Controlling Tomato Fusarium Welt Disease via Streptomyces rochei in Actinophage Resistant Forms

This study aimed to control tomato welt disease caused by Fusarium oxysporum using Streptomyces rochei which known to have high antagonistic activity against the plant pathogenic fungi.Since presence of actinophages in the soil can reduce the density of such antagonistic microorganism (i.e. S. rochei) it was of a particular interest to prepare S. rochei inoculum in actinophage resistant forms.Therefore, a spontaneous phage resistant mutant of S. rochei was successfully isolated.Moreover, S. rochei inoculum was prepared in alginate immobilized form.The obtained results indicated that tomato plants that were inoculated with S. rochei free cells and Fusarium oxysporum showed moderate resistance to welt disease.The percentage of infection increased when treated with S. rochei free cells and actinophages.Immobilized cells of S. rochei significantly decreased the disease severity of infected plants, even in presence of actinophages.Furthermore, inoculation with actinophage-resistant mutant of S. rochei in presence of actinophage can protect plants and reduce welt disease symptoms.Results in this study revealed that the depressive effect of the actinophages can be avoided by application of S. rochei inoculum in the form of alginate immobilized cells.Moreover, isolation of phage resistant mutants of such desired bacteria can be used as well to avoid the phage attack.Therefore, application of immobilized cells or phage resistant mutants of these desired bacteria as a biological control agent against pathogenic fungi is highly recommended to avoid the phage attack and to promote the efficiencies and maintenance of this microorganism in the soil.