In September 2025, a total of 15 soybean fields were surveyed in Muan and Gongju, Korea. Irregular leaf blight symptoms were observed in five fields, with approximately 1–10% of soybean plants showing symptoms in each affected field. To isolate the causal pathogen, symptomatic leaf tissue was surface-disinfected with 1% NaOCl for 1 min, rinsed with sterile distilled water, and placed on potato dextrose agar (PDA). The plates were incubated at 20℃ for 7 days, and olive-brown hyphae growing from the tissues were subcultured twice on PDA. Five isolates with similar morphology were obtained from symptomatic leaves, and one representative isolate, DA17-37, was selected for further morphological, molecular, and pathogenicity analyses. The conidia were predominantly oval to ellipsoidal and aseptate, measuring 3.71-6.45 x 1.77-2.83 μm, with a mean size of 5.11 x 2.14 μm (n=30). The ascospores were mostly oval and 1-septate, measuring 12.49-18.25 x 4.13-5.41 μm with a mean size of 15.08 x 4.48 μm (n=30). Additionally, multicellular chlamydospores were observed. Overall, these morphological characteristics were consistent with those of the genus Didymella. To genetically characterize isolate DA17-37, genomic DNA was extracted, and the internal transcribed spacer (ITS), beta-tubulin (tub2), and RNA polymerase II second largest subunit (rpb2) genes were amplified by PCR using the respective primer sets described previously (Gorny et al. 2016; Liu et al. 1999; Woudenberg et al. 2009). The resulting sequences were deposited in GenBank under accession numbers PZ274701, PZ433240, and PZ439292. Maximum likelihood phylogenetic analysis of the concatenated dataset showed that isolate DA17-37 clustered with the reference strains of Didymella americana. To confirm the pathogenicity of isolate DA17-37, a conidial suspension (1 x 10
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conidia/mL) prepared from 30-day-old PDA cultures grown at 20℃ was sprayed onto 2-week-old potted soybean plants. Control plants were sprayed with sterile distilled water. The inoculated plants were incubated in a dew chamber at 26℃ for 3 days and then transferred to a growth chamber maintained at 26℃ and 70% relative humidity under a 16-h photoperiod. Symptoms first appeared at 7 days post-inoculation (dpi), and representative symptoms showing disease progression were photographed at 14 dpi, whereas the uninoculated control plants remained healthy. To satisfy Koch’s postulates, the same pathogen was re-isolated from symptomatic leaves and identified based on morphology and DNA sequence analysis. Didymella americana has been reported as a causal pathogen of leaf blight on lima bean in the United States. To the best of our knowledge, this is the first report of leaf blight caused by D. americana on soybean in Korea. Continued monitoring is needed to assess the potential spread of this disease in Korea and to support the development of appropriate disease management strategies.
In September 25, 2025, numerous symptoms resembling leaf spot were observed on the leaves of Welsh onions planted at the Beijing Academy of Agricultural and Forestry Sciences (39°57′N, 116°18′E). Samples were taken from the diseased leaves. The lesions mostly appeared at the leaf tips and middle parts of the leaves, exhibiting a yellowish-white discoloration, circular or oval shapes, slightly sunken, and in severe cases. The samples were isolated in a hood, soaked in 75% alcohol for 30 s, rinsed twice with sterile water for 5 s each time, and finally cut into leaf pieces（5 × 5 mm）. These pieces were inoculated onto Potato Dextrose Agar (PDA) medium and cultured in a dark incubator at 25°C. Two isolates (designated BJST4 and BJST6) were isolated. Mycelia were white and irregularly floccular at the initial stage. The medium gradually turned yellow, later, they turned cottony-woolly. The medium gradually turned reddish-brown. Conidia are pale yellowish-brown, elliptical, and muriform with transverse septa, constricted at the central septum. After 10 d, the mycelia were picked and DNA was extracted using the CTAB method. Primers ITS1/ITS4 were used to amplify the Internal Transcribed Spacer (ITS) regions (White et al., 1990), and primers gpd1/gpd2 were used to amplify the glyceraldehyde-3-phosphate dehydrogenase (gpd) gene (BerBee et al., 1999). The amplification products were sent to Tsingke BiotechnologyCo., Ltd. for sequencing. BLASTn analysis revealed that the ITS sequences of both isolates were 100% homology to Stemphylium vesicarium (YLXXC10-21 and YLXXC08-9), and the gpd sequences showed over 99% homology to multiple S. vesicarium. MEGA7 was used to align and trim the obtained sequences, and phylogenetic trees were constructed for the ITS and gpd sequences separately. The ITS and gpd sequences have been