Inhibitory effect of boron against Botrytis cinerea on table grapes and its possible mechanisms of action

Effects of washing with boric acid solutions on residual boric acid content, microbiological load, and quality of fresh-cut spinach

Insufficient disinfection of fresh-cut spinach poses significant health risks, along with potential issues like odor, color changes, and softening during short-term storage. To address these challenges, boric acid solutions were explored as an alternative to chlorine washes, which are known to produce toxic compounds. Among various concentrations, 1 % boric acid exhibited the most effective microbial inactivation, leading to substantial reductions in total mesophilic aerobic bacteria, total yeast and mold, and Enterobacteriaceae counts, with reductions of 1.64, 1.38, and 1.77 logs, respectively. Additionally, washing spinach leaves with this solution for 1 min maintained quality parameters, with enhanced antioxidant activity (55.26 mg kg-1 Trolox equivalent), increased total phenolic content (1214.06 mg kg-1 gallic acid equivalent), retention of chlorophyll a (839.16 mg kg-1), chlorophyll b (539.61 mg kg-1) and ascorbic acid content (264.72 mg kg-1). Mechanical properties such as puncture strength (1.81 N) and puncture distance (52.78 mm) also showed favorable outcomes, alongside optimal moisture content at 89.81 %. Notably, residual boric acid content was lowest in spinach leaves (1252.49 mg kg-1) and highest in the wash water (53.88 mg kg-1) after treatment. Scanning electron microscopy images demonstrated maintained tissue integrity, while Hunter Lab readings indicated minimal color changes post-washing. Additionally, sensory evaluations and various physicochemical analyses further supported the efficacy of boric acid washing. Consequently, washing spinach leaves with a 1 % boric acid solution for 1 min yielded favorable results across multiple quality parameters. These findings suggest the potential of boric acid as a safe and effective alternative disinfectant in the fresh-cut produce industry, highlighting its practical implications for food safety and quality. Future research should focus on exploring long-term effects and optimizing washing protocols for broader applications.

Propionate poses antivirulence activity against Botrytis cinerea via regulating its metabolism, infection cushion development and overall pathogenic factors

Botrytis cinerea is a devastating pathogen causing gray mold in fruits and vegetables if not properly managed. Although the mechanisms remain unclear, we previously revealed that the safe food additive calcium propionate (CP) could suppress gray mold development on grapes. The present study reports that sub-lethal dose of CP (0.2 % w/v) could allow growth with substantial reprograming the genome-wide transcripts of B. cinerea. Upon CP treatment, the genes related to fungal methylcitrate cycle (responsible for catabolizing propionate) were upregulated. Meanwhile, CP treatment broadly downregulated the transcript levels of the virulence factors. Further comparative analysis of multiple transcriptomes confirmed that the CP treatment largely suppressed the expression of genes related to development and function of infection cushion. Collectively, these findings indicate that CP can not only reduce fungal growth, but also abrogate fungal virulence factors. Thus, CP has significant potential for the control of gray mold in fruit crops.

Macrolactin R from Bacillus siamensis and its antifungal activity against Botrytis cinerea

Botrytis cinerea is listed among the most important fungal pathogens infecting strawberries. The use of biological control agents, such as Bacillus species, offers an alternative and effective way to reduce airborne pathogens. The aim of this research was to select the macrolactin R produced by Bacillus siamensis with potential for using as biological agents against the pathogenetic fungi (Botrytis cinerea) of strawberries, and to assess the mechanisms involved. Macrolactin R had significant inhibitory effects on spore germination, germ tube elongation, and mycelial growth of Botrytis cinerea. The MICs of macrolactin R inhibitions in vitro was 12.5 mg/L and The EC₅₀ value of NJ08-3 to Botrytis cinerea spores and mycelial was 1.93 and 2.88 mg/L, respectively. Macrolactin R impacted the membrane structure of Botrytis cinerea, resulting in changes in membrane permeability and leakage of proteins and nucleic acids, then cell death. The application of the macrolactin R of Bacillus siamensis reduced the disease severity index of gray mold on strawberries. This study demonstrated that the production of macrolactin R produced by Bacillus siamensis are involved in the antifungal activity against Botrytis cinerea.

