Volatile organic compounds from Stenotrophomonas geniculata J-0 as potential biofumigants manage bulb rot caused by Fusarium oxysporum in postharvest Lanzhou lily

The Lanzhou lily bulbs are often vulnerable to postharvest infections by pathogenic fungi, leading to lily bulb rot. This study investigated the ability of volatile organic compounds (VOCs) produced by Stenotrophomonas geniculata J-0 to control the highly pathogenic fungus Fusarium oxysporum BH-7 in postharvest Lanzhou lily bulbs. VOCs of S. geniculata J-0 showed inhibitory effect on the mycelial growth of F. oxysporum BH-7, with a maximum inhibition of 100%. Scanning electron microscope (SEM) observed that VOCs caused a shift in mycelial morphology from elongated and uniform tubular to collapsed and wrinkled. Moreover, VOCs of J-0 significantly reduced pathogenic fungal spore germination and sporulation. Through headspace gas chromatography-ion mobility spectrometry analysis, J-0 emitted 15 volatile compounds. The fumigation test of BH-7 with single pure synthetic compounds showed that 1-penten-3-one had excellent antifungal activity, with an inhibition rate of 100% at 4 mu L/L. Additionally, our results revealed 1-penten-3-one destroyed the integrity and increased the permeability of BH-7 mycelial cell membranes, leading to leakage of intracellular electrolytes and substances, a reduction in extracellular pH, a blockage of ergosterol synthesis and an elevation in malondialdehyde content. In vivo experiments, fumigation of 1-penten-3-one at an exceptionally low concentration (4 mu L/L) for a very short period of time (0.5 h) was effective in delaying the onset and prevalence of postharvest diseases. Hence, this study provides novel antifungal agents to control disease in postharvest Lanzhou lily and enhances our understanding of the biocontrol potential of volatiles from S. geniculata.