First report of botrytis blight on <i>Tulipa iliensis</i> caused by <i>Botrytis tulipae</i> in Xinjiang, China

Tulipa iliensis Regel, a species widely distributed in Xinjiang, China, is valued for its ornamental and economic importance (Wang et al. 2025) and is listed as a nationally protected plant (Category II). In May 2024, typical gray mold (botrytis blight) was observed on T. iliensis at Nalati Natural Grassland, Xinjiang (43.22°N, 83.94°E). Across nine quadrats (each 1 × 1 m; total 9 m²), approximately 30% of plants were symptomatic. Infected plants exhibited ovoid, water-soaked lesions that later developed localized necrosis and extensive leaf curling and wilting. After 24 h of cool, humid incubation, symptomatic tissues developed a gray mold; prolonged incubation produced irregular, firm black sclerotia. Diseased specimens were deposited in the Herbarium of Mycology, Xinjiang Agricultural University (HMAAC). To isolate the pathogen, tissues from the lesion margins of ten symptomatic leaves were surface-sterilized (75% ethanol, 1 min; 1% NaClO, 30 s), rinsed, air-dried, plated on potato dextrose agar (PDA), and incubated at 25°C for 3 days; single colonies were subcultured. Colonies were near-circular with white, floccose to cottony mycelium; the obverse was white to pale gray, and the reverse white to gray, with faint yellow marginal rings. After approximately 14 days, white sclerotia developed, rapidly turning black, flattened, and irregular with rounded edges (1-3 mm in diameter), evenly distributed on the medium surface. Conidia were single-celled, hyaline to light brown (appearing pale gray in mass), ellipsoid to ovoid, 7.5-11.2 × 4.6-7.6 μm (mean 8.8 × 5.4 μm; n = 50). Sporulation was limited under standard conditions but occurred after static incubation at 4°C for 2 months; conidiophores were not observed. The isolate sporulated poorly under standard culture, possibly reflecting adaptation to its native natural grassland habitat. These morphological features and the host association are consistent with those of Botrytis tulipae, as reported by Erper et al. (2019). Genomic DNA of isolate XJNLT-WH11 (7-day culture; CTAB) was amplified for ITS, RPB2, HSP60, and G3PDH (Li et al. 2022) and sequenced (GenBank: ITS PX488320; RPB2 PX686736; HSP60 PX686735; G3PDH PX686734). BLAST showed 99–100% identity to B. tulipae, and maximum-likelihood analyses placed XJNLT-WH11 in a well-supported B. tulipae clade (bootstrap=100%). Based on morphology and multilocus sequence data, the fungus was identified as B. tulipae. Pathogenicity was tested on detached T. iliensis leaves by stab-inoculation with agar plugs bearing B. tulipae; sterile plugs served as controls (three replicates). After 2 days at 20 °C, gray mold symptoms developed only on inoculated leaves, while control leaves remained symptomless. The pathogen was reisolated and matched the original isolate by morphology and sequence, fulfilling Koch’s postulates. B. tulipae is a host specialist restricted to Tulipa species (Staats 2007). Although wild tulips are often considered disease resistant (Wilson et al. 2021), the broad Tulipa host range of B. tulipae suggests a potential threat to other protected wild tulips in the region. To our knowledge, this is the first report of B. tulipae infecting wild Tulipa in China. These findings provide a scientific foundation for conserving T. iliensis and optimizing disease surveillance and management in other wild Tulipa species, while also supporting the protection of rare plant resources in their native habitats.