Exploring boron applications in modern agriculture: Antifungal activities and mechanisms of phenylboronic acid derivatives

BACKGROUND

The unreasonable use of chemical fungicides causes common adverse consequences that not only affect the environment, but also cause resistance and resurgence problems of plant pathogens, which are extremely harmful to human health, the economy, and the environment. Based on the rich biological activities of boron-based compounds, 82 phenylboronic acid derivatives were selected and their antifungal activities against six agricultural plant pathogens were determined. Combined with transcriptomics tools, the mechanism of action of compound A49 (2-chloro-5-trifluoromethoxybenzeneboronic acid) against Botrytis cinerea Pers (B. cinerea) was studied.

RESULTS

The EC₅₀ values of compounds A24, A25, A30, A31, A36, A41, A49 and B23 against all six fungi were under 10 μg/mL. Compound A49 displayed significant activity against B. cinerea (EC₅₀  = 0.39 μg/mL), which was better than that of commercial fungicide boscalid (EC₅₀  = 0.55 μg/mL). A49 not only inhibited the germination of B. cinerea spores, but also caused abnormal cell morphology, loss of cell membrane integrity, enhanced cell membrane permeability, and accumulation of intracellular reactive oxygen species. Further findings showed that A49 reduced cellular antioxidant activity, and peroxidase and catalase activities. Transcriptomic results indicated that A49 could degrade intracellular redox processes and alter the metabolism of some amino acids. Meanwhile, A49 showed obvious activity in vivo and low cytotoxicity to mammal cells.

CONCLUSION

The boron-containing small molecule compounds had high efficiency and broad-spectrum antifungal activities against six plant pathogens, and are expected to be candidate compounds for a new class of antifungal drugs. © 2023 Society of Chemical Industry.

Bacterial adhesion and antibacterial property of coating materials containing theobromine and S-PRG filler

Theobromine (TB) has been reported to promote tooth remineralization, strengthen tooth substance, and relieve dentin hypersensitivity. This study aimed to evaluate experimental tooth coating materials containing TB and surface pre-reacted glass-ionomer (S-PRG) fillers by examining the effects on bacterial adhesion and antibacterial properties. In addition, the amount of TB eluted from the coating material was measured. There was no significant difference in bacterial adhesion depending on the presence or absence of TB in the coating material, however, a significant decrease in the amount of bacterial adhesion was observed when S-PRG fillers were added to the coating material. The amount of eluted TB did not differ depending on the type of the filler in the coating material. It was suggested that TB could be used to develop a new dental material with the potential ability to inhibit the initiation and progression of dental caries.

The peroxins BcPex8, BcPex10, and BcPex12 are required for the development and pathogenicity of Botrytis cinerea

Peroxisomes have been proved playing roles in infection of several plant pathogens. Although the contribution of a portion of peroxins in pathogenicity was demonstrated, most of them are undocumented in fungi, especially, Botrytis cinerea. The homologs of Pex8, Pex10, and Pex12 in B. cinerea were functionally characterized in this work using gene disruption strategies. Compared with the wild-type strain (WT), the Δbcpex8, Δbcpex10, and Δbcpex12 mutants exhibited significant reduction in melanin production, fatty acid utilization, and decreased tolerance to high osmotic pressure and reactive oxygen species (ROS). The mycelial growth and conidiation of were significantly inhibited in Δbcpex8, Δbcpex10, and Δbcpex12 strains. The mycelial growth rates of Δbcpex8, Δbcpex10, and Δbcpex12 were reduced by 32, 35, and 34%, respectively, compared with WT and ectopic transformant (ET), and the conidiation was reduced by approximately 89, 27, and 88%, respectively. The conidial germination, germ tube elongation, and the formation of initiate infection structures (IFSs) were also reduced by the deletion of the genes. The pathogenicity was tested on the leaves of tobacco and strawberry, and fruits of tomato. On the leaves of tobacco and strawberry, the Δbcpex8, Δbcpex10, and Δbcpex12 mutants could not induce necrotic lesions, and the lesions on tomato fruits infected with the mutants were significantly reduced than those of the wide type. The results indicated that BcPEX8, BcPEX10, and BcPEX12 are indispensable for the development and pathogenicity of B. cinerea.

