Spore Germination Rate Research Articles

Biocontrol Potential of Streptomyces Strain FY4 Against Heterobasidion Root Rot Pathogen In Vitro

Root and butt rot, caused by Heterobasidion species, poses a significant threat to coniferous forests in the Northern Hemisphere. Innovative and effective strategies are crucial to enhance the control of this disease. This study aimed at identifying a Streptomyces strain, FY4, and evaluating its biocontrol potential against H. annosum and H. parviporum. Strain FY4 was identified as Streptomyces blastmyceticus based on morphological, physiological, and biochemical characteristics, supported by a multigene phylogenetic analysis using the 16S rRNA, atpD, rpoB, and trpB genes. In vitro dual-culture experiments showed that S. blastmyceticus exhibited antagonistic activity against both H. annosum and H. parviporum, with an inhibition zone diameter exceeding 15 mm. Moreover, the fermentation broth of S. blastmyceticus FY4 displayed significant inhibitory effects on the mycelial growth and spore germination of both Heterobasidion species. At a 10% concentration, the fermentation broth inhibited the mycelial growth by over 90% and reduced the spore germination rate by more than 60%. Additionally, the fermentation broth exhibited significant inhibitory effects on the mycelial growth of four common pathogenic fungi—Phytophthora cinnamomi, P. sojae, Rhizoctonia solani, and Verticillium dahlia, with an inhibition rate over 50%. These findings suggest that S. blastmyceticus FY4 produces antifungal substances capable of effectively suppressing infection of Heterobasidion species in conifers. Consequently, strain FY4 holds great promise as a biological control agent for managing root and butt rot caused by these pathogens, as well as potential for controlling other fungal diseases.

From Germination to Stagnation: Sodium Diacetate's Impact on Clostridium perfringens Spores

ABSTRACTSodium diacetate is recognized for its high efficiency as a preservative, demonstrating strong antibacterial properties that help extend the shelf life of food products. However, it is still unclear how it influences spores. This research investigated the influence of sodium diacetate on the germination and outgrowth stage in the revival process of Clostridium perfringens (C. perfringens) spores. The germination and outgrowth rate of spores after sodium diacetate treatment were measured. The changes of spore inner membrane were monitored by laser confocal microscope, electron scanning microscope and macromolecular leakage. The interaction between sodium diacetate and DNA was investigated by EB fluorescence probe, and the finding was verified by the outgrowth of spores in ham sausage. An investigation into the effects of sodium diacetate treatment on the biological activity, inner membrane permeability, morphology, and DNA integrity of spores devoid of both the coat and cortex revealed that sodium diacetate significantly hindered the transition of germinated spores into vegetative cells. In the presence of sodium diacetate, C. perfringens spores underwent germination, characterized by the hydrolysis of the spore cortex and the disassembly of the spore coat. As the spores advanced into the outgrowth phase, sodium diacetate penetrated their structure, causing damage to the inner membrane and compromising DNA integrity. Moreover, sodium diacetate was demonstrated to effectively inhibit spore outgrowth in ham sausage. This study provided theoretical guidance and references for the application of sodium diacetate in food to control the germination and outgrowth of spore‐forming bacteria.

Cold storage promotes germination and colonization of arbuscular mycorrhizal fungal hyphae as propagules.

The inoculants of arbuscular mycorrhizal fungi (AMF) propagated by the in vitro culture system is important in scientific research; however, the long-term storage reduces the spore germination rate. The propagules of AMF consist of three components, including spores, hyphae and colonized root fragments. It is well known that cold storage can improve the germination rate of AMF spores, with limited investigations on the germination of other propagules. In this study, AMF inoculants were stored at 25°C or at 4°C (cold storage) to investigate the effect of cold storage on the propagule viability of the AMF Rhizophagus irregularis DAOM197198. The germination rate of propagules (spores, hyphae, root fragments) and their colonization ability were determined at 3 and 6 months after storage. The results showed that the spore germination rate remained unchanged after storage for 0 and 1 month at 25°C, but decreased rapidly after storage for 3 months. Furthermore, we investigated the hyphal germination rate for the first time. The germination rates of spores, hyphae and root fragments were significantly higher under cold storage compared to those at 25°C. Additionally, we classified the germ tubes of hypha into two types: long-type (L-type) and short type (S-type). The germination rate and the proportion of L-type germ tubes of hyphae significantly increased with cold storage time, which was conducive to colonization. The results of mycorrhizal colonization confirmed that cold storage significantly increased the colonization of hypha compared with 25°C treatment. Cold storage may break the dormancy of AMF propagules and activate related enzymes to promote the germination and colonization of propagules, which needs further investigation.

