Determining Redundancy of Short-Day, Onion (Allium cepa L. var. cepa) Accessions in a Germplasm Collection

The U.S. National Plant Germplasm System is one of the world’s largest national genebank networks focusing on preserving the genetic diversity of plants by acquiring, preserving, evaluating, documenting and distributing crop-related germplasm to researchers worldwide. Maintaining viable germplasm collections is essential to world food security, but comes at a cost. Redundancy within the collection can incur needless expense and occurs as a result of donations of similar material under different names from different donors. Alternatively, similarly named accessions from different donors can actually be genetically distinct. We evaluated 38 short-day onion accessions using SSR and TRAP molecular markers to compare newly acquired germplasm with current accessions in the collection to determine differences and redundancies. Both marker types distinguished differences and found similarities, but the results didn’t always agree. Discriminating among closely related accessions using molecular markers can require a large number of random marker loci, especially when differences may be limited to a single trait. TRAP markers were more efficient, uncovering about 10 polymorphic loci per primer pair.