Fungal Pathogen Infection Research Articles

Secondary Metabolites of Trichoderma sp. as Antifungal Against Rice Seed-borne Pathogen Fungi

The use of quality seeds is necessary to increase rice productivity. The existence of pathogenic fungi infections causes the quality of rice seeds to decrease and impacts the ability to grow plants. Trichoderma sp. is known to produce secondary metabolites that can inhibit the growth of pathogens. This study aimed to examine the ability of the secondary metabolites of Trichoderma sp. at various concentration levels and immersion time to suppress pathogenic fungi infections carrying rice seeds. The research was carried out by giving seed immersion treatment. Then identify the pathogenic fungi the seeds carry for further testing with the blotter test method. The parameters tested were infection rate, infection suppression, and seed viability. The identification results showed types of pathogenic fungi carried by rice seeds included Fusarium sp., Alternaria sp., Aspergillus sp. Penicillium sp., and Rhizopus sp. Research also shows that the secondary metabolites of Trichoderma sp. are effective in improving the quality of rice seeds. The test results showed that the secondary metabolites of Trichoderma sp. can suppress the level of pathogenic fungi infection. There was no interaction between the treatment of metabolite concentrations and immersion time on all test parameters. Seed immersion treatment with secondary metabolites in the 5-20% concentration range has effectively reduced fungi infection rates and increased seed viability. Meanwhile, various levels of soaking time did not affect reducing the level of fungi infection but instead affected the viability of the rice seeds.

The preparation and therapeutic effects of β-glucan-specific nanobodies and nanobody-natamycin conjugates in fungal keratitis.

Fungal keratitis (FK) is a severe infectious corneal disease. Since traditional eye drops exhibit poor dissolution and high corneal toxicity, the efficacy of current treatments for FK remains limited. It is needed to develop new approaches to control the cornea damage from FK. In this study, a nanobody (Nb) specific to β-glucan in the fungal cell wall was prepared. The conjugate of the Nb with natamycin (NAT), a traditional antifungal drug, was synthesized. Firstly, we found the Nb specific to β-glucan inhibited fungal growth by disrupting cell wall and biofilm formation.. In addition, the content of β-glucan in the fungal cell wall decreased after Nb treatment. The Nb also reduced the adhesion ability of fungal conidia to human corneal epithelial cells (HCECs). Further, we examined the difference between NAT and Nb-NAT in antifungal growth. Nb-NAT showed better antifungal effects than NAT which was caused by the interaction between Nb and β-glucan. Moreover, Nb concentration below 0.5 mg/mL did not affect the viability of HCECs. Nb-NAT had less cytotoxicity and ocular surface irritation than NAT. Nb specific to β-glucan attenuated Aspergillus fumigatus (A. fumigatus) virulence and relieved inflammatory responses in FK. Nb-NAT treatment of the cornea improved therapeutic effects compared with NAT. It decreased clinical scores and expression level of inflammatory factors. To our knowledge, this study is the first to report a Nb specific to β-glucan and Nb-NAT for the treatment of FK. These unique functions of the Nb specific to β-glucan and Nb-NAT would render it as an alternative molecule to control fungal infections including FK. STATEMENT OF SIGNIFICANCE: Fungal keratitis is a corneal disease with a high rate of blindness. Due to the poor dissolution and high corneal toxicity exhibited by traditional eye drops, the efficacy of current therapeutic treatments for fungal keratitis (FK) remains limited. To enhance the therapeutic effect of natamycin in treating fungal keratitis, this study developed an innovative approach by preparing a β-glucan-specific nanobody and loading it with the antifungal drug natamycin. The β-glucan-specific nanobody has the ability to control both fungal pathogen invasion and inflammation, which can cause damage to the cornea in FK. The conjugation with the β-glucan-specific nanobody significantly increased the antifungal capacity of natamycin and reduced its toxicity. The further application of natamycin conjugated with the β-glucan-specific nanobody could be expanded to other diseases caused by fungal pathogen infections.

