Biocontrol of Potato Common Scab by Serratia rubidaea A14 and Characterization of Its Inhibitory Volatile Organic Compounds

Potato common scab, mainly caused by Streptomyces scabies, is a widespread soil-borne disease that greatly reduces tuber quality and market value. Conventional control strategies are often inadequate or environmentally harmful, necessitating eco-friendly biocontrol alternatives. Here, strain A14, isolated from tea rhizosphere, was identified as Serratia rubidaea via polyphasic taxonomy. In vitro assays demonstrated strong antagonism against S. scabies, with a 25 mm inhibition zone. Pot trials confirmed its biocontrol efficacy of 45.45%. Mechanistic investigation indicated that volatile organic compounds (VOCs) from A14 were responsible for pathogen suppression. GC-MS/MS detected 14 VOCs; 2,4-di-tert-butylphenol (2,4-DTBP), 2-mercapto-4-phenylthiazole (2-MPT), and dimethyl disulfide (DMDS) showed potent inhibitory activity. 2,4-DTBP fully inhibited pathogen growth at 0.05 g/L, and 2-MPT (EC50 = 0.018 g/L) was newly found to be active against streptomycetes. This work identifies S. rubidaea A14 as a promising biocontrol agent and provides novel VOC candidates for developing biofumigants toward sustainable potato scab management.