Abstract Detail

Crops and Wild Relatives

Steele, Kelly [1], Sandoval, Natalie [2], Hopkins, Andrew [3], Wojciechowski, Martin [4].

Confirmation of USDA germplasm identification in Medicago (Fabaceae).

Germplasm of agriculturally important crop species and their wild relatives is collected, managed and stored by the United States Department of Agriculture, Agricultural Research Service, US National Germplasm System (NPGS) for use by a wide variety of researchers. Approximately 580,000 accessions are managed and stored at various locations throughout the United States with about 20% of those accessions also stored at the Svalbard Seed Vault in Norway. The value of those stored accessions ultimately depends on the accuracy of their identification. To obtain an estimate of the proportion of accessions that are misidentified we choose to examine a selected number of accessions of the genus Medicago (Fabaceae) based on our past experience with NPGS germplasm of this genus for phylogenetic analyses of the genus using DNA sequence data of selected molecular markers, whole genome sequence data and our current studies of genome size evolution in the genus. Within Medicago we chose selected accessions from two clades within the genus, sect. Medicago that includes alfalfa (M. sativa) and related species and another clade that includes the barrel medic (Medicago truncatula), the forage and model legume species. For species in both groups we used morphological characteristics (flower color and leaflet shape) and obtained DNA sequence data of the following molecular markers, the plastid-encoded trnK/matK and ycf1 genes and nuclear ribosomal DNA internal transcribed spacers (nrDNA ITS) to estimate support for species identification. For species in sect. Medicago we also used flow cytometry for ploidy level determination as some species have consistent differences in ploidy level. We distinguish between simple misidentification of biologically distinct entities and situations where identification problems reflect an underlying biological situation such as hybridization. A total of 67 accessions in 10 species in sect. Medicago and 85 accessions in 13 species in the M. truncatula clade were examined. For most accessions we sampled multiple individuals. In sect. Medicago approximately 30% of accessions tested were incorrectly identified with most of those accessions currently, but incorrectly, identified as M. cancellata, M. hybrida, or M. papillosa. Many are more accurately identified as M. sativa. Accessions of some of the most morphologically distinct species including M. arborea, M. cretacea and M. marina were uniformly correctly identified. Species in the M. truncatula clade were less often misidentified with some being simple misidentifications of similar species, but some misidentifications also reflect hybridization among related species.

1 - Sciences And Mathematics, 6073 S. Backus Mall, MC 2780, Mesa, AZ, 85212, United States
2 - Arizona State University, Science and Mathematics, 6073 S. Backus Mall, MC 2780, Mesa, AZ, 85212, USA
3 - Arizona State University, 6073 S. Backus Mall, MC 2780, Mesa, AZ, 85212, USA
4 - Arizona State University, School Of Life Sciences, PO Box 874501, Tempe, AZ, 85287, United States

Keywords:
Medicago
flow cytometry
germplasm.

Presentation Type: Oral Paper
Session: CWR1, Crops and Wild Relatives
Location: Tucson D/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 9:15 AM
Number: CWR1006
Abstract ID:947
Candidate for Awards:None