Actions antibiotique, mycolytique et parasitaire de deux actinomycètes envers Fusarium oxysporum f.sp. albedinis et autres formae speciales

Abstract

Two actinomycètes (X9 and X10) isolated on a Fusarium oxysporum f.sp. albedinis strain showed antibiotic, mycolytic, and parasitism actions against nine "formae speciales" of Fusarium oxysporum. Strain X10 is included in genus Streptomyces and strain X9 in Nocardiopsis dassonvillei species (Lechevalier and Lechevalier) Meyer. The antibiotic action of Streptomyces strain is stronger towards F. o. dianthi, F. o. albedinis, and F. o. cyclaminis. It seems that the mycolytic power of N. dassonvillei is more specific to F. o. eleaidis, whereas the parasitism action varies depending on the "formae speciales" tested and the quantity of fungal mycelium produced. As a response to this parasitism, all the fungi produce resistance organs that can either be polymorphous thallospores or chlamydospores. The thallospores studied on a F. o. albedinis strain germinate faster than the microconidies of the same nonparasited fungus. However, many strains obtained from these thallospores are as susceptible as the mother strain to the antagonistic action of both actinomycetes