First Report of <i>Fusarium equiseti</i> Causing Crown Rot of Wheat in the Drought–Alkali Wheat-Growing Area of Cangzhou, China

Fusarium crown rot (FCR) is a major disease of wheat (Triticum aestivum) worldwide. F. pseudograminearum is reported as the main causal agent of FCR in China (Deng et al. 2020). In 2025, FCR occurred on wheat in Cangzhou city, Hebei Province, China, at an incidence of 20.3%. The diseased wheat plants showed brown discoloration on the crown, followed by stem necrosis. Symptomatic plant samples were collected from fields in late May 2025. The tissues at the junction of healthy and diseased stems were surface-sterilized with 75% ethanol for 30 s, followed by 1% NaClO for 2 min, and rinsed three times with sterile water. When cultured on potato dextrose agar (PDA), the 8 isolates from Cangzhou samples (11.1% frequency) initially produced dense, white aerial mycelium, which turned pale yellow with age. One isolate (FL-8-4) was selected for morphological and molecular identification. To observe conidial morphology, a mycelial plug from the pure culture was transferred to mung bean culture solution and cultured with shaking (220 r/min) at 26 °C for five days. Microconidia were oval, measuring 4.2–6.5 × 1.2–2.0 μm (n=50). Macroconidia were slightly curved, with tapered apical cells, 3–5 septate, measuring 21.0–34.0 × 3.0–5.0 μm (n=50). The morphological characteristics were consistent with those described for F. equiseti (Ramchandra et al. 2012). PCR amplification and DNA sequencing were performed using primers ITS1/ITS4, EF1F/EF2R and 5f2/7cr (O’Donnell et al. 1998; White et al. 1990) to amplify the internal transcribed spacer region (ITS), partial elongation factor 1-alpha (TEF1-α) gene and RNA polymerase subunits (RPB2) gene, respectively. The ITS (GenBank accession no. PX285774), TEF1-α (GenBank accession no. PX376983) and RPB2 (GenBank accession no. PX600429) sequences showed 99%, 97% and 99% identity, to the ex-type strain F. equiseti (ON501071) respectively. Based on morphological and molecular data, the pathogen was identified as F. equiseti. To verify the pathogenicity of isolate FL-8-4, a seedling inoculation assay was conducted. Uniformly germinated wheat seeds (coleoptile length 0.5–2.0 cm) were immersed in spore suspension (1 × 10⁶ spores/mL) of FL-8-4 for 1 min, then, five treated seeds were arranged in a row on a moist paper towel, which was rolled into a cylinder and maintained at high humidity for 48 h before being transferred to a growth chamber cultured at 25 °C, 65% relative humidity, and a 12-h photoperiod. Upon appearance of initial wilting symptoms, the paper rolls were briefly rehydrated by immersing in sterile water for 30 s (Yang et al. 2010). The plants were treated with sterile water as controls. The experiment was repeated three times. Inoculated seedlings developed symptoms similar to those observed in the field (brown necrosis on the crown) within 7 days, while the control plants were healthy. F. equiseti was reisolated from the diseased stem of wheat and identified by morphological and molecular analysis, fulfilling Koch’s postulates. The F. equiseti has previously been reported as pathogen causing wheat crown rot in Henan and Shandong in China (Xu et al. 2025). To the best of our knowledge, this is the first report of F. equiseti causing crown rot of wheat in Cangzhou, Hebei Province, China. This finding contributes valuable information for epidemiologic studies and management of FCR in the region.