Detail

Systematics Section/ASPT

Steier, Julia [1], Steele, Kelly [2], Mandakova, Terezie [3], Wojciechowski, Martin [4].

Genome size and chromosome number evolution in early diverging species of Medicago (Fabaceae).

There is a relative lack of basic information about early diverging species of the genus Medicago that, for the most part, were formerly considered to be in the genus Trigonella. Species boundaries are not always clear, for example, the most recent treatment of the genus Medicago submerged four previously recognized species into Medicago monantha, a widely distributed species. These species are recognized on the basis of morphological characters such as fruit number, shape, length and areole shape and size, but species identification is still challenging and further clarification of species boundaries is needed. There is also a lack of cytogenetic information. Some of the relatively few published chromosome numbers, e.g. 2n=28, and 44, differ from those of the rest of the genus, which are mostly 2n=16 or multiples thereof, although seven species are 2n=14. As part of a larger study of the genome and chromosome number evolution in the genus Medicago, we obtained genome size data using flow cytometry for multiple accessions of a number of these early diverging species (the exact number depends on how one delimits the species). Chromosome numbers were obtained using standard cytological methods, and morphological data on those same accessions were also obtained. Our chromosome number data confirm a chromosome number of 2n=16 for M. brachycarpa (genome size of 1.33 pg), and M. monspeliaca (1.88 pg), and 2n=28 for M. polyceratia (2.77 pg) and give new numbers for some species; 2n= 16 for M. biflora (2.7 pg), and a previously unknown chromosome number for these early diverging species of 2n=14 for Medicago fischeriana (1.45 pg). Interestingly, our data support the hypothesis that there are at least two entities within M. monantha as currently recognized that differ in chromosome number and genome size; one accession is 2n= 30 with a genome size of 2.84 pg and other accessions are 2n=44 with an average genome size of 3.96 pg. There are also some significant morphological differences between these two entities, such as fruit length, vein thickness, and areole area. These data lead to both further clarification of the relationships of early diverging Medicago and help build a platform for more in-depth research concerning the evolution of chromosome number and genome size within Medicago.

1 - 6625 N 40th St., Paradise Valley, AZ, 85253, USA
2 - Arizona State University Polytechnic, Dept. Of Applied Biological Sciences, East College, 6073 S. Backus Mall, Mesa, AZ, 85212, USA
3 - Central European Institute of Technology, Laboratory of Plant Cytogenomics, Masaryk University, Brno, CZ-62500, Czech Republic
4 - Arizona State University, School of Life Sciences, Tempe, AZ, 85287-4501, USA

Keywords:
Medicago
genome size
Chromosome number.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PSY022
Abstract ID:1265
Candidate for Awards:None