submitted to GenBank (GenBank accession nos. PZ169639, PZ169640, PZ179494, and PZ179495, respectively). To verify Koch's postulates, inoculation was performed on detached Welsh onion leaves. The leaves were cleaned with 75% alcohol and rinsed with sterile water. The edge hyphae of a 5-day-old strain were inoculated onto the pricked and wounded leaves. The control group used PDA medium without inoculation. The inoculated leaves were placed in a light incubator (humidity 99%, temperature 25°C with a 12-h photoperiod). On the third day of inoculation, disease spots appeared in the treatment, while the control group remained healthy. The strain re-isolated from the lesions was identical to the original inoculated strain. To our knowledge, this is the first report of leaf spot disease caused by S. vesicarium on Welsh onions in Beijing, China. This discovery provides an effective direction for the identification and treatment of Welsh onion diseases in production.
Yexuan Zheng, Mifeng Bai, Yujie Yang et al.· Plant Disease· 0 citations
To determine the species, the four isolates were molecularly identified by amplifying and sequencing the internal transcribed spacer (ITS) region and the translation elongation factor 1‑α (EF‑1α) using primers ITS1/ITS4 and EF1‑728F/EF1‑986R, respectively (White et al. 1990).
Juan Antonio Castro-Diego, Verónica Delgado-Pacheco, N. Ley-López et al.· Plant Disease· 0 citations
In August 2025, fruit rot symptoms were observed on peach (Prunus persica) in four open-field orchards located in Chuncheon (three orchards) and Wonju (one orchard), Gangwon Province, Korea. The disease occurred at a low incidence of approximately 1% in each orchard. Initial symptoms appeared as small lesions on the fruit surface, which expanded and developed into sunken rot accompanied by grayish-white mycelial growth. Symptoms were limited to fruit, and no symptoms were observed on leaves or branches. Four symptomatic fruits were collected (three from Chuncheon and one from Wonju). Small tissue pieces were excised from the margins of lesions, surface sterilized, and plated onto potato dextrose agar (PDA). After incubation at 25°C for 3 days, morphologically similar fungi were obtained by hyphal tip isolation, yielding four representative isolates (25-484, 25-488, 25-489, and 25-502). The representative isolates were deposited in the Korean Agricultural Culture Collection(KACC) under accession numbers KACC 411323, KACC 411324, KACC 411325, and KACC 411326. Colonies on PDA were initially white, dense, and cottony, becoming ivory to pale apricot with age and gradually turning brownish in the center. Conidia were hyaline, cylindrical with rounded ends, straight, and measured 41.8–47.7 × 3.2–4.7 μm (n = 30). Sphaeropedunculate vesicles were observed, and these morphological characteristics were consistent with the current circumscription of Calonectria canadiana (Liu et al. 2020). For molecular identification, five gene regions(act, tef1, tub2, his3, and cmdA) were amplified using previously published primers (Crous et al. 2004) and sequenced. All sequences generated from the four isolates(25-484, 25-488, 25-489 and 25-502) have been deposited in GenBank database on NCBI(GenBank accession numbers PX920276, PX920278, PX920279 and PX920280 for act; PX920281, PX920282, PX920283 and PX920285 for cmdA; PX920286, PX920287, PX920288 and PX920290 for his3; PX920291, PX920292, PX920293 and PX920295 for tef1, and PX920296, PX920297, PX920298, and PX920299 for tub2). Phylogenetic analysis based on concatenated sequences was performed using the maximum likelihood method with 1,000 bootstrap replicates implemented in RAxML (Stamatakis 2014). All four isolates clustered with reference strains of C. canadiana with high bootstrap support(≥95%). Recent taxonomic studies have recognized C. montana as a synonym of C. canadiana based on multilocus sequence comparisons and overlapping morphological characteristics (Liu et al. 2020); therefore, the isolates were identified as C. canadiana in this study. Pathogenicity tests were conducted on attached peach fruits (cv. Kawanakajima Hakuto) in the field. A conidial suspension of a representative isolate, adjusted to 1 x 105 spores/ml, was sprayed onto the surfaces of 10 fruits until runoff. Each fruit was considered a biological replicate. Inoculated fruits were maintained under natural field conditions. After 5-7 days, typical fruit rot symptoms identical to those observed in the field developed on inoculated fruits, whereas non-inoculated control fruits remained symptomless. The pathogen was consistently re-isolated from symptomatic tissues. C. canadiana has previously been reported on peach in China (Zhang et al. 2022); however, to our knowledge, this is the first report of fruit rot caused by C. canadiana on peach in Korea.
