Occurrence of Leaf Spot Disease on Festuca arundinacea Caused by Epicoccum latusicollum in China

Tall fescue (Festuca arundinacea Schreb.) is a major cool-season turfgrass widely planted across China for lawns and sports fields (Yang et al. 2022). In June 2024, a severe leaf spot was observed on tall fescue swards in Linghu Park, Anqing City, Anhui Province, China (30.53°N, 117.07°E). Initial symptoms were chlorotic flecks turning brown and expanding into irregular necrotic lesions with yellow haloes and dark-brown centers. Lesions frequently coalesced, causing leaf wilt. Disease incidence reached ~85% of tillers, which was determined by visually assessing 10 random 1-m² quadrats within the affected area and calculating the percentage of infected tillers against the total number of tillers. To identify the causal agent, 20 symptomatic leaves were collected. Leaf segments (5 × 5 mm) from lesion margins were surface-sterilized (70% ethanol 30 s, 1.5% NaClO 60 s), rinsed three times in sterile distilled water, dried, and placed on potato dextrose agar (PDA) with streptomycin sulfate (50 mg/L). Plates were incubated at 25°C in darkness for 7 days. Sixteen fungal isolates with similar morphology were obtained and purified by hyphal-tip transfer. Two representative isolates (XY2 and XY4) were used for further study. On PDA, colonies reached 55–63 mm diameter after 5 days, initially pink-white, then grayish-white, exuding a reddish-brown pigment into the medium. Conidiomata and pycnidia were globose, dark-brown to black, 54–121 μm diameter (mean = 88 ± 14 μm, n = 30). Conidia were oval, hyaline, smooth-walled, aseptate, 3.9–7.2 × 2.2–3.0 μm (mean = 5.6 ± 0.8 × 2.6 ± 0.3 μm, n = 100). These morphological features matched Epicoccum latusicollum. To further identify the species, rDNA internal transcribed spacer (ITS) regions, beta-tubulin (TUB2), and RNA polymerase subunits (RPB2) were amplified using the primer pairs, ITS1/ITS4, RPB2-5f2/7cR, and TUB2-Fd/TUB2-Rd (Lim et al. 2019, O′Donnell et al. 2022). The sequences were submitted to GenBank (ITS: PX401580 and PX401581; RPB2: PX423928 and PX423929; TUB2: PX411272 and PX411273). A maximum-likelihood phylogenetic tree based on concatenated ITS–RPB2–TUB2 sequences placed XY2 and XY4 within a highly supported clade containing the reference strain of E. latusicollum. For pathogenicity testing, five pots containing three plants each were used for each treatment and control. Ninety-day-old healthy F. arundinacea plants were sprayed with a conidial suspension (1 × 106 conidia/mL) of XY2 and XY4; control plants received sterile water. Plants were maintained at 25°C, 75% relative humidity, under a 12-h photoperiod. After 4 days, inoculated plants developed brown lesions that enlarged and coalesced by 6–10 days, causing leaf wilting; controls remained asymptomatic. The test was repeated three times with similar results. E. latusicollum was reisolated only from symptomatic tissues and confirmed by morphology and sequencing, fulfilling Koch’s postulates. E. latusicollum has been reported causing leaf spot on Acer rubrum, Nicotiana tabacum, and Elaeagnus pungens in China (Chang et al., 2024; Liao et al., 2023; Qi et al., 2021). However, there are no previous records of this pathogen infecting F. arundinacea. Therefore, to our knowledge, this is the first report of E. latusicollum causing leaf spot on tall fescue worldwide. This finding provides important information for turfgrass disease management, particularly under the humid summer conditions of the Yangtze River basin.