Genetic diversity and cultivar variants in the NCGR cranberry ( Vaccinium macrocarpon Aiton) collection.

The American cranberry ( Vaccinium macrocarpon ) is an endemic domesticated species that has become an economically important commercial fruit crop. The USDA-ARS National Clonal Germplasm Repository (NCGR) houses the national Vaccinium collection, which includes representatives of historical cranberry cultivars and wild-selected germplasm. The objective of this study wasto examine the genotypes of 271 cranberry plants from 77 accessions representing 66 named cultivars using 12 simple-sequence repeats to assess clonal purity and cultivar relatedness. Using principal components analysis and neighbour-joining based on estimated genetic distances between individuals, we identified 64 unique genotypes and observed that intracultivar variants (i.e. subclones) existed in the germplasm collection and in the commercial bogs where some accessions originated. Finally, through a comparison of the genotypes of this study with the previous studies, pedigree analysis and the study of the geographic distribution of cranberry diversity, we identified consensus genotypes for many accessions and cultivars. We highlight the important role that the NCGR collection playsfor ex situ conservation of cranberry germplasm for future breeders and researchers. The NCGR continues to search for historically relevant cultivars absent from the collection in an effort to preserve these genotypes before they are lost and no longer commercially grown.