The synergistic potential of polyethylene glycol 400 for the control of Hyphantria cunea larvae by Beauveria bassiana

The efficacy of entomopathogenic fungi as pest control agents is constrained by both their physiological state and external environmental factors. This study identified synergists capable of enhancing the insecticidal activity of Beauveria bassiana (Bb) and investigated the underlying synergistic mechanisms. Our results found that among 6 potential synergists, polyethylene glycol 400 (PEG) and trehalose significantly improved Bb's lethality against Hyphantria cunea larvae, with PEG demonstrating the most pronounced effect. PEG treatment markedly increased Bb spore adhesion and germination rates, while spore hydrophobicity and growth rates remained unaffected. Moreover, PEG-treated spores exhibited higher thermal tolerance compared to untreated ones. In the Bb + PEG treatment group, the hemocyte count, encapsulation and melanization activities, and the expression of related regulatory genes were significantly lower than those in the Bb treatment group. Additionally, pathogen recognition, signal transduction, and humoral immunity effector genes expression were markedly suppressed in the Bb + PEG group. A significant reduction in the content of total amino acids, free fatty acids, glucose, and trehalose, alongside decreased expression of key regulatory genes in the tricarboxylic acid cycle and glycolysis pathways, was observed in the Bb + PEG treatment group. Furthermore, PEG enhanced Bb-induced apoptosis in H. cunea larvae, as evidenced by the upregulation of apoptosis-related genes. Notably, PEG alone did not significantly impact the innate immunity, energy metabolism, or apoptosis in H. cunea larvae. Overall, PEG exhibits considerable potential in amplifying Bb's insecticidal activity by directly optimizing spore performance and indirectly modulating the larvae's innate immunity, energy metabolism, and apoptosis.

Genetic structure and pyrimethanil resistance of Botrytis spp. causing gray mold on strawberry from greenhouses in Zhejiang, China

Gray mold caused by Botrytis spp. is a common disease on various hosts, including strawberries. In this study, we obtained 59 Botrytis isolates from strawberries from greenhouses in Zhejiang Province, China. Identification of the sampled isolates at species level was performed by a duplex PCR assay method, the result showed that, in Zhejiang, gray mold on strawberry fruits is caused by a complex of Botrytis groups including B. cinerea group N (47.5 %) and B. cinerea group S (52.5 %). The sensitivities of all Botrytis isolates to pyrimethanil were determined based on discriminatory dose method on L-asparagine-based agar medium plate. Our results showed that the isolates obtained from the greenhouses with continuous use of pyrimethanil developed severe resistance to pyrimethanil, and the resistance frequencies of B. cinerea group N and group S isolates were 89.3 % and 41.9 %, respectively. By sequencing, four different resistance-related point mutations were identified in 38 Botrytis isolates: Bcpos5L412F (16 isolates, 42.1 %), Bcpos5L412V (14 isolates, 36.8 %), Bcmdl1E407K (2 isolates, 5.3 %), and Bcpos5L412S⸱Bcmdl1E407K (1 isolate, 2.6 %). The exogenous addition of methionine could not completely alter the resistance of Botrytis isolates to pyrimethanil. In this study, the pyrimethanil resistance in Botrytis isolates was steadily inherited, and compared to the pyrimethanil-sensitive isolates, the resistant mutants exhibited good fitness in sporulation capacity, spore germination rate, and virulence on strawberries. In conclusion, our results provided a description of the genetic structure of Botrytis groups complex on strawberry fruits and reminded growers to focus on the stable pyrimethanil resistance in Botrytis isolates, caused by point mutations in BcPos5 and BcMdl1.

In Situ Antimicrobial Properties of Sabinene Hydrate, a Secondary Plant Metabolite.

