First report of Fusarium solani causing root rot of cucumber in Kosovo

In July 2023, symptoms of foliar wilting and yellowing, and cortical rot of stems were observed on cucumber (Cucumis sativus cv. Ekol) in a commercial greenhouse located in Mamusha, Kosovo (Figure 1). The disease incidence was estimated to be approximately 30%. Diseased material (stem and root fragments) was collected from affected plants. Samples were surface sterilised using 75% ethanol for one minute and rinsed in sterile distilled water. The sterilised fragments were then placed on potato dextrose agar (PDA) and incubated at 27°C in the dark for seven days. Colonies had white mycelial growth with an orange to purple pigmentation in the centre (Figure 2). Macroconidia were slightly curved with three to five septa (Figure 3). The morphology of two representative isolates, DLS2081 (stem) and DLS2082 (root), was consistent with Fusarium solani (Li et al., 2010). Single spore isolates of DLS2081 and DLS2082 were used for DNA extraction using a CTAB-based method. The internal transcribed spacer (ITS) region, translation elongation factor (TEF1α) and second largest subunit of nuclear RNA polymerase II (RPB2) from both isolates were amplified and sequenced with primer pairs ITS1/ITS4 (White et al., 1990), EF-1/EF-2 (Karlsson et al., 2016) and 5F2/7cR (Liu et al., 1999), respectively. Sequences were deposited in GenBank under Accession Nos. PP940094 and PP940095 (ITS), PP963514 and PP963515 (TEF1α), PQ119501 and PQ119502 (RPB2) for DLS2081 and DLS2082 isolates, respectively. A BLAST analysis of ITS sequences showed 100% identity with F. solani (MT371374.1, HQ384397.1), TEF1α sequences showed 99–100% identity with F. solani (HQ731056.1, MT305228.1), and RPB2 sequences showed 100% identity with F. solani (MF276966.1, MF276931.1). Phylogenetic analysis revealed that both DLS2081 and DLS2082 isolates clustered with F. solani strains (Figure 4). To fulfil Koch's postulates, two-week-old cucumber (cv. Ekol) plantlets (twelve per isolate) were inoculated with DLS2081 and DLS208 isolates. Plant roots were cleaned by removing ...