Natamycin as a safe food additive to control postharvest green mold and sour rot in citrus

AIMS

The purpose of this study was to explore the potential inhibitory mechanism and assess the feasibility of natamycin as an antifungal agent in the utilization of citrus storage.

METHODS AND RESULTS

In this study, the mycelial growth, spore germination as well as germ tube elongations of Geotrichum citri-aurantii and Penicillium digitatum were significantly inhibited by natamycin treatment. The relative conductivities of G. citri-aurantii and P. digitatum mycelia were increased as time went by and the damages of plasma membranes were up to 17.43 % and 28.61 %. The mitochondria abnormalities and vacuolation were also observed in the TEM. Moreover, the sour rot and green mold decay incidences were reduced to 18.33 % and 10 % post-incubation with G. citri-aurantii and P. digitatum under 300 mg L^-1 natamycin application, respectively. For the citrus storage experiment, there was no significant difference in edible rate, juice yield, total soluble solid (TSS) content, titratable acid (TA) and decay incidences of the 'Newhall' navel orange fruit treated with 300 mg L^-1 natamycin stored for 90 d.

CONCLUSIONS

Natamycin could decrease the expansions of green mold and sour rot and maintain quality and improve storability on citrus fruit.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work explores the potential inhibition mechanism of natamycin G. citri-aurantii and P. digitatum, and assesses the feasibility of natamycin as an antifungal agent in the utilization of citrus storage.

Synergistic Effect of Melatonin and Selenium Improves Resistance to Postharvest Gray Mold Disease of Tomato Fruit

Melatonin (MT) is a ubiquitous hormone molecule that is commonly distributed in nature. MT not only plays an important role in animals and humans but also has extensive functions in plants. Selenium (Se) is an essential micronutrient for animals and humans, and is a beneficial element in higher plants at low concentrations. Postharvest diseases caused by fungal pathogens lead to huge economic losses worldwide. In this study, tomato fruits were treated with an optimal sodium selenite (20 mg/L) and melatonin (10 μmol/L) 2 h and were stored for 7 days at room temperature simulating shelf life, and the synergistic effects of Se and MT collectively called Se-Mel on gray mold decay in tomato fruits by Botrytis cinerea was investigated. MT did not have antifungal activity against B. cinerea in vitro, while Se significantly inhibited gray mold development caused by B. cinerea in tomatoes. However, the interaction of MT and Se showed significant inhibition of the spread and growth of the disease, showing the highest control effect of 74.05%. The combination of MT with Se treatment enhanced the disease resistance of fruits by improving the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as increasing the gene expression level of pathogenesis-related (PR) proteins. Altogether, our results indicate that the combination of MT and Se would induce the activation of antioxidant enzymes and increase the expression of PR proteins genes that might directly enhance the resistance in tomato fruit against postharvest pathogenic fungus B. cinerea.

Involvement of Organic Acid in the Control Mechanism of ε-Poly-L-lysine (ε-PL) on Blue Mold Caused by Penicillium expansum in Apple Fruits