The objective of this research was to investigate natural products for their potential against pathogenic microorganisms. Sabinene hydrate (SH), a monoterpenoid, is synthesised by numerous different plants as a secondary metabolite. At present, there is a lack of definite investigations regarding the antimicrobial activity of SH itself and its different isomers. The antimicrobial effects of commercially available SH (composed mainly of trans-isomer) were evaluated within a range of concentrations in three types of contact tests: solid and vapor diffusion and the macro-broth dilution method. Moreover, the effects of SH on the rate of linear growth and spore germination were also examined. Ethanolic SH solutions were tested against an array of microorganisms, including blue-stain fungi (Ceratocystis polonica, Ophiostoma bicolor, O. penicillatum), frequently originating from bark beetle galleries; three fungal strains (Musicillium theobromae, Plectosphaerella cucumerina, and Trichoderma sp.) isolated from a sapwood underneath bark beetle galleries (Ips typographus) on spruce (Picea abies) stems; Verticillium fungicola, isolated from diseased I. typographus larvae; two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa); five yeasts (Candida albicans, C. krusei, C. parapsilosis, Saccharomyces cerevisiae, and Rhodotorula muscilaginosa), and two saprophytic fungi (Aspergillus niger and Penicillium notatum). In solid agar disc diffusion tests, Gram-positive bacteria exhibited greater susceptibility to SH than Gram-negative bacteria, followed by yeasts and fungi. The most resistant to SH in both the disc diffusion and broth macro-dilution methods were P. aeruginosa, A. niger, and Trichoderma sp. strains. Blue-stain fungi and fungi isolated from the Picea sapwood were the most resistant among the fungal strains tested. The minimum inhibition concentrations (MICs) generated by SH and determined using a disc volatilization method were dependent on the fungal species and played an important role in the development of microorganism inhibition. The two Gram-positive bacteria, B. subtilis and S. aureus (whose MICs were 0.0312 and 0.0625 mg/mL, respectively), were the organisms most susceptible to SH, followed by the Gram-negative bacterium, E. coli (MIC = 0.125 mg/mL) and two yeasts, C. albicans and C. kruei (MIC was 0.125 mg/mL and 0.25 mg/mL, respectively). C. parapsilosis (MIC = 0.75 mg/mL) was the yeast most resistant to SH. The investigation of antimicrobial properties of plant secondary metabolites is important for the development of a new generation of fungicides.

Isolation, antioxidant and antifungal activity of furanocoumarins from the leaves of Heracleum vicinum Boiss.

In this work, coumarin compounds were extracted by ultrasonic-microwave synergistic extraction from the leaves of Heracleum vicinum Boiss.. The five furanocoumarins—pimpinellin, isopimpinellin, bergapten, xanthotoxin, and imperatorin—that were isolated from the leaves of Heracleum vicinum Boiss. were quantified using HPLC and GC, and their quantities in the aboveground sections was determined. The antioxidant activities of five furanocoumarins were assessed with ABTS radicals and DPPH radicals, with the best scavenging effects of xanthotoxin and bergapten, with half maximal inhibitory concentration (IC50) of xanthotoxin for ABTS radicals and DPPH radicals of 1.85 mg/mL and 3.95 mg/mL, respectively, and bergapten for ABTS radicals and DPPH radicals IC50 of 1.68 mg/mL and 4.61 mg/mL, respectively. The antifungal activities of five furanocoumarins against trichophyton rubrum were evaluated. The minimum inhibitory concentration (MIC) of xanthotoxin (200 μg/mL) and imperatorin (12.5 μg/mL) showed the highest inhibitory effects against trichophyton rubrum. The inhibitory mechanism of xanthotoxin was discussed. When trichophyton rubrum was treated with 200 μg/mL of xanthotoxin, the spore germination rate was 34.92%, the nucleic acid leakage was 52.22%, the inhibition of radial growth of mycelium could reach 87.87%, and the content of ergosterol was reduced by 37.37%. It indicates that xanthotoxin was found to be able to damage mycelium shape, prevent spore germination and mycelium growth, kill mycelium cells and release intracellular materials, and obstruct the production of ergosterol. These results indicate that furanocoumarin is a potent active component that has an important role in Heracleum vicinum Boiss. leaves.

