Résumé
Populations of Magnaporthe, the causal agent of rice blast disease, are pathotypically and genetically diverse and therefore their interaction with different rice cultivars and also antagonistic microorganisms are very complicated. The objectives of the present study were to characterize phylogenetic relationships of 114 native Magnaporthe strains, isolated from rice and different weeds in the North region of Iran and to study their interaction with the fungal and bacterial antagonists. Phylogenetic studies [lineage structure, cluster analysis and gene flow] were performed using AFLP DNA fingerprinting. Antagonistic effects of the native fungal [Trichoderma harzianum] and bacterial [Bacillus subtilis and Pseudomonas fluorescens] against Magnaporthe strains were assayed at In vitro levels using factorial experiments based on completely randomized designs [CRD] and mean comparison tests. In total, 39 clonal lineages including 48 haplotypes were identified among the strains of M. grisea and designated here as A-Z. AFLP marker could finely differentiate the strains isolated from various hosts. The strains isolated from Setaria sp. were much close to those from rice [Oryza sativa L.]. Magnaporthe strains isolated from Digitaria sp. showed higher genetic variation than other strains. Genetic distances revealed by the AFLP markers could be finely differentiated M. grisea and M. salvinii. The rate of gene flow was an evidence of low gene transferring among Magnaporthe populations and the existence of a complex species for Magnaporthe strains. The fungal and bacterial antagonists showed different reactions against different Magnaporthe strains. These results confirmed high genetic diversity between the Magnaporthe strains which was also previously determined by the AFLP experiments. It was concluded that the Magnaporthe populations in Iran have a complex genetic diversity, and therefore, to achieve an efficient control of the different strains and pathotypes of Magnaporthe sp, it is necessary to use different bacterial and fungal biocontrol agents as a dynamic and integrated control system