Tree Genetics & Genomes

, 11:81 | Cite as

Patterns of genetic diversity and differentiation in resistance gene clusters of two hybridizing European Populus species

  • Celine CaseysEmail author
  • Kai N. Stölting
  • Thelma Barbará
  • Santiago C. González-Martínez
  • Christian Lexer
Original Article
Part of the following topical collections:
  1. Disease Resistance


Resistance genes (R-genes) are essential for long-lived organisms such as forest trees, which are exposed to diverse herbivores and pathogens. In short-lived model species, R-genes have been shown to be involved in species isolation. Here, we studied more than 400 trees from two natural hybrid zones of the European Populus species Populus alba and Populus tremula for microsatellite markers located in three R-gene clusters, including one cluster situated in the incipient sex chromosome region. The results indicate that all three R-gene clusters present extensive linkage disequilibrium (LD). Outlier tests suggest balancing selection as a potential driver of R-gene diversity, but divergent selection was also detected. Nucleotide-binding site leucine-rich repeat (NBS-LRR) type R-gene clusters exhibit low species differentiation and appear to be affected by shared selection pressures between species, recurrent interspecific gene flow, or both. Our results are consistent with a role for R-gene clusters in the evolution of chromosome XIX, recently put forward as an incipient sex chromosome in Populus.


Resistance gene cluster NBS-LRR Plant defense Hybridization Sex chromosome Selection 



This study was supported by grants 31003A_127059 and 31003A_149306 of the Swiss National Science Foundation (SNF) to CL.

Data archiving statement

Microsatellite genotype data can be found on dryad doi: 10.5061/dryad.2593t.

Supplementary material

11295_2015_904_MOESM1_ESM.pdf (1.4 mb)
ESM 1 (PDF 1,389 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Unit of Ecology and Evolution, Department of BiologyUniversity of FribourgFribourgSwitzerland
  2. 2.Department of Botany and Biodiversity Research CentreUniversity of British ColumbiaVancouverCanada
  3. 3.Department of Forest Ecology and GeneticsINIA-Forest Research CentreMadridSpain
  4. 4.Department of Botany and Biodiversity ResearchUniversity of ViennaViennaAustria

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