Biochemical mechanism of chlorine dioxide fumigation in inhibiting Ceratocystis fimbriata and black rot in postharvest sweetpotato

The inhibitory properties and underlying mechanism of chlorine dioxide (ClO2) fumigation on the pathogen Ceratocystis fimbriata (C. fimbriata) and resultant sweetpotato black rot were investigated in vitro and in vivo. Results revealed that the ClO2 fumigation effectively inhibited fungal growth and induced obvious morphological variation of C. fimbriata mycelia. Furthermore, the mycelial membrane suffered damage, as evidenced by a significant increase in malondialdehyde content and the leakage of protein and nucleic acid from mycelia cells, accompanied by a marked decrease in ergosterol content. Additionally, ClO2 fumigation caused spores cell membrane damage, a notable decrease in spore viability, and induced cell apoptosis as indicated by reductions in spore germination rate, two fluorescence staining observations, and flow cytometry analysis. Moreover, the decay diameter of sweetpotato black rot lesions decreased significantly after ClO2 fumigation, and the growth of C. fimbriata was also inhibited. These findings present a novel and effective technology for inhibiting the progression of sweetpotato black rot.

Study on the chemical composition and anti-fungi activities of anthraquinones and its glycosides from Rumex japonicus Houtt.

Fungi, such as Trichophyton rubrum (T. rubrum) and Microsporum canis Bodin Anamorph (M. canis Bodin Anamorph) are the main pathogens of dermatophysis. According to ancient books records, Rumex japonicus Houtt. (RJH) has a miraculous effect on the treatment of dermatophysis. To reveal the anti-fungi (T. rubrum and M. canis Bodin Anamorph) components and its mechanism of the Rumex japonicus Houtt. The vinegar extraction and alcohol precipitation, HPLC and nuclear magnetic resonance spectroscopy (NMR) were employed for analyzing the chemical compositions of RJH; in vitro anti-fungal experiment was investigated including test the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC), spore germination rate, nucleic acid, protein leakage rate, biofilm structure, and the mechanism of anti-fungal and anti-fungal biofilms in RJH. Seven anthraquinones and their glycoside compounds were obtained in this study respectively, such as chrysophanol, physcion, aloe-emodin, emodin, rhein, emodin-8-O-β-D-glucoside and chrysophanol-8-O-β-D-glucoside. In vitro anti-fungal experiment results showed that RJH extracts have good anti-fungal activity for dermatophytic fungi. Among them, the MIC of the rhein, emodin and aloe-emodin against T. rubrum are 1.9µg/ml, 3.9µg/ml and 15.6µg/ml, respectively; the MIC of emodin and aloe-emodin against M. canis Bodin Anamorph are 7.8µg/ml and 62.5µg/ml, respectively. In addition, its active components can inhibit fungal spore germination and the formation of bud tube, change cell membrane permeability, prevent hyphal growth, destroy biofilm structure, and down-regulate the expression of agglutinin-like sequence family 1 of the adhesion phase of biofilm growth. The study shows that RJH play a fungicidal role.

Transcriptional RNA sequencing reveals the molecular mechanism of dielectric barrier discharge cold plasma against postharvest pathogen Alternaria alternata

Alternaria alternata (A. alternata), a pervasive pathogen, infects fruits and vegetables, posing a significant contamination threat. Dielectric barrier discharge cold plasma (DBD-CP), a novel physical treatment technology, effectively prevents and controls postharvest diseases. This study investigated CP treatment's antifungal mechanism on A. alternata. Biochemical assays, laser confocal microscopy, flow cytometry analysis, and fluorescence staining demonstrated that CP treatment reduces spore germination, inhibits hyphal growth, disrupts cell membrane integrity and permeability, induces intracellular accumulation of reactive oxygen species, and interferes with energy metabolism. Specifically, following 100-kV CP treatment, hyphal growth was entirely inhibited within 24 h, and the spore germination rate decreased to only 18.48% of that of the control group. Furthermore, CP treatment significantly reduced the quantity of A. alternata inoculated on dried goji berries, with 80-kV CP treatment resulting in a 48.2% reduction. According to transcriptomic analysis, CP treatment resulted in 2954 differentially expressed genes. Among these genes, CP treatment downregulated those associated with membrane composition and functionality, DNA replication and repair, oxidative stress, and energy metabolism pathways. These findings highlight CP as a promising alternative technique for controlling postharvest fungal diseases.

