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

AIMS: Biocontrol products based on micro-organisms 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 greenhouse strongly reduced Z. tritici disease severity (> 90%). In vitro bioassays showed that CFCFs inhibited completely the spore germination and fungal growth (100%). In planta cytological investigations revealed a significant impact of the treatments on both spore germination (around 40% inhibition) and fungal growth of Z. tritici (> 80% inhibition). HPLC analysis showed that the Bacillus strains displayed different lipopeptides profiles. The CFCF obtained from Bacillus GA1 contained 90 mg.L-1 of iturins 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.