Ex situ conservation of Black poplar in Europe: genetic diversity in nine gene bank collections and their value for nature development

V. Storme • A. Vanden Broeck • B. Ivens • D. Halfmaerten • J. Van Slycken • S. Castiglione • F. Grassi • T. Fossati • J.E. Cottrell • H.E. Tabbener • F. Lefèvre • C. Saintagne • S. Fluch • V. Krystufek • K. Burg • S. Bordács • A. Borovics • K. Gebhardt • B. Vornam • A. Pohl • N. Alba • D. Agúndez • C. Maestro • E. Notivol • J. Bovenschen • B.C. van Dam • J. van der Schoot • B. Vosman • W. Boerjan • M.J.M. Smulders

Theoretical and Applied Genetics 108(6):969-981, 2004

Abstract

 Populus nigra L. is a pioneer tree species of riparian ecosystems which is threatened with extinction because of the loss of its natural habitat. To evaluate the existing genetic diversity of P. nigra within ex-situ collections, 675 P. nigra L. accessions from nine European gene banks were analyzed with three AFLP® (AFLP® is a registered trademark of Keygene) and five microsatellite (or simple sequence repeat (SSR)) primer combinations, and 11 isozyme systems. With isozyme analysis, hybrids could be detected and only 3% were found in the gene bank collection. AFLP and SSR analyses revealed effectively that 26% of the accessions were duplicated and that the level of clonal duplication varied from 0% in the French gene bank collection up to 78% in the Belgian gene bank collection., although SSR analysis was preferred because AFLP was technically more demanding and more prone to scoring errors. To assess the genetic diversity, material from the gene banks was grouped according to topography of the location from which the accessions were originally collected (river system or regions separated by mountains). Genetic diversity was expressed in terms of the following parameters: % polymorphic loci, observed and effective number of alleles, and Nei’s expected heterozygosity or gene diversity (for AFLP). Genetic diversity varied from region to region and depended, to some extent, on the marker system used. The most unique alleles were identified in the Danube region (Austria), the Rhône region (France), Italy, the Rijn region (The Netherlands), and the Ebro region (Spain). In general, the diversity was largest in the material collected from the regions in Southern Europe. Dendrograms and principal component analysis (PCA) resulted in a clustering according to topography. Material from the same river systems, but from different countries, clustered together. The genetic differentiation among the regions (Fst/Gst) was moderate.

Key words Populus nigra, gene bank, ex-situ conservation, genetic diversity

Table 2
The assignment of syllables to the microsatellite alleles for a selection of the EUFORGEN Core Collection (Van Slycken 1995).

(1) (REF) indicates that the clone was used as reference sample to standardise the designation of alleles among laboratories for that particular locus
(2) For this locus, the third reference sample was P. nigra ‘Italica’of the EUFORGEN reference collection (genotype: SX)