Cathaya argyrophylla Chun et Kuang is a tertiary relict plant unique to China, with important scientific and practical value, and is a Class I key protected wild plant in China (Qian et al., 2016; Qu et al., 2018; Yang et al., 2020). In June 2025, during a field study in the Dashahe National Nature Reserve (107.6 E, 28.89 N) in Daozhen County, Guizhou Province, leaf spot symptoms were observed on C. argyrophylla for the first time. As a core distribution area of C. argyrophylla, the Dashahe National Nature Reserve in Guizhou Province has a distribution area of approximately 8.81 hectares, with a total of 866 C. argyrophylla trees. According to the survey, 217 trees were affected by leaf spot disease, with a disease incidence rate of about 25%. Symptoms appeared as irregular necrotic lesions on infected leaves, reddish brown with dark brown margins, gradually expanding. Ten symptomatic leaves were collected. Tissue segments (5 × 5 mm) cut from lesion margins were surface-disinfected in 75% ethanol for 30 s, then in 3% sodium hypochlorite for 2 min, and rinsed three times with sterile distilled water. Hyphal tips were transferred to PDA and incubated at 28 ℃ for 7 days. Three single-spore isolates (YB-1, YB-2, LE-1) were obtained, showing identical morphological characteristics. DNA was extracted, and the ITS region was amplified using ITS1/ITS4 (White et al. 1990). Results confirmed that YB-1, YB-2 and LE-1 belong to the same species, Diaporthe eres. YB-1 was selected as the representative strain. After 3–5 days on PDA, colonies showed slightly raised centers with dense white mycelium. After 7 days, mycelium turned from white to light gray, with distinct radial growth. Colony margins were indistinct, villous, with white granular protrusions. Spherical to subspherical black conidiomata were embedded in the white mycelium. Alpha conidia are unicellular, translucent, fusiform, and measure 9.2 to 10.6 × 5.4 to 6.3 µm (n = 50). Beta conidia were hyaline, aseptate, filiform, hamate, and 9.05 to 33.12 × 0.5 to 1.2 µm.（n = 10). For molecular identification, total genomic DNA was extracted. The complete internal transcribed spacer (ITS), translation elongation factor-1 alpha (TEF1), and calmodulin (CAL) regions were amplified and sequenced using primers ITS1/ITS4 (White et al., 1990), EF1 728F/EF1-986R, and CAL-228F/CAL 737R (Carbone and Kohn, 1999), respectively. The ITS, TEF1, and CAL sequences were obtained and deposited in GenBank under accession nos. PX999695, PZ094119, and PZ094118, respectively. BLAST searches in GenBank showed 100% identity with Diaporthe eres GH06. Phylogenetic analysis further confirmed that the isolate clustered within a well-supported clade with D. eres. Pathogenicity tests were conducted using isolate LE-1 on three 2-year-old C. argyrophylla plants. Per plant, three leaves were inoculated with spore suspension (10⁶ conidia/mL); three control plants received sterile water. Incubation: 25℃, 12-h photoperiod, 75% relative humidity. Experiment repeated three times. At 14 days post-inoculation, inoculated leaves showed reddish brown lesions (similar to field symptoms); controls were asymptomatic. The fungus was re-isolated from symptomatic leaves and identified by morphological and molecular methods, fulfilling Koch's postulates. This is the first report of leaf spot on Cathaya argyrophylla in China, providing a basis for disease control strategies and understanding of pathogen effects on host health.

Leaf area index (LAI) is a critical parameter for characterizing canopy structures. The spatiotemporal patterns of LAI reflect the multi-scale adaptive mechanisms of forests, spanning from individual leaf expansion and population structure optimization to coordinated ecosystem functionality. However, research on the spatiotemporal dynamics of LAI remains limited, particularly in karst primary forests that feature complex community structures, high rock exposure rates, and heterogeneous soil distribution patterns. Our research focused on a 1.28 ha karst forest plot in southwest China, where we quantified LAI seasonality using the LAI-2200 analyzer during four critical phenophases: January (dormant period), April (growth period), July (maturation period) and October (senescence period). Structural equation modeling (SEM), variance partitioning and hierarchical partitioning analysis were employed to quantify the relative contributions of biological, abiotic and spatial factors (represent community spatial connectivity shaped by ecological processes including seed dispersal, resource distribution and competition) to LAI variation. The results revealed distinct seasonal fluctuations in LAI, with significant spatial autocorrelation occurring at characteristic scales of 11.4 m (dormant period), 20.1 m (growth period), 66.3 m (maturation period), and 19.2 m (senescence period), respectively. Spatial factors were the dominant factors in explaining LAI variation across growth, maturation and maturation periods, accounting for 32