Ha-Kyoung Lee, Da-Ran Kim, Jung-Eun Kim et al.· Plant Disease· 0 citations
Pepper (Capsicum annuum L.) is one of the most economically important cash crops in China. In July 2024, leaf spot was observed on pepper cv. ‘Sujiao 5’ in a 1-ha pepper plantation in Hangzhou (30°17′N, 118°52′E), Zhejiang Province. Among eight greenhouses surveyed, 30 plants per greenhouse were inspected. Disease incidence ranged from 10% to 20%. Early symptoms were round, grayish-white lesions. As the disease advanced, lesions expanded into circular spots with grayish-white centers and brown margins, and a grayish-brown mold layer emerged on the lesions. Thirty diseased leaves were randomly sampled from twenty infected plants for pathogen isolation. Under a stereomicroscope, a single conidium from the mold layer on diseased leaves was transferred onto potato dextrose agar (PDA) medium using a sterilized inoculating needle and incubated at 26°C for 7 days. Twenty single-conidium isolates were successfully obtained. After 15 days on PDA, colonies were grayish-green, velvety, with grayish-white margins. On synthetic nutrient-poor agar (SNA), colonies were light grayish-green with sparse mycelium. The conidiophores were solitary, erect, light brown, and septate. Ramoconidia were light brown, cylindrical to obovoid, aseptate, and measured 6.0-15.3 × 2.5-4.3 μm (n = 30). Conidia were light brown, obovoid to limoniform, forming branched chains with one to four conidia per branch, and measured 3.3-5.7 × 2.3-3.3 μm (n = 30). The morphological features were consistent with Cladosporium sp. (Bensch et al. 2015). All 20 single-conidium isolates shared identical colony morphology and conidial characteristics, so three representative isolates were randomly selected for sequencing. The primer pairs ITS1/4 (White et al., 1990), EF728/EF986 (Carbone and Kohn, 1999), and ACT512/ACT783 (Carbone and Kohn, 1999) were used to amplify the partial fragments of the internal transcribed spacers (ITS, GenBank: PZ437871-PZ437873), translation elongation factor 1-α gene (tef1, GenBank: PZ445478-PZ445480), and actin gene (act, GenBank: PZ445475-PZ445477). The sequences of the three isolates were identical at all three loci. BLASTn analysis showed 99% identity with Cladosporium sp. (ITS: OQ629129; tef1: HM148442; act: MT154165). The phylogeny suggests that three isolates were integrated into the Cladosporium tenuissimum clade (ML bootstrap support values/Bayesian posterior probabilities = 93/1). Based on morphology and phylogeny, the isolates were identified as C. tenuissimum. Since all isolates were morphologically and molecularly identical, isolate LJYB-LA1 was selected as a representative strain for pathogenicity testing. The isolate was cultured on PDA at 26°C in continuous darkness for 14 days. Conidia were rinsed with sterile water containing 0.1% Tween-80 and adjusted to 2 × 10
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conidia/mL using a hemocytometer. Two-month-old pepper plants cv. ‘Sujiao 5’ were each sprayed with 200 mL of conidial suspension; the negative control plants were sprayed with 200 mL of sterile water. The plants were incubated in a greenhouse at 26°C and 85% relative humidity for 48 h. The experiment was repeated three times with five plants per replicate. After 10 days, inoculated plants developed symptoms similar to those observed in the field, whereas control plants remained asymptomatic. The species C. tenuissimum was reisolated from symptomatic tissues and confirmed by morphology and molecular data, confirming Koch’s postulates. The species C. tenuissimum has been reported to infect Hydrangea paniculata in China (Li et al. 2021) and Phaseolus vulgaris in China (Gao et al. 2024). To our knowledge, this is the first report of C. tenuissimum causing leaf spot on C. annuum in China.
