Fusarium oxysporum, the cause of Fusarium wilt on cucumber (Cucumis sativus L.) in Serbia

Cucumber (Cucumis sativus L.) is a vegetable crop with a global production of approximately 87 million tons in 2021, according to FAO data. It is also an important vegetable species cultivated in both greenhouses and open fields in Serbia. One of the most devastating diseases affecting cucumbers is Fusarium wilt, caused by Fusarium oxysporum. Infected older plants may exhibit yellowing starting from the oldest leaves, stunted growth, or wilting. Affected plants can develop lesions on the lower stem. The fungus infects the vascular system, and symptoms may remain unnoticed until the plant begins to bear fruit. This paper presents the results of a preliminary study on Fusarium wilt in cucumbers in Serbia. Samples were collected in 2022 from the Trebotin locality, Kruševac. A total of 15 samples from Mirabelle F1 hybrid cucumber plants were analyzed. Our research has shown that, based on morphological, molecular, and pathogenic characteristics, cucumber wilting in Serbia is caused by F. oxysporum. The morphological characteristics of the isolates (appearance, size, and septation of macro- and microconidia) were as follows: microconidia dimensions ranged from 3.8–15.5 µm×2.8–4.9 µm, macroconidia from 14.6–37.9 µm×2.4–5.6 µm, with the number of septa ranging from 1 to 4. PCR analysis using F. oxysporum-specific primers resulted in the amplification of the expected 315 bp fragment in all tested isolates. The pathogenicity test showed that symptoms of Fusarium wilt initially appeared as yellowing of the oldest leaves. The disease progressed, eventually leading to plant wilting and death. The characterization and confirmation of F. oxysporum on cucumber in Serbia is a significant finding, emphasizing the need for an effective disease management program to reduce yield losses.