Fungal pathogen infection intensity associated with reproductive mode and elevation in an afrotropical anuran community

The effects of host ecology and environmental conditions on infection dynamics of the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) have been documented in several tropical and montane regions across the globe. These interactions are often complex and unique at local scales. Data on the historical and current chytridiomycosis-amphibian system is largely lacking in Africa, especially central Africa. We conducted the first survey of Bd in continental Equatorial Guinea in 2019, and extensively sampled the land-bridge island, Bioko, in 2011 and 2019. Our results provide novel information on the distribution and prevalence of Bd in Equatorial Guinea and demonstrate the effects of host developmental mode and elevation on Bd infections. We found that Bd infection loads are positively linked with elevation and that direct-developing species have higher average Bd loads than aquatic breeding species at all elevations. These patterns corroborate previous findings in afrotropical amphibian assemblages. Additionally, our study confirms the presence of Bd in continental Equatorial Guinea, providing updated information on the distribution of Bd in central Africa, and confirming the need for careful monitoring of this biodiverse region. Keywords: Bioko, Equatorial Guinea, Bd infection load, amphibian conservation Los efectos de la ecología del huésped y las condiciones ambientales en la dinámica de infección del hongo quítrido anfibio Batrachochytrium dendrobatidis (Bd) se han documentado en varias regiones tropicales y montañosas de todo el mundo. Estas interacciones suelen ser complejas y únicas a escala local. Los datos sobre el sistema quitridiomicosis-anfibios histórico y actual faltan en gran medida en África, especialmente en África central. Realizamos la primera encuesta de Bd en Guinea Ecuatorial continental en 2019, y un muestreo extenso de la isla Bioko en 2011 y 2019. Nuestros resultados brindan información novedosa sobre la distribución y prevalencia de Bd en Guinea Ecuatorial y demuestran el efecto del modo de desarrollo del huésped y la elevación de las infecciones por Bd. Descubrimos que las cargas de infección por Bd están relacionadas positivamente con la elevación y que las especies en desarrollo directo tienen cargas promedio de Bd más altas que las especies acuáticas reproductoras a lo largo de la elevación. Estos patrones corroboran hallazgos previos en conjuntos de anfibios afrotropicales. Además, nuestro estudio confirma la presencia de Bd en Guinea Ecuatorial continental, proporcionando información actualizada sobre la distribución de Bd en África Central y confirmando la necesidad de un seguimiento cuidadoso de esta región biodiversa.

General Regulatory Factor7 regulates innate immune signalling to enhance Verticillium wilt resistance in cotton.

Sessile growing plants are always vulnerable to microbial pathogen attacks throughout their lives. To fend off pathogen invasion, plants have evolved a sophisticated innate immune system that consists of cell surface receptors and intracellular receptors. Somatic embryogenesis receptor kinases (SERKs) belong to a small group of leucine-rich repeat receptor-like kinases (LRR-RLKs) that function as co-receptors regulating diverse physiological processes. GENRAL REGULATORY FACTOR (GRF) proteins play an important role in physiological signalling transduction. However, the function of GRF proteins in plant innate immune signalling remains elusive. Here, we identified a GRF gene, GauGRF7, that is expressed both constitutively and in response to fungal pathogen infection. Intriguingly, silencing of GRF7 compromised plant innate immunity, resulting in susceptibility to Verticillium dahliae infection. Both transgenic GauGRF7 cotton and transgenic GauGRF7 Arabidopsis lines enhanced the innate immune response to V. dahliae infection, leading to high expression of two helper NLRs (hNLR) genes (ADR1 and NRG1) and pathogenesis-related genes, and increased ROS production and salicylic acid level. Moreover, GauGRF7 interacted with GhSERK1, which positively regulated GRF7-mediated innate immune response in cotton and Arabidopsis. Our findings revealed the molecular mechanism of the GRF protein in plant immune signaling and offer potential opportunities for improving plant resistance to V. dahliae infection.

Synthesis and biological evaluation of Argemone mexicana-inspired antimicrobials.

Due to the lack of new antimicrobial drug discovery in recent years and an ever-growing prevalence of multidrug-resistant "superbugs", there is a pressing need to explore alternative ways to combat pathogenic bacterial and fungal infections. Building upon our previous work in the field of medicinal phytochemistry, the present study is focused on designing, synthesizing, and testing the altered bioactivity of new variants of two original bioactive molecules found in the Argemone mexicana plant. Herein, we report upon 14 variants of berberine and four variants of chelerythrine that have been screened against a pool of 12 microorganisms (five Gram-positive and four Gram-negative bacteria, and three fungi). Additionally, the crystal structures of two berberine variants are described. Several berberine variants show enhanced antibacterial activity compared to the unaltered plant-derived molecule. We also report promising preliminary tumor cytotoxicity effects for a number of the berberine derivatives.

