Cabbage (Brassica oleracea L.) is a cool-season crop of the Brassicaceae family. In late autumn 2022, irregularly shaped yellow to translucent spots, which later turned brown to black, were observed on savoy cabbage ‘Famosa F1’ in commercial fields in the Apulia region, Southern Italy. Lesions, primarily on outer leaves, resulted in yellowing and wilting. Disease severity in affected fields reached approximately 70%, and prevalence was estimated between 70% and 80%. Ten symptomatic cabbage plants were collected, and small pieces of tissue from the margin of lesions were disinfected with 1% hypochlorite solution for 1 min, soaked in 70% ethanol for 30 s, and rinsed twice with sterile distilled water. These samples were placed on potato dextrose agar (PDA) medium supplemented with 0.5 g/L streptomycin sulfate and incubated at 25 ± 1°C in the dark. After five days, purified cultures morphologically resembling Fusarium were obtained through hyphal tip culture on PDA. The mycelium was white to pale yellow, composed of septate hyphae, and colonized the entire Petri dish (90 mm diam) within one week. A total of 100 conidia were examined, including macroconidia (measuring: 40 (32-49) × 5.5 (3.7-6.9) μm), which were slender, falcate, hyaline, with 2-5 septa dividing the conidia into 3-6 cells, and microconidia, which were smaller (measuring 13 (7.5-20.0) × 4.4 (2.6-6.4) μm), with one or two cells, ellipsoidal to reniform, and borne on short undifferentiated monophialides. Genomic DNA was extracted according to De Miccolis Angelini et al. (2010), and multi-locus sequence analysis was performed. The internal transcribed spacer (ITS) region, fragments of the β-tubulin (TUB), translation elongation factor 1-alpha (TEF 1-α), and RNA-binding protein 2 (RPB2) genes were amplified by polymerase chain reaction (PCR) and Sanger-sequenced using primers ITS5/ITS4 (McBreen et al. 2003; White et al. 1990), Bt2b/T1 (Glass et al. 1995; O'Donnell et al. 1998a), EF-1/EF-2 (O'Donnell et al. 1998b), and RPB2-5F/RPB2-7CR (Liu et al. 1999), respectively. Sequences were deposited in GenBank with accession numbers PV606470.1 for ITS, PV612384.1 for TUB, PV612385.1 for TEF 1-α, and PV954741.1 for RPB2. When searched in the non-redundant GenBank and Fusarium MLST (www.fusarium.org) databases, the highest sequence similarity (≥99.29%) was reached with the ITS region (GU170651.1), TUB (MW534050), TEF 1-α (MW620166.1), and RPB2(MW474690.1) genes of Neocosmospora falciformis. Phylogenetic analysis of concatenated TEF1-α and RPB2 nucleotide sequences confirmed the identification of the isolates. Pathogenicity test was carried out in a greenhouse (25 ± 1°C; 12 h photoperiod) by inoculating leaves of ninety healthy plants of B. oleracea L. var. botrytis, var. italica, and var. sabauda with mycelium plugs (5 mm diam) excised from the actively growing margin of 10-day-old PDA cultures of the two isolates. For inoculation, a single plug was placed onto the adaxial surface of the third and or fourth true leaf of each plant. Fifteen days after inoculation, necrotic spots similar to those observed in the field samples were detected. The fungus was reisolated from infected tissues of inoculated plants and exhibited the same morphological and molecular characteristics as the original isolates, thereby fulfilling Koch's postulates. Pathogenicity tests were repeated to confirm the reproducibility. This study represents the first report of N. falciformis on B. oleracea in Italy.
Dongiovanni et al. (Sun,) studied this question.