Determination of microbial content of commercial vermicomposts and investigation of their antagonistic effects on some fungal pathogens

In this study, the effects of microorganisms developing during vermicompost production on some soil pathogens (Rhizoctonia solani, Macrophomina phaseolina, Fusarium oxysporum, Fusarium solani ve Sclerotinia minör) were investigated in vitro. Bacterial population came to the fore in the microbial content of vermicompost. As fermentation was completed, 100 million bacteria were reached in 1 g of vermicompost, while the fungal population increased to 67 thousand propagules. Commercial biological fertilizer containing Bacillus spp. contributed positively to the development of the bacterial population in vermicompost. In the isolations made from vermicompost, 110 bacterial and 19 fungal isolates showing different morphologies were obtained. After the preliminary screening, 15 bacteria and 12 fungi were tested for biological activity against pathogens. In dual culture studies, 3 Bacillus species (Bacillus subtilis, B. licheniformis and B. amyloliquefaciens ssp. plantarum) showed high activity against almost all pathogens. In fungal isolates, species belonging to the Aspergillus, Scapulariopsis and Cladosporium genera had higher effectiveness against different pathogens. The effect of vermicompost extract on mycelial growth of pathogenic fungi was generally low. However, two commercial Trichoderma harzianum preparations added to the medium during composting were deemed more promising.