Masson pine (Pinus massoniana) is the principal reforestation conifer in southern China, but drought affects seedling cultivation. Although, plant growth-promoting rhizobacteria (PGPR) have been widely applied to promote plant growth, and biochar has been shown to serve as both a microbial refuge and a slow-release nutrient reservoir that improves PGPR colonization and stress tolerance. However, the mechanistic basis underlying the synergistic effects of PGPR and biochar on drought-resistance traits in Pinus spp. remains poorly understood. The present study first formulated a PGPR-based biochar agent and then integrated metagenomics with plant physiological analyses to elucidate how the agent modulates drought resistance in P. massoniana seedlings—translating rhizosphere microenvironmental changes into above-ground physiological responses. Coconut-shell biochar effectively immobilized the drought-tolerant PGPR (Bacillus thuringiensis IP3), resulting in a 20

BACKGROUND:Fusarium oxysporum causes damping-off disease in Pinus massoniana seedlings. While Trichoderma koningiopsis can enhance seedling resistance by regulating rhizosphere plant growth-promoting rhizobacteria (PGPR), the specific bacterial compositions and their role in disease resistance remained undefined. To elucidate this mechanism, we used amplicon and metagenomic sequencing to identify T. koningiopsis-assembled PGPR. Synthetic PGPR communities were constructed from isolated strains to validate their effects on disease suppression and growth promotion. RESULTS:Microbial community analysis indicated that T. koningiopsis reshaped the bacterial community: Actinospica, Dyella, and Streptomyces decreased in presence, and Bacillus and Arthrobacter increased. A total of 153 PGPR strains were isolated from the T. koningiopsis-inoculated treatment. Of these, eight strains demonstrated significant inhibitory effects against F. oxysporum, ranging from 33.81% to 59.52%. Four synthetic communities (SynComs) (C1, C2, HT, and 2K) were further constructed, exhibiting superior inhibitory effects against F. oxysporum compared to individual strains. Compared to the control, the C2 and HT SynComs increased seedling height by 10.18% and 9.44%, and reduced disease incidence by 50% and 36.67%, respectively. These treatments also enhanced protective enzyme activity and alleviated membrane damage. At the molecular level, the C2 and HT SynComs boost plant resistance by modulating the plant hormone and mitogen-activated protein kinase (MAPK) signaling pathways, thereby activating the expression of crucial resistance genes such as PR1, FLS2, and CAT1. CONCLUSION:Trichoderma koningiopsis alters the composition of rhizosphere PGPR community. The synthetic PGPR community assembled under the influence of T. koningiopsis effectively enhances damping-off resistance and promotes the growth of Masson pine seedlings. © 2026 Society of Chemical Industry.

Cathaya argyrophylla, a relict species endemic to China in the Pinaceae family, is classified as endangered on the IUCN Red List of Threatened Species. Needle cast caused by the fungal pathogen Neofusicoccum parvum is one of the most prevalent diseases affecting C. argyrophylla, leading to needle discoloration and necrosis, which poses a serious threat to its growth. Currently, there is a lack of effective biological control methods for this disease. In this study, we isolated an endophytic bacterium, Bacillus proteolyticus X6-1, from healthy needles of C. argyrophylla. This strain demonstrated a 65.5% inhibition of N. parvum in vitro. The pot experiment demonstrated that after inoculation with B. proteolyticus X6-1, the disease incidence and index of needle cast in C. argyrophylla were reduced by 42% and 20.3% respectively. Given its potential efficacy against needle cast in C. argyrophylla, we employed co-culture techniques alongside transcriptomics and high-throughput sequencing to elucidate the biological control mechanisms of strain X6-1. Furthermore, X6-1 enhanced the photosynthetic activity and antioxidant enzyme levels of C. argyrophylla. Inoculation with the B. proteolyticus strain further altered the phyllosphere microbiome by promoting the enrichment of beneficial microorganisms while decreasing the abundance of Neofusicoccum spp. Transcriptomic analysis revealed that B. proteolyticus regulates key biological pathways associated with growth in C. argyrophylla. Moreover, strain X6-1 produces protease and β-glucanase enzymes, which which may contribute to its antifungal activity. Collectively, these findings suggest that B. proteolyticus may serve as an effective biocontrol agent for managing needle cast in C. argyrophylla.

