Effets de fondation et différenciation génétique aux échelles continentale et locale chez Mycosphareella fijiensis, champignon responsable de la maladie des raies noires du bananier

The fungus Mycosphaerella fijiensis is a pathogen of banana. The objective of this work was to describe populations structure of M. fijiensis at continental and local scales and to infer gene flow and dispersal processes of this fungus at these two sales. Samples of isolates collected in Latin America-Caribbean region and in Africa were analyzed using neutral molecular markers. A high level of genetic diversity and recombination were maintained in M. fijiensis populations even at the plant scale. At continental scale, the spread of M. fijiensis might be stochastic and could be due either to movement of infected plant material or to limited ascospore dispersal for distance of several hundred kilometers. The level of genetic differentiation between populations decreased after with geographic scale suggesting an increase of gene flow through ascospores dispersal. (Résumé d'auteur