Identification of the causal agent of stem basal rot in Cyclocodon lancifolius and screening of potential biocontrol bacteria

Background: Stem base rot disease poses a serious threat to the Cyclocodon lancifolius industry, yet its causal agent remains unidentified. Aims: In this study, we aimed to identify the pathogenic fungi responsible for this disease and to screen for effective biocontrol strains against the causal agent. Methods: We isolated and identified the fungal pathogen from the stem base of diseased plants and confirmed its pathogenicity by fulfilling Koch's postulates. Multilocus sequence analysis identified the pathogen as Stemphylium lycopersici. Results: An antagonistic strain, Bacillus subtilis YHYS1, exhibited significant inhibition (51.8%) of S. lycopersici growth in a plate confrontation assay. Volatile compound analysis further confirmed the fungistatic potential of YHYS1. These findings highlight the promise of YHYS1 as an eco-friendly alternative to chemical fungicides for controlling stem base rot disease in C. lancifolius caused by S. lycopersici. Conclusions: Our characterization of this novel disease in C. lancifolius has elucidated the pathogenic features of Stemphylium species, an essential yet understudied group of plant pathogens. These findings provide valuable references for the diagnosis and control of diseases affecting C. lancifolius.