Genetic Characterization of Eastern Filbert Blight-resistant Hazelnut Seedlings from Turkey, Latvia, and Lithuania

The production of hazelnuts (Corylus avellana) in the eastern U.S. has been severely limited by the disease eastern filbert blight (EFB), caused by the fungus Anisogramma anomala.  The development of EFB-resistant plants is considered to be the most effective means to control this disease and much progress has been made in the past decade to develop improved, EFB-resistant cultivars.  To search for new sources of resistance, germplasm based on open-pollinated (OP) seed was obtained from Turkey, Latvia, and Lithuania. Over 1000 seedlings were exposed to A. anomala annually over 6 years in the field at Rutgers University.  From this collection, 46 trees were found to be highly resistant or tolerant to the disease (30 from Turkey, 13 from Latvia, and 3 from Lithuania).  However, since they are from OP seed little is known of their genetic background.  The purpose of this study was to use simple sequence repeat (SSR) markers to characterize the relationships and genetic diversity of these new EFB-resistant plants in comparison to a panel of reference cultivars.  Thirty SSR markers were amplified and used to fingerprint each accession.  The resulting peaks were scored using GeneMapper v4.1 and the resulting allelic data was analyzed in Powermarker v3.5 to obtain marker summary statistics, including PIC, gene diversity, and heterozygosity.  The allelic data was then used to create a UPGMA dendrogram.  Following the cluster analysis, a population structure analysis was run with the program STRUCTURE 2.3.4.  Our preliminary results show that the Turkish and Latvian seedlings were placed into distinct clusters generally along with reference cultivars from similar origins.  Interestingly, most of the new seedlings were grouped into genetically distinct clusters devoid of previously known sources of resistance.  Thus, these new accessions should contribute to the germplasm base available for breeding new resistant plants while providing a means to maintain and/or increase genetic diversity.