Blue mold is one of the most serious postharvest diseases in apples caused by Penicillium expansum. The purpose of this study is to determine the effect of ε-poly-L-lysine (ε-PL) on the pathogenicity of P. expansum and explore the potential mechanism from the perspective of organic acid. The study investigates the effect of ε-PL treatment on the growth and acid production of P. expansum in vitro and in vivo. When the concentration of ε-PL was 50 mg/L, the growth of P. expansum was inhibited and the decrease in pH value was delayed in the medium. For example, on the third day of culture, P. expansum reduced the pH of the medium from 6.1 to 4.15, and ε-PL inhibited the decrease in the pH value at most 34.4%. When the concentration reached 1000 or 2000 mg/L, the infection of P. expansum in fruits was effectively inhibited. During the growth and infection of P. expansum, gluconic acid is one of the main factors leading to the pH value falling in the local environment. After ε-PL treatment, the accumulation of gluconic acid decreased, the activity of glucose oxidase was suppressed, and then the decline in the local environmental pH slowed down. In addition, after ε-PL treatment, the activities of cell-wall-degrading enzymes, such as cellulase (CL) and polygalacturonase (PG), in the different areas of the P. expansum–apple interaction were also affected by pH change. The results show that ε-PL inhibited the pathogenicity of P. expansum by affecting the accumulation of gluconic acid and slowing the decline in pH in fruit tissues, so as to affect the pathogenicity of P. expansum. This is the first time that the mechanism of ε-PL interfering with the pathogenicity of P. expansum from the perspective of organic acids is clarified.

Antifungal activities of fluoroindoles against the postharvest pathogen Botrytis cinerea: In vitro and in silico approaches

Botrytis cinerea is a common necrotrophic fungal pathogen, leading cause of gray mold diseases in plants and fruit. Several benzimidazoles are used for controlling B. cinerea-associated infection in fruit and vegetables, but benzimidazoles resistance restricts its further uses. Therefore, it is a need for alternative drugs that control B. cinerea. Indoles are multi-faceted compounds and their structural similarities with antifungal benzimidazoles make them a choice for further investigation. Thus, the main objective of the study was to investigate the antifungal potencies of indoles against B. cinerea and to decipher the molecular mechanism involved. We conducted in vitro antifungal assays, fruit assays, and computational studies of interactions between indoles and fungal microtubule polymerase. Of the 16 halogenated indoles examined, 4-fluoroindole, 5-fluoroindole, and 7-fluoroindole (MIC range 2-5 mg/L) were found to be more potent than the fungicides fluconazole and natamycin. Fluoroindoles inhibited or eradicated B. cinerea infections in tangerines and strawberries. Molecular dynamic simulation and density functional theory showed that these fluoroindoles stably interacted with microtubule polymerase. Quantitative structure-activity relationship analyses of halogenated indoles revealed that the presence of a fluoro group in the indole moiety is essential for anti-Botrytis activity. The plausibility of the underlying antifungal mechanism was confirmed by in vitro tubulin polymerization. Collective outcomes of this study indicates that fluoroindoles could be used as alternative fungicidal agents against B. cinerea.

With a Little Help from My Cell Wall: Structural Modifications in Pectin May Play a Role to Overcome Both Dehydration Stress and Fungal Pathogens

Cell wall structural modifications through pectin cross-linkages between calcium ions and/or boric acid may be key to mitigating dehydration stress and fungal pathogens. Water loss was profiled in a pure pectin system and in vivo. While calcium and boron reduced water loss in pure pectin standards, the impact on Allium species was insignificant (p > 0.05). Nevertheless, synchrotron X-ray microscopy showed the localization of exogenously applied calcium to the apoplast in the epidermal cells of Allium fistulosum. Exogenous calcium application increased viscosity and resistance to shear force in Allium fistulosum, suggesting the formation of calcium cross-linkages ("egg-box" structures). Moreover, Allium fistulosum (freezing tolerant) was also more tolerant to dehydration stress compared to Allium cepa (freezing sensitive). Furthermore, the addition of boric acid (H3BO3) to pure pectin reduced water loss and increased viscosity, which indicates the formation of RG-II dimers. The Arabidopsis boron transport mutant, bor1, expressed greater water loss and, based on the lesion area of leaf tissue, a greater susceptibility to Colletotrichum higginsianum and Botrytis cinerea. While pectin modifications in the cell wall are likely not the sole solution to dehydration and biotic stress resistance, they appear to play an important role against multiple stresses.

