First Report of <i>Diaporthe eres</i> Causing Canker on Peach in Korea

In February 2025, canker symptoms were observed on peach (Prunus persica) trees in an orchard in Suncheon, Jeollanam-do, Korea. Peach is a major deciduous fruit crop in Korea, with approximately 20,300 ha under cultivation in 2024. Symptoms included bark browning, inner-bark necrosis, elongated cankers, swollen lesions, and severe gummosis. Tissue pieces (5 × 5 mm) from lesion margins were surface-sterilized in 70% ethanol for 1 min, rinsed three times with sterile distilled water, and placed on potato dextrose agar (PDA) at 25°C in darkness for 2 weeks. Four single-spore isolates (KYB-1 to KYB-4) were obtained. Colonies produced gray aerial mycelium and pale-yellow conidial masses. Alpha conidia were hyaline, smooth, fusiform to cylindrical, 6.2–9.7 × 3.0–4.7 μm (n = 100); beta conidia were hyaline, curved, 21–29 × 1.0–1.6 μm (n = 30), consistent with Diaporthe eres (Udayanga et al. 2014). ITS, TUB2, tef1, CAL, and HIS3 regions from representative isolates were sequenced and deposited in GenBank (PZ413111–13, PZ418368–70, PZ418365–67, PZ418374–76, and PZ418371–73, respectively). BLASTn identities to D. eres were 99.63% (ITS, MK335715), 99.59% (TUB2, KJ420828), 98.48% (tef1, LC316672), 99.75% (CAL, PQ093688), and 99.78% (HIS3, OP968957). Maximum-likelihood analysis of the concatenated sequences in MEGA X with 1,000 bootstrap replicates placed the isolates in the D. eres clade. Pathogenicity of KYB-2 was tested on attached one-year-old grafted peach plants and detached shoots. Mycelial plugs were applied to wounded and non-wounded stems of attached plants; detached shoots were inoculated with a conidial suspension (1 × 10⁶ conidia mL⁻¹). Five plants or shoots were used per treatment, and each assay was independently repeated three times. Attached plants were kept at 25°C and approximately 95% relative humidity for 48 h and then transferred to a greenhouse; detached shoots were kept in moist boxes at 25°C. Symptoms were assessed qualitatively. Typical cankers developed only at wounded sites on attached plants within 14 days, whereas non-wounded and mock-inoculated plants remained symptomless. Detached shoots developed necrotic lesions, severe gummosis, and internal browning within 3 days. D. eres was consistently re-isolated, and ITS, TUB2, tef1, CAL, and HIS3 sequences were identical to those of KYB-2, fulfilling Koch’s postulates. Wound-dependent disease suggests that D. eres behaves as an opportunistic pathogen and that pruning wounds may serve as infection courts. To our knowledge, this is the first report of D. eres causing peach canker in Korea. Previous studies reported D. eres and other Diaporthe species associated with peach canker, dieback, or trunk disease in Italy and China (Prencipe et al. 2017; Dissanayake et al. 2017; Wang et al. 2021; Zhou et al. 2024). Accurate identification of D. eres will aid diagnosis and management of peach canker in Korea.