Microbiome and volatile organic compound profiling of diseased soils and their association with tomato wilt caused by Ralstonia solanacearum

Abstract

<title>Abstract</title> Soil volatile organic compounds (VOCs) are critical in suppressing soil-borne pathogens, yet their microbial origin, functional mechanisms, and contribution to disease suppression remain underexplored. This study investigated the role of VOCs in the disease-suppressive capacity of soils from two tomato monocropping regions against <italic>Ralstonia solanacearum</italic> , the causative agent of bacterial wilt. Among the disease-conductive and suppressive soils, suppressive soil showed the lowest disease incidence (0.37%) and pathogen load (9.6 × 10³ CFU/g), which was linked to potent soil VOC-mediated suppression of <italic>R. solanacearum</italic> growth and disease occurrence. GC-MS analysis identified 13 VOCs significantly related to disease index, including naphthalene, 2-undecanone, and humulene, which inhibited pathogen growth <italic>in vitro</italic> and promoted plant growth and defense enzymes (CAT, SOD). Amplicon sequencing revealed differences in microbial community diversity and composition between conductive and suppressive soils, with <italic>Streptomyces</italic> as a key disease-suppressive taxon. Isolation of 10 <italic>Streptomyces</italic> strains from suppressive soil confirmed their role in restoring VOC-mediated suppressiveness in sterilized soil, with strain Stre2 achieving 46.17% pathogen inhibition. Correlation, Procrustes, and variation partitioning analyses (VPA) demonstrated that soil physicochemical and microbial factors jointly shaped soil VOC composition, but bacterial communities also exerted a significant direct influence (11.1% unique contribution). Our findings demonstrate that disease-suppressive soils harness microbiota-derived VOCs to inhibit <italic>R. solanacearum</italic> and prime plant defenses, offering novel insights for sustainable pathogen management through microbial metabolite engineering.

Affiliated Institutions

• Nanjing Agricultural University CN
• Chinese Academy of Tropical Agricultural Sciences CN

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