Chinese fir (Cunninghamia lanceolata) is an important timber species that has been widely cultivated in southern China. It is extensively applied in medicine, environmental monitoring, furniture, u...

Ginkgo biloba L., one of the oldest living tree species in the world, is a valuable ornamental and medicinal plant widely cultivated in China. In May 2024, a previously unreported leaf blight disease was observed in Chengdu city (30°26'-31°16'N, 102°52'-104°16'E). Field surveys revealed a high incidence of the disease, affecting about 71.2% of the trees. The symptoms initially appeared as yellowing along the leaf margins, which progressively developed into brown, dry, and deformed areas. As the disease advanced, necrotic lesions spread toward the center of the leaf, eventually leading to complete defoliation. Infected tissues from ten samples were cut into 5×5 mm pieces, surface disinfested with 3% sodium hypochlorite (30 s) and 75% ethanol (60 s), rinsed in sterile water, blot-dried, and cultured on potato dextrose agar (PDA) amended with streptomycin sulfate (50 μg/mL) at 25°C for 4-8 days. A hyphal fragment from the colony edge was transferred to fresh PDA. After 8 days (25°C, 12h light/dark), colonies reached 71.3-79.9 mm in diameter, initially grayish-brown and cottony, later turning light pink to white centrally. The reverse was light orange to pink with a brown ring. Conidia were aseptate, single-celled, smooth-walled, cylindrical, straight, and hyaline, measuring 11.9-15.7 × 5.6-7.8 μm (n=100), consistent with C. karsti (Zhang et al. 2023). For molecular identification, genomic DNA from isolate GB202405 was extracted using a fungal DNA kit (Solarbio, Beijing). ITS, CAL, and GAPDH regions were amplified with ITS1/ITS4 (Zhang et al. 2022), CL1C/CL2C (Weir et al. 2012), and GDF/GDR (Templeton et al. 1992) primers. Sequences (GenBank: ITS PQ595992, CAL PQ621055, GAPDH PQ656800) showed 99-100% identity with C. karsti (GenBank PP907060.1, MK569156.1, MK949005.1). The identification was confirmed by Bayesian inference using MrBayes, performed through PhyloSuite version 1.2.2. Pathogenicity was tested on ten G. biloba trees. Ten healthy leaves per tree were surface-disinfested with 75% ethanol and inoculated with a conidial suspension (1×10⁷ conidia/mL). Sterile water served as the control. Transparent plastic bags maintained humidity. After 15 days (26°C, 14-h light/10-h dark), inoculated leaves developed symptoms resembling natural infections, whereas controls remained asymptomatic. C. karsti was re-isolated and confirmed morphologically and molecularly. Repeated pathogenicity tests fulfilled Koch's postulates. This study represents the first documented occurrence of C. karsti-induced leaf blight on G. biloba in China. As G. biloba is widely cultivated for medicinal and ornamental purposes, this disease may pose a potential threat to its production and landscape value. The report highlights the need for early detection and effective management strategies.

Soil-borne pathogens cause devastating root rot diseases in forest ecosystems, often by inducing dysbiosis in the rhizosphere microbiome. While antagonistic bacteria can suppress disease, their effects frequently extend beyond direct inhibition to include ecological restructuring of resident microbial communities. However, the causal relationships between such microbiome restructuring and disease suppression in tree species remain poorly understood. Here, we show that the antagonistic bacterium B. mojavensis dxk33 effectively suppresses F. solani-induced root rot in C. lanceolata, and that this disease suppression coincides with a partial reversal of pathogen-associated dysbiosis in the rhizosphere. Inoculation with dxk33 significantly promoted plant growth and reduced the disease index by 72.19%, while concurrently enhancing soil nutrient availability and key C-, N- and P-cycling enzyme activities. High-throughput sequencing revealed that dxk33 inoculation substantially reshaped the rhizosphere microbiome, counteracting the pathogen’s negative impact on microbial diversity and coinciding with a shift toward a more stable community structure. Under pathogen stress, dxk33 enriched beneficial bacterial taxa such as Pseudomonas and Sphingomonas and suppressed pathogenic fungi while promoting beneficial fungi such as Mortierella. Linear discriminant analysis and functional prediction further indicated that dxk33 remodeled ecological guilds enriched for mycorrhizal and saprotrophic fungi, and reactivated bacterial metabolic pathways and signaling networks that were suppressed by the pathogen. Taken together, our findings are consistent with a multi-tiered mode of action in which direct antagonism by B. mojavensis dxk33 operates alongside associated changes in the rhizosphere microbiome that resemble a disease-suppressive state, although the present experimental design does not allow a strictly causal role for microbiome reconfiguration in disease suppression to be established. This study provides a mechanistic framework for understanding how microbiome engineering may mitigate soil-borne diseases in perennial trees and highlights the potential of targeted microbial interventions for sustainable forest management.

