Fusarium oxysporum is the pathogen responsible for stem rot of the succulent plant Echeveria \u2018Perle von N\xfcrnberg\u2019 and observation of the infection process

Abstract

Echeveria ‘Perle von Nürnberg’ is a popular ornamental potted plant. In 2017–2018, stem rot lesions caused by Fusarium spp. were repeatedly observed on Echeveria ‘Perle von Nürnberg’ in Zhangzhou, Fujian Province, China. In this study, samples were collected to isolate the pathogen. After morphological observations, molecular identification, and pathogenicity measurements, the pathogen was confirmed as Fusarium oxysporum. Green fluorescent protein was used to label F. oxysporum to observe the pathogenic process in the host plant. Two to three days after inoculation, the pathogen conidia adhered to the surface of the host stem and germinated into hyphae. The hyphae invaded the host cortex through wounds on the plant or the stem-leaf junction. The host stem produced greyish-brown circular or irregular lesions. Five days after inoculation, the expanded hyphae invaded the vascular cylinder and proliferated. The lesions on the host stem became larger and the neighboring leaves gradually fell off. Seven days after inoculation, the thalli continued to proliferate in the host, the hyphae continued to expand, and the host pith was damaged. The lesions on the stem continued to expand; the stems and branches became withered and lodged, and numerous leaves fell off. Given the rapid infection of F. oxysporum in Echeveria ‘Perle von Nürnberg’ plants, necessary prevention and control measures should be employed prior to infection. In summary, this study demonstrated that the pathogen responsible for stem rot disease in Echeveria ‘Perle von Nürnberg’ is F. oxysporum and further revealed the invasion modes and pathways of F. oxysporum in this plant, providing an empirical basis for the diagnosis and treatment of this stem rot pathogen.