Paprika Damping-off Outbreak Caused by Fusarium oxysporum Contaminated Seeds in Cheorwon Province in 2023

Abstract

In 2023, symptoms like damping-off disease were observed in 74 paprika growing in greenhouses in Cheorwon-gun, Gangwon-do, Korea. In this study, we tried to find the cause of the damping-off disease outbreak. We collected symptomatic seedlings and observed the typical crescent-shaped conidia of <i>Fusarium oxysporum</i> by microscope. To confirm the presence of <i>F. oxysporum</i> in the samples, polymerase chain reaction was performed using primers specific for <i>F. oxysporum</i>; the resulting sequence showed 99.11% identity with <i>F. oxysporum</i>. To confirm the pathogenicity of the <i>F. oxysporum</i> (CW) isolated from the samples, healthy paprika plants were inoculated with <i>F. oxysporum</i> CW and damping-off symptoms were observed 2 weeks later. To investigate whether the damping-off disease outbreak in Cheorwon-gun was caused by <i>F. oxysporum</i>-contaminated seeds, 100 paprika seeds were disinfected and placed in Murashige and Skoog medium. Typical pink <i>F. oxysporum</i> hyphae were found only in control non-disinfected seeds. An 18S rRNA-based and a <i>TEF</i> gene-based phylogenetic analysis showed that the <i>F. oxysporum</i> CW isolate was not grouped with a <i>F. oxysporum</i> isolate reported from Cheorwon-gun in 2019. This study is the first report that an outbreak of damping-off disease in paprika in Cheorwon-gun, Gangwon-do, Korea, was caused by contamination of <i>F. oxysporum</i> seeds.