Accurate pedigree information is not only essential for proper parental selection in breeding programs, but it also allows geneticists to infer trait heritability, understand genetic correlations among phenotypes of interest, and estimate breeding values ( Kouassi et al. Finally, the use of molecular markers will aid in the elucidation of parentage for hundreds of cultivars and breeding material in the collection. Additionally, since in the past germplasm to be preserved at the NCGR was selected based on morphological, geographical and passport data, there is a need to implement molecular marker screening to verify the trueness-to-type of the accessions maintained, as well as to eliminate redundancies.
An understanding of the genetic diversity of this collection will better support the use of this germplasm for the improvement of scion and rootstock pear cultivars ( Volk et al. This collection represents, therefore, a useful tool for population and evolutionary genetic studies in Pyrus, as well as a valuable source of material for breeding purposes. It includes 2,300 clonal pear accessions and 364 seed lots, encompassing 36 different species or interspecific hybrids from 55 countries ( Postman 2008b). The USDA-ARS National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon, maintains one of the world’s largest and most diverse collection of Pyrus ( Postman 2008a). In this study, we have analyzed this rich dataset to discover new synonyms and mutants, identify putative labeling errors in the collection, reconstruct the largest pear cultivar pedigree and further elucidate the genetic diversity of Pyrus. However, the recent development of the Applied Biosystems Axiom Pear 70K Genotyping Array has allowed high-density single nucleotide polymorphism (SNP)-based genotyping of almost the entire collection. In the last two decades simple sequence repeat (SSR) markers have been used at the NCGR for cultivar identification and small population structure analysis. A thorough genetic characterization of this germplasm will provide relevant information to optimize the conservation strategy of pear biodiversity, support the use of this germplasm in breeding, and increase our knowledge of Pyrus taxonomy, evolution, and domestication. The USDA-ARS National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon, maintains one of the world’s largest and most diverse living Pyrus collection.
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