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Tree Genetics & Genomes

, 15:5 | Cite as

Genetic diversity and structure of natural Juglans regia L. populations in the southern Kyrgyz Republic revealed by nuclear SSR and EST-SSR markers

  • Nurlan TorokeldievEmail author
  • M. Ziehe
  • O. Gailing
  • R. Finkeldey
Original Article
Part of the following topical collections:
  1. Population structure

Abstract

Persian walnut (Juglans regia L.), also known as common walnut, is an economically and ecologically important species in the Kyrgyz Republic. Natural forests of J. regia, walnut forests, grow between western and southwestern slopes of the Fergana and Chatkal mountain ridges in the southern Kyrgyz Republic. We investigated 11 natural populations of J. regia across its geographic range in the Kyrgyz Republic using eight nuclear microsatellite (nSSR) and eight expressed sequence tag (EST)-derived SSR (EST-SSR) markers. The SSR markers revealed comparatively high levels of genetic diversity (HO = 0.538, HE = 0.524). The overall genetic differentiation among populations was low, but statistically significant (FST = 0.068). Significant correlation between genetic and geographic distances was observed, indicating an isolation-by-distance (IBD) model for J. regia. Spatial analysis of molecular variance (SAMOVA) and Bayesian analysis assigned individuals to two main genetic groups separating central region walnut populations (Jalal-Abad province) and southeastern region walnut populations (Osh province). Genetic diversity parameters such as gene diversity and allelic richness were significantly lower in the Osh province than in the Jalal-Abad province. Detection of significant genetic discontinuities suggested the existence of physical barriers to migration and gene flow among regions. We suggest that the Osh province and Jalal-Abad province populations should be considered as two evolutionary significant units (ESUs) for conservation efforts.

Keywords

Juglans regia Genetic diversity Microsatellites Walnut-fruit forests Landscape genetics Conservation units 

Notes

Acknowledgments

We thank Dr. Almazbek Orozumbekov for sampling establishments and Muratali Torokeldiev for his assistance with fieldwork. We also thank Oleksandra Dolynska for her laboratory assistance. We are grateful to two anonymous reviewers for their helpful recommendations on earlier versions of the manuscript.

Data archiving statement

Population names of Persian walnut collection, geographic location of Persian walnut populations, and microsatellite data for 550 Persian walnut genotypes were submitted to the TreeGene Database (http://treegenesdb.org/Drupal/user/241/TPPS; accession number TGDR081).

Funding information

This research was supported by a scholarship from Deutscher Akademischer Austauschdienst (DAAD) to the first author.

Supplementary material

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Authors and Affiliations

  1. 1.Department of Forest Genetics and Forest Tree BreedingUniversity of GöttingenGöttingenGermany
  2. 2.Department of Natural and Mathematical Sciences, Faculty of MedicineAla-Too International UniversityBishkekKyrgyz Republic
  3. 3.School of Forest Resources and Environmental ScienceMichigan Technological UniversityHoughtonUSA
  4. 4.University of KasselKasselGermany

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