Biological Control of Vascular Wilt Disease of Carnation Caused by Fusarium oxysporum f.sp. dianthi by Bacillus and Pseudomonass Strains Isolated from Rhizosphere of Carnation

In order to study the biological control of carnation vascular wilt disease caused by Fusarium oxysporum f.sp. dianthi, 141 bacterial strains were isolated from carnation rhizosphere, and their antagonistic activity was evaluated against fungal pathogen in dual culture method. Among the tested strains, 16 strains showed antagonistic activity seven of them with more activity were selected for further investigation. Based on phenotypic features, strains E31 and E57 were identified as Bacillus cereus E76, E93, E102 and E121 as Bacillus subtilis and E130 as Pseudomonas fluorescens bv. III. All bacterial strains inhibited mycelial growth of F. o. f. sp. dianthi by production of non-volatile and volatile metabolites under laboratory condition. Microscopical analysis showed that all strains caused deformation of pathogen mycelium, and metabolites of these strains reduced conidia production rate and as well as the ability of conidia germination. In the in vivo tests, in sterilized and nonsterilized soils, the effect of bacterial strains was studied on disease severity, percentage of healthy plants and the growth rate of plants using soil inoculating and root-dipping into bacteria-methyl cellulose mixture methods. The E57 and E121 strains, in both methods, and E130 in root-dipping method showed highest effect on decreasing of disease severity and increasing of healthy plants percentage. Strains E57, E121 and E130 significantly increased total dry weight of carnation. Maximum dry weight was obtained by E57 and E130 in soil inoculating and root –dipping methods respectively.