A soil-like substrate (SLS) obtained via biocon-version of wheat straw was studied for its ability to suppress Bipolaris sorokiniana and Alternaria sp. conidia germination. Three samples of SLS were used in the study: 1) freshly prepared SLS, 2) SLS which was used as a growth substrate for Cyperus esculentus and Stellaria media for 30 days, 3) SLS which was used as a growth substrate for Triticum aestivum for 2.5 generations. It was found out that aqueous extracts of all the samples statistically sig-nificantly suppress conidia germination. The level of suppression varied from 60.6 % to 100 % (com-plete suppression) depending on the SLS sample and genus of fungi. Adding of 2 % sucrose as an inductor of germination increased conidia germina-tion both in control and in the extracts of SLS by 10.7-47.1 percentage points. Nevertheless, statis-tically significant suppression of conidia germina-tion (by 21.7 % - 63.8 % depending on the SLS sample and genus of fungi) was also observed in the presence of sucrose. On the sum of the results the maximal antifungal activity was observed in the sample 3 (average suppression of conidia germina-tion 80.9 %), and the minimal activity - in the sam-ple 1 (average suppression of conidia germination 57.3 %). This increasing of antifungal activity of SLS after plants cultivation can be explained by the development of microbial community based on root exudates, which suppresses growth of the phyto-pathogenic fungi.