Étude in vitro de l’activité antagoniste de quelques microorganismes à l’encontre de Fusarium oxysporum f. sp. lentis

This investigation shows the in vitro antagonist action of Rhizobium leguminosarum, Trichoderma harzianum ADS, Trichoderma harzianum Bg and Rhizopus stolonifer towards Fusarium oxysporum f. sp. lentis. The antagonists inhibition on mycelial growth and the mode of action are different. The antagonistic properties of R. leguminosarum and the T. harzianum strains against F. oxysporum are related to the excretion of antibiotic substances. The antimicrobial activity of R. leguminosarum is of protein nature and has fungicidal action on conidia of F. oxysporum. However, the active products of the T. harzianum strains are not of protein nature and have a lower fungicidal action. A fungistatic action that is considered to be by volatile metabolites is also observed. Our study show that the mechanism by which R. stolonifer inhibits the mycelial growth of F. oxysporum is not antibiosis but probably is compétition for nutrients that is related to the rapid spread in culture medium. The four antagonists have not a specific action because they can inhibit mycelial growth of other fungi such as Botrytis cinerea, Alternaria alternata, Verticillium albo-atrum and Absidia glauca. These results suggest that these antagonists may be efficients for controlling different diseases caused by soit borne plant pathogens.