First Report of <i>Allium tuberosum</i> Root Rot Caused by <i>Fusarium falciforme</i> in China

Chinese chive (Allium tuberosum) is a perennial herb belonging to the genus Allium within the family Liliaceae. It is widely recognized for its medicinal and culinary applications, particularly for its stomachic, digestive, and blood pressure-reducing properties (Hong et al., 2016). In December 2024, a wilt disease was observed in a 20,000 m² chive plantation in Liaocheng City, Shandong Province (116.3560°E, 36.3142°N). The disease symptoms included wilting of the upper leaves, progressive necrosis and browning of the basal vascular bundles, and eventual wilting and death of the entire plant. Several symptomatic plants were randomly selected to identify the causal fungus on chive roots using the tissue isolation method. The infected chive root tissues at the healthy-diseased interface were immersed in 75% alcohol for 3–5 s, disinfected in 5% NaClO for 5 min, rinsed three times with sterile distilled water, and then placed on potato dextrose agar (PDA) plates containing 0.1% Triton X-100 for incubation at 28°C. A fungal strain (FF-4) was purified using the single spore isolation method and selected for subsequent characterization and pathogenicity tests. The single-spore isolate of FF-4 was inoculated onto PDA and incubated at 28°C for five days. On PDA medium, the aerial mycelium became densely packed with a velvety or felt-like texture, and yellow pigmentation developed on the reverse side of the plate. Macroconidia were sickle-shaped and fusiform, with dimensions of 4.5–6.3 × 13.6–26.1 μm (n=50). Microconidia were ovoid or mallet-shaped, ranging from 2.8–4.3 × 11.2–16.6 μm (n=50). These morphological characteristics indicated that strain FF-4 belonged to Fusarium spp. (Chehri et al., 2015). Genomic DNA from strain FF-4 was extracted using a commercial kit (Omega Bio-Tek, Norcross, GA, USA). The universal primers TUBT1/TUBT4, ITS1/ITS4, TEF-1/TEF-2, and RPB2-5f2/RPB2-7cr (O'Donnell et al., 2010) were employed to amplify the β-tubulin (TUB2), internal transcribed spacer of rDNA (ITS), translation elongation factor 1-alpha (TEF1-α), and RNA polymerase II beta subunit (RPB2) regions, respectively. The sequences were submitted to GenBank with the accession numbers: TUB2 (PV643900), ITS (PV549582), TEF1-α (PV660666), and RPB2 (PV643901). A Neighbor-Joining phylogenetic analysis (Zhang et al., 2020) revealed that FF-4 clustered with Fusarium falciforme strain NRRL 43441 with 99% bootstrap support. A spore suspension of FF-4 was adjusted to a concentration of 1 × 10⁷ CFU/mL for pathogenicity testing. Inoculation was performed by drenching 10 mL of the spore suspension directly onto the root zone of each healthy one-week-old chive seedling (8 seedlings per replicate) without wounding the root system. Sterile distilled water was used as the control treatment with the same drenching method. All treatments were maintained in a greenhouse at 25 ± 1°C and 80% relative humidity with three biological replications. At 20 days post-inoculation, the inoculated plants exhibited typical symptoms of leaf yellowing, wilting, root rot, and browning of the basal plate vascular bundles, consistent with the symptoms observed in the field. The fungus re-isolated from the diseased inoculated plants showed identical morphological and molecular characteristics to FF-4, fulfilling Koch’s postulates. These findings confirm that FF-4 is the causal agent of chive root rot. This is the first report of Fusarium falciforme causing root rot on Chinese chive (Allium tuberosum) in China, which lays a foundational basis for the development of effective control strategies against this disease.