Peppermint Essential Oil Suppresses Geotrichum citri-aurantii Growth by Destructing the Cell Structure, Internal Homeostasis, and Cell Cycle

Peppermint essential oil (Peo) is an efficient antifungal agent, and 2.0 μL of Peo per milliliter culture medium can completely inhibit the mycelium growth and spore germination of Geotrichum citri-aurantii. In vitro experiments showed that the main functional component in Peo was l-menthol, which could lead to changes in sugar and protein contents, reduce the content of alkaline phosphatase (AKP), and destroy the spore membrane structure, with a significant increase in electrical conductivity. Meanwhile, the content of reactive oxygen (ROS) accumulated sharply, and the enzyme activity changed significantly with the change in the gene expression level. In addition, l-menthol could cause degradation in spore genetic material differently. Furthermore, a total of 1704 differentially expressed genes (DEGs) in G. citri-aurantii after 1.6 μL/mL l-menthol exposure for 2 h were obtained by the transcriptome sequencing. These DEGs were involved in transmembrane transport, carbohydrate transmembrane transport protein activity, and mitogen-activated protein kinase (MAPK) signaling pathway. The protein-protein interaction (PPI) analysis of DEGs yielded 10 highly cross-linked nodes, and these genes were associated with DNA replication and cell cycle. The expression level of the hub gene was confirmed by real-time quantitative PCR (RT-qPCR), with the most significant changes in POL 30 (5.9-fold). Molecular simulation was performed and it was found that the binding site between l-menthol and POL 30 was the 44th ARG residue in POL 30, and it was speculated that l-menthol and POL 30 may be combined by hydrogen bonding interaction. The results of flow cytometry assay showed that l-menthol blocked the replication process in the S-phase of G. citri-aurantii. This study provides new insights into the development and application of Peo in food safety.

Molecular basis of pathogenesis of postharvest pathogenic Fungi and control strategy in fruits: progress and prospect

The disease caused by pathogenic fungi is the main cause of postharvest loss of fresh fruits. The formulation of disease control strategies greatly depends on the understanding of pathogenic mechanism of fungal pathogens and control strategy. In recent years, based on the application of various combinatorial research methods, some pathogenic genes of important postharvest fungal pathogens in fruit have been revealed, and their functions and molecular regulatory networks of virulence have been explored. These progresses not only provide a new perspective for understanding the molecular basis and regulation mechanism of pathogenicity of postharvest pathogenic fungi, but also are beneficial to giving theoretical guidance for the creation of new technologies of postharvest disease control. Here, we synthesized these recent advances and illustrated conceptual frameworks, and identified several issues on the focus of future studies.

Antifungal effects of lycorine on Botrytis cinerea and possible mechanisms

Botrytis cinerea cause postharvest diseases on fruit and lead economic losses. Application of environment-friendly natural compounds is an alternative for synthetic fungicides to control postharvest disease. Lycorine is an indolizidine alkaloid which is widely used for human drug design, however, application of lycorine in controlling postharvest disease and the underlying mechanisms have not been reported. In this study, the effects of lycorine on mycelium growth, spore germination, disease development in apple fruit, cell viability, cell membrane integrity, cell wall deposition, and expression of mitogen-activated protein kinase (MAPK) and GTPase of B. cinerea were investigated. Our results showed that lycorine was effective in controlling postharvest gray mold caused by B. cinerea on apple fruit. In the in vitro tests, lycorine strongly inhibited spore germination and mycelium spreading in culture medium. Investigation via fluorescein diacetate and propidium iodide staining suggested that lycorine could damage the membrane integrity and impair cell viability of B. cinerea. Furthermore, the expression levels of several MAPK and GTPase coding genes were reduced upon the lycorine treatment. Taken together, lycorine is an effective and promising way to control postharvest disease caused by B. cinerea.

