First Report of <i>Fusarium luffae</i> Causing Crown Rot of Wheat in China

Fusarium crown rot (FCR) ranks among the most devastating fungal disease affecting wheat globally. During a wheat disease survey in 2023 across counties in Li, Qingyuan, Wangdu, Boye, and Gaoyang in Baoding, Hebei Province, China (38°50′N–39°10′N, 115°20′E–115°45′E), FCR was detected with incidence ranged from 30% to 40% in wheat fields. Symptomatically, the disease is characterized by the appearance of brown lesions on the wheat crown, which subsequently extended to two or more stems causing necrosis, leading to the formation of white heads during grain filling. To determine the Fusarium diversity causing FCR in Baoding, pathogen isolation was performed on the collected 150 diseased crown tissues. Small sections of diseased tissue from each plant were first surface-sterilized with 75% ethanol for 10 s, followed by 2% sodium hypochlorite treatment for 3 min, and rinsed three times with sterile distilled water. The sterilized tissues were then transferred onto potato dextrose agar (PDA) plates and incubated at 25°C for 2 days before mycelium tip purification. Totally, 147 isolates were acquired, in which four isolates (2.72%) presented dense, white aerial mycelium, which were clearly distinguishable from F. pseudograminearum. When proceeding with molecular identification, no band of 520 bp specific for F. pseudograminearum was detected by using the Fp1-1/Fp1-2 primer set amplification (Demeke et al. 2005). Amplification and sequencing of ITS4/5 (White et al. 1990) for the four isolates showed that they were classified as F. luffae within the Fusarium incarnatum-equiseti complex. Thus, one isolate (QY3-4) was selected for further identification by morphological and multi-locus amplification. When cultured on PDA plate, the average mycelial growth rate of the isolate QY3-4 was 8.0 mm per day. The macroconidia are slightly curved, with acute apical cells, 3-5 septa, and measure 32.4-68.7 × 4.7-6.9 μm (n=50). Besides ITS4/ITS5, amplification and sequencing were carried out using CAMF/CAMR, EF1F/EF2R, and RPB2F/RPB2R (O’Donnell et al. 2020; O’Donnell et al. 1998; Reeb et al. 2004). The ITS (GenBank accession no. PX879050), CAM, TEF1α, and RPB2 (GenBank accession no. PX907447-PX907449) sequences showed similarities of 99.79%, 99.51%, 99.67%, and 99.64% with the type species of F. luffae (CGMCC3.19497). The phylogenetic tree was constructed based on multilocus concatenated sequences thus identifying QY3-4 as F. luffae. To confirm pathogenicity, PDA plugs colonized with QY3-4 were inoculated into sterile wheat grain medium, and 15 wheat seedlings were inoculated. The control group seedlings were inoculated with sterile wheat grain without QY3-4 inoculum. The pathogenicity experiment was conducted in a greenhouse and repeated three times. The inoculated plants exhibited obvious FCR symptoms after 30 d, while no disease symptoms observed in the control. The pathogen identical with QY3-4 was re-isolated from the symptomatic stems and confirmed by amplification and sequencing of CAM, consistent with Koch’s postulates. F. luffae has been reported to cause soybean wilt (Sharma et al. 2024; Zhao et al. 2022) and wilt disease on strawberry (Zhang et al. 2025). To the best of our knowledge, this is the first report of F. luffae causing crown rot of wheat in China. This finding contributes valuable information for epidemiological studies and management of FCR in the region.