Re-Evaluation of the Cross-Reactions of the Antibody against the Causative Agent for Paracoccidioidomycosis Ceti; Paracoccidioides ceti and the Related Fungal Species.

Paracoccidioidomycosis ceti (PCM-C) is a chronic granulomatous keloidal dermatitis in cetaceans that has been reported worldwide and is caused by Paracoccidioides ceti. Serological cross-reactions among highly pathogenic fungal infections and related diseases have been reported. However, the true cross-reaction of antibodies against P. ceti has remained unknown due to the use of positive control sera from infected dolphins. This study aimed to re-evaluate antibodies from mechanically dislodged fungal cells in the infected tissue of a PCM-C case and demonstrate the actual cross-reaction. The results revealed a limited cross-reaction between PCM-C and paracoccidioidomycosis, while the antibodies did not react with other pathogens such as Coccidioides posadasii, Histoplasama capsulatum, and Arthrographis kalrae. Thus, the method for evaluation of the antibody against PCM-C is reliable, and there is potential for epidemiological study.

Reconstruction of Gut Bacteria in Spodoptera frugiperda Infected by Beauveria bassiana Affects the Survival of Host Pest.

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a migratory agricultural pest that is devastating on a global scale. Beauveria bassiana is a filamentous entomopathogenic fungus that has a strong pathogenic effect on Lepidoptera pests but little is known about the microbial community in the host gut and the dominant populations in fungus-infected insects. B. bassiana AJS91881 was isolated and identified from the infected larvae of Spodoptera litura. The virulence of AJS91881 to the eggs, larvae, pupae and adults of S. frugiperda was measured. Moreover, the gut microbial community diversity of healthy and fungus-infected insects was analyzed. Our results showed that after treatment with B. bassiana AJS91881, the egg hatching rate, larval survival rate and adult lifespan of the insects were significantly reduced, and the pupae rigor rate was significantly increased compared to that of the control group. Additionally, the gut microbial community was reconstructed after B. bassiana infection. At the phylum and genus level, the relative abundance of the Proteobacteria and Serratia increased significantly in the B. bassiana treatment group. The KEGG function prediction results showed that fungal infection affected insect gut metabolism, environmental information processing, genetic information processing, organism systems and cellular processes. Fungal infection was closely related to the metabolism of various substances in the insect gut. Serratia marcescens was the bacterium with the highest relative abundance after infection by B. bassiana; intestinal bacteria S. marcescens inhibited the infection of insect fungi B. bassiana against the S. frugiperda. The presence of gut bacteria also significantly reduced the virulence of the fungi against the insects when compared to the group with the larvae fed antibiotics that were infected with fungal suspension (Germfree, GF) and healthy larvae that were infected with fungal suspension prepared with an antibiotic solution (+antibiotic). In conclusion, the reconstruction of the insect intestinal bacterial community is an indispensable link for understanding the pathogenicity of B. bassiana against S. frugiperda. Most importantly, in the later stage of fungal infection, the increased abundance of S. marcescens in the insect intestine inhibited the virulence of B. bassiana to some extent. The findings aid in understanding changes in the gut microbiota during the early stages of entomopathogenic fungal infection of insects and the involvement of insect gut microbes in host defense mediated by pathogenic fungal infection. This study is also conducive to understanding the interaction between entomopathogenic fungi, hosts and gut microbes, and provides a new idea for the joint use of entomopathogenic fungi and gut bacteria to control pests.

Increased Fungal Infection Mortality Induced by Concurrent Viral Cellular Manipulations.

Certain respiratory fungal pathogen mono-infections can cause high mortality rates. Several viral pathogen mono-infections, including influenza viruses and coronaviruses including SARS-CoV-2, can also cause high mortality rates. Concurrent infections by fungal pathogens and highly manipulative viral pathogens can synergistically interact in the respiratory tract to substantially increase their mortality rates. There are at least five viral manipulations which can assist secondary fungal infections. These viral manipulations include the following: (1) inhibiting transcription factors and cytokine expressions, (2) impairing defensive protein expressions, (3) inhibiting defenses by manipulating cellular sensors and signaling pathways, (4) inhibiting defenses by secreting exosomes, and (5) stimulating glucocorticoid synthesis to suppress immune defenses by inhibiting cytokine, chemokine, and adhesion molecule production. The highest mortality respiratory viral pandemicsup to now have had substantially boosted mortalities by inducing secondary bacterial pneumonias. However, numerous animal species besides humans are also carriers of endemic infections by viral and multidrug-resistant fungal pathogens. The vast multi-species scope of endemic infection opportunities make it plausible that the pro-fungal manipulations of a respiratory virus can someday evolve to enable a very high mortality rate viral pandemic inducing multidrug-resistant secondary fungal pathogen infections. Since such pandemics can quickly spread world-wide and outrun existing treatments, it would be worthwhile to develop new antifungal treatments well before such a high mortality event occurs.

