Toxicity of Volatile Organic Compounds Produced by Pathogens Ewingella americana and Cedecea neteri Associated with Pleurotus pulmonarius

Bacterial diseases of <i>Pleurotus pulmonarius</i>, caused by diverse pathogens and associated with a range of symptoms, reduce its commercial value and lead to substantial economic losses. While most research has focused on <i>Pseudomonas tolaasii</i> and its non-volatile toxin tolaasin, little is known about other bacterial pathogens and their volatile metabolites. In this study, two bacterial pathogens were isolated from symptomatic <i>P. pulmonarius</i> fruiting bodies in Guangxi, China, and identified as <i>Ewingella americana</i> and <i>Cedecea neteri</i>. Using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), we identified 16 volatile organic compounds (VOCs) produced by these two species, seven of which exhibited toxicity-inducing sunken lesions, discoloration, and inhibition of mycelial growth. Symptom severity was quantified by colorimetric analysis. Among the toxic VOCs, 2,4-di-tert-butylphenol was the most potent, inducing sunken lesions and slight discoloration at concentrations as low as 0.5 mg/mL, and causing significant inhibition of mycelial growth at 5 μg/L. The remaining VOCs also caused varying degrees of sunken lesions, yellowing or browning, and suppression of mycelial growth. This study is the first to demonstrate the pathogenic potential of VOCs produced by bacterial pathogens in <i>P. pulmonarius</i>, underscoring their role as important virulence factors and providing a foundation for further investigation into their mechanisms and control strategies.