Leaf Blight Caused by <i>Neopestalotiopsis dolichoconidiophora</i> on <i>Liquidambar formosana</i> in China

Liquidambar formosana Hance is one of the main afforestation species in Longquan Mountain Forest Park, where a large number of seedlings have recently been planted. In October 2024, leaf blight was observed on over 10% of 100 two-year-old seedlings (30°52′41.73″N, 104°21′33.85″E, 509 m). The disease initially appeared as marginal necrosis, especially at the leaf tips, accompanied by shrinkage and curling. Severe infections led to complete leaf necrosis, with conidiomata forming on the upper surface of affected tissues. Five symptomatic leaves were randomly collected from different trees. From these, five fungal isolates were obtained by single-conidium isolation (Chomnunti et al. 2014) and cultured on PDA. The colonies showed consistent morphology: entire margin, smooth, dense, abundant aerial mycelium, white on the obverse and white to pale yellow on the reverse, conidiomata semi-immersed or mostly immersed, exudating black conidial masses. The conidia on PDA were fusiform to ellipsoid, straight or slightly curved, with 4 septate, measuring 19-27.5 × 7-10.5 μm (x̄ = 23.7 × 8.3 μm, n = 50). The basal cell was hyaline, conical to obconical, and bore a tubular appendage. The three median cells were olive-brown, with the central cell darker and adjacent cells slightly lighter. The apical cell was hyaline and conical, bearing 2-4 filamentous apical appendages. The morphological characteristics were similar to those of Neopestalotiopsis species (Razaghi et al. 2024). Two representative isolates (SICAUCC 25-0158 and SICAUCC 25-0159) were selected for DNA extraction, and the ITS (ITS1/ITS4) (White et al. 1990), tef1-α (EF1-728F/1567R) (Carbone et al. 1999), and tub2 (T1/Bt-2b) (O’Donnell et al. 1997) regions were amplified and sequenced. All sequences were deposited in GenBank (ITS: PX206798-PX206799; tub2: PX216750-PX216751; tef1-α: PX216752-PX216753). BLASTn analysis showed that the sequences had 98.7%-100% similarity to species of N. dolichoconidiophora P. Razaghi, F. Liu & L. Cai (CGMCC 3.23490, epitype): ITS: 485/485 bp (100%), 487/487 bp (100%); tef1-α: 835/846 bp (98.7%), 845/856 bp (98.7%); tub2: 732/733 bp (99.9%), 732/733bp (99.9%) (Razaghi et al. 2024). Phylogenetic analysis based on a combined dataset of ITS, tef1-α, and tub2 sequences showed that the two isolates clustered within the clade of the N. dolichoconidiophora complex. Integrating morphological with molecular evidence, the isolates were identified as N. dolichoconidiophora. To confirm pathogenicity, three healthy two-year-old seedlings were inoculated with 500 μl of a spore suspension (1 × 10⁵ conidia/ml) on five leaves each. Three control seedlings were inoculated with sterile distilled water. All treated leaves were bagged and maintained in a greenhouse at 25°C and 70% relative humidity. The test was repeated three times. After ten days, symptoms similar to those observed in the field developed on the inoculated leaves, while no symptoms were observed on the control plants. Neopestalotiopsis dolichoconidiophora was reisolated from symptomatic leaves (100% frequency) and identified based on morphological and molecular characters, fulfilling Koch’s postulates. Neopestalotiopsis dolichoconidiophora was first reported on needle leaves of Cycas revoluta in Jiangxi Province, China (Razaghi et al. 2024). This is the first report of this fungus causing leaf blight on L. formosana. In follow-up studies, it is necessary to further clarify the disease’s occurrence patterns and impacts, and to investigate prevention and control strategies.