Résumé
One of the control strategies of fungal crop diseases is planting highly resistant varieties. However selection pressure on the pathogen, imposed by major resistance genes, leads to the development of new virulent races. In most cases breakdown of resistance has been reported for crop-pathogen systems with a genetically uniform crop distributed over large areas[2]. To derive strategies leading to durable resistance we focus on studying the role of recombination of pathogen genotypes and their spread in the process of succes-sive breakdowns of resistant hosts carrying different major resistance genes and their pyramids.