Low temperatures restrict the development and spread of Camellia weiningensis in Guizhou Province, China. Exogenous sugars have demonstrated effectiveness in alleviating low-temperature damage in plants. However, the function of exogenous sugars and their mechanisms remain to be explored in depth. The current study assessed the effects of various exogenous sugars on the physiology, transcriptional regulation, and phyllospheric microorganisms of C. weiningensis under low-temperature stress. The results revealed that low temperature led to significant changes in endogenous sucrose, trehalose, and galactose levels. Spraying exogenous sugars effectively lowered reactive oxygen species, malondialdehyde and relative electrical conductivity levels. Field experiments showed that exogenous galactose (Gal) treatment had the best effect and significantly enhanced the fruit setting rate by 71 % compared to the control. Physiological analyses revealed that Gal treatment notably elevated the proline content by 1.6 times, as well as peroxidase and glutathione activities by 65 % and 46 %; exogenous sucrose treatment significantly enhanced the activities of superoxide dismutase and catalase by 79 % and 2.2 times, respectively, and also increased the contents of jasmonic acid and flavonoids by 48 % and 3.3 times, respectively. Transcriptome data indicated that brassinosteroid biosynthesis, carotenoid and chlorophyll metabolic pathways were activated in C. weiningensis under low-temperature stress. In addition, exogenous sugar spraying changed the community structure of C. weiningensis phyllosphere microbes in response to lowtemperature stress. The bacterial ACE and Shannon indices were elevated by 1.2-fold and 1.1-fold, respectively, following Gal treatment. Specific sugar spraying selectively decreased some common pathogenic genera (Ramularia, Alternaria, Cladosporium, etc.), and recruited potentially beneficial dominant genera (Sphingomonas, Arthrobacter, Pseudomonas, etc.). This study provides important theoretical support for reducing low-temperature injury in C. weiningensis cultivation through exogenous sugar application.

BACKGROUND:Phoebe bournei, a rare and endangered plant species in China, exhibits low seedling survival rates and slow growth. Although Trichoderma longibrachiatum-based organic fertilizer is beneficial, it remains unclear whether it can reduce chemical fertilizer dependence while promoting P. bournei growth. Here, P. bournei seedlings were treated with a combination of T. longibrachiatum-based organic fertilizer and reduced chemical fertilizer (designated as the HF treatment). This study was employed to investigate the synergistic mechanisms underlying growth promotion. RESULTS:Plant physiology, pedology, and amplicon sequencing were used to evaluate the growth of P. bournei seedlings. The HF treatment optimally promoted P. bournei seedling growth, with a 39.8% increase in seedling height compared to the control. Specifically, the treatment elevated the levels of auxin (IAA), abscisic acid (ABA), and jasmonic acid (JA) by 43.6, 50.2, and 63.1%, respectively, compared to the control. This treatment also enhanced plant nitrogen and phosphorus utilization. An increase in the relative abundances of potentially beneficial fungi (e.g., Trichoderma and Trichocladium) and bacteria (e.g., Gemmatimonas and Streptomyces) was observed under the HF treatment, which also suppressed fungal pathogens such as Fusarium. CONCLUSIONS:This study revealed the synergistic mechanism by which T. longibrachiatum-based organic fertilizer and chemical fertilizer co-promote P. bournei seedling growth. Our findings offer a practical strategy for sustainable forestry to enhance the productivity of this rare and endangered tree species.

Cathaya argyrophylla Chun et Kuang is a first-grade protected tree in China with significant conservation value. In June 2022, needle cast was observed in approximately 27 to 34% of C. argyrophylla (n=200, covering about 1 ha) at Dashahe National Nature Reserve (28.89° N, 107.6° E) in Daozhen County, Guizhou, China. Initial symptoms were small red lesions (3 to 5 mm in diameter) on needles. Over time, these lesions expanded, turned necrotic, and led to needle cast. In addition, the diseased needles exhibit brown spots surrounded by a yellowish discoloured area measuring 0.5 mm2. The disease is most severe in young trees, with over 60% of the needles displaying discoloration in 15% of young trees (n=100). Forty infected conifer tissues were randomly selected, surface sterilized, and incubated on PDA in the dark at 26°C for 5d. Among the 40 samples, 39 exhibited fungi with similar morphology. Single-spore isolation method was used to obtain pure cultures for 9 isolates. The isolates were morphologically identical. On PDA medium, colonies were white with abundant aerial mycelium. After 14 days of growth under light, the colonies became greyish black with septate mycelium. Conidia were hyaline, thin-walled, smooth-surfaced, and ranged from ellipsoid to ovoid in shape, measuring 6.5 to 15.2 ×2.0 to 3.1 μm (n=50). Based on these morphological characteristics, the isolates were identified as belonging to Neofusicoccum spp. (Pavlic et al., 2009). For molecular identification, genomic DNA was extracted from 3 selected isolates. The internal transcribed spacer (ITS) region was amplified using primers ITS1/ITS4 (White et al., 1990). In addition, chitin synthase 1 (CS1) was amplified using primers CT-WK3-S/CT-WK3-A (Zimoch et al., 2003). The ITS (OR710949) and CS1 (OR714767) sequences of isolate JY1-1 were deposited in GenBank, exhibiting a homology of 99% to 100% (537/538, 191/192) with N. parvum MUCC211 (accession numbers EU301017 and EU339495). The reconstructed phylogenetic tree further substantiated the genetic relationship between isolate JY1-1 and N. parvum. Consequently, the isolate associated with needle cast on C. argyrophylla was identified as N. parvum. Isolates JY1-1, JY1-2, and JY1-3 were used to confirm Koch's postulates. The needles of 15 healthy 2-year-old C. argyrophylla saplings were inoculated with a conidial suspension of N. parvum (2.0 × 105 conidia/mL). As a control, the needles of C. argyrophylla saplings were treated with sterile water (n=10). The needles were covered with Ziplock bags, and maintained at humidity levels exceeding 90%. All treatments were placed in a greenhouse at 26℃. After 7 days of inoculation, the needles exhibited a change in color, with reddish-brown symptoms observed on day 30 (disease rate=100%). Furthermore, the lesion expanded, and needles were shed after 4 months. No symptoms were observed in the control group. Pathogens reisolated from all diseased plants exhibited morphological and ITS sequence identity to N. parvum (separation rate=100%), and no pathogens were isolated from control plants. Consistent results were obtained through two repeated experiments. While this pathogen is known to induce foliar disease in various plants (Sun et al., 2020; Shi et al., 2019), our study represents the first report Needle Cast of C. argyrophylla caused by N. parvum in China. These findings provide a foundation for developing effective strategies to monitor and manage C. argyrophylla.