Pathogen-induced m6A dynamics affect plant immunity.

Posttranscriptional regulation of mRNA mediated by methylation at the N6 position of adenine (N6-methyladenosine [m6A]) has profound effects on transcriptome regulation in plants. Focused studies across eukaryotes offer glimpses into the processes governed by m6A throughout developmental and disease states. However, we lack an understanding of the dynamics and the regulatory potential of m6A during biotic stress in plants. Here, we provide a comprehensive look into the effects of m6A on both the short-term and long-term responses to pathogen signaling in Arabidopsis (Arabidopsis thaliana). We demonstrate that m6A-deficient plants are more resistant to bacterial and fungal pathogen infections and have altered immune responses. Furthermore, m6A deposition is specifically coordinated on transcripts involved in defense and immunity prior to and proceeding the pathogen signal flagellin. Consequently, the dynamic modulation of m6A on specific stress-responsive transcripts is correlated with changes in abundance and cleavage of these transcripts. Overall, we show that the m6A methylome is regulated prior to and during simulated and active pathogen stress and functions in the coordination and balancing of normal growth and pathogen responses.

Effects of maize resistance and leaf chemical substances on the structure of phyllosphere fungal communities.

It is well known that plant genotype can regulate phyllosphere fungi at the species level. However, little is known about how plant varieties shape the fungal communities in the phyllosphere. In this study, four types of maize varieties with various levels of resistances to Exserohilum turcicum were subjected to high-throughput sequencing to reveal the properties that influences the composition of phyllosphere fungal communities. The dominant fungi genera for all four maize varieties were Alternaria at different relative abundances, followed by Nigrospora. Hierarchical clustering analysis, non-metric multidimensional scaling and similarity analysis confirmed that the fungal communities in the phyllosphere of the four varieties were significantly different and clustered into the respective maize variety they inhabited. The findings from Redundancy Analysis (RDA) indicated that both maize resistance and leaf chemical constituents, including nitrogen, phosphorus, tannins, and flavonoids, were the major drivers in determining the composition of phyllosphere fungal communities. Among these factors, maize resistance was found to be the most influential, followed by phosphorus. The co-occurrence network of the fungal communities in the phyllosphere of highly resistant variety had higher complexity, integrity and stability compared to others maize varieties. In a conclusion, maize variety resistance and leaf chemical constituents play a major role in shaping the phyllosphere fungal community. The work proposes a link between the assembled fungal communities within the phyllosphere with maize variety that is resistant to pathogenic fungi infection.

Temporal transcriptomics provides insights into host‒pathogen interactions: a case study of Didymella pinodella and disease-resistant and disease-susceptible pea varieties

Ascochyta blight is a fungal disease affecting peas, causing significant damage to the plant and reducing crop yield. Host‒pathogen interactions can inform disease prevention and control strategies but remain poorly understood. Here, we generate a near-chromosome-level assembly for Didymella pinodella HNA18, a pathogenic fungus that causes pea ascochyta blight. Comparative genomic analysis of D. pinodella HNA18 and seven publicly available Didymella genomes revealed that the genome of D. pinodella HNA18 encodes the most conserved biosynthetic gene clusters (BGCs) and a similar number of carbohydrate-activating enzyme (CAZyme) genes compared to other Didymella species. Furthermore, by sequencing and analyzing the transcriptomic data of D. pinodella HNA18 and disease-susceptible and disease-resistant pea varieties during the infection process, we found that the pathogenic fungus mobilized a similar set of infection genes to attack the disease-susceptible and disease-resistant pea varieties, but the timing and intensity of these infection genes were different. For pea varieties in response to the pathogenic fungus, disease-susceptible and disease-resistant pea varieties mobilized similar types of defense genes, while the disease-resistant pea used a higher number of defense genes relative to the disease-susceptible pea during the entire infection process. This study not only provides multiomic resources for the study of the pathogenic fungus D. pinodella HNA18 against its disease-susceptible and disease-resistant pea varieties but also deciphers the mode of interaction between pathogenic fungal infection and plant defense.