Preparation of salicylic acid nano-protectant with dual synergistic mechanism: High direct fungicidal activity and plant defence toward cotton Verticillium wilt

Nanomaterials exhibit a wide range of potential applications in agricultural field. Here we construct a series of nano-protectants based on one model plant elicitor salicylic acid (SA) and six types of nanomaterials, including mesoporous silica nanosphere (MSN), mesoporous Fe3O4 nanosphere (Fe3O4), carbon quantum dot (CQD), polylactic acid-glycolic acid copolymer (PLGA), star polycation (SPc) and hydrophilic and lipophilic diblock polymer (HLDP), and explore the best nanomaterial for plant disease control. Our results demonstrate that the HLDP-SA nano-protectant displays the best control effects on cotton Verticillium wilt caused by one of the most notorious soil-borne fungi (Verticillium dahliae). The HLDP self-assembles with SA via electrostatic interaction into HLDP-SA nano-protectant, which changes the morphology of SA from needle-like particles to spherical particles. The loading efficiency of HLDP toward SA is calculated to be 49.28%, and the plant uptake of HLDP-loaded SA significantly increases by 3–4 times. HLDP-SA nano-protectant can suppress the spore germination of V991 strain with the spore germination rate of merely 2%, and its colony diameter is significantly decreased by 64.9%. Our transcriptome data demonstrate that the HLDP-SA nano-protectant accelerates the delivery and translocation of exogenous substances into V. dahliae, which exhibits the highest direct fungicidal activity via inhibiting the metabolism and weakening the pathogenicity. Meanwhile, its enhanced plant uptake with better adhesion performance on leaves amplifies the plant defense induced by SA via accelerating the biosynthesis of plant secondary metabolites, such as SA, abscisic acid (ABA) and gossypol. This study provides a powerful nanomaterial with dual synergistic mechanism for designing nano-protectant with high fungicidal activity and amplified plant defense.

Propolis extract and Hermetia illucens larval proteins synergistically inhibit the growth of Aspergillus niger

The individual and combined inhibitory activities of propolis extract (PE) and Hermetia illucens larval proteins (Black soldier fly larvae proteins) (BSFLP) against Aspergillus niger were investigated. The antifungal effects of PE, BSFLP and Synergy of PE and BSFLP (SPB) against Aspergillus niger were determined by mycelial growth, spore germination rate and hyphal elongation. Membrane integrity was measured by assessing changes in extracellular proteins, reducing sugars, and electrical conductivity. Intracellular MDA, H2O2, ergosterol, and mannan contents were also evaluated. SEM was used to observe the morphology of the Aspergillus niger mycelium. Additionally, AutoDock Tools software and multi-ligand docking methods were used to study the synergistic interactions of ligand combinations on the receptor. The results showed that the combination of PE and BSFLP had excellent effects. During the treatment of antifungal agents, the membrane permeability changed and a large amount of content leaked, while control check (CK) remained almost unchanged. Ergosterol content was found to increase, while mannan content decreased significantly, leading to cell death. In addition, SPB can cause abnormal accumulation of MDA and H2O2, leading to oxidative stress in cells. SEM results showed that morphology of Aspergillus niger treated with SPB was severe wrinkling, distortion and even breakage. Multi-ligand docking results showed that the binding affinity of receptor 1KS5 to 14 complex ligands increased, as indicated by the decrease in docking energy values. These results provide scientific basis for further study on the application of SPB and development of effective antifungal products.

Inhibition and Mechanism of Citral on Bacillus cereus Vegetative Cells, Spores, and Biofilms.

