P-487 - Site-specific microbial community restructuring in response to Phytophthora nicotianae infection in tobacco fields

Plant pathogen infection can indirectly alter soil microbiome assembly. However, the microbial community structure in rhizosphere compartments of diseased flue-cured tobacco is not fully understood. This study analyzed the rhizosphere and bulk soil microbiota of healthy flue-cured tobacco ‘NC196’ and plants exhibiting black shank disease symptoms from four Virginia farms to investigate how black shank disease affects the assembly and co-occurrence patterns of plant-associated microbiome. DNA concentrations of Phytophthora nicotianae, the causal agent of tobacco black shank, were also quantified. Levels of P. nicotianae varied among farms and soil compartments, with the highest concentrations in the rhizosphere of symptomatic plants at C&C Farm, where disease severity was greatest. Bacterial and fungal Shannon diversity and richness were generally lower in the rhizosphere than in bulk soil, regardless of plant health status. Microbial beta diversity was significantly influenced by farm location rather than soil compartment or plant health status. The rhizosphere soil of symptomatic plants at C&C and Bass Farms had more complex bacterial or fungal networks, with more nodes and edges than healthy plants. However, microbial networks at other locations remained similar between healthy and symptomatic plants. These findings suggest microbial community restructuring in response to P. nicotiana infection is site-specific, emphasizing the need for tailored black shank disease management strategies.