Isolement Des Microorganismes Possédant Une Activité Anti- Fusarium

Résumé: This study was carried out in order to fight against the phytopathogenic fungus ""Fusarium"". eight species from the genus Fusarium have been isolated from different organs of infected plants. genus identification was conducted using morphological characters, while the identification of species was performed by molecular pathway within the LMBA Laboratory (Laboratory of Microbiology and Biomolecules Assets). Indeed, according to affiliation results, the eight pathogenic strains belong to three Fusarium species in the circumstances; Fusarium verticillioides, Fusarium solani and Fusarium oxysporum. Biological control against the phytopathogens is highlighted using seven strains from the genus Trichoderma isolated from three Algerian agricultural soils. The molecular identification of isolats conducted in the laboratory of LMBA has divided the seven strains into five main species: Trichoderma album, Trichoderma harzianum, Trichoderma virens, Trichoderma longibrachiatum, Trichoderma viride. Indeed, This study showed a significant diversity of Trichoderma species in Algeria. However, to our knowledge, there are no previous published studies on the isolation of Trichoderma album, Trichoderma virens and Trichoderma longibrachiatum, from the Algerian soil. The effect of the antagonist activity of Trichoderma strains against the eight isolated Fusarium species was studied using two methods, direct and indirect confrontation. Direct confrontation results show a percentage of inhibition ranging from 55% to 72% depending on the tested pathogenic and antagonists species, while the results of the confrontation from distance reveals low percentage of inhibition varied from 2% to 43%. The seven tested Trichoderma strains show considerable capacity of resistance on the media with a different pH from 2 to 9. Enzymatic activity test of antagonistic strains shows that the seven tested strains represent very important sources of lytic enzymes namely chitinase, cellulase, protease, lipase and laccase. Both test for anti-Fusarium activity, and culture filtrates antagonistic strains show a low inhibition of mycelial growth of pathogenic strains. Furthermore, this study showed a remarkable change of color and appearance of the Fusarium strains due to antagonistic metabolits. chloroformic extract effect of the seven antagonistic strains, was tested by the BIOLOG technic and by the technical soaked disks, both techniques show a good inhibitory activity of the extracts, no matter what the concentration used is (50 mg / ml , 25 mg / ml and 1mg / ml)

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