Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2006
Publication Date: July 20, 2006
Citation: Bassil, N.V., Hummer, K.E., Postman, J.D. 2006. Microsatellites are used to examine apple and pear identities and genetic relationships [abstract]. HortScience. 41(4):993. Interpretive Summary: This study used genetic tools specifically short fragments of DNA containing repeated elements called simple sequence repeats (SSRs). SSRs frequently vary in size and are reliable markers. The first part of this study used SSR markers to compare family relationships of 18 apple and nine heritage European pear cultivars from the Azores, Portugal and the United States. They identified five groups of synonyms in apple and three pairs of synonyms in pear. Fingerprints of 12 unique apples and seven pears were developed. In the second study, these markers were used to evaluate relationships among 144 European and Asian pears maintained as part of the USDA-ARS germplasm collection, in Corvallis, Oregon. They detected five sets of duplicates and four sets of trees that have the same name but are genetically different. These marker-based analyses provide powerful tools for fingerprinting pear and detecting duplications as well as incorrectly labeled plants. Duplicate removal from the collection will contribute to increased management efficiency in preserving genetic resources.
Technical Abstract: Simple Sequence Repeat (SSR) markers developed in apple and pear were used to determine genetic relationships among heritage apple and pear cultivars from Portugal’s Azore Islands, and to develop identity fingerprints for European and Asian pear accessions at the USDA-ARS National Clonal Germplasm Repository (NCGR). We used 11 SSR markers (six from apple and five from pear) to examine 18 heritage apple and 9 heritage pear cultivars from the Azores. Eight additional Portuguese and economically important cultivars of apple and eight of pear were used as standards. Cluster analysis separated the apple and pear accessions into two distinct groups. Among apple genotypes, 12 unique accessions and five groups of synonyms were identified while in pear, seven unique genotypes and three pairs of synonyms were found. None of the accessions obtained from the Azores corresponded to widely grown standard Portuguese apple or pear cultivars. To examine 144 NCGR pear accessions, we used nine polymorphic SSR loci that were developed from GenBank sequences. Cluster analysis identified five sets of synonyms (four in P. communis L. and one in P. ussuriensis Maxim.) and four pairs of homonyms (three in P. communis and one in P. pyrifolia Burm. f. Nakai), and confirmed three clonal sets. Morphological evaluations and additional SSR markers will be used to confirm these results, and to genetically document the identities of pear genotypes. SSR markers will greatly assist the management of ex situ pome fruit germplasm collections by helping to eliminate duplicate accessions and expanding the genetic diversity represented.