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.
Abstract
Polygonatum cyrtonema, a traditional Chinese medicinal plant, is predominantly cultivated in southeastern and southwestern China (Tang et al. 2026). From July 2022 to August 2023, leaf blight symptoms were observed on P. cyrtonema in Yanshan County (23.52°N, 104.32°E). Brown necrotic lesions appeared at leaf apices and margins, accompanied by yellowing and withering. Disease incidence ranged from 45 to 95% among four surveyed plantations. Twenty-two symptomatic samples were randomly collected. Leaf tissue segments (5 × 5 mm) were cut from symptomatic leaves, surface-sterilized, and incubated on potato dextrose agar (PDA) at 25 °C. Among the obtained 54 fungal isolates, 34 isolates were identified as Alternaria alternata molecularly and morphologically. The remaining 20 fungal isolates differed morphologically and molecularly; pathogenicity assays and identification collectively confirmed them as A. sp. The symptom development on P. cyrtonema of the isolates was highly consistent across three independent pathogenicity assays. Therefore, strain AB3-4 was selected for detailed characterization. Strain AB3-4 featured brownish-green centers, white peripheral mycelium, darker central reverse fading radially. On potato carrot agar, conidiophores were branched or occasionally unbranched. On branched conidiophores, conidia were in dwarf tree-like branched chains of 2 to 5 conidia. On unbranched conidiophores, conidia were simple or in chains of 3 to 11 conidia. After 15 days of incubation on PDA, conidia were observed; they were light to dark brown, beakless or short-beaked, obclavate to ellipsoid, with distinct 1–3 transverse and 0–2 longitudinal septa, and measured 8.1–39.3 × 7.0–17.3 μm (n = 100). For molecular identification, partial sequences of the Alternaria major allergen gene (Alt a 1), translation elongation factor 1-α (TEF1), endopolygalacturonase (EndoPG), RNA polymerase second largest subunit (rpb2), internal transcribed spacer (ITS), and glyceraldehyde-3-phosphate dehydrogenase (G3P) gene were amplified and sequenced using primers Alt-for/Alt-rev, EF-728F/EF-986R, EPG-F/EPG-R, fRPB2-6f/fRPB2-7cr, ITS1/ITS4, gpd1/gpd2 (Woudenberg et al. 2015). BLAST analysis of AB3-4 sequences (GenBank PV624379, OR001992, PV624433, PV624495, PV651598, and OR052172) showed 99% identity with Alternaria spp. A maximum likelihood phylogenetic tree based on the combined six-locus dataset placed AB3-4 on a branch adjacent to A. gossypina and A. longipes. Based on morphology and phylogenetic pattern, AB3-4 was identified as Alternaria sp. Pathogenicity was tested on healthy 3-year-old P. cyrtonema plants. Fifteen healthy leaves from three individual plants were abraded to create micro-wounds with sterile sandpaper, followed by droplet application of 0.1 mL conidial suspension (106 conidia/mL) with sterile water as control. All treatments were incubated at 25±1℃, 80% RH. Five days postinoculation, inoculated leaves developed typical blight symptoms identical to field observations, whereas controls remained symptomless. The experiment was replicated twice with consistent results. The pathogen was successfully re-isolated from diseased tissues and confirmed as A. sp. via morphological observation and DNA sequencing. A. alternata has been already reported to cause leaf blight on P. cyrtonema in Hunan Province (Fan et al. 2024). But to our knowledge, this is the first report of A. sp. causing leaf blight on P. cyrtonema in China.
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.
