Aug 2026· Journal of Fungi· Vol 12· 0 citations· 64 references
Medicine
TL;DR
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.
Abstract
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.
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.
Xiaobo Zhang, Xiaoyi Zuo, Jianhua Lu et al.· PLoS ONE· 0 citations
Jackfruit (
Artocarpus heterophyllus
Lam.) is a valuable tropical fruit crop in southern China, yet little information is available regarding the pathogens affecting its foliage. In July 2023, typical leaf spot symptoms were observed on jackfruit plants in Nanning, Guangxi, China, which prompted an investigation into the causal agent. The colonies of the pathogen isolated from the symptomatic leaves appeared white initially, and gradually turned gray, the conidia were black, spherical to subspherical. Based on morphological observations and phylogenetic analyses, the pathogen was identified as
Nigrospora sphaerica
. The symptoms caused by inoculation of healthy leaves with
N. sphaerica
isolates were similar to those of jackfruit leaf spot observed in the field, and the pathogen was re-isolated from artificially inoculated symptomatic leaves. This was the first report of
N. sphaerica
causing leaf spot on jackfruit in China. Further biological characterization demonstrated that the pathogen achieved optimal mycelial growth at 28 °C on PDA medium, with maximal mycelial growth obtained at pH 8 and pH 9, which were not significantly different (
P
< 0.05); among all tested media, malt extract agar was the optimum medium for mycelial growth. Soluble starch and beef extract powder served as the optimal carbon and nitrogen sources, respectively. In addition, 55 °C for 10 min was the lethal temperature for mycelial growth. These findings provide critical insights into the biology of
N. sphaerica
and its potential impact on jackfruit production. Understanding its optimal growth conditions may aid in developing management strategies to mitigate disease spread and reduce crop losses. Subsequent studies should explore disease epidemiology and potential control measures.
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
Yam (Dioscorea opposita Thumb.) is an economically important crop with dual food and medicinal uses, and is extensively grown in China, notably in Shandong Province. In 2024, a disease survey was conducted in Heze, Shandong Province, China (35.5346°N, 115.5504°E), during which a leaf spot disease was observed on yam, with disease incidence ranging from 25% to 30% in the affected fields. Initial symptoms appeared as small, circular to subcircular, brown spots with pale yellow halos on the upper leaf surface. With disease progression, the lesions enlarged and developed characteristic grayish-white necrotic centers with dark-brown margins, while the surrounding tissues gradually turned chlorotic, leading to pronounced chlorosis around the lesions. On severely affected leaves, adjacent lesions coalesced into large, irregular necrotic areas (Fig. 1), while severely affected plants exhibited extensive foliar chlorosis, marginal blight, premature senescence, and defoliation under field conditions (Fig. 2). To isolate the causal agent, 60 symptomatic yam leaves were collected from representative diseased plants in the surveyed fields for fungal isolation. Tissue pieces (approximately 5 × 5 mm) excised from the margins of lesions were surface‑disinfested sequentially in 1% NaClO for 30 s and 5% ethanol for 30 s, rinsed three times with sterile distilled water, and dried on sterile filter paper. The sterilized tissues were placed on potato dextrose agar (PDA) plates and incubated at 25°C. After 7 days of incubation, hyphae emerging from the tissues were transferred to fresh PDA plates, and pure cultures were obtained by hyphal tip isolation. Five fungal isolates with similar cultural and morphological characteristics were consistently isolated from symptomatic tissues. One representative isolate, designated YBB-5, was selected for subsequent morphological, molecular, and pathogenicity analyses. On PDA, colonies of isolate YBB-5 reached approximately 80–85 mm in diameter after 7 days at 25°C, appearing white with abundant aerial mycelia. With continued incubation for 10 days, colonies gradually turned gray to black. Conidia were black, spherical to subspherical, and unicellular, measuring 14.6 ± 1.7 μm in diameter (n = 50) (Fig. 3). Based on these cultural and morphological characteristics, isolate YBB-5 was preliminarily identified as Nigrospora spp., which is in agreement with the description of this species (Wang et al. 2017). To further confirm the identity of the isolate, genomic DNA was extracted from isolate YBB-5, and the internal transcribed spacer (ITS) region was amplified using the primer pair ITS1/ITS4. The obtained ITS sequence was deposited in GenBank under accession number PZ574363. For phylogenetic analysis, ITS sequences of representative Nigrospora species and related taxa were retrieved from GenBank. Multiple sequence alignment and phylogenetic analyses were conducted using MEGA version 11.0. A neighbor-joining phylogenetic tree was constructed based on the Tamura–Nei model with 1,000 bootstrap replications. Isolate YBB-5 clustered with N. sphaerica isolate QYN6 (PV336075.1) with strong bootstrap support (99%) and was clearly separated from other Nigrospora species included in the analysis. These results, in conjunction with morphological characteristics, confirmed the identification of the isolate as N. sphaerica (Fig. 4). To assess pathogenicity, mycelial plugs (5 mm in diameter) obtained from the margin of 7-day-old PDA cultures of isolate YBB-5 were placed onto 15 detached healthy yam leaves (five leaves per replicate, three replicates) after surface sterilization. Fifteen detached healthy leaves treated with sterile PDA plugs served as controls. The inoculated leaves were maintained in sterile Petri dishes containing moist filter paper and incubated at 25 ± 1°C under a 12 h light/dark photoperiod. The experiment was repeated three times. At 3–5 dpi, typical symptoms, resembling those observed in the field, developed around the inoculation sites, whereas the control leaves remained symptomless. To further verify pathogenicity under natural conditions, 30 healthy yam leaves were slightly wounded with sterile syringes and sprayed with a conidial suspension obtained from cultures grown in potato dextrose broth (PDB) at 27°C for 7 days. Thirty healthy leaves sprayed with sterile water served as controls. Approximately 14 days after inoculation, inoculated leaves developed characteristic leaf spot symptoms consisting of grayish-white necrotic centers surrounded by dark-brown margins, closely resembling those observed under natural conditions, whereas control leaves remained symptomless(Fig. 5). The fungus was consistently re-isolated from symptomatic tissues. The recovered isolates exhibited cultural and morphological characteristics matching those of the original isolate, including the production of typical black spherical conidia. These results fulfilled Koch’s postulates. No obvious symptoms were observed on tubers, and no obvious differences in tuber size or individual tuber weight were noted among the limited number of plants examined; however, the effect of the disease on overall tuber yield was not quantitatively evaluated. Nigrospora sphaerica has previously been reported to cause leaf spot or leaf blight on watermelon, passion fruit, cacao, and peach (Ismail and Abd Razak 2021; Li et al. 2024; Villanueva et al. 2023; Wang et al. 2022). These diseases are associated with extensive foliar necrosis, premature defoliation, and reduced yield. To our knowledge, this is the first report of N. sphaerica causing leaf spot on yam in China. This finding extends the known host range of N. sphaerica and provides a basis for future monitoring and disease management in yam production systems.
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
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
6
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.
