Genetic structure of the poplar rust fungus Melampsora larici-populina : Evidence for isolation by distance in Europe and recent founder effects overseas

• Published in: Infection, Genetics and Evolution
• Main Authors: Barres, Benoît, Halkett, Fabien, Dutech, Christian Cyril, Andrieux, Axelle, Pinon, Jean, Frey, Pascal
• Other Authors: Biologie et Génétique des Interactions Plantes-Agents Pathogènes, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure Agronomique de Montpellier (ENSA M)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Interactions Arbres-Microorganismes (IAM), Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), Biodiversité, Gènes & Communautés (BioGeCo), Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2008
• Subjects: plant pathogen; isolation by distance; long distance dispersal; gradual dispersal; stochastic dispersal; rust fungus; virulence; melampsora larici-populina; populus nigra; microsatellites; peuplier noir; génétique des populations; [SDV.BID.EVO]Life Sciences [q-bio]/Biodiversity/Populations and Evolution [q-bio.PE]; Canada; Iceland
• Online Access: https://hal.inrae.fr/hal-02669196; https://doi.org/10.1016/j.meegid.2008.04.005

International audience Dispersal has a great impact on the genetic structure of populations, but remains difficult to estimate by direct measures. In particular, gradual and stochastic dispersal are often difficult to assess and to distinguish, although they have different evolutionary consequences. Plant pathogens, especially rust fungi, are suspected to display both dispersal modes, though on different spatial scales. In this study, we inferred dispersal capacities of the poplar rust fungus Melampsora larici-populina by examining the genetic diversity and structure of 13 populations from eight European and two overseas countries in the Northern hemisphere. M. larici-populina was sampled from both cultivated hybrid poplars and on the wild host, Populus nigra. The populations were analyzed with 11 microsatellite and 8 virulence markers. Although isolates displayed different virulence profiles according to the host plant, neutral markers revealed little population differentiation with respect to the type of host. This suggests an absence of reproductive isolation between populations sampled from cultivated and wild poplars. Conversely, studying the relationship between geographic and genetic structure allowed us to distinguish between isolation by distance (IBD) patterns and long distance dispersal (LDD) events. The European populations exhibited a significant IBD pattern, suggesting a regular and gradual dispersal of the pathogen over this spatial scale. Nonetheless, the genetic differentiation between these populations was low, suggesting an important gene flow on a continental scale. The two overseas populations from Iceland and Canada were shown to result from rare LDD events, and exhibited signatures of strong founder effects. Furthermore, the high genetic differentiation between both populations suggested that these two recent introductions were independent. This study illustrated how the proper use of population genetics methods can enable contrasted dispersal modes to be revealed.