Damping-off disease, primarily caused by Fusarium oxysporum, poses a significant challenge to the cultivation of Masson pine (Pinus massoniana) seedlings. Although Trichoderma koningiopsis improves damping-off disease resistance in Masson pine by regulating the rhizosphere microbial community, the underlying mechanisms remain unknown. Metabolomic analysis showed that T. koningiopsis altered Masson pine root exudates, especially plant organic acids such as capric acid (CA), lauric acid (LA) and pelargonic acid (PA). Co-culturing rhizosphere microbes with 0.1 mM CA, LA, PA and a combination of the three (1:1:1, CDNs1) significantly inhibited F. oxysporum and promoted the growth of rhizosphere biocontrol strains (Trichoderma, Penicillium and Bacillus), with CDNs1 exerting a superior effect. Amplicon sequencing and RT-qPCR showed that CDNs1 significantly altered the microbial community composition in the rhizosphere, especially inhibited the growth of Fusarium and enriched beneficial microbes (Trichoderma and Penicillium). CDNs1 effectively decreased the incidence and severity index of damping-off disease in Masson pine seedlings by 73.33% and 41.67%, respectively. Mechanistically, CDNs1 enhanced resistance to damping-off disease by modulating plant hormones, oxidative stress defences and the photosynthesis pathway. Collectively, this study provides insight into the mechanism by which T. koningiopsis enhances damping-off disease resistance by regulating the rhizosphere microbial community.

Camellia oleifera Abel. is one of the native and important natural edible oil species in China. The cultivation of C. oleifera has vigorously increased in Guizhou Province in recent years. From June to August 2022, a severe leaf spot blight was observed on C. oleifera in Longli Plantation, with an incidence of 53.5% (n=200), which caused severe defoliation, negatively affected plant growth, and led to significant economic losses. Pale yellow and sub-circular leaf spots of 2-5 mm in diameter first appeared in the margin. The center of the spots then turned grey, and the edges turned brown. The symptomatic leaves gradually developed symptoms of blight with some brown acervular conidiomata, died, and fell off, with many deep black spots on the leaves (Fig. 1A-B). The fungal isolates GZU-Y2 and GZU-Y3 were obtained from the infected leaves of five-year-old symptomatic C. oleifera trees using the tissue isolation method, and a voucher specimen was deposited in the Forest Protection Laboratory, Guizhou University. Cultures grown on potato dextrose agar medium (PDA) were incubated at 28℃, 16L/8D. A round cream-like colony was formed on PDA, with a white surface, while the back gradually turned brown (Fig. 1C-E). The aerial hypha grew vigorously with an initial milky white color before turning grayish white. At 10 days after incubation, the pycnidia were dark brown to black and spherical, with a diameter of 563.3 μm (500 to 700) (n=20). The alpha conidia were unicellular, hyaline, aseptate, oval or fusiform and measured 6.1 μm (4.1 to 8.0) × 2.6 μm (1.9 to 3.6) (n=50). However, no beta conidia were observed (Fig. 1I). For further identification, total DNA from the pure culture was extracted using a DNA extraction kit (Sangon, Shanghai, China), and the internal transcribed spacer (ITS), translation elongation factor 1-α (TEF-1α), and beta-tubulin (TUB2) were amplified by PCR using the primers ITS1/ITS4 (White et al., 1990), EF1-728F/EF1-986R (Carbone and Kohn, 1999) and Bt2a/Bt2b (Glass and Donaldson, 1995), respectively, and sequenced for a BLASTn analysis and phylogenetic tree construction. The sequences of ITS, TEF-1α and TUB2 were deposited in GenBank as accession numbers OQ168242 (99.25%), OQ689451 (99.71%) and OQ689453 (100.00%) for GZU-Y2 and OQ674554 (99.25%), OQ689452 (99.71%) and OQ689454 (100.00%) for GZU-Y3, respectively. A phylogenetic tree (Fig. 2) was constructed with the software MEGA X using the Neighbor-Joining algorithm (Felsenstein, 1985). Based on its morphological and molecular characteristics, the pathogen was identified as Diaporthe mahothocarpus, one of the synonyms of D. eres and the teleomorph of Phomopsis mahothocarpi (Gao et al., 2014 and 2015; Chaisiri et al., 2021). A pathogenicity test was conducted by spraying spore suspensions (2 × 107 spores/mL) of isolate GZU-Y2 on the leaves of 20 pots of annual C. oleifera seedlings in vivo. The same number of control seedings were sprayed with sterile water. The seedlings were placed at a constant room temperature of 28°C, with the inoculation points wrapped in Parafilm for 5 d to retain moisture. After 10 d, typical symptoms appeared on the inoculated leaves (Fig. 1F-H), and the re-isolated fungal culture was identical in morphology and ITS sequence to that originally obtained, fulfilling Koch's postulates. To our knowledge, this is the first report of D. mahothocarpus causing leaf spot blight of C. oleifera in China. In our future work, we tend to study the green prevention and control of this disease.

