These findings provide a critical basis for the accurate diagnosis of this newly emerging disease on the medicinal plant, and are the first report of C. cassiicola causing leaf spot on B. fimbristipula in China.
Abstract
Background Begonia fimbristipula, an economically important medicinal plant in southern China, has recently suffered severe yield losses from leaf spot disease in Guizhou and Hunan Provinces; the causal pathogen remains unknown. Methods Field surveys were conducted across multiple locations in Guizhou and Hunan Provinces to record disease symptoms and incidence. The pathogen was isolated from diseased leaves via tissue culture, and identified by combining morphological characteristics and multilocus phylogenetic analysis (ITS, TEF1α, RPB2). Pathogenicity was verified by fulfilling Koch’s postulates through artificial inoculation and re-isolation assays. Results Severe leaf spot outbreaks were observed in August 2024, with over 60% disease incidence across 667 hectares and >20% fresh leaf yield loss. The isolated pathogen was identified as Corynespora cassiicola based on gray to dark-gray colonies, pale-brown olivaceous conidia with 0–15 pseudosepta, and ≥98% bootstrap support in phylogenetic clustering with known C. cassiicola strains. Koch's postulates were fulfilled by reproducing typical field symptoms on inoculated B. fimbristipula seedlings and re-isolating the pathogen. Conclusions This is the first report of C. cassiicola causing leaf spot on B. fimbristipula in China, expanding the host range of this pathogen. Our findings provide a critical basis for the accurate diagnosis of this newly emerging disease on the medicinal plant.
Amomum villosum is an evergreen perennial herb widely distributed in tropical and subtropical regions, with significant economic and medicinal importance. Throughout the cultivation process, it faces severe fungal disease problems that significantly impact its yield and quality. In July 2025, leaf spot disease with a 56% incidence was observed on A. villosum in Wenshan, Yunnan, China. Affected leaves initially developed irregular grayish-white lesions surrounded by brown margins. As symptom development progressed, semi-submerged black spots formed on the lesion surfaces. Severe infections resulted in premature leaf abscission and, ultimately, death of the entire plant. To identify the pathogen responsible, we conducted isolation and pathogenicity studies. Through morphological characterization, phylogenetic analysis (ITS, LSU, and TUB), and pathogenicity tests, Pestalotiopsis microspora was determined as a pathogen. Koch’s postulates were fulfilled on attached leaves. After 15 days, typical necrotic lesions appeared on inoculated leaves, while controls remained symptom-free. This is the first report of A. villosum leaf spot caused by P. microspora in China. Biocontrol assays revealed that Trichoderma harzianum T15 and T. asperellum T16 exhibited significant antagonistic activity against P. microspora, with inhibition rates of 44.77% and 50.70%, respectively. In addition, Bacillus velezensis SWFU41, isolated from healthy A. villosum leaves, showed superior disease suppression, achieving a control efficacy of 60.52%. Compared with the fungal biocontrol agents, B. velezensis demonstrated greater inhibitory activity against the pathogen, suggesting that bacterial antagonists may provide a more effective biological control strategy for managing A. villosum leaf spot disease. This is the first report of P. microspora-caused leaf spot disease on A. villosum. Furthermore, 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. These findings provide a scientific basis for pathogen monitoring, epidemiological studies, and the development of integrated biological control strategies for A. villosum cultivation.
Namchul Pu, Rui Wang, Wan-Shan Shao et al.· Journal of Fungi· 0 citations
The findings provide a theoretical foundation for accurate disease diagnosis, epidemiological surveillance, and the development of effective chemical control strategies for rubber plantations.
Zhiying Cai, Lili He, Li-Ming Dai et al.· Plants· 0 citations
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.
Qirui Zhang, Haijiao Yang, Zhong-Shun Mao et al.· Plant Disease· 0 citations
Bambusa multiplex, one of the most acclimatized clumping-bamboo species, has been broadly cultivated in China and has significant economical, ecological and ornamental importance (Yuan et al. 2009). In November 2025, more than 30% of B. multiplex plants exhibiting typical witches’ broom, internode shortening, leaf proliferation and clustering of leaves were observed in a horticultural landscaping field in Zhangjiang city, Guangdong Province, China. To confirm the presence of a phytoplasma, total DNA was extracted from fresh leaves of ten symptomatic and four asymptomatic plants using the CTAB method. Conventional nested PCR was performed using primer pairs P1/P7 followed by R16F2n/R16R2 (Gundersen and Lee, 1996), and expected fragment amplified only from the symptomatic plants. The PCR products were sequenced, and deposited in GenBank under the accession number PX998769. BLAST analysis revealed that the sequence shared 99.60% identity with that of the SPLL subgroup reference strain ‘Candidatus Phytoplasma australasiaticum subsp. Ipomoeae’ o7C (GenBank accession no. GCA_024425275.1, 1,244/1,249 bp) (Rodrigues Jardim et al. 2023). Further virtual RFLP pattern analysis of the 16S rRNA sequence by iPhyClassifier (Zhao et al. 2009) verified that the phytoplasma strain, designated as BMW-ZJ, was a member of the 16SrII-A subgroup with a 1.00 similarity coefficient to the reference phytoplasma strain (GenBank accession no. L33765). Moreover, the secY gene was amplified using primer pairs secYwbF1/secYwbR1 followed by secYwbF2/secYwbR2 (Wang et al. 2025), and the sequence(GenBank accession no. PZ135411) shared 100% identity to several ‘Ca. P. australasiaticum’ strains (NTU2011, BAWM-TWN and BAWM-THA-CLP). Phylogenetic analysis based on the 16S rRNA and secY genes conducted by MEGA 12 (Kumar et al. 2024), confirmed that BMW-ZJ was related to ‘Ca. P. australasiaticum’(Bertaccini et al. 2022; Rodrigues Jardim et al. 2023). Earlier, 16SrII phytoplasma associated with bamboo species Dendrocalamus giganteus (Che et al. 2024), and 16SrI phytoplasma associated with Sasa fortunei (Zhang et al. 2009) were reported in Hainan and Shaanxi Province, China, respectively. To our knowledge, this is the first report a ‘Ca. P. australasiaticum’ -related strain associated with Bamboo Witches’ Broom Disease (BWB) in Guangdong, China. The BWB caused by Ca. Phytoplasma (16SrI, 16SrII, 16SrVIII and 16SrXIV group), has been confirmed in several bamboo species in Southeast Asian countries such as India (Yadav et al. 2016; Ravi et al. 2022), Philippines (Dolores et al. 2023), Indonesia (Prasetya et al. 2020) and China (Zhang et al. 2009; Che et al. 2024). This study highlight the need to identify insect vectors and alternative hosts, which will provide theoretical guide to the control of Bamboo Witches’ Broom Disease.