Chitosan/silica nanocomposite-based formulation alleviated gray mold through stimulation of the antioxidant system in table grapes

The main purpose of this study was to explore the ability of a novel silica/polysaccharide polymer-based formulation, namely, chitosan/silica nanocomposites (CSNs), to directly affect Botrytis cinerea in vitro and in inoculated berries, and indirectly to induce natural host resistance via enzymatic and nonenzymatic antioxidants against gray mold of table grapes. The results indicated a positive correlation in in vitro tests in terms of radial growth, spore germination and germ tube elongation, where those parameters were completely inhibited by CSN at 1%. SEM and TEM investigations showed that morphological and internal structural damage was observed in B. cinerea-hyphae/spores treated with CSN. Additionally, most of the treated spores were affected, and cellular vacuolization and cytoplasmic disorganization were observed. The results revealed that CSN reduced gray mold incidence and severity on inoculated berries directly and indirectly. In direct activity, CSN (1%) reduced mold incidence and severity by 100% compared to the control. In indirect activity, mold incidence and severity was reduced by 51% and 64%, respectively. CSN significantly increased superoxide dismutase, ascorbate peroxidase, peroxidase, total phenol and flavonoid at 48 h post-treatment by 1.2-, 1.6-, 1.3-, 1.3- and 1.6-fold, respectively, in grape-treated tissues. It could be concluded that CSN, as a promising alternative control method against gray mold of table grapes, can directly affect the pathogen and indirectly enhance the natural host resistance of the antioxidant system.

Antibacterial activity and mode of action of potassium tetraborate tetrahydrate against soft-rot bacterial plant pathogens

Bacterial soft rot caused by the bacteria Dickeya and Pectobacterium is a destructive disease of vegetables, as well as ornamental plants. Several management options exist to help control these pathogens. Because of the limited success of these approaches, there is a need for the development of alternative methods to reduce losses. In this study, we evaluated the effect of potassium tetraborate tetrahydrate (PTB) on the growth of six Dickeya and Pectobacterium spp. Disc diffusion assays showed that Dickeya spp. and Pectobacterium spp. differ in their sensitivity to PTB. Spontaneous PTB-resistant mutants of Pectobacterium were identified and further investigation of the mechanism of PTB resistance was conducted by full genome sequencing. Point mutations in genes cpdB and supK were found in a single Pectobacterium atrosepticum PTB-resistant mutant. Additionally, point mutations in genes prfB (synonym supK) and prmC were found in two independent Pectobacterium brasiliense PTB-resistant mutants. prfB and prmC encode peptide chain release factor 2 and its methyltransferase, respectively. We propose the disruption of translation activity due to PTB leads to Pectobacterium growth inhibition. The P. atrosepticum PTB-resistant mutant showed altered swimming motility. Disease severity was reduced for P. atrosepticum-inoculated potato stems sprayed with PTB. We discuss the potential risk of selecting for bacterial resistance to this chemical.

Actin Is Required for Cellular Development and Virulence of Botrytis cinerea via the Mediation of Secretory Proteins

The cytoskeleton is an important network that exists in cells of all domains of life. In eukaryotic cells, actin is a vital component of the cytoskeleton. Here, we report that BcactA, an actin protein in B. cinerea, can affect the growth, sporulation, and virulence of B. cinerea. Furthermore, iTRAQ-based proteomic analysis showed that BcactA affects the abundance of 40 extracellular proteins, including 11 down-accumulated CWDEs. Among them, two CWDEs, cellobiohydrolase (BcCBH) and β-endoglucanase (BcEG), contributed to the virulence of B. cinerea, indicating that bcactA plays a crucial role in regulating extracellular virulence factors. These findings unveil previously unknown functions of BcactA in mediating growth, sporulation, and virulence of B. cinerea.

