AKTIVITAS ANTAGONIS ISOLAT BAKTERI DARI RIZOSFER JERUK SIAM (CITRUS NOBILIS LOUR.) TERHADAP FUSARIUM OXYSPORUM

Potential of Bacterial Isolates from the Rhizosphere of Citrus nobilis Lour.as Antagonistic Agents against Fusarium oxysporum

Abstrak

Fusarium oxysporum is a phytopathogenic fungus that causes Fusarium wilt in Citrus nobilis. One environmentally friendly alternative to control this disease is the use of rhizosphere bacteria, which are known to suppress plant pathogens. This study aimed to identify the antagonistic activity of rhizosphere bacteria from C. nobilis against F. oxysporum. Rhizosphere soil samples were collected from C. nobilis plantations in Bagun Purba Timur Jaya Village, Bangun Purba District, Rokan Hulu Regency, Riau Province. Bacterial isolation was conducted using nutrient agar medium, followed by characterization based on colony morphology, Gram reaction, cell shape, catalase activity, and the ability to inhibit F. oxysporum growth. Five bacterial isolates (RJS1, RJS2, RJS3, RJS4, and RJS5) were obtained, with cell counts ranging from 0.41×10⁸ to 1.41×10⁸. The isolates exhibited diverse colony morphologies; all belonged to Gram-negative groups, with rod-shaped cells (RJS1, RJS4, and RJS5) and coccoid-shaped cells (RJS2 and RJS3). All isolates showed catalase activity and inhibited the growth of F. oxysporum by 14.20–57.14%. However, all of the isolates demonstrated antagonistic activity against F. oxysporum.