First Report of Tea Leaf Spot Caused by Fusarium graminearum in Guizhou, China

Duyun Maojian tea is one of the top ten famous teas in China. Its source plant (tea plant, Camellia sinensis) is widely planted in Guizhou Province, spanning roughly 25,522 hectares. In August 2022, a leaf spot disease was observed in the Hongmin Tea Garden (107.31° E, 26.20° N, 1200 m a.s.l.). The disease was characterized by initially irregular light brown leaf lesions that subsequently enlarged and darkened with clear demarcation from healthy tissue, with the plant incidence rate of 30% and an affected area of 66.67 hectares. Ten symptomatic leaves were collected from 10 plants (one leaf per plant) to identify the pathogen. Tissue pieces (4 mm × 4 mm) excised from the lesion margins were surface-sterilized with 75% ethanol for 1 min, rinsed three times with sterile water, and placed on potato dextrose agar (PDA) at 28 °C for 4 days. Eight isolates with identical morphology were recovered, all of which yielded pure cultures. The colonies had white and floccose aerial hyphae with pink pigment at the bottom. Macroconidia were hyaline, sickle shaped, 28.5 to 67.5 μm × 3.4 to 5.8 μm ( n = 30 ), and contained 2-6 septate. These morphological features were consistent with the description of Fusarium graminearum (Kang et al. 2020). The fungus was confirmed to be F. graminearum by amplifying and sequencing the RNA polymerase largest subunit (RPB1), RNA polymerase second largest subunit (RPB2), and translation elongation factor 1-α (TEF1-α) genes using the primers F5/G2R, 5f2/7cr, and EF1/EF2 (O’Donnell et al. 2010), respectively. Sequences from three randomly selected strains MY01, MY02, and MY03 were deposited in GenBank with accession numbers: RPB1-(PZ013460, PZ013461, PZ013462); RPB2-(PZ013463, PZ013464, PZ013465); TEF1-α-(PQ197028, PV055444, PV055445). Blastn analysis showed 100% identity with the F. graminearum strains LC13775 and CBS 185.32 for RPB1 (MW024639, PQ280880), RPB2 (MW474597, KT855202), and TEF1-α (MW620072, PQ260856), respectively. Based on molecular and morphological evidence, these strains were identified as F. graminearum. A pot assay was conducted for pathogenicity tests. Nine healthy plants inoculated with 20 μL of spore suspensions (1×106 spores/mL) of one isolate MY01 on wounded leaves developed leaf symptoms consistent with those observed in the field, and F. graminearum was consistently reisolated from the symptomatic tissues; morphological observation and sequencing of RPB1, RPB2, and TEF1-α confirmed that the reisolated strains were identical to the original inoculated isolate, whereas control plants (n = 9) inoculated with sterile water remained symptomless. These results fulfilled Kochʼs postulates, demonstrating that F. graminearum is the pathogen of leaf spot disease on C. sinensis. F. graminearum has been previously reported as a pathogen causing various diseases on different hosts, including dry rot on Solanum tuberosum (Ali et al. 2005), ear rot on Setaria italica (Li et al. 2015), root and stem rot on Glycine max (Kang et al. 2020), flower blight on Cannabis sativa (Yulfo-Soto et al. 2022), wilt disease on Panax notoginseng (Cai et al. 2023), fruit rot on Citrus reticulata (Wang et al. 2023), crown rot on Triticum aestivum (Yang et al. 2024), and tuber rot on Gastrodia elata (Son et al. 2025). To our knowledge, this is the first report of F. graminearum causing apparent symptoms on C. sinensis leaves in China and worldwide. The tea plantation area in Guizhou has stabilized at approximately 466,700 hectares, ranking among the largest in China. This economically vital crop, with an annual output value exceeding 90 billion yuan, now faces a yield threat from this emerging leaf spot pathogen. Therefore, accurate etiological diagnosis is essential for early disease warning and targeted control.