Lipopeptide culture filtrates from Bacillus spp. provide effective protection to wheat against the foliar pathogen Zymoseptoria tritici

Aims Biocontrol products based on microorganisms and natural substances are promising alternatives to chemical pesticides that could contribute to develop a more sustainable agriculture. Here, we investigated the potential of cell-free culture filtrates (CFCFs) from two strains of the Bacillus subtilis group to inhibit Zymoseptoria tritici, a major fungal pathogen of wheat. Methods and results Foliar application of CFCFs from Bacillus velezensis GA1 and Bacillus sp. III1 on wheat seedlings in a greenhouse strongly reduced Z. tritici disease severity (>90%). In vitro bioassays showed that CFCFs completely inhibited the spore germination and fungal growth (100%). In planta cytological investigations revealed a significant impact of the treatments on both spore germination (similar to 40% inhibition) and fungal growth of Z. tritici (>80% inhibition). High Performance Liquid Chromatography (HPLC) analysis showed that the Bacillus strains displayed different lipopeptide profiles. The CFCF obtained from Bacillus GA1 contained 90 mg l(-1) of iturin A + surfactins + fengycins and the CFCF obtained from Bacillus sp. III1 contained 25 mg l(-1) of mojavensin A (iturin family) + surfactins + fengycins. Conclusions Strains of the B. subtilis group producing different iturins could provide several CFCF-based solutions for the biocontrol of Z. tritici.