Actin is a vital component of the cytoskeleton of living cells and is involved in several complex processes. However, its functions in plant-pathogenic fungi are largely unknown. In this paper, we found that deletion of the Botrytis cinerea actin gene bcactA reduced growth and sporulation of B. cinerea and lowered virulence. Based on iTRAQ (isobaric tags for relative and absolute quantification)-based proteomic analysis, we compared changes of the secretome in ΔbcactA and wild-type strains. A total of 40 proteins exhibited significant differences in abundance in ΔbcactA mutants compared with the wild type. These proteins included 11 down-accumulated cell wall-degrading enzymes (CWDEs). Among them, two CWDEs, cellobiohydrolase (BcCBH) and β-endoglucanase (BcEG), were found to contribute to the virulence of B. cinerea, indicating that bcactA plays a crucial role in regulating the secretion of extracellular virulence factors. These findings unveil previously unknown functions of BcactA to mediate the virulence of B. cinerea and provide new mechanistic insights into the role of BcactA in the complex pathogenesis of B. cinerea.

IMPORTANCE The cytoskeleton is an important network that exists in cells of all domains of life. In eukaryotic cells, actin is a vital component of the cytoskeleton. Here, we report that BcactA, an actin protein in B. cinerea, can affect the growth, sporulation, and virulence of B. cinerea. Furthermore, iTRAQ-based proteomic analysis showed that BcactA affects the abundance of 40 extracellular proteins, including 11 down-accumulated CWDEs. Among them, two CWDEs, cellobiohydrolase (BcCBH) and β-endoglucanase (BcEG), contributed to the virulence of B. cinerea, indicating that bcactA plays a crucial role in regulating extracellular virulence factors. These findings unveil previously unknown functions of BcactA in mediating growth, sporulation, and virulence of B. cinerea.

The Effect of (1S,2R-((3-bromophenethyl)amino)-N-(4-chloro-2-trifluoromethylphenyl) cyclohexane-1 -sulfonamide) on Botrytis cinerea through the Membrane Damage Mechanism

In recent years, Botrytis cinerea has led to serious yield losses because of its resistance to fungicides. Many sulfonamides with improved properties have been used. (1S,2R-((3-bromophenethyl)amino)-N-(4-chloro-2-trifluoromethylphenyl)cyclohexane-1-sulfonamide) (abbreviation: SYAUP-CN-26) is a new sulfonamide compound that has excellent activity against B. cinerea. This study investigated the effect of SYAUP-CN-26 on electric conductivity, nucleic acids leakage, malondialdehyde (MDA) content, and reducing sugars and membrane structure reduction of B. cinerea. The results showed that the cell membrane permeability of B. cinerea increased with increasing concentrations of SYAUP-CN-26; meanwhile, the sugar content decreased, the malondialdehyde content increased, and relative electric conductivity and nucleic acid substance leakage were observed in the cell after exposure to 19.263 mg/L SYAUP-CN-26 for 24 h. After 48 h of exposure to 1.823 mg/L and 19.263 mg/L SYAUP-CN-26, the cell membranes of B. cinerea mycelia were observed to be damaged under propidium iodide (PI) and transmission electron microscopy (TEM) observations. It is assumed that SYAUP-CN-26 was responsible for the damage of cell membrane. Overall, the results indicate that SYAUP-CN-26 could inhibit the growth of B. cinerea cells by damaging the cell membranes.

Selenium reduces the pathogenicity of Sclerotinia sclerotiorum by inhibiting sclerotial formation and germination

Sclerotinia sclerotiorum (S. sclerotiorum) is a devastating fungal pathogen with worldwide distribution, and threatened the agro-ecological safety in the long term. To control the damage caused by Sclerotinia diseases, as well as consider the fungicide resistance and chemical residues, strategy of which plant nutritional regulation, as an eco-friendly approach, is gaining much significance. Selenium (Se), as a beneficial microelement for plant, has been manifested to be effective in inhibiting the mycelial growth of S.sclerotiorum in our previous study. In the present study, we observed that Se (both selenate and selenite) inhibited the formation of sclerotia, which is an important life form in the disease cycle of S. sclerotiorum. And the inhibition ratios of number of sclerotia in treatