Human-associated genetic landscape of walnuts in the Himalaya: implications for conservation and utilization

Li-Jun Yan, Peng-Zhen Fan, Moses C Wambulwa, Hai-Ling Qi, Ying Chen, Zeng-Yuan Wu, Richard I. Milne, Raees Khan, Ya-Huang Luo, Lian-Ming Gao, Shi-Kang Shen, Irfan Rashid, Shujaul Mulk Khan, Debabrata Maity, De-Zhu Li, Jie Liu

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Aims: A comprehensive understanding of the genetic variation of walnuts (Juglans regia and J. sigillata) in the Himalaya and its potential drivers are essential for the conservation and sustainable utilization of these plant genetic resources. In this study, we aimed to uncover the genetic landscape of walnuts and potential drivers in the Himalaya for better utilization, awareness, sustainable management and conservation of the extant genetic resources of walnuts in the vast Himalayan landscape. 

Location: The Himalaya biodiversity hotspot. 

Methods: A total of 1410 wild or feral walnut trees from 65 populations of J. regia and J. sigillata across four countries in the Himalaya were collected. The genetic diversity, population structure, hybridization and gene flow were thoroughly investigated based on the chloroplast genome and 31 nuclear microsatellite markers. The patterns and drivers of the walnut genetic landscape were further explored. 

Results: We detected three genetic groups of J. regia (JR1, JR2, JR3), one of J. sigillata (JS) and two hybrid types (JR1 × JS and JR3 × JS) of walnut in the Himalaya, with the western Himalaya identified as the genetic diversity hotspot of J. regia. The spatial genetic pattern of the J. regia was significantly influenced by geographic and climatic factors. Human-mediated dispersal probably promoted the hybridization and gene introgression between J. regia and J. sigillata, which reshaped the genetic landscape of walnut populations in the Himalaya. 

Main Conclusions: The extant genetic landscape of walnuts in the Himalaya was driven by natural and anthropogenic forces. Regarding conservation, the western and eastern Himalaya are the genetic reservoir of J. regia and J. sigillata, and hence, pure individuals should be urgently protected from frequent hybridization and introgression. In addition, we propose the utilization of natural hybrid resources coupled with new breeding techniques that combine genomic and phenotypic data.

Original languageEnglish
Article numbere13809
Number of pages15
JournalDiversity and Distributions
Issue number4
Early online date12 Jan 2024
Publication statusPublished - Apr 2024

Keywords / Materials (for Non-textual outputs)

  • domestication
  • genetic diversity
  • Himalaya
  • hybridization
  • introgression
  • walnuts


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