الملخص

Abstract The antagonistic ability tests of the biocontrol agent Trichoderma viride against pathogenic fungi, indicated a high inhibiting effect on the growth of two isolates of Fusarium solani and Rhizoctonia solani with modrate degree of antagonism and weak with Macrophomina phasealina. The effect of the fungal polysaccharide produced by Alternaria alternata on the radial growth of pathogenic fungi and the biocontrol agent showed that the relatively high concentrations (i.e. 4 and 5 gm/l) reduced their growth slightly, but stimulated the development of spores of Trichioderma viride simultaneously and increased their numbers. Seed treatment with spore suspension of T. viride cause significant reduction in infection percentage and disease severity of both pre and post emergence seedlings damping-off, and led to an increase in seedling length and dry weight of the seedlings in pot experiments. The addition of adhesive material (i.e. Fungal polysaccharide or gum Arabic) to the seeds increased the reduction in infection percentage and degree of severity of the disease, and also increased length and dry weight of the seedling. The microbial polysaccharide was better than gum arabic in controlling the disease, although no significant differences were noticed between them. Moreover, it improved growth characters of the plants.