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<p>This study investigates the dual function of the endophytic bacterium <i>Bacillus subtilis</i> strain DWA as a biocontrol agent against <i>Pythium aphanidermatum</i> and a growth promoter in cucumber (<i>Cucumis sativus</i> L.) plants. <i>In vitro</i>, antagonistic assays revealed that <i>B. subtilis</i> DWA inhibited <i>P. aphanidermatum</i> growth by 46%. Scanning electron microscopy confirmed hyphal deformation and cell wall degradation. A simplex-lattice mixture design optimized chitinase activity (6.23 IU) and total phenolic content (20.98 mg/mL) using 1.39 g/L chitin and 0.61 g/L phenylalanine. GC–MS analysis identified hexanoic acid (15.94%), (S)-( +)-6-methyl-1-octanol (10.02%), and other bioactive metabolites, while phytohormone profiling confirmed indole-3-acetic acid (204.59 µg/mL) and gibberellic acid (178.38 µg/mL) production. In greenhouse trials, the granular bioformulation of <i>B. subtilis</i> DWA reduced seed rot and seedling mortality caused by <i>P. aphanidermatum</i> by 41.33% and 67.31%, respectively, while increasing plant survival to 70.24% and boosting dry weight by 218.97%. Treated plants exhibited enhanced photosynthetic pigments (chlorophyll a, b, and total chlorophyll), antioxidant activity (ABTS: 26.08%; DPPH: 15.68%), and phenolic/flavonoid content. Molecular identification via 16S rRNA gene sequencing confirmed the isolate as <i>B. subtilis</i> (accession number: OR577131). These findings underscore <i>B. subtilis</i> DWA as a promising dual bioagent for sustainable cucumber production and pathogen suppression.</p>

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Endophytic Bacillus subtilis DWA: a dual-function for suppressing Pythium aphanidermatum and enhancing Cucumis sativus growth

  • 期刊论文

  • 发表日期：

    2026年4月30日

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  • Ehsan M. Rashad,
  • Abeer A. Ghoniem,
  • WesamEldin I. A. Saber,
  • Dalia Wael,
  • Ayman Y. El-Khateeb,
  • Yosra A. Helmy,
  • Abdulaziz A. Al-Askar

摘要

This study investigates the dual function of the endophytic bacterium Bacillus subtilis strain DWA as a biocontrol agent against Pythium aphanidermatum and a growth promoter in cucumber (Cucumis sativus L.) plants. In vitro, antagonistic assays revealed that B. subtilis DWA inhibited P. aphanidermatum growth by 46%. Scanning electron microscopy confirmed hyphal deformation and cell wall degradation. A simplex-lattice mixture design optimized chitinase activity (6.23 IU) and total phenolic content (20.98 mg/mL) using 1.39 g/L chitin and 0.61 g/L phenylalanine. GC–MS analysis identified hexanoic acid (15.94%), (S)-( +)-6-methyl-1-octanol (10.02%), and other bioactive metabolites, while phytohormone profiling confirmed indole-3-acetic acid (204.59 µg/mL) and gibberellic acid (178.38 µg/mL) production. In greenhouse trials, the granular bioformulation of B. subtilis DWA reduced seed rot and seedling mortality caused by P. aphanidermatum by 41.33% and 67.31%, respectively, while increasing plant survival to 70.24% and boosting dry weight by 218.97%. Treated plants exhibited enhanced photosynthetic pigments (chlorophyll a, b, and total chlorophyll), antioxidant activity (ABTS: 26.08%; DPPH: 15.68%), and phenolic/flavonoid content. Molecular identification via 16S rRNA gene sequencing confirmed the isolate as B. subtilis (accession number: OR577131). These findings underscore B. subtilis DWA as a promising dual bioagent for sustainable cucumber production and pathogen suppression.