Geranium (Pelargonium spp.) is an important ornamental plant susceptible to diseases caused by phytopathogenic fungi, among which Alternaria sp. stands out as the causal agent of brown necrotic leaf spots with concentric zones. Symptomatic samples were collected in March 2025 in the vicinity of Kruševac, and five isolates (MA1–MA5) were selected for further investigation.Pathogenicity was confirmed using the stem wounding method, and inoculated plants developed typical symptoms, including drying and plant death. Morphological and cultural characteristics were examined on PDA, CMA, and WA media; the average conidial size was 29.45 × 13.16 μm, and the highest mycelial growth was recorded on CMA. PCR analysis (ITS1/ITS4 and EF1-728F/EF-2) confirmed the presence of fragments of the expected size (~500 bp) in all isolates. The results confirm the presence of A. alternata on geranium in Serbia and emphasize the importance of timely identification for disease management
Panax notoginseng, a traditional Chinese medicinal herb, is susceptible to various fungi (Li et al. 2024). In Jun 2024, symptoms of black necrotic lesions on root was observed on P. notoginseng in Wenshan City, China (23.41°N, 104.18°E). The disease incidence was approximately 10%, with a total affected planting area of around 100 ha. Ten diseased plants were used to isolate the pathogen. Small tissue segments (5 × 5 mm) were cut from symptomatic roots, surface-sterilized, and incubated on potato dextrose agar (PDA) at 25 °C for 4 days. Eight monosporic strains obtained from six samples were conducted pathogenicity tests and were reisolated. Morphological and molecular identification demonstrated they were consistent with Neocosmospora ipomoeae. The symptom development on P. notoginseng of the strains was highly consistent across three independent pathogenicity trials. Therefore, strain LHGF12-3 was selected for detailed characterization. Cultured on PDA medium for 7 days, the colony was white with dense aerial mycelia, the reverse side was white to buff. After 20 days incubation on carnation leaf agar (CLA) medium, spore characteristics of the isolates were evaluated (Zheng et al. 2024). Macroconidia, falcate, 3 to 6 septa, measured 21.7 to 60.1 × 2.5 to 7.8 μm (n = 60). Microconidia, aseptate or 1-septa, measured 1.5 to 21.0 × 3.0 to 6.8 μm (n = 100). Chlamydospores, globose to subglobose, measured 10.1 to 20.6 × 10.1 to 19.6 μm (n = 50). The morphological features were consistent with the description of N. ipomoeae (Custódio et al, 2022). For molecular identification, partial gene sequences of translation elongation factor 1-α (TEF1), the second subunit region of RNA polymerase (rpb2), and the internal transcribed spacer (ITS) were amplified and sequenced using primers EF1/EF2 (O 'Donnell et al., 1998), fRPB2-6f/fRPB2-7cr (Eddouzi et al., 2013), and ITS1F/ITS4 (White et al., 1990). Based on polyphasic identification, the sequences of TEF1 (GenBank accession PV461722), rpb2 (PV461787), and ITS (PV453061) from the strain LHGF12-3 were compared with all sequences in the FUSARIUM-ID database (O' Donnell et al., 2022). The results demonstrated 99.9% identity with GenBank sequences of N. ipomoeae, including CBS 833.97, NRRL 52699 and CBS 353.87. A concatenated phylogenetic analysis of these loci confirmed the strain as N. ipomoeae. The pathogenicity of the strain LHGF12-3 was confirmed by inoculating onto one-year-old P. notoginseng plants. The roots were washed with sterilized water, and then surface-sterilized with 75% ethanol. Before inoculation the roots were wounded with a sterile needle. Root of each plant was inoculated by brushing 1 mL of a conidial suspension (1 × 106 spores/mL) of the corresponding strain; sterile water was used for controls. Plants were grown in 25 cm plastic pots (five plants per pot) filled with sterilized sand-vermiculite substrate (1:1, v/v) and maintained in the greenhouse at 20 to 26 °C and 80 % RH. After 15 days, inoculated plants developed root rot symptoms similar to those observed in the field, whereas controls remained symptomless. The experiment was repeated twice with similar results. The re-isolated strain was verified as N. ipomoeae via TEF1 sequencing. To date, this is the first report of N. ipomoeae causing root rot in P. notoginseng in Wenshan, China. Given the economic importance of P. notoginseng in China, this finding highlights the need for targeted management strategies against this emerging pathogen.
Y. Long, Qirui Zhang, Shang-Ge Huang 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
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.
S. Choi, Eun Young Kim, Shinhwa Kim et al.· Plant Disease· 0 citations
The comparative evaluation of fungal and bacterial antagonists demonstrated that B. velezensis SWFU41 outperformed T. harzianum and T. asperellum in disease suppression, highlighting its potential as a promising biocontrol agent for sustainable disease management.
Namchul Pu, Rui Wang, Wan-Shan Shao et al.· Journal of Fungi· 0 citations
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