Cathaya argyrophylla [Chun & Kuang.] is an ancient relict plant and its embryonic development is similar to that of Pinus species. This has important scientific value for studying the phylogeny of Pinaceae (Wu et al. 2023). In July 2022, root rot was detected in the seedling cultivation base of C. argyrophylla in Daozhen County, Guizhou Province, China (28.89 °N, 107.6 °E). The incidence of the disease was 30% (n = 100); the susceptible plants wilted, leaves withered, and roots showed brown-to-black lesions and rot. Ten root tissues were randomly collected from the edges of the lesions of six symptomatic susceptible plants. The tissues were sterilized with 75% alcohol for 30 seconds, followed by 2-minute immersion in 3% sodium hypochlorite. After washing with sterile water, the tissues were incubated on potato dextrose agar (PDA; BoWei, Shanghai) at 28 ℃ for five days. Four single-spore cultures were obtained using a single-spore isolation method (Gong et al., 2010). Single-spore cultures grew rapidly on PDA. After five days of incubation, the colonies were white and pink, indicating a large amount of aerial mycelia. Microconidia were ovate or ellipsoid, measuring 5.0-10.0 × 1.5-3.0 μm (n = 50); Macroconidia were falcate, slightly curved or straight, measuring 19.5-28.5 × 2.0-6.0 μm (n = 50). Based on morphological features, the pathogen was considered to be Fusarium spp. (Leslie and Summerell 2006). Three representative strains, GF5, GF6, and GF7, were selected for molecular identification, and genomic DNA was extracted to confirm morphological diagnosis. The internal transcribed spacer (ITS) (White et al. 1990) was amplified using primers ITS1/ITS4, and the β-tubulin gene (Varga et al. 2011) was amplified using primers Bt2a/Bt2b. The ITS and β-tubulin sequences were aligned with GenBank, and amplification of the genes from the three isolates was consistent. The ITS (OP482273) and β-tubulin (OR825353) sequences of GF5 were stored in GenBank, and their homology with Fusarium oxysporum HC131(accession numbers MW600442 and MW670451) was 99 to 100%. Maximum likelihood analysis using MEGA 11.0 showed that isolate GF5 belongs to F. oxysporum. The reconstructed phylogenetic tree confirmed the phylogenetic position of the isolate GF5. The pathogenicity test was carried out using GF5 and GF6 isolates. The taproots of ten 3-year-old C. argyrophylla plants were washed, and then the roots were immersed in a 2 × 106/mL conidial suspension for one hour. Ten plants with sterile water were used as controls. After planting in pots (30 × 25 cm) with sterilized forest soil, the plants were cultured in a greenhouse (25 ℃ and 12-hour photoperiod). Thirty days after inoculation, all plants inoculated with the isolated pathogen showed wilting symptoms, and the roots showed typical root rot symptoms, whereas the control group showed no symptoms. The pathogens re-isolated from all inoculated plants were morphologically identical and had ITS sequences identical to F. oxysporum, validating Koch's hypothesis. The pathogenicity test was repeated twice and similar results were obtained. Although this fungus has been previously reported to cause root diseases in hosts, such as Musa nana Lour. and Pinus massoniana Lamb. (He et al. 2010; Luo et al. 2020), to our knowledge, this is the first report of F. oxysporum causing root rot in C. argyrophylla. These findings provide a basis for the development of management strategies for C. argyrophylla infection.

