Tree Genetics & Genomes

, 11:1 | Cite as

The genetic diversity and introgression of Juglans regia and Juglans sigillata in Tibet as revealed by SSR markers

  • Hua Wang
  • Gang Pan
  • Qingguo Ma
  • Junpei Zhang
  • Dong PeiEmail author
Original Paper


While walnuts are grown worldwide, two species are predominantly cultivated in China, Juglans regia and Juglans sigillata. J. regia is a widespread species, while J. sigillata is an indigenous species mainly distributed in southwestern China. In Tibet, unique plateau climatic conditions and relatively low-intensity agriculture aid walnuts to preserve a great variety of genetic resources. Knowing the genetic diversity and genetic structure of walnut populations in Tibet is essential when planning genetic conservation and screening for superior germplasm resources. The objectives of this study were to reveal the genetic diversity and genetic structure of walnut populations in Tibet and to infer the relationship between two species, J. regia and J. sigillata, using 12 molecular markers. The results based on screening 209 walnut trees from nine populations showed that the level of polymorphism is moderately high. However, the number of rare alleles (allele frequency <0.05) was higher than that reported in previous studies. An analysis of molecular variance revealed that significant genetic variation existed both among populations of J. regia (10.25 %, p < 0.0001) and J. sigillata (11.07 %, p < 0.0001) and between the two species (7.91 %, p < 0.0001). A Bayesian approach divided the 209 walnut samples into two clusters and presented the differentiation pattern of these two species. The assignment analysis revealed the presence of J. regia × J. sigillata hybrids among the sampled individuals. The results suggest unique germplasm preservation among the walnut populations in Tibet and that introgression between J. regia and J. sigillata may account for the convoluted boundary between the two species.


Genetic diversity Genetic structure Juglans sigillata Juglans regia SSR Introgression Tibet 



The authors thank Zheng Weilie (Tibet Institute of Agriculture and Animal Husbandry, Linzhi) for logistical help and Dr. Ma Heping and Bianbaduoji (Tibet Institute of Agriculture and Animal Husbandry, Linzhi) for assistance with sampling. We warmly thank the crew from the local District Forestry Bureau for providing information of local walnut resources and assisting with sampling, and the local Tibetan people for their hospitality and help in sample collecting. We also thank Zeng Yanfei (the Chinese Academy of Forestry, Beijing) for her support in data analysis. Financial support was received from the National Science & Technology Pillar Program (2013BAD14B01) and from the National Natural Science Foundation of China (31400558).

Data Archiving Statement

The raw data of this research was submitted to the TreeGenes Database. The accession numbers of genotypes and environmental descriptors of Juglans sigillata and J. regia are under TGDR029 and TGDR030, respectively.

Supplementary material

11295_2014_804_MOESM1_ESM.docx (19 kb)
ESM 1 (DOCX 18 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Hua Wang
    • 1
    • 2
  • Gang Pan
    • 3
  • Qingguo Ma
    • 2
  • Junpei Zhang
    • 2
  • Dong Pei
    • 2
    Email author
  1. 1.Key Laboratory of Horticultural Plant Biology, Ministry of Education, College of Horticulture and Forestry SciencesHuazhong Agricultural UniversityWuhanPeople’s Republic of China
  2. 2.Key Laboratory of Silviculture, The Institute of ForestryThe Chinese Academy of ForestryBeijingPeople’s Republic of China
  3. 3.Agricultural and Animal Husbandry Collage of Tibet UniversityLinzhiPeople’s Republic of China

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