Treatment with the Antimicrobial Product Diallyl Disulfide Is Associated with Major Changes to Soil Microbiota

Natural products derived from Allium spp., such as garlic oil, garlic powder, and diallyl disulfide (DADS), are strong elicitors of sclerotia germination in the fungus Sclerotium cepivorum (syn. Stromatinia cepivora), the causal agent of Allium white rot. However, these compounds can also have broad antimicrobial activity against a wide range of bacteria, oomycetes, and other fungi when they are applied to soil. The objective of this study was to determine the potential impacts that DADS application has on soil microbial communities. DADS was applied to two soil types and incubated under aerobic and anaerobic conditions. Metabarcodes for bacterial, fungal, and oomycete communities were analyzed to identify changes. A significant effect of DADS treatment on the overall compositions of bacterial, fungal, and oomycete communities was observed compared with the mock-treated control. Soil type and incubation conditions did not have a significant effect on soil microbial communities, and significant interactions were not observed with DADS treatment in this study. Potential changes in soil microbial communities should be considered when applying DADS to field soils.