Aims Damping-off disease, caused by Fusarium oxysporum , affects the growth of Pinus massoniana seedlings. Plant growth-promoting fungi and rhizobacteria (PGPF and PGPR) are widely used in agriculture to control plant soil-borne disease, however, the joint mechanism by which they inhibit damping-off disease in forestry requires further exploration. Methods The current study screened for the ability of antagonistic PGPF and PGPR strains to inhibit the pathogen, and used soil microbiome and plant transcriptome technologies to characterize the biocontrol mechanism. Results PGPF strain 3Y, identified as Trichoderma longibrachiatum , and PGPR strain K29, identified as Burkholderia stabilis , were screened and found to strongly inhibit the growth of F. oxysporum through direct contact with the hyphae. The combined use of T. longibrachiatum and B. stabilis effectively reduced disease incidence and severity, and promoted the growth of P. massoniana seedlings, and enhanced soluble sugar, proline, SOD and POD activities. Compound strains treatment impacted the structure of rhizosphere bacterial microbial community, causing significant differences in the relative abundances of some key phyla and genera, promoting the enrichment of some beneficial microorganisms. Transcriptome profiles showed that combination treatment with the biocontrol strains induced the expressions of 8541 differentially expressed genes (DEGs). These genes participated in key biological pathways associated with starch and sucrose metabolism, plant hormone signal transduction, photosynthesis, antioxidant enzymes, and proline synthesis. Conclusion The combined use of PGPF and PGPR strains controlled F. oxysporum infection of P. massoniana seedlings by regulating physiological responses and soil microbial community.

Cerasus subhirtella (Miq.) Sok. is a widely used ornamental tree in urban areas around China and has a high ornamental value. From 2018 to 2020, a root rot disease was observed in C. subhirtella in Meitan County, Weng'an County, and Guiyang city of Guizhou, China (106.71 E, 26.57 N). Diseased C. subhirtella trees exhibited wilting with leaf chlorosis accompanied by brown to black root discoloration. In an area of 100 ha in total, with disease incidence ranging from 60 to 80%. Six symptomatic plants with root rot were randomly collected from three locations where disease symptoms were observed for pathogen isolation. Fifty fragments of diseased roots (5×5mm) were disinfected in 3% sodium hypochlorite for 30 s and 75% alcohol for 60 s, rinsed three times in sterile distilled water, plated on potato dextrose agar (PDA; BoWei, Shanghai), and incubated at 28 °C in the dark for 7 days. Eighteen isolates were purified by single spore culturing. Typical Fusarium spp. colonies were obtained from all root samples. On PDA, the colonies showed white and the hyphae were dense, while the colony of isolate YH15 showed pale yellow on the back, radial growth and produced chlamydospores. The macrospores (YH15) were straight to subarcuate, measured 15.3 to 25.1 × 2.5 to 6.2 μm (n=50). The microconidia (YH26) were ellipsoid to ovoid, measured 8.6 to 12.7 × 1.6 to 5.1 μm (n=50). These morphological characteristics were consistent with Fusarium spp., as described recently in Vitullo et al. (2014). To confirm the morphological diagnosis, genomic DNA from the isolates was extracted. The internal transcribed spacer (ITS) (White et al, 1990) region of rDNA and a β-tubulin (Varga et al, 2011) gene fragment were amplified with the primers ITS1/ITS4 and Bt2a/Bt2b, respectively, and were subsequently sequenced. Maximum likelihood analysis was carried out using MEGA 11.0. BLAST analysis revealed that the ITS and β-tubulin sequences of isolate YH15 were 100% homologous with F. oxysporum, and the isolate YH26 had a 99.69~100% homology with F. solani. Sequences of isolate YH15 and YH26 were deposited in GenBank (ITS: OQ363005 and OQ363049; β-tubulin: OQ398187 and OQ398180). The isolate YH15 was thus identified as F. oxysporum by the morphological characteristics and sequences analysis, and the isolate YH26 was identified as F. solani. A reconstructed phylogenetic tree also confirmed their phylogenetic position. The healthy 2-year-old C. subhirtella plants grown in autoclaved acid yellow soil were used for the pathogenicity tests. Then, 50 mL of conidial suspension (2.0×105 conidia/mL, in medium) of 7-day-old isolates YH15 and YH26 were gently applied to the soil in each of the 10 pots as the treatment. A sterilized fungal culture matrix (PDB; BoWei, Shanghai) was applied to each of 10 pots as a control. All pots (30 cm high, 25 cm upper diameter, 15 cm base diameter) were placed in a greenhouse (25 °C, 12 h photoperiod). After 30 days of inoculation, all plants inoculated with the isolates showed wilting symptoms, and the roots showed light-brown to dark-brown lesions. No symptoms were observed in the controls. The pathogen was reisolated from all symptomatic roots and identified as F. oxysporum and F. solani as described above. The pathogenicity test was repeated twice with similar results. Although this fungus was previously reported to cause root disease in many hosts (Li et al., 2020; Gibert et al., 2022), this is the first report of F. oxysporum and F. solani causing root rot in C. subhirtella in China.

