First Report of <i>Phyllosticta capitalensis</i> Causing Leaf Spot on <i>Eriobotrya japonica</i> in China

Loquat (Eriobotrya japonica), a member of the Rosaceae family that has been widely grown in South China, is rich in triterpenoids and has numerous medicinal uses (Su et al. 2021). In August 2024, leaf spots on E. japonica were observed in Libo (25.4°N, 107.8°E) and Guanling (25.9°N, 105.6°E), Guizhou province of China with a disease incidence of 20%-40%. Leaf spots were initially yellow and gradually spread and turned dark brown. Fifteen symptomatic leaves were randomly collected from five fields. Leaves were cut into 4×4 mm pieces and disinfested with 75% ethanol for 30 s, 2% NaCIO solution for 2 min, rinsed three times in sterile water, dried on sterilized paper, placed on potato dextrose agar (PDA) containing chloramphenicol (100 mg/L), and incubated at 25°C for 7 days (16 h light, 8 h dark). Five morphologically identical isolates were obtained. Fungal colonies were greyish-green with a granular surface and white wavy edges, and the colony reverse turned black over time. Conida were hyaline, obovoid to ellipsoid, 9.7 to 16.3 × 6.6 to 13.4 µm (n=50). These morphological characteristics are similar to Phyllosticta capitalensis (Wikee et al. 2013). For molecular identification, the internal transcribed spacer (ITS) region, transcription elongation factor (TEF1) gene, and actin (ACT) gene were amplified and sequenced using ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Druzhinina et al. 2005), and ACT512F/ACT783R (Wikee et al. 2013) primers, respectively. Sequences were deposited in GenBank with accession number PV366753 to PV366757 (ITS); PV394247 to PV394251 (ACT); and PV394252 to PV394256 (TEF1). A phylogenetic tree based on neighbor joining (NJ) method using MEGA 5.0 software was constructed from concatenated sequences of ITS, ACT and TEF1, and it confirmed that five isolates (LB1-2-3, LB1-3-3, LB1-4-1, LB2-1-5 and GL1-2-7) were clustered with P. capitalensis. Pathogenicity tests of the LB1-2-3 isolate were performed on five healthy 2-year-old loquat plants grown in pots. A wound was created using a sterile syringe on each leaf and one mycelial plug (5 mm diameter) from 7-day-old colony of the LB1-2-3 isolate was placed on the wound. Three healthy plants inoculated by noncolonized PDA were used as controls. The pathogenicity test was performed under natural field conditions. After 7 days, plant exhibited similar symptoms to those observed in the field while the control plants remained asymptomatic. The experiment was repeated three times with similar results. P. capitalensis was successfully reisolated from the symptomatic leaves, and the identity of the fungus was confirmed by morphological and molecular evidence, fulfilling Koch's postulates. P. capitalensis has been reported as a pathogen causing leaf spot in Mahonia fortunei (Xiong et al. 2022), lllicium difengpi (Jiang et al. 2023) and Alpinia oxyphylla (Yan et al. 2023). Alternaria spp., Colletotrichum spp., Fusarium spp., Neopestalotiopsis spp. and Pestalotiopsis spp. (Yan et al. 2024) have been previously reported as foliar pathogens of loquat, but to our knowledge, this is the first report of P. capitalensis causing leaf spot on E. japonica in China. This finding expands the known host range of P. capitalensis and provides a basis for developing detection and disease control strategies for the loquat industry.