First Report of Colletotrichum endophyticum Causing Leaf Brown Spot on Bauhinia variegata in Fujian Province, China

Bauhinia trees are key landscape species in southern China, offering ornamental, ecological, cultural, and medicinal value (Sun et al. 2024). Bauhinia plays a pivotal role in urban greening across Fujian Province, particularly as street trees. In August 2025 (summer), brown spot disease on Bauhinia variegata was observed on landscape trees in Fuzhou City, Fujian Province, including parks and street plantings, with disease incidence reaching up to 80%. Initial infection presents as punctate yellowish-brown lesions (1-2 mm in diameter) on leaves. These lesions progressively expand to 0.5-1 cm, developing irregular shapes. At maturity, the lesions are often surrounded by a pronounced chlorotic halo. Symptomatic leaves were collected from the campus of Fujian Agriculture and Forestry University (26°5'2"N, 119°13'48"E) for pathogen isolation and identification. Isolation from the collected leaf samples obtained strains FAFU-YTJ-1 to 4. The colony of the strain reached to 6.7 cm in diameter on PDA for 7 days at 25℃ under 12-hour light/dark, with gray surface, beige center reverse and white edge. Acervulus dark and cushion-like. Conidiophores hyaline to pale brown, smooth-walled, septate, branched, and conidiogenous cells hyaline, cylindrical. Conidia hyaline, 1-celled, ellipsoidal, with obtuse ends and a slight central constriction, measuring 17.53-22.28×6.16–8.15 μm (n = 50). Morphologically, the isolates are similar with Colletotrichum endophyticum, exhibiting similar ellipsoidal conidia (Manamgoda et al. 2013; Bhunjun et al. 2021). To confirm the identification, six genes: internal transcribed spacer (ITS), actin(act), calmodulin(cal), chitin synthase(chs), glyceraldehyde 3-phosphate dehydrogenase (gapdh), β-tubulin (tub2), gene were amplified using primers ITS1F/ITS4, ACT-512F/ACT-783R, CL1C/CL2C, CHS-79F/CHS-345R, GDF/GDR, T1/ BT2b, respectively (Liu et al. 2022). Sequences were submitted to GenBank (ITS: PX717400- PX717404, act: PX725381- PX725384, cal: PX725385- PX725388, chs: PX725393- PX725396, gapdh: PX753063- PX753066, tub2: PX725389- PX725392). The sequences of the six genes were concatenated to construct Maximum Likelihood (ML) phylogenetic tree. The phylogenetic analyses results identified the isolates as C. endophyticum. To confirm the pathogenicity of C. endophyticum, healthy B. variegata leaves were surface-sterilized with 75% ethanol, rinsed, and wounded with 0.5 mm circular cuts. The fungus was subcultured on PDA at 25°C for one week before inoculation. 5 mm diameter mycelial plugs (FAFU-YTJ-1) were inoculated onto the wounded leaves using attachment method, with the same size sterile PDA plugs serving as control. Each treatment was replicated three times. Within 3 days, all inoculated leaves developed brown lesions, while controls remained asymptomatic. C. endophyticum was reisolated from diseased tissues and showed the same morphological characters, fulfilling Koch’s postulates. Previously, C. endophyticum has been reported exclusively on B. purpurea within the genus Bauhinia (Liang et al. 2023). Therefore, this is the first report in China of B. variegata brown spot disease caused by C. endophyticum. This finding will provide a basis for epidemiological investigations and future disease control.