Pinus massoniana is an important afforestation and industrial timber tree species in China; However, its growth and productivity are often suffered from phosphorus deficiency. Phosphate-solubilizing microorganisms (PSMs) can increase phosphorus efficiency and may have the important potential for use in forestry ecosystem. In order to evaluate whether the co-inoculation of PSMs would enhance plant growth than single inoculation, and better understand the synergistic mechanisms of PSM compound strains regulating P. massoniana growth, we used plant physiology, microbiome, and transcriptome technologies to assess the effects of combined PSMs on plant growth, rhizosphere microecology and plant physiological system. The results demonstrated that combined endophytic fungus (Penicillum oxalicum G17) and rhizosphere bacteria (Burkholderia sp. WJ27) significantly increased phosphate-dissolving ratio and promoted P. massoniana growth compared with a single strain or non-inoculation. The combination of G17 and WJ27 strains (G17&WJ27) evidently enhanced soil nutrients, as well as P, N, and K contents in seedlings. Although the diversities of fungi and bacteria were reduced under G17&WJ27 treatment, the relative abundances of ectomycorrhizal fungi (Trichophaea and Thelephora) and plant growth-promoting rhizobacteria (Sphingomonas, Burkholderia, Chitinophaga, Ramlibacter, and Rhodanobacter) increased. Transcriptome profiles showed that compared with non-inoculated plants, there were 7115 differentially expressed genes (DEGs) identified in G17&WJ27 treatment, which were involved in various biological pathways associated with growth regulation, including photosynthesis, sugar metabolism, antioxidant enzyme activity, plant hormones, amino acid biosynthesis, and inorganic phosphate transporters. This study would provide a theoretical basis for the development of compound microbial fertilizers for cultivation and management of Masson pine forests.

为筛选溶磷效果较好的根际细菌(phosphate-solubilizing rhizobacteria,PSB),并明确其对马尾松苗的促生效果和作用机制.利用土壤稀释平板法进行PSB菌株的分离和纯化,通过形态学和 16S rDNA分子测序等方法进行PSB菌株的鉴定,最后将PSB菌株接种至马尾松苗,培养 60 d后测定马尾松苗生长、生理、苗根际土壤理化性质和根际细菌群落结构和组成.结果表明:由马尾松根际土中分离获得溶磷能力较强的 3 个PSB菌株WJ10、WJ25 和WJ41 均为伯克霍尔德菌Paraburkholderia spp.;3 个PSB菌株对磷酸铝的增溶能力最强,其次是磷酸三钙、磷酸氢钙和磷酸铁;盆栽试验表明,3 个PSB菌株均可促进幼苗的生长,其中WJ25 对苗高、根长的促进效果最明显,WJ41 和WJ10 次之.3 个PSB菌株对苗促生的主要机制包括,PSB提高了马尾松苗的根系活力、叶绿素b、可溶性蛋白等生长指标及氮、磷和钾等养分含量;同时,提升了根际土有效磷、速效钾、活性氮、土壤养分含量、土壤酶活性;此外,3 个PSB菌株的添加还影响了马尾松苗根际细菌群落的组成和多样性,促进了Bacillus、Nitrosospira、Gemmata和Cytophaga等有益菌在根际土壤中的显著富集.综上,本研究筛选获得的 3 个溶磷伯克霍尔德菌,它们能够通过调控植物生理及改变根际微环境从而促进马尾松苗的生长.通过本研究,为马尾松根际溶磷细菌菌肥的开发和应用提供了理论依据.

[目的] 对筛选到具有抑菌效果且产蛋白酶的菌株H进行分类地位的确定,同时对其产蛋白酶的条件进行优化,以期为其在植物病害防治上的应用奠定基础.[方法] 通过生理生化、电子显微镜扫描及16sRNA测序相结合的方法明确菌株H的分类地位;通过单因素和正交试验对菌株H产蛋白酶条件进行优化,并检测其优化前后对病原真菌的抑菌效果.[结果] 菌株H鉴定为高知芽孢杆菌(Cytobacillus kochii);菌株H产蛋白酶的优化条件为:pH8.0、葡萄糖20.0 g·L?1、蛋白胨8.0 g·L?1、MgSO41.0 g·L?1、CaSO4·2H2O 0.1 g·L?1,在装有50 mL发酵培养基的250 mL三角瓶中接种2.5 mL108 CFU·mL?1的种子液,培养24 h后蛋白酶活力达到402.2 U·mL?1,较初始培养条件下的蛋白酶活力提高13.92倍;优化后菌株H对尖孢镰刀菌(Fusarium oxysporum)和辣椒疫霉病菌(Phytophthora capsici)的抑菌率分别为67.32％和44.87％,较优化前抑菌率提升值分别为9.15％和12.82％.[结论] 明确菌株H为高知芽孢杆菌(C.kochii),优化了高知芽孢杆菌产蛋白酶条件及抑菌效果.

