Genetic diversity of Persian walnut (Juglans regia) in the cold-temperate zone of the United States and Europe
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We compared the genetic diversity of Juglans regia L. growing in the cold temperate region of the eastern U.S. with J. regia growing in the cold-temperate and Mediterranean regions of Europe. Ten microsatel-lite (SSR) loci were used to assess the genetic relationships among 114 total trees originating from the Midwestern USA (n = 34), Hungary (n = 30), Slovakia (n = 28), and Italy (n = 22). All SSR loci were highlypolymorphic with an average of 7.4 alleles per locus. All 114 trees were confirmed to be unique geno-types. Cluster analysis using Neighbor-joining (NJ) placed genotypes according to their geographic origin. STRUCTURE software confirmed the results of the NJ analysis and produced three main groups consistent with the geographic origins of the samples. According to Nei's genetic identity, samples from Slovakiaand Hungary showed the highest similarity (0.94), while samples from the USA and Hungary had the lowest similarity (0.37). The genetic diversity of J. regia from the USA and Eastern Europe was relatively high compared to Italian samples. We found little genetic similarity between J. regia sampled from the eastern USA with J. regia currently growing near the Carpathian Mountains. There was strong evidence for a bottleneck in the U.S. population, but no evidence of inbreeding.
Ebrahimi, Aziz; Zarei, AbdolKarim; McKenna, James R.; Bujdoso, Geza; Woeste, Keith E. 2017. Genetic diversity of Persian walnut (Juglans regia) in the cold-temperate zone of the United States and Europe. Scientia Horticulturae. 220: 36-41. https://doi.org/10.1016/j.scienta.2017.03.030.