|Cruz, Von Mark|
|Brummer, E. Charles|
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2006
Publication Date: 8/31/2006
Citation: Cruz, V.V., Nason, J.D., Luhman, R., Marek, L.F., Shoemaker, R.C., Brummer, E., Gardner, C.A. 2006. Analysis of bulked and redundant accessions of Brassica germplasm using assignment tests of microsatellite markers. Euphytica. 152:339-349. Interpretive Summary: Effective use of resources is key to a successful plant germplasm management program. If multiple accessions are identical, they should be bulked into one lot. This saves labor, space, and resources in a genebank and also enables researchers who need to choose among many plant varieties for an experiment to focus on fewer materials. In the past, a decision to bulk accessions was made based on morphological (plant structure and form) and phenological (plant development) data. Molecular information can greatly increase the confidence in a determination of degree of similarity.
Technical Abstract: This study was conducted to determine if Brassica germplasm bulks created and maintained by the USDA-ARS North Central Plant Introduction Station (NCRPIS) were made with genetically indistinguishable component accessions and to examine newly identified putative duplicate accessions to determine if they can be bulked. Using ten microsatellite primer pairs, we genotyped two bulks of B. rapa L. ssp. dichotoma (Roxb.) Hanelt comprising four accessions and three bulks of B. rapa L. ssp. trilocularis (Roxb.) Hanelt comprising fourteen accessions, as well as four pairs of putatively duplicate accessions of B. napus L. Assignment tests on ten individual plants per accession were conducted using a model-based clustering method to arrive at probabilities of likelihood of accession assignment. The assignment tests indicated that one of the two bulks of B. rapa ssp. dichotoma involves genetically heterogeneous accessions. It was observed in the B. rapa ssp. trilocularis bulks that the component accessions could be differentiated into groups, with mis-assignments observed most frequent within groups. In B. napus, only one of the four pairs of putative duplicates showed significant genetic differentiation. The other three pairs of putative duplicates lack differences and support the creation of bulks. The results of the assignment tests were in agreement with cluster analyses and tests of population differentiation. Implications of these results in terms of germplasm management include the maintenance and/or re-creation of some Brassica germplasm bulks by excluding those accessions identified as being unique in this study.