Integrated transcriptome and physiological analysis revealed core transcription factors that promote flavonoid biosynthesis in apricot in response to pathogenic fungal infection.

Integrated transcriptome and physiological analysis of apricot leaves after Fusarium solani treatment. In addition, we identified core transcription factors and flavonoid-related synthase genes which may function in apricot disease resistance. Apricot (Prunus armeniaca) is an important economic fruit species, whose yield and quality of fruit are limited owing to its susceptibility to diseases. However, the molecular mechanisms underlying the response of P. armeniaca to diseases is still unknown. In this study, we used physiology and transcriptome analysis to characterize responses of P. armeniaca subjected to Fusarium solani. The results showed increasing malondialdehyde (MDA) content, enhanced peroxidase (POD) and catalase (CAT) activity during F. solani infestation. A large number of differentially expressed genes (DEGs), which included 4281 upregulated DEGs and 3305 downregulated DEGs, were detected in P. armeniaca leaves exposed to F. solani infestation. Changes in expression of transcription factors (TFs), including bHLH, AP2/ERF, and WRKY indicated their role in triggering pathogen-responsive genes in P. armeniaca. During the P. armeniaca response to F. solani infestation, the content of total flavonoid was changed, and we identified enzyme genes associated with flavonoid biosynthesis. Ectopic overexpression of PabHLH15 and PabHLH102 in Nicotiana benthamiana conferred elevated resistance to Fspa_1. Moreover, PabHLH15 and PabHLH102 positively interact with the promoter of flavonoid biosynthesis-related genes. A regulatory network of TFs regulating enzyme genes related to flavonoid synthesis affecting apricot disease resistance was constructed. These results reveal the potential underlying mechanisms of the F. solani response of P. armeniaca, which would help improve the disease resistance of P. armeniaca and may cultivate high-quality disease-resistant varieties in the future.

The PcMYB44-mediated miR397-PcLACs module regulates defence-induced lignification in pear resistance to fungal disease.

Diseases caused by Alternaria alternata and Botryosphaeria dothidea diminish pear yield and quality, and restrict the pear agricultural industry. Lignification is a conserved mechanism for plant resistance against pathogen invasion. The regulatory mechanisms underlying defence-induced lignification in pear in response to fungal pathogen infection remain unknown. In this study, analysis of lignification level and lignin content in pear revealed that A. alternata and B. dothidea induced lignification, and transcriptomics showed that lignin biosynthesis was affected. To explore whether laccases (LACs) mediated by miR397 regulate lignification in pear, we investigated the role of PcmiR397 in repressing the expression of PcLACs using 5'-RNA ligase-mediated-RACE and co-transformation in tobacco. Opposite expression patterns for PcmiR397 and PcLAC target genes were observed in pear in response to pathogens. Transient transformation in pear demonstrated that silencing PcmiR397 and overexpressing a single PcLAC enhanced resistance to pathogens via lignin synthesis. To further reveal the mechanism underpinning the PcMIR397 response of pear to pathogens, the PcMIR397 promoter was analysed, and pMIR397-1039 was found to be inhibited by pathogen infection. The transcription factor PcMYB44 was up-regulated, and it bound to the PcMIR397 promoter and inhibited transcription following pathogen infection. The results demonstrate the role of PcmiR397-PcLACs in broad-spectrum resistance to fungal disease, and the potential role of PcMYB44 involved in the miR397-PcLAC module in regulating defence-induced lignification. The findings provide valuable candidate gene resources and guidance for molecular breeding to improve resistance to fungal disease in pear.

Genome Sequence Resource of Curvularia clavata Causing Leaf Spot Disease on Tobacco by Oxford Nanopore PromethION.

Genome Sequence Resource of Curvularia clavata Causing Leaf Spot Disease on Tobacco by Oxford Nanopore PromethION.

Effects of Exogenous Nitric Oxide Treatment on Grape Berries Against Botrytis cinerea and Alternaria alternata Related Enzymes and Metabolites.

