Cherry blossom (Cerasus serrulata) is a plant with important garden applications. It is a newly introduced exotic plants in the Arar region of Xinjiang, China (40°41'18.19″N,81°43'50.55″E). In October 2022, it was discovered that about 30% of cherry blossoms had a canker disease. The leaves of the sick branches were dired, the branches themselves were damaged, with dark brown color inside. Orange-yellow conidia horns were produced in humid condition. Samples were collected from fifteen trees exhibiting notable symptoms. The diseased junctions of the infected shoots were chopped into small pieces and subjected to surface sterilization by using 70% ethanol for 30s, 1% NaClO solution for one minute, and sterile distilled water three times (Chen et al. 2016). The representative strain YINGHUA-1 was chosen for identification by molecular biology and morphology. After five days of incubation at 26℃ on PDA media, colonies of white fluffy mycelium were produced from the YINGHUA-1 strain. After 25 days of PDA culture, the production of pycnidia was first observed, circular, black. The pycnidia began to produce conidia at 30 days. The conidia was translucent without septum, with a slightly curved single cell and smooth surface. Pycnidia was spherical and flat, with a single black aperture at the top that resembles a nearly round hole, the chamber was made up of several tiny chambers separated by a shared wall, and its diameter ranges from 900-1900 µm. The size of the conidium was 3.7-6.6×1.1-1.9 μm (n=20). The intrinsic transcriptional spacer (ITS), transcriptional elongation factor (tef-1α), and β-tubulin (tub2) gene moieties of rDNA were sequenced using ITS1/ITS4, EF1-728F/EF1-986R, and Bt2a/Bt2b primers, respectively(Zhang et al. 2014). The amplified sequences of ITS region (Accession No. OR855907), tub2 (Accession No. OR865863) and tef-1α (Accession No. OR865864) were deposited in the GenBank. BLAST searches of the sequences revealed 99.59% identity (474/476 bp) of the ITS sequence, 98.63% identity (216/219 bp) of the tef-1α sequence, and 98.55% identity of the tub2 sequence (339/344 bp) with C. ailanthicola CFCC59446 (accessions OR826163, OR832040, and OR832062, respectively.) Phylogenetic analyses were performed with Iqtree v.1.6.12 for maximum likelihood (ML). Confidence levels for the nodes were determined using 1000 replicates of bootstrapping methods. Based on phylogenetic analysis and morphological characteristics, the pathogen was identified as C. ailanthicola. The pathogenicity of C. ailanthicola was confirmed by inoculation of 1-year-old shoots (5 replicates of this experiment). After 7 days, symptoms of inner bark discoloration were visible on xylem of branches and the same fungus was re-isolated from the inoculated shoots, with no lesions on the control shoots. C. ailanthicola is only known from a single host plant, Ailanthus altissima,in China (Fan et al.2020). As far as we know, this is the first report of C. ailanthicola harmings C. serrulata in China.
Keywords: Canker; Cerasus serrulata; Cytospora ailanthicola; Pathogen identification.