Bacillus cereus causes food poisoning by producing toxins that cause diarrhea and vomiting and, in severe cases, endocarditis, meningitis, and other diseases. It also tends to form biofilms and spores that lead to contamination of the food production environment. Citral is a potent natural antibacterial agent, but its antibacterial activity against B. cereus has not been extensively studied. In this study, we first determined the minimum inhibitory concentrations and minimum bactericidal concentrations, growth curves, killing effect in different media, membrane potential, intracellular adenosine triphosphate (ATP), reactive oxygen species levels, and morphology of vegetative cells, followed by germination rate, morphology, germination state of spores, and finally biofilm clearance effect. The results showed that the minimum inhibitory concentrations and minimum bactericidal concentrations of citral against bacteria ranged from 100 to 800 μg/mL. The lag phase of bacteria was effectively prolonged by citral, and the growth rate of bacteria was slowed down. Bacteria in Luria-Bertani broth were reduced to below the detection limit by citral at 800 μg/mL within 0.5 h. Bacteria in rice were reduced to 3 log CFU/g by citral at 4000 μg/mL within 0.5 h. After treatment with citral, intracellular ATP concentration was reduced, membrane potential was altered, intracellular reactive oxygen species concentration was increased, and normal cell morphology was altered. After treatment with citral at 400 μg/mL, spore germination rate was reduced to 16.71%, spore morphology was affected, and spore germination state was altered. It also had a good effect on biofilm removal. The present study showed that citral had good bacteriostatic activity against B. cereus vegetative cells and its spores and also had a good clearance effect on its biofilm. Citral has the potential to be used as a bacteriostatic substance for the control of B. cereus in food industry production.

Immune signaling of Litopenaeus vannamei c-type lysozyme and its role during microsporidian Enterocytozoon hepatopenaei (EHP) infection.

The microsporidian Enterocytozoon hepatopenaei (EHP) is a fungi-related, spore-forming parasite. EHP infection causes growth retardation and size variation in shrimp, resulting in severe economic losses. Studies on shrimp immune response have shown that several antimicrobial peptides (AMPs) were upregulated upon EHP infection. Among those highly upregulated AMPs is c-type lysozyme (LvLyz-c). However, the immune signaling pathway responsible for LvLyz-c production in shrimp as well as its function against the EHP infection are still poorly understood. Here, we characterized major shrimp immune signaling pathways and found that Toll and JAK/STAT pathways were up-regulated upon EHP infection. Knocking down of a Domeless (DOME) receptor in the JAK/STAT pathways resulted in a significant reduction of the LvLyz-c and the elevation of EHP copy number. We further elucidated the function of LvLyz-c by heterologously expressing a recombinant LvLyz-c (rLvLyz-c) in an Escherichia coli. rLvLyz-c exhibited antibacterial activity against several bacteria such as Bacillus subtilis and Vibrio parahaemolyticus. Interestingly, we found an antifungal activity of rLvLyz-c against Candida albican, which led us to further investigate the effects of rLvLyz-c on EHP spores. Incubation of the EHP spores with rLvLyz-c followed by a chitin staining showed that the signals were dramatically decreased in a dose-dependent manner, suggesting that rLvLyz-c possibly digest a chitin coat on the EHP spores. Transmission electron microscopy analysis revealed that an endospore layer, which is composed mainly of chitin, was digested by rLvLyz-c. Lastly, we observed that EHP spores that were treated with rLvLyz-c showed a significant reduction of the spore germination rate. We hypothesize that thinning of the endospore of EHP would result in altered permeability, hence affecting spore germination. This work provides insights into shrimp immune signaling pathways responsible for LvLyz-c production and its anti-EHP property. This knowledge will serve as important foundations for developing EHP control strategies.

Leaf litter from Cynanchum auriculatum Royle ex Wight leads to root rot outbreaks by Fusarium solani, hindering continuous cropping.

Cynanchum auriculatum Royle ex Wight (CA) is experiencing challenges with continuous cropping obstacle (CCO) due to soil-borne fungal pathogens. The leaf litter from CA is regularly incorporated into the soil after root harvesting, but the impact of this practice on pathogen outbreaks remains uncertain. In this study, a fungal strain D1, identified as Fusarium solani, was isolated and confirmed as a potential factor in CCO. Both leave extract (LE) and root extract (RE) were found to inhibit seed germination and the activities of plant defense-related enzymes. The combinations of extracts and D1 exacerbated these negative effects. Beyond promoting the proliferation of D1 in soil, the extracts also enhanced the hypha weight, spore number, and spore germination rate of D1. Compared to RE, LE exhibited a greater degree of promotion in the activities of pathogenesis-related enzymes in D1. Additionally, caffeic acid and ferulic acid were identified as potential active compounds. LE, particularly in combination with D1, induced a shift in the composition of fungal communities rather than bacterial communities. These findings indicate that the water extract of leaf litter stimulated the growth and proliferation of fungal strain D1, thereby augmenting its pathogenicity toward CA and ultimately contributing to the CCO process.

