First Report of <i>Curvularia intermedia</i> Causing Leaf Blight on <i>Festuca arundinacea</i> in Anhui Province, China

Tall fescue (Festuca arundinacea Schreb.) is a major cool-season turfgrass widely planted across China for lawns and sports fields because of its strong stress tolerance. In June 2024, a leaf blight was observed on tall fescue swards at Anqing Normal University, Anqing, Anhui Province, China. Yellow to yellow-brown necrotic spots first appeared on the tips and margins of lower leaves, later expanding to cover the entire leaf and progressing upward through the canopy. Approximately 80% of tillers were symptomatic. To identify the causal agent, 25 symptomatic leaves were collected from 25 randomly selected plants. Leaf segments (5 × 5 mm) excised from lesion margins were surface-sterilized (75% ethanol for 10 s, followed by 5% NaClO for 30 s), rinsed three times in sterile distilled water, dried, and placed on potato dextrose agar (PDA) supplemented with penicillin (0.5 µg/mL). Plates were incubated at 28°C in darkness. Nine fungal isolates with similar morphology were obtained and purified by hyphal-tip transfer. A representative isolate (XY-1) was used for further study. On PDA, colonies were initially white, becoming gray-green with floccose aerial mycelia. Conidiophores were solitary or clustered, 79–136 × 5–8 µm (n = 50). Conidia were obclavate to ellipsoid or fusiform, brown, 27–40 × 13–17 µm (n = 50), with 3-distoseptate. These morphological features were consistent with Curvularia intermedia Boedijn (Sivanesan 1987). For molecular identification, genomic DNA was extracted from aerial mycelia. The rDNA internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and RNA polymerase II second-largest subunit (RPB2) were amplified using primers ITS1/ITS4, GPD1/GPD2, and RPB2-5f2/7cR (White et al. 1990; Raza et al. 2019). In a BLASTn search, the sequences showed 100%, 99.77%, and 100% similarity to C. intermedia strains in the NCBI database (e.g., ITS: OL677168.1; RPB2: HG779169.1; GAPDH: LT715828.1). A maximum-likelihood phylogenetic tree constructed with MEGA X, based on the concatenated ITS–RPB2-GAPDH dataset, placed isolate XY-1 within a highly supported clade containing a reference strain of C. intermedia. For pathogenicity testing, five healthy F. arundinacea plants were sprayed with a conidial suspension (1.0 × 10⁵ conidia/mL) and maintained in a greenhouse at 28°C under a 12-h light/12-h dark cycle; five control plants were sprayed with sterile water. After five days, all inoculated plants developed spots that coalesced into blight symptoms similar to those observed in the field, whereas control plants remained asymptomatic. The pathogenicity test was repeated three times with similar results. C. intermedia was reisolated only from symptomatic tissues of inoculated plants and confirmed by morphology and sequencing, thus fulfilling Koch’s postulates. Curvularia species are known pathogens of various grasses (Tilley et al. 2002). C. intermedia has been reported to cause leaf blight on annual ryegrass (Lolium multiflorum) in China (Li et al. 2019). To our knowledge, this is the first report of C. intermedia causing leaf blight on tall fescue in China. This finding provides important information for turfgrass disease management, particularly under the humid summer conditions of the Yangtze River basin that favor disease development.