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Title: Comparison of accessions from the UK and US national pear germplasm collections with a standardized set of microsatellite markers

Author
item EVANS, K.E. - Washington State University
item FERNANDEZ-FERNANDEZ, F. - East Malling Research
item Bassil, Nahla
item Nyberg, April
item Postman, Joseph

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2015
Publication Date: 9/20/2015
Publication URL: http://Acta Horticulturae
Citation: Evans, K., Fernandez-Fernandez, F., Bassil, N.V., Nyberg, A.M., Postman, J.D. 2015. Comparison of accessions from the UK and US national pear germplasm collections with a standardized set of microsatellite markers. Acta Horticulturae. 1094:41-46.

Interpretive Summary: The identities of 61 pear cultivars present in both the UK National Pear Collection in Brogdale, England and the US National Clonal Germplasm Repository in Corvallis, Oregon were compared using a standard set of DNA fingerprints. Freeze dried leaves from eight standard varieties at the Brogdale collection were sent to the Corvallis lab to allow validate the results. Comparison of the data from the 61 accessions revealed 41 pairs of individuals with the same name and with identical DNA fingerprints. Twelve accessions from Brogdale were different from those with the same name at NCGR at more than six of the 12 DNA sites compared, indicating the possibility of mis-identified trees. Six accessions from Brogdale were identical to those with the same name at NCGR at 11 of the 12 DNA sites. Differences between the two labs scoring of the results were responsible for the discrepencies between results for the six accessions, bringing to 47 the number of identical accessions in the two collections. Two accessions from Brogdale were identical to those with the same name at NCGR at 10 of the 12 DNA sites. Further comparison of data is required before these accessions can be confirmed as different. Characterization of germplasm collections at this level should result in more accurate labeling of accessions reducing the possibility of confusion when attempting to compare results between varieties that may be mis-labeled.

Technical Abstract: A standardized set of 12 microsatellite markers, previously agreed upon following an ECP/GR workshop in 2006, was used to screen accessions from the UK National Pear Collection at Brogdale and from the US National Pear Germplasm Repository (NCGR), Corvallis. Eight standard varieties were chosen from the UK collection and freeze-dried leaves were provided to the US group to allow harmonization of calling amplification product sizes. Comparison of the data from 61 accessions revealed 41 pairs of individuals with the same name and with identical allele sizes. Twelve accessions from Brogdale were different from those with the same name at NCGR at more than six of the 12 microsatellite loci indicating the possibility of mis-identified trees. Six accessions from Brogdale were identical to those with the same name at NCGR at 11 of the 12 microsatellite loci. Detailed comparisons of electropherograms revealed that three of these were in fact mis-scored and consequently these accessions can also be added to the original 41 identical pairs. Two accessions from Brogdale were identical to those with the same name at NCGR at 10 of the 12 microsatellite loci. Further comparison of electropherograms and comparison of phenotypic data is required before these accessions can be confirmed as different. Characterization of germplasm collections at this level should result in more accurate labeling of accessions reducing the possibility of confusion when attempting to compare results between varieties that may be mis-labeled.