Investigation of disease-suppressive soil from a long-term, organically-managed field in Shiga Prefecture, Japan

Disease-suppressive soils, in which soilborne pathogens are naturally suppressed, offer a promising model for sustainable crop protection. Although disease suppression in these soils is thought to rely on biological microbial control, the underlying mechanisms remain poorly understood. In this project, we investigated disease-suppressive soil from a long-term, organically-managed field in Shiga Prefecture, Japan, and compared it with nearby conventional and greenhouse soils. The 16S rRNA gene amplicon sequencing indicated distinct bacterial communities in the disease-suppressive soil, with the genus Lysobacter being markedly enriched following the application of organic compounds, such as rice bran, bovine serum albumin, egg white albumin, and arginine. This enrichment was reproducible across sampling times and specific to certain organic inputs, whereas minimal effects were observed for chitin, GlcNAc, or cysteine. Broader soil surveys indicated that Lysobacter enrichment was not strictly associated with farming history (organic or conventional).