Cd pollution in agroforestry ecosystems: An abiotic factor affecting the passive and active lethal efficiency of Beauveria bassiana to Lymantria dispar larvae

This study evaluated the effects of cadmium (Cd) exposure on the passive and active lethal efficiency of Beauveria bassiana (Bb) to Lymantria dispar larvae and analyzed the corresponding mechanism from mycelial vegetative growth, fungal and host nutrient competition, and fungal spore performance. The results showed that the passive lethal efficiency of Bb to Cd-exposed L. dispar larvae was significantly higher than that of larvae not exposed to Cd. After Bb infection, the fungal biomass in living larvae and the mycelium encapsulation index of dead larvae were significantly decreased under Cd exposure. Cd exposure damaged the mycelial structure, as well as inhibited the mycelial growth and sporulation quantity. A total of 15 and 39 differentially accumulated mycotoxin metabolites were identified in Bb mycelia treated with low Cd and high Cd, respectively, and the contents of these differentially accumulated mycotoxins in the low Cd and high Cd treatment groups were overall lower than those in the control group. Nutrient content and energy metabolism-related gene expression were significantly decreased in Cd-exposed larvae, both before and after Bb infection. Trehalose supplementation alleviated the nutritional deficiency of larvae under the combined treatment of Cd and Bb and decreased the larval susceptibility to Bb. Compared with untreated Bb, the lethal efficiency of low Cd-exposed Bb to larvae increased significantly, while high Cd-exposed Bb was significantly less lethal to larvae. Cd exposure promoted at low concentrations but inhibited the hydrophobicity and adhesion of spores at higher concentrations. Spore germination rate and stress resistance of Bb decreased significantly under the treatment of both Cd concentrations. Taken together, heavy metals can be regarded as an abiotic environmental factor that directly affects the lethal efficiency of Bb to insect pests.

Evaluation of the Most Effective Plant Extracts, Bioagents and Chemical Fungicides In vitro against Powdery Mildew of Pea

The present investigation was carried during 2022-23 at Plant Pathology Section, College of Agriculture, Pune-05 with the objectives of evaluation of the most effective plant extracts, bioagents and chemical fungicides in vitro. Effect of six plant extracts, bioagents and chemical fungicides were studied in vitro by hanging drop method where the study revealed that garlic (Allium sativum), followed by neem (Azadiracta indica) showed highest inhibition of spore germination for powdery mildew. After 48 hours of incubation, the spore germination rate ranged from 3.15 % to 34.45 %, where garlic showed the highest inhibition at 95.30 %, followed by neem at 91.03 %. The efficacy of bioagents was evaluated by preparing the bacterial and fungal culture filtrates where Trichoderma harzianum and Pseudomonas fluorescens were found to be the most effective with tune of 56.86% and 50.72% of efficacy respectively against Erysiphe pisi. Among all chemical fungicides, hexaconazole (0.05 %) resulted as the most effective chemical fungicide against powdery mildew of pea. These findings can be useful in developing safer and more eco-friendly methods to control powdery mildew and protect crops.

Identification of a transcription factor AoMsn2 of the Hog1 signaling pathway contributes to fungal growth, development and pathogenicity in Arthrobotrys oligospora

IntroductionArthrobotrys oligospora has been utilized as a model strain to study the interaction between fungi and nematodes owing to its ability to capture nematodes by developing specialized traps. A previous study showed that high-osmolarity glycerol (Hog1) signaling regulates the osmoregulation and nematocidal activity of A. oligospora. However, the function of downstream transcription factors of the Hog1 signaling in the nematode-trapping (NT) fungi remains unclear. ObjectiveThis study aimed to investigate the functions and potential regulatory network of AoMsn2, a downstream transcription factor of the Hog1 signaling pathway in A. oligospora. MethodsThe function of AoMsn2 was characterized using targeted gene deletion, phenotypic experiments, real-time quantitative PCR, RNA sequencing, untargeted metabolomics, and yeast two-hybrid analysis. ResultsLoss of Aomsn2 significantly enlarged and swollen the hyphae, with an increase in septa and a significant decrease in nuclei. In particular, spore yield, spore germination rate, traps, and nematode predation efficiency were remarkably decreased in the mutants. Phenotypic and transcriptomic analyses revealed that AoMsn2 is essential for fatty acid metabolism and autophagic pathways. Additionally, untargeted metabolomic analysis identified an important function of AoMsn2 in the modulation of secondary metabolites. Furtherly, we analyzed the protein interaction network of AoMsn2 based on the Kyoto Encyclopedia of Genes and Genomes pathway map and the online website STRING. Finally, Hog1 and six putative targeted proteins of AoMsn2 were identified by Y2H analysis. ConclusionOur study reveals that AoMsn2 plays crucial roles in the growth, conidiation, trap development, fatty acid metabolism, and secondary metabolism, as well as establishes a broad basis for understanding the regulatory mechanisms of trap morphogenesis and environmental adaptation in NT fungi.