Ginkgo (Ginkgo biloba L.), the oldest existing tree species in the world, is an important ornamental and medicinal plant, widely planted in China. In October 2022, a new leaf blight disease was observed in Chengdu city (30°05'to 31°26'N, 102°54'to 104°53'E). Disease incidence averaged 82.5% across five foci. The typical symptomatology begins when leaf margins turn yellow and small black spots appear at the edge of the leaf, chlorotic areas turn brown, dry and deformed. Gradually, the necrotic lesions spreads to the middle of the leaf and eventually the whole leaf falls off. Infected tissues from ten leaves were cut into small pieces (5 × 5 mm); surface sterilized for 30 s in 3% sodium hypochlorite; 60 s in 75% ethanol; rinsed three times in sterile water; placed onto potato dextrose agar (PDA) amended with streptomycin sulfate (50 μg/mL); and incubated at 25°C for 3 to 8 days. A hyphae was removed from the edge of the fungal colony and placed onto potato dextrose agar (PDA) plates. After incubation at 25℃ with a 12-hour light/dark cycle for 8 days, the colony diameter reached 77.5 to 81.5 mm. Colonies grown on PDA were white, cotton, flocculent, undulating on the surface, dense in aerial hyphae and light yellow on the back. Black pycnidia formed superficially, scattered over the PDA, following two weeks of incubation. Pycnidia contained sticky black conidia. The spores were were spindle shaped, with five cells, and four septations measuring 20.9 to 34.8 µm × 6.8 to 8.8 µm (avg. 28.4 × 7.6 µm; n=40). The three median cells were versicolored, typically two dark brown cells and one light brown cell, whereas the basal and apical cells were hyaline. Conidia had a single basal appendage (2.87 to 4.1 µm long; n = 40) and two to three apical appendages (18.3 to 29.1 µm long; n = 40). Based on colony and conidial morphology, the isolate was identified as N. clavispora (Maharachchikumbura et al. 2014). The partial sequence of the internal transcribed spacer (ITS), β-tubulin gene (TUB2), and translation elongation factor subunit 1-a gene (TEF1) were amplified and sequenced using the universal primer pairs ITS1/ITS4(Zhang et al. 2022), BT2A/BT2B (Li Yuan et al. 2022), and EF1-526F/EF1-1567R (Maharachchikumbura et al. 2012), respectively. Sequences of representative isolate LQYX were deposited in GenBank (ITS: OQ152504, TUB: OQ168328, and TEF1: OQ168329). BLAST results indicated that the ITS, TUB, and TEF1-α sequences showed 99 to 100% identity with N. clavispora sequences at NCBI (GenBank MG729689, MG740735, and MG740758). Identification was confirmed by Bayesian inference using Mr. Bayes. Next, inoculations were conducted on leaves of ten G. biloba in the field to verify the pathogenicity of LQYX. Ten healthy leaves of each plant were surface sterilized with 75% ethanol, and the wound was rubbed out on the leaf edge on the sterilized sanding paper. A conidia suspension (1 × 107 ml-1) was sprayed on the leaves, aseptic water was used as the control, and the transparent plastic bag was used to maintain relative humidity. After 14 days (26 ℃, 14 hours light / 10 hours dark), the inoculated leaves had similar symptoms as the original diseased plants, whereas controls were asymptomatic. The N. clavispora was re-isolated from the infected leaves and identified by morphological characteristics and DNA sequence analysis. The pathogenicity test was repeated three times with similar results, confirming Koch's postulates. To our knowledge, this is the first report of leaf blight of G. biloba caused by N. clavispora in China, which has greatly affected the appearance of the city and should be further studied. This report can help identify this disease and further develop effective control measures.

The Pharbitis purpurea (L.) Voisgt, a member of the Convolvulaceae, is a graceful plant with an air purifying function and ornamental values. It is often cultivated in parks and roadsides. In April...