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The impact of a biofungicide based on Bacillus subtilis Ch-13 on mushroom yield and efficacy in suppression of Trichoderma aggressivum f. europaeum T77 from Serbia was estimated in comparision with a similar microbial fungicide, Bacillus velezensis QST713, and the chemical fungicide prochloraz manganese. The biofungicide B. velezensis QST713 is registered for treatments of mushrooms and other crops in many countries but it is not currently available on the Serbian market. The tested B. subtilis Ch-13 fungicide enhanced mushroom yield 12%, compared with an uninoculated control, and notably more than B. velezensis QST713 applied at its higher test concentrations. Regarding the efficacy of the biofungicides in control of the compost pathogen T. aggressivum f. europaeum, B. subtilis Ch-13 applied in concentration of 3 × 10 8 CFU per m 2 showed higher efficacy than the higher concentrations (5 × 10 9 and 1 × 10 10 CFU per m 2) of B. velezensis QST713. The biofungicide based on B. subtilis Ch-13 should be further investigated regarding its different modes of application to ensure better efficacy in disease control as it showed beneficial features in both promoting A. bisporus production and suppressing the growth of the aggressive compost pathogen T. aggressivum, the causal agent of devastating green mould disease.

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The isolation of bacteria was carried out from samples of straw and chicken manure, compost at various stages of the composting process and casing soil used for growing button mushrooms. A preliminary screening of 108 bacterial isolates for antagonistic activity against Trichoderma aggressivum f. europaeum showed that 23 tested isolates inhibited mycelial growth of the pathogenic fungus. Further screening with four indicator isolates of fungi revealed that all 23 bacterial isolates inhibited the growth of T. aggressivum f. europaeum, T. harzianum and T. koningii, while only 13 isolates inhibited the growth of T. atroviride. T. aggressivum f. europaeum proved to be the most sensitive, with many bacterial isolates generating a high percentage of growth inhibition. Only two bacterial isolates (B-129 and B-268) were successful in inhibiting the growth of all 4 tested pathogens. All 23 bacterial isolates were characterized as Gram-positive and catalase-positive and were subjected to molecular identification based on the partial sequence, the hypervariant region of the 16S rDNA. It was shown that the obtained bacterial strains belong to Bacillus subtilis, B. amyloliquefaciens, B. licheniformis and B. pumilus species.

In this work, we demonstrate that the rhizosphere of common duckweed (Lemna minor) is inhabited with various phenol-resistant bacterial strains. Based on 16S rRNA sequencing, we have identified 60 rhizosphere-associated bacterial isolates belonging to 10 different bacterial genera (Pseudomonas, Hafnia, Serratia, Enterobacter, Micrococcus, Stenotrophomonas, Xanthomonas, Bacillus, Staphylococcus and Klebsiella). All isolates have been tested for phenol resistance and ability to utilize phenol as the sole carbon source. 70% of all isolates survived high doses of phenol (≥200 mg/L) and at least 27% can be potentially acclimatized by gradual increase of phenol concentration. Finally, based on high phenol resistance, ability to utilize phenol as the sole carbon source and documented low pathogenicity, we propose 5 strains as potentially excellent candidates for bioremediation. These 5 strains taxonomically correspond to Klebsiella sp., Serratia sp., and Hafnia sp., respectively. To the best of our knowledge, this is the first attempt to assess decontamination capacity of Serratia nematodiphila and Hafnia sp. in the context of bioremediation of phenol-contaminated aqueous media. Although additional analyses are needed, interaction between the common duckweed and the selected bacterial strains may be utilized in future bioremediation strategies.