Antimicrobial mechanisms of g-C3 N4 @ZnO against oomycetes Phytophthora capsici: from its metabolism, membrane structures and growth.

Phytophthora capsici, a refractory and model oomycete plant pathogen, especially threatens multiple vegetable crops. A limited number of chemical pesticides play a vital role in controlling oomycete plant diseases. However, this approach often leads to excessive use of chemical agent, exacerbates environmental issues and more and more drug-resistant strains of oomycete. Therefore, it is imperative to devise innovative solutions that can effectively address the infection of oomycete while maintaining high levels of environmental sustainability and low toxicity. In this study, g-C3 N4 @ZnO heterostructure was synthesized and characterized. The g-C3 N4 @ZnO showed higher toxicity on Phytophthora capsici than graphitic carbon nitride (g-C3 N4 ) nanosheets and zinc oxide (ZnO) nanoparticles in vitro and in vivo. Except the hyphal growth of Phytophthora capsici, their germination rate of spores, sporangium formation and number of spores were all suppressed by g-C3 N4 @ZnO heterostructure. Furthermore, we found that this g-C3 N4 @ZnO heterostructure has higher photocatalytic activity under visible light, which potentially enhanced the reactive oxygen species (ROS) mediated stress on Phytophthora capsici. Ultrastructural morphology, global changes of gene expression and weighted gene co-expression network analysis all supported that the anti-oomycete activity of g-C3 N4 @ZnO was manifested in the destruction of membrane system and inhibition of multiple metabolisms of Phytophthora capsici under visible irradiation, which also could be attributed to the ROS and zinc ion (Zn2+ ) mediated stress. This works offers a novel oomycete disease management strategy by using g-C3 N4 @ZnO, which were attributed to the ROS stress, destruction of membrane system and inhibition of multiple metabolisms. © 2023 Society of Chemical Industry.

Identification of the Ilex macrocarpa anthracnose pathogen and the antifungal potential of the cell-free supernatant of Bacillus velezensis against Colletotrichum fioriniae.

Anthracnose is a significant fungal disease that affects tree growth and development, with Colletotrichum spp. exhibiting host non-specificity and targeting various organs, making disease control challenging. This study aimed to identify the pathogenic species causing anthracnose in Ilex macrocarpa in Nanchong, Sichuan Province, and screen effective fungicides, particularly biological ones. The pathogen was identified as Colletotrichum fioriniae through morphological observation, pathogenicity assays, and molecular biological methods. Three biological and five chemical fungicides were evaluated for their effects on the mycelial growth and spore germination rate of the pathogen. The results indicated that prochloraz was the most effective chemical fungicide, while the cell-free supernatant (CFS) of Bacillus velezensis had the most significant inhibitory effect among the biological fungicides. Transcriptome analysis revealed that the CFS of B. velezensis significantly reduced the expression of genes associated with ribosomes, genetic information processing, membrane lipid metabolism, and sphingolipid biosynthesis in C. fioriniae. Additionally, the glutathione pathway's expression of various genes, including key genes such as GST, GFA, Grx, TRR, and POD, was induced. Furthermore, the expression of 17 MFS transporters and 9 ABC transporters was increased. Autophagy-related ATGs were also affected by the B. velezensis CFS. These findings suggest that the B. velezensis CFS may inhibit C. fioriniae through interference with ribosomes, genetic information processing, cell membrane metabolism, and energy metabolism. These results provide potential target genes for the B. velezensis CFS and insights into the antifungal mechanism by which B. velezensis inhibits C. fioriniae.