Plant Diversity ›› 2022, Vol. 44 ›› Issue (06): 530-541.DOI: 10.1016/j.pld.2021.08.005

• Research paper • Previous Articles     Next Articles

Genetic analysis of walnut cultivars from southwest China: Implications for germplasm improvement

Moses C. Wambulwaa,b,c, Peng-Zhen Fana,b,d, Richard Milnee, Zeng-Yuan Wub, Ya-Huang Luoa,b, Yue-Hua Wangf, Hong Wanga, Lian-Ming Gaoa, Zuo-Ying Xiahoub, Ye-Chuan Jinf, Lin-Jiang Yea, Zu-Chang Xub, Zhi-Chun Yangg, De-Zhu Lia,b,h, Jie Liua,b   

  1. a. CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China;
    b. Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China;
    c. Department of Life Sciences, South Eastern Kenya University, 170-90200, Kitui, Kenya;
    d. University of the Chinese Academy of Sciences, Beijing, 100049, China;
    e. Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh, UK;
    f. School of School of Ecology and Environmental Science, Yunnan University, Kunming, 650091, Yunnan, China;
    g. Yangbi Forestry and Grassland Administration, Dali, 672500, Yunnan, China;
    h. College of Life Sciences, University of Chinese Academy of Sciences, Kunming, 650201, Yunnan, China
  • Received:2021-06-17 Revised:2021-07-26 Online:2022-11-25 Published:2022-12-13
  • Contact: De-Zhu Li,;Jie Liu,
  • Supported by:
    This research was funded by the National Natural Science Foundation of China (31770367, 41971071), Top-notch Young Talents Project of Yunnan Provincial “Ten Thousand Talents Program” (YNWR-QNBJ-2018-146), the Key Research Program of Frontier Sciences, CAS (ZDBS-LY-7001), and Natural Science Foundation of Yunnan (2017FB027). Zeng-Yuan Wu was supported by CAS’ Youth Innovation Promotion Association (2019385), the Biological Resources Program, Chinese Academy of Sciences (KFJ-BRP-017-XX).

Abstract: Walnuts are highly valued for their rich nutritional profile and wide medicinal applications. This demand has led to the intensification of breeding activities in major walnut production areas such as southwest China, in order to develop more superior cultivars. With the increasing number of cultivars, accurate identification becomes fundamental to selecting the right cultivar for grafting, industrial processing or development of new cultivars. To ensure proper identification of cultivars and understand the genetic structure of wild and cultivated material, we genotyped 362 cultivated and wild individuals of walnut trees from southwest China (with two additional populations from Xinjiang, plus three cultivars from Canada, France and Belgium) using 36 polymorphic microsatellite loci. We found relatively low indices of genetic diversity (HO?=?0.570, HE?=?0.404, NA?=?2.345) as well as a high level of clonality (>85% of cultivars), indicating reliance on genetically narrow sources of parental material for breeding. Our STRUCTURE and PCoA analyses generally delineated the two species, though considerable levels of introgression were also evident. More significantly, we detected a distinct genetic group of cultivated Juglans sigillata, which mainly comprised individuals of the popular ‘Yangbidapao’ landrace. Finally, a core set of 18 SSR loci was selected, which was capable of identifying 32 cultivars. In a nutshell, our results call for more utilization of genetically disparate material, including wild walnut trees, as parental sources to breed for more cultivars. The data reported herein will significantly contribute towards the genetic improvement and conservation of the walnut germplasm in southwest China.

Key words: Cultivars, Genetic diversity, Juglans sigillata, Southwest China, Walnut