First Report of <i>Fusarium verticillioides</i> Causing Fusarium Blight on Tall Fescue in Anhui, China

Tall fescue (Festuca arundinacea Schreb.), adaptable across subtropical to temperate zones, is extensively cultivated in northern China and the Yangtze River basin (Richard et al. 2020, Yang et al. 2022). In September 2023, the symptoms of leaf blight were observed on F. arundinacea lawns of Linghu Park (117.07°E, 30.53°N, located in Anqing, Anhui Province, China), with 15～30% of the area being infected. The leaf tissues (5 × 5 mm) from the border of diseased and healthy areas were surface disinfested in a 1% sodium hypochlorite (NaOCl) for 5 min, washed three times with sterile water. After drying on sterile filter paper, leaf tissues were placed on potato dextrose agar (PDA) at 28°C for 3 days. Pure cultures were obtained by transferring hyphal tips from the edges of colonies onto PDA. Among the 22 isolates, 18 exhibited similar morphological characteristics, and one representative strain GYB-1 was selected for further identification. Colonies on PDA were pink with a white outer ring and a cottony surface, while the reverse side was light pink with some areas appearing red. Microconidia were hyaline, oval or ellipsoidal, had zero to two septa, and measured 4.3 to 14 × 1.8 to 4.2 μm (n = 50). Macroconidia were slightly curved with three to five septa, and measured 22 to 64 × 3.1 to 5.0 μm (n = 50). According to the morphological characteristics, the isolates were identified as Fusarium verticillioides. To further identify the species, rDNA internal transcribed spacer (ITS) regions, beta-tubulin (TUB2), translation elongation factor 1-alpha (TEF1), and RNA polymerase subunits RPB2 were amplified using the primer pairs, ITS1/ITS4, BT2A/BT2B, EF1/EF2 and 7cf/11ar (Lim et al. 2019, O′Donnell et al. 2022). The obtained sequences were deposited in GenBank with the accession numbers PP783464 for ITS, PQ351671 for TUB2, PQ557396 for RPB2, and PQ557397 for TEF1. Polyphasic identification of the TEF1, ITS, TUB2, and RPB2 sequences from GYB-1 showed 100% identity as the sequences of Fusarium verticillioides strain LC13655 in the FUSARIOID-ID database. To further assess the phylogenetic relationships, a neighbor-joining tree was constructed in MEGA-X, confirming that GYB-1 clusters with F. verticillioides. To confirm pathogenicity, five healthy F. arundinacea plants were inoculated by spraying the leaves with 10 ml of a spore suspension (1 × 106 macroconidia/ml), while five plants were sprayed with sterilized water as controls. All plants were placed in the same growth chamber with a 12-hour day/night cycle at 30/25°C, and 80% humidity. Ten days post-inoculation, typical lesions were observed on the treated plants. Pathogenesis involves three stages: initial light yellow spots on leaf margins/tips, progression to yellow, irregular lesions, and subsequent leaf curling and wilting. The fungi were re-isolated from the diseased leaves and confirmed to be the original pathogens through morphological and molecular identification. Thus, Koch’s postulates were fulfilled. The experiment was repeated three times with similar results. F. verticillioides is known to cause Fusarium blight on Artemisia argyi (Wang et al. 2024) and Schizonepeta tenuifolia (Li et al. 2024). This is the first report of F. verticillioides causing Fusarium blight on tall fescue in China. Identification of the pathogen is crucial for implementing management approaches to reduce lawn losses.