Postharvest losses of grape berries caused by the pathogenic fungi Botrytis cinerea and Alternaria alternata have been widely reported, and nitric oxide (NO) as a plant signaling molecule to control postharvest diseases has recently become an active research topic. This study aimed to investigate the regulatory effect of NO on the interaction between grape berries and fungi. During interactions between grape berries and pathogenic fungi, treatment with 10 mM sodium nitroprusside (SNP, an NO donor) delayed the decline of the physiological quality of the grape berries and had positive effects on the weight loss rate, firmness, and respiration intensity. SNP treatment increased the activities of superoxide dismutase (SOD) and polyphenol oxidase (PPO) and inhibited the activities of peroxidase (POD) and catalase (CAT) of grape berries during the resistance to fungal pathogen infection. In addition, the increase in browning degree and the accumulation of hydrogen peroxide were inhibited by SNP treatment. In the phenylpropane metabolic pathway, the activities of phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumaric acid coenzyme A ligase (4CL) were increased during the activation of grape berries during the resistance to pathogen infection by SNP, and the intermediate metabolites lignin, flavonoids, and total phenols were accumulated. In addition, SNP treatment had a regulatory effect on the gene expression levels of SOD, POD, PPO, PAL, and 4CL. These results suggested that SNP treatment was effective for the preservation and disease reduction of grape berries.

Transcriptome analysis reveals a common adaptive transcriptional response of Candida glabrata to diverse environmental stresses

Candida glabrata, an opportunistic fungal pathogen, causes superficial and life-threatening infections in humans. In the host microenvironment, C. glabrata encounters a variety of stresses, and its ability to cope with these stresses is crucial for its pathogenesis. To gain insights into how C. glabrata adapts to adverse environmental conditions, we examined its transcriptional landscape under heat, osmotic, cell wall, oxidative, and genotoxic stresses using RNA sequencing and reveal that C. glabrata displays a diverse transcriptional response involving ∼75% of its genome for adaptation to different environmental stresses. C. glabrata mounts a central common adaptation response wherein ∼25% of all genes (n = 1370) are regulated in a similar fashion at different environmental stresses. Elevated cellular translation and diminished mitochondrial activity-associated transcriptional signature characterize the common adaptation response. Transcriptional regulatory association networks of common adaptation response genes revealed a set of 29 transcription factors acting as potential activators and repressors of associated adaptive response genes. Overall, the current work delineates the adaptive responses of C. glabrata to diverse environmental stresses and reports the existence of a common adaptive transcriptional response upon prolonged exposure to environmental stresses.

Recent Advances in the Ecoepidemiology, Virulence and Diagnosis of Cryptococcus Neoformans and Cryptococcus Gattii Species Complexes

Emerging environmental pathogenic fungal infections, including cryptococcosis, continue to pose a significant threat to humans with compromised immunity and, to some extent, healthy ones. Cryptococcus neoformans was originally identified as the main etiological agent of human cryptococcosis, but recent studies have also identified the occurrence of opportunistic infections caused by Cryptococcus gattii. These two saprophytic facultative yeasts present a paradox as they can infect humans without requiring a host for replication or survival, a phenomenon termed readymade virulence. Many cryptococcal virulence traits appear to have dual effects that provide survival advantages in both animal hosts and the environment. Several molecular techniques have been developed to provide in-depth knowledge of these species complexes. This review will focus on the description of the Cryptococcus neoformans and Cryptococcus gattii (CnCg) species complexes and associated cryptococcal pathogenesis, ecological niches, and virulence factors employed by the pathogens to cause disease.

Design, synthesis and antifungal evaluation of phenylthiazole-1,3,4-oxadiazole thione (ketone) derivatives inspired by natural thiasporine A.

Plant pathogenic fungal infections have become a severe threat to the yield and quality of agricultural products, and new green antifungal agents with high-efficiency and low-toxicity are needed. In this study, a series of thiasporine A derivatives containing phenylthiazole-1,3,4-oxadiazole thione (ketone) structures were designed and synthesized, and their antifungal activities against six invasive and highly destructive phytopathogenic fungi were evaluated. The results showed that all compounds showed moderate to potent antifungal activity against six phytopathogenic fungi, and most of E the series compounds showed remarkable antifungal activity against S. sclerotiorum and C. camelliaet. In particular, compounds E1 - E5, E7, E8, E13, E14, E17, and E22 showed more significant antifungal activity against S. sclerotiorum, with EC50 values of 0.22，0.48, 0.56, 0.65, 0.51, 0.39, 0.60, 0.56, 0.60, 0.63, and 0.45 μg/mL, respectively, which were superior to that of carbendazim (0.70 μg/mL). Further activity studies showed that compound E1 showed superior curative activities against S. sclerotiorum in vivo and better inhibitory effects on sclerotia germination and formation of S. sclerotiorum compared to those of carbendazim. Therefore, this study indicates that these thiasporine A derivatives containing phenylthiazole-1,3,4-oxadiazole thione structures might be applied as antifungal agents against S. sclerotiorum. This article is protected by copyright. All rights reserved.

