First Report of Wheat Crown Rot Caused by Fusarium commune in China

Fusarium crown rot (FCR) is one of the economically important wheat diseases worldwide. In May 2023 and 2024, winter wheat plants exhibiting typical symptoms of FCR were collected in 124 commercial fields from Hebei and Henan (Zhang et al. 2024) provinces in China. The disease incidence ranged from approximately 6%–11% in the surveyed fields. For pathogen isolation, symptomatic basal stems from 632 diseased samples were excised (~3 cm in length), surface sterilized in 1% NaClO for 2 min, rinsed with sterile distilled water, dried and placed onto potato dextrose agar (PDA) plates. After incubating in the dark at 25 °C for 3–5 days, colonies resembling Fusarium were transferred to fresh PDA plates for further purification. Combined analysis with morphological and molecular characteristics was employed in the identification of these isolates. Among the 549 Fusarium isolates obtained, Fusarium pseudograminearum was the dominant pathogen causing FCR in China. However, one isolate from Hebei (Tangshan) and three isolates from Henan (Anyang, Xuchang, and Zhoukou) were identified as Fusarium commune, accounting for approximately 0.73% of the total. On PDA, F. commune produced fluffy aerial mycelium, with colonies appearing white and exhibiting an average radial growth rate of 6.0 mm per day at 25 °C in the dark. Macroconidia were generated on carnation leaf agar plates, measuring 37.6 ± 7.6 × 3.7 ± 0.5 μm (n = 63). The macroconidia were slightly curved, predominantly containing three to four septa, with a slightly curved apical cell and a foot-shaped basal cell. Microconidia were generally cylindrical, straight to slightly curved, aseptate, measuring 11.6 ± 3.4 × 3.2 ± 0.5 μm (n = 50). Species identification was confirmed by sequence analyses of portions of the translation elongation factor 1α (TEF) and the second largest subunit of the RNA polymerase (RPB2) using primer pairs EF1/EF2 and 5f2/7cr (O’Donnell et al. 2022), respectively. Sequences of the partial TEF from the four isolates showed 100% similarity to those of F. commune (accession nos. PQ823451, PQ823456, MW620162) via alignment against the Fusarioid-ID reference database (https://www.fusarium.org/). Similarly, their RPB2 sequences exhibited 100% identity with the corresponding sequences of F. commune strains NRRL 28387 and CBS 110090 (GenBank accession nos. JX171638 and MW934368). The sequences generated in this study were deposited in GenBank: TEF (accession nos. PQ667787, PX627786–PX627788) and RPB2 (accession nos. PV090863, PX627789–PX627791). To fulfill Koch’s postulates, 8-mm-diameter mycelial plugs from 3-day-old cultures of each isolate were placed around the coleoptiles of one-leaf stage potted wheat seedlings (cultivar Zhengmai1860), following the method described by Wang et al. (2025) with five replicates per isolate. Twenty seedlings inoculated with blank PDA plugs served as controls. All seedlings were incubated in a humid chamber at 25 °C with a 12-h photoperiod. After 14 days, all inoculated plants (five per isolate) developed similar symptoms of FCR, characterized by dark brown necrotic lesions around the inoculation sites, while no symptoms were observed in controls. The pathogen was consistently re-isolated from artificially inoculated plants and confirmed as F. commune, with no fungi isolated in the controls. To our knowledge, this is the first report of F. commune causing wheat crown rot in China.