Biocontrol potential of endophytic strain Pseudomonas chlororaphis subsp. piscium YX-3 isolated from Morchella against white mold disease

• First report VOCs of Pseudomonas chlororaphis inhibite Pseudodiploöspora longispor a. • First report VOCs of Pseudomonas chlororaphis control white mold disease of Morchella . • 2-Nonanol is pinpointed as the key volatile with significant antifungal toxicity. • The antifungal mechanism is linked to cellular structure disruption. • Demonstrates a broad-spectrum antifungal profile of the VOCs. White mold disease caused by Pseudodiploöspora longispora is destructive to the production and quality of Morchella . In this study, an endophytic bacterial strain YX-3 was isolated from the ascocarp of Morchella and exhibited significantly antagonistic effects against P. longispora with the inhibition rate of 91.5%. The strain YX-3 was identified to be Pseudomonas chlororaphis subsp. piscium through multi-locus sequence analysis and morphological characteristics. The gene features and functional annotation were analyzed according to the whole genome sequencing. The VOCs produced by strain YX-3 demonstrated significant inhibitory effects on mycelial growth, spore germination of P. longispora and reduced the severity of white mold disease through fumigation during storage. In field experiments, the biological control effect of YX-3 reached to 57.3%. The scanning and transmission electron microscope (SEM and TEM) and fluorescence microscopy revealed that VOCs from YX-3 caused abnormal changes and damaged the cell membrane integrity. Ten VOCs produced by YX-3 were detected through gas chromatography-mass spectrometry, of which seven were evaluated for their antifungal activity against P. longispora. The volatiles, namely 2-undecanone and 2-undecanol exhibited notable inhibitory effects on P. longispora with inhibition rate of 100%, 77.06% at 80 μL/plate and the minimum inhibition concentration of 2-nonanol was 0.75 μL/plate and reduced the severity of white mold disease. Overall, these findings elucidate the biocontrol mechanisms of P. chlororaphis subsp. piscium strain YX-3 and support its potential application as a biocontrol agent against white mold disease in Morchella .