In 2024 fall, symptoms of leaf blade and petiole spots were observed on strawberry plants 'Rociera FNM' and 'Marisma FNM'. In 450 randomly selected plants from 3 nurseries of Segovia province (Spain) 3.5% of incidence was recorded. Lesions on the leaf were reddish-brown with yellowish halos and became necrotic. Dark brown lesions with defined edges were noted on petioles. Affected tissue sections were excised, rinsed with 0.1% Tween 20, submerged in 70% ethanol (20 s), followed by 1% NaOCl (60 s), and then placed onto potato dextrose agar (Condalab, Madrid, Spain) with 50 mg/l of streptomycin sulphate. Plates were incubated at 28°C under darkness. From 6 crowns and 2 petioles 8 isolates (Di 3 to Di 10) were obtained from different pycnidia via single conidia isolation. Colonies had petal-shaped margins. Hyphae were initially hyaline, later developing an orange coloration in the center of the colony, and black conidiomata were visible two weeks post-incubation. Conidiomata were ellipsoidal to globose. Single-celled conidia were brown, ellipsoidal with slightly mucronate apices, narrowly truncated bases and smooth walls. This morphology was consistent with Coniella sp. as described by Álvarez et al. (2016). Isolates were stored in 50% glycerol solution at -80ºC. Genomic DNA was extracted from the 8 selected isolates. The internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (TEF1), and large subunit ribosomal RNA (LSU) were amplified using the primer pairs ITS1/ITS4 (White et al. 1990), EF728/EF986 (Carbone and Kohn 1999), and LR0R/LR7 (Chethana et al. 2017), respectively. Sequence alignments performed in MEGA v11.0 (Tamura et al. 2021) showed that all isolates were identical across the three analyzed loci. Sequences of Di6 and Di10 isolates were deposited in GenBank. BLASTn analyses revealed that ITS (PX663172, PX663173), TEF1 (PX666006, PX666007), and LSU (PX663628, PX663629) sequences showed 100% identity with C. fragariae strain CBS 198.18 for ITS and 99% and 100% identity with strain CBS 167.84 for TEF1 and LSU, respectively. A concatenated phylogenetic tree was constructed with representative Coniella species and outgroup sequences from NCBI GenBank (Chethana et al., 2017) and confirmed the identity. Pathogenicity test was conducted using isolates Di6 and Di10. Inoculation with each isolate was performed by spraying 25 mL of a conidial suspension (5 x 104 conidia/mL) onto 5 plants of 'Rociera FNM'. Control plants were sprayed with sterile water. The assay was carried out twice. After inoculation, plants were covered with a plastic bag and kept in darkness for two days. Growth chamber was maintained at 25±2°C with 12-h photoperiod. Identical symptoms to the initially observed appeared on inoculated plants 6 days post-inoculation. Both isolates exhibited comparable severity (proportion of symptomatic leaf area) 20 days after inoculation. An assay was also performed on 'Marismas FNM', giving the same results. Fungal colonies re-isolated from the lesions had the same morphology and ITS, TEF-1 and LSU sequences of the inoculated isolates, thereby fulfilling Koch's postulates. In Switzerland and Great Britain C. fragariae has previously been isolated from strawberry plants (Rigotti et al. 2003; Jones and Baker, 2007). To our knowledge, this is the first report of C. fragariae on strawberry in Spain. Monitoring of the pathogen is essential since it can spread through asymptomatic plants into strawberry’s nurseries and fields.
Strain AB3-4 featured brownish-green centers, white peripheral mycelium, darker central reverse fading radially, and based on morphology and phylogenetic pattern, AB3-4 was identified as Alternaria sp.
Qirui Zhang, Hai-Jiao Yang, Zhong-Shun Mao et al.· Plant Disease· 0 citations
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