First Report of Fusarium Patch on Festuca arundinacea Caused by Fusarium incarnatum-equiseti Species Complex (FIESC 1) in China

In June 2017, tan circular patches ranging from 10 to 30 cm in diameter were observed on 5 to 10% of Festuca arundinacea (tall fescue) on the campus of Nanjing Agricultural University, China. Symptoms of foliar dieback appeared at the early stage of the disease. As the disease progressed, the entire plants inside the patches died. Over 15 turf samples that exhibited similar symptoms were collected. Nearly all of the roots were necrotic and discolored. Sections of symptomatic root tissue were surface sterilized in 1% sodium hypochlorite (NaOCl) for 5 min, washed twice with sterile water, air dried for 5 min, and placed on potato dextrose agar (PDA) containing 50 mg/liter of streptomycin sulfate and tetracycline. Plates were incubated in the dark at 25°C for 4 days, and a fungus with white mycelium was consistently isolated. The fungus was isolated by transferring a hyphal tip onto a fresh PDA plate and incubated at 25°C for 5 days. The aerial mycelium changed from white to light yellow, and the back of the plate turned pale brown with time. Hyaline macroconidia (mostly three-septate) were slightly curved at the apex and ranged from 17.2 to 34.1 × 2.9 to 6.3 μm. Globose chlamydospores, ranging from 5.9 to 15.2 μm, were produced on carnation leaf agar after 10 days at 25°C. DNA was extracted from the fungal mycelium of a representative isolate (NNGF1) using a cetyltrimethylammonium bromide extraction method (Cubero et al. 1999). A portion of the translation elongation factor 1-α (TEF1) region of the isolate was amplified by PCR with primers TEF1/TEF2 (O’Donnell et al. 2000). PCR products were sequenced (accession MF766108), and a BLAST search in the Fusarium MLST database showed 99.68% similarity to accession GQ505636.1 (NRRL34034) from an unnamed phylogenetic species within the Fusarium incarnatum-equiseti species complex designated Fusarium sp. FIESC 1 (O’Donnell et al. 2009). To confirm pathogenicity, four pots of 2-month-old healthy Festuca arundinacea were inoculated with a spore suspension (1 × 10⁶ macroconidia/ml) prepared by inoculating the sequenced isolate into mung bean broth (Chen et al. 2008). Two pots inoculated with distilled water served as negative controls. All six pots were covered with plastic bags, placed in a growth chamber with a 12-h day/night cycle at 28/24°C, and watered every other day to keep high humidity. After 10 days, foliar dieback was visible on F. arundinacea, and roots discolored in 2 weeks. The pathogen was reisolated from diseased roots, and species identification was confirmed by the molecular method described above. To our knowledge, this is the first report of F. incarnatum-equiseti species complex (FIESC 1) causing Fusarium patch on F. arundinacea in China. This report provides a foundation for designing effective strategies to manage this disease in the future.