Dayuan Sun, Chun-Yan Fan, Pingping Liu et al.· Plant Disease· 0 citations
Jackfruit (Artocarpus heterophyllus Lam.) is an economically important fruit tree widely cultivated in tropical and subtropical regions (Gupta et al. 2023). In July 2025, a leaf spot disease was observed on jackfruit trees in Zhanjiang, Guangdong Province, China. Diseased leaves initially developed small brown necrotic spots that gradually enlarged and coalesced, resulting in leaf yellowing and premature defoliation. Field surveys indicated that the disease was present in approximately 25% of the surveyed orchards. Symptomatic leaf tissues collected from diseased plants were surface-disinfested in 70% ethanol for 30 s, followed by 1% sodium hypochlorite for 1 min, rinsed five times with sterile distilled water, and plated onto potato dextrose agar (PDA). After incubation at 28°C in the dark for 5 days, 16 fungal isolates with similar morphological characteristics were obtained. Colonies exhibited an average radial growth rate of 17.1 ± 1.6 mm day⁻¹. Conidiophores were septate, pale brown, simple, smooth, straight to slightly curved, exhibiting sympodial proliferation and often bearing clusters of conidia at the apex. Conidia were solitary, ellipsoidal to oblong, straight or slightly curved, pale to dark brown, mostly 3-distoseptate, with a conspicuously darkened median septum and paler terminal cells. Conidia measured 16.3–30.9 × 5.6–11.2 μm (mean ± SD = 21.8 ± 4.9 × 8.1 ± 1.6 μm, n = 50), consistent with descriptions of Curvularia eragrostidis. For molecular identification, the internal transcribed spacer region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and translation elongation factor 1-alpha (TEF1-α) genes of three representative isolates (LNU-16, LNU-17, and LNU-18) were amplified using primer pairs ITS1/ITS4 (White et al. 1990), GDF/GDR (Templeton et al. 1992), and EF1-983F/EF1-2218R (Rehner and Buckley 2005), respectively. The obtained sequences were deposited in GenBank (ITS: PZ528505–PZ528507; TEF1-α: PZ538484–PZ538486; GAPDH: PZ538487–PZ538489). BLASTn showed 100% ITS identity with C. eragrostidis TD4.2 (OR135782), 100% GAPDH identity with C. eragrostidis RU1 (PQ442766), and 99.77% TEF1-α identity with C. eragrostidis CD15 (MK886803). Maximum-likelihood analysis of concatenated ITS, GAPDH, and TEF1-α sequences placed the three isolates within the C. eragrostidis clade. Based on morphology and multilocus analyses, the pathogen was identified as C. eragrostidis (Gan et al. 2018). Pathogenicity tests were conducted on healthy detached jackfruit leaves. Leaves were surface-disinfested with 0.1% sodium hypochlorite and rinsed three times with sterile distilled water and allowed to air dry. A conidial suspension (10⁶ conidia mL⁻¹) prepared from a 12-day-old culture was sprayed onto leaves. Control leaves received sterile distilled water. Ten leaves were used for each treatment, and the experiment was repeated twice. Inoculated leaves were maintained at 25°C and 80–85% relative humidity. Seven days after inoculation, brown lesions surrounded by chlorotic halos developed on all inoculated leaves and were similar to those observed under field conditions, whereas no symptoms were observed on control leaves. The fungi reisolated from the inoculated leaves were identified as C. eragrostidis through morphological examination and sequence analyses of ITS, GAPDH, and TEF1-α, thus fulfilling Koch’s postulates. To our knowledge, this is the first report of Curvularia eragrostidis causing leaf spot on jackfruit in China. This finding expands the known host range of C. eragrostidis and provides a basis for future studies on disease epidemiology and management.
Xiang Lu, Chumiao Chen, Yunzhi Bai 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.