In order to screen out the fungicides with better control effect on dampingoff disease in Pinus massoniana,the 1-year-old P.massoniana seedlings were taken as the research object, determination of the bacteriostatic ability and field control effect of eight kinds of fungicides（prequel, desenzin, carbendazim, mancozeb, metalaxyl, chlorothalonil, thiophanate-methyl, dixon）on the pathogen——Fusarium oxysporum by the method of confrontation between fungicides and pathogens and field control effect determination, effective control on dampingoff disease in P.massoniana by selecting better fungicides.The results showed that the antibacterial effects of metalaxyl and chlorothalonil on pathogenic bacteria were more obvious among the 8 fungicides tested, thiophanate-methyl, mancozeb, desenzin, prequel, carbendazim, dixon, the antibacterial rate of dixon against pathogenic bacteria was relatively low; the screening results of chemical concentration showed that the antibacterial rate of 10 mg/mL metalaxyl to pathogenic bacteria reached 77.3%;the antibacterial rate of 8 mg/mL chlorothalonil reached 100%;the field control results showed that 10 mg/mL metalaxyl had better control effect on masson pine blight, the disease incidence rate was 20.0%,and the control effect was 70.0%.

筛选有效抑制白腐真菌生长并降低其对木材腐朽能力的生防菌株,为白腐真菌所致木材腐朽的生物防治提供新思路.以樟子松(Pinus.sylvestris)倒木中分离纯化的3株木霉(Trichoderma spp.)作为生防菌株,利用离体对峙培养法测定分离菌株对多种白腐真菌的拮抗效果,结合形态学、分子生物学和系统进化树分析对拮抗效果较好的真菌进行鉴定,并通过检测生防真菌的代谢产物及其与白腐真菌菌丝间的作用关系初步探究其生防机制,最后利用质量损失法检测该生防菌株防治白腐真菌对樟子松木材腐朽的能力.结果表明:筛选得到1株有较好拮抗效果的生防真菌SF2,对峙培养8 d时,该菌株对5种白腐真菌的抑菌率从高到低排序为白囊耙齿菌(Irpex lacteus)＞一色齿毛菌(Cerrena unicolor)＞粗毛拟 革盖菌(Coriolopsis aspera)＞彩绒革盖菌(Coriolus versicolor)＞裂褶菌(Schizophyllum commune);经过形态观察、ITS1/ITS4 DNA序列扩增比对和系统发育树分析,发现SF2菌株属于长枝木霉(Trichoderma longibrachiatum);生防菌对白腐真菌的抑菌机理显示,菌株SF2可以通过重寄生以及分泌代谢产物对白囊耙齿菌产生抑制;木材接种试验结果表明,接种SF2菌株能显著减少白囊耙齿菌所致樟子松木材质量损失,减少率达46.43％.综上,本研究筛选鉴定的SF2菌株为长枝木霉,其对白腐真菌生长及其所致木材腐朽具有一定的防治效果,本研究为木材白腐病的生物防治奠定理论基础.

In this study, four species of Trichoderma,T. koningiopsis, T. virens, T. spirale and T. longibrachiatum, which are endophytic in Pinus massoniana,were studied for their drought resistance. The effects of simulated drought, using polyethylene glycol 6 000（PEG-6 000）, on the growth of four Trichoderma species were evaluated, and the physiological responses of drought-resistant strains to stress were analyzed.The results showed that T. longibrachiatum had the strongest adaptability to PEG-6 000 stress among the four species of Trichoderma, and its hyphal and spore growth were less affected by the stress. With the increase in PEG-6 000 concentration, the antioxidant enzyme activities of T. longibrachiatum tendedto increase first and then decrease, the superoxide dismutase（SOD）, catalase（CAT） and peroxidase（POD） activities reached peaks under 200 and 300 g·L -1 PEG-6 000s, and showed activity levels of 0.922, 98.136 and 4.516 U·g -1 , respectively; the osmotic regulatory substances increased with rise in the contents of soluble sugars（SS） and soluble proteins（SP） after the PEG-6 000 concentration increased, reaching peaks of 35.317 and 29.554 mg·g -1 under 200 and 300 g·L -1 PEG-6 000s, respectively. Meanwhile, the proline（Pro） content of T. longibrachiatum showed an increase under PEG-6 000 stress. Correlation analysis showed that under PEG-6 000 stress, antioxidant enzymes and cell osmotic regulators play an essential role in maintaining the normal life activities of T. longibrachiatum. The study findings can be used as a reference for screening drought-resistant strains and improving plant drought resistance.