Biocontrol mechanisms of Bacillus velezensis against Fusarium oxysporum from Panax ginseng

Root rot caused by Fusarium oxysporum severely reduces ginseng root yield and quality, leading to large economic losses. Biological control has attracted extensive attention because it is safe, environmentally friendly, and sustainable. Screening for biocontrol strains to suppress soil-borne diseases is important for improving ginseng quality. A Bacillus velezensis strain was isolated from the forest rhizosphere of Pinus sylvestris could inhibited F. oxysporum in ginseng. To explore the strain’s biocontrol effects and mechanism of action against F. oxysporum, four treatments were established in pot experiments: no inoculation (CK), F. oxysporum inoculation (F), B. velezensis YW 17 (B), and mixed inoculation of B. velezensis and F. oxysporum (BF). After 4 months of cultivation, the ginseng plants in the F treatment grew more slowly, and the withering degree was most serious among all the treatments. The results from high-throughput sequencing showed that the relative abundance of Fusarium in the roots of the BF treatment was significantly lower than that of the F treatment. B. velezensis inoculation improved the relative abundance of other beneficial microorganisms in the ginseng rhizosphere, such as Arthrobacter and Mortierella. The experimental results indicated that YW17 had strong abilities to produce biofilms and IAA, and could colonize roots. The whole genome sequencing results showed that some genes (trpA-C, gatA) were involved in the synthesis of the plant growth-promoting hormone IAA and other genes (efp, hfq, epsA-O, spo0A, sinI/sinR, lysC, yjbB, flgK, fliD, srfABC) were involved in biofilm formation and root colonization. The results of whole genome sequencing showed that there are 18 gene clusters related to the synthesis of secondary metabolite with antifungal activities. In addition, some genes involved in the biosynthetic pathway of acetoin, such as ilvB and alsD, were also found. Based on the above results, we infer that B. velezensis YW17 could inhibit pathogenic F. oxysporum by secreting antifungal lipopeptides, proteins and volatile substances, thereby indirectly protecting ginseng from pathogenic fungal infections. These results indicated that B. velezensis could control ginseng root rot indirectly by regulating the root and rhizosphere microbial community structures and directly by secreting antifungal substances.

Isolation and molecular identification of agarwood-inducing fungi and their virulence test using Aquilaria sp. seedlings

Abstract. Lukman, Dinarti D, Siregar UJ, Turjaman M, Sudarsono. 2023. Isolation and molecular identification of agarwood-inducing fungi and their virulence test using Aquilaria sp. seedlings. Biodiversitas 24: 140-148. Agarwood is a lump of fragrant resin with a dark color and distinctive aroma from secondary metabolite products that accumulate in wood fibers produced from the genus Aquilaria and Gyrinops, a plant defense mechanism against damage caused by wounds and infection of specific fungal pathogens. The three main factors in producing agarwood sapwood are the presence of plants that have the potential to produce agarwood (family Thymelaceae) as a host, a supportive environment, and the presence of specific fungal pathogens. The isolation, identification, and virulence testing of local isolates must be made to get the correct agarwood-inducing pathogens without posing potential environmental problems. A total of five explants of Aquilaria sp. branches producing agarwood from the study site were used. This study aims to isolate local strains of fungi associated with agarwood formation from North Aceh regency, Aceh province, Indonesia, figure out their virulence against and ability to induce agarwood from seedlings of target trees, and determine their species identity. The experiments comprised isolation, macroscopic and microscopic identification, virulence tests, and species identification based on ITS sequences. The study resulted in five local Aceh isolates (LAI-1- LAI-5). Four isolates (LAI-1 - LAI-4) can induce agarwood formation, and oneisolate (LAI-5) is a white rot fungus. The ITS sequence analysis showed that LAI-1 - LAI-4 were Fusarium solani, while two colonies taken from LAI-5 isolate were identified as Ceriporia lacerataor Irpex laceratus (LAI-5 colony#1), and Daldinia eschscholtzii (LAI-5 colony #3). Based on these findings, the LA-5 isolate was probably a mixture of the two white rot fungus isolates.