Fungal communities colonizing the stems of three potato cultivars fertilized with Basfoliar 12-4-6, ADOB Mn, and Solubor DF were analyzed in the present study. The response of eight fungal potato pathogens (Alternaria alternata, Colletotrichum coccodes, Fusarium concolor, F. culmorum, F. oxysporum, F. solani, Helminthosporium solani, and Rhizoctonia solani) to the above foliar fertilizers added to the PDA medium at the following concentrations: 10, 100, 500, 1,000, and 10,000 mg·dm^-3 was determined during in vitro tests.
The predominant fungal species isolated from potato stems were Colletotrichum coccodes (Basfoliar 12- 4-6 treatment and control treatment) and Alternaria alternata (ADOB Mn and Solubor applied in combination). Fungi showing antagonistic activity against pathogens had a low share of the fungal community.
Foliar fertilizers added to the PDA medium at the studied concentrations significantly inhibited the mycelial growth of A. alternata, C. coccodes, F. solani, and R. solani. F. concolor, F. culmorum, H. solani, and F. oxysporum grown on the PDA medium containing ADOB Mn were least sensitive to the applied fertilizers. Solubor DF had the most toxic effect on fungal pathogens – when applied at the highest concentration, it almost completely suppressed the mycelial growth of pathogenic fungi, except for A. alternata and F. concolor.