Epimedium sagittatum (Sieb.et Zucc.) Maxim, belonging to the family Berberidaceae and the genus Epimedium, is effective in dispersing wind and cold, tonifying the kidneys and bones, and strengthening muscles and bones (Song et al. 2024). In June 2023, a new leaf disease appeared on 33.35 hm2 of E. sagittatum cultivation in Xinning County, Shaoyang City, Hunan Province, China (111°43'00″N, 27°26'40″E), with symptoms appearing on about 50% of the cultivation area. Initially lesions appear on the leaf tips, then the spots gradually widen and become yellowish-white and dry, with a dark yellow halo around the periphery. We collected ten infected leaves from different growing areas and rinsed them with running sterile water. To isolate the pathogen, small infected parts cut from the leaves were surface disinfected with 3% hydrogen peroxide for 30 s and then treated with 75% alcohol for 45 s. Finally, the diseased parts were rinsed five times with sterile water and incubated on water agar (WA) plates at 28°C for 3-5 days. After mycelial growth was observed, the hyphae were transferred to potato dextrose agar (PDA) plates and incubated for 3-5 days at 28°C in the dark. Finally, eight isolates were obtained, and six of them belonged to Colletotrichum genus based on their morphological characterisation on PDA plates (isolation frequency 75%). Three representative strains (YYH5, YYH6 and YYH7) were selected for further study. The colonies were initially round with white aerial and later grey-black to white on the back. Under the microscope the conidia were short and cylindrical. They had rounded ends and measured 12.936 to 15.894 × 6.119 to 8.137μm (n = 100). To further confirm the identity of the isolates, five gene regions of the isolates, including internal transcribed spacer (ITS), actin (ACT), chitin synthase (CHS), calmodulin (CAL) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) were amplified and sequenced using the universal primers ITS4/ITS5, ACT-512F/ACT-783R, CHS-79F/CHS-345R, CL1C/CL2C and GDF/GDR respectively (Weir et al. 2012). Sequences were submitted to GenBank (ITS: PP898147, PP898149, PP898150; ACT: PP925578, PP925579, PP925585; CHS: PP925576, PP925577, PP925584; CAL: PP925580, PP925581, PP925586; GAPDH: PP925582, PP925583, PP925587). Analysis of the constructed five-gene joint phylogenetic tree showed that these three isolates were significantly clustered with Colletotrichum karstii. Pathogenicity was tested using three representative strains. The epidermis of young E. sagittatum leaves was punctured with a sterile needle and 6 × 6 mm mycelial blocks cultured on PDA for 7 days were placed on the wound. Controls were treated in the same way except that sterile PDA blocks were used. There were three replicates for each treatment. All plants used in the experiment were kept in a constant climate chamber at 28°C. The photoperiod was 12 hours and the relative humidity of the chamber was maintained at 80%. Three days later, lesions appeared at the inoculation sites on the plants. Symptoms worsened after five days. All strains re-isolated from diseased spots had the same colony characteristics as the representative strain and were confirmed as C. karstii by DNA sequencing. Therefore, Koch's postulates is fulfilled. C. karstii has been shown to cause anthracnose on Fragaria x ananassa Duch (Soares et al. 2021), Piper nigrum L. (Lin et al. 2022) and Glycine max (Luo et al. 2024). To our knowledge, this is the first report of C. karstii causing anthracnose on E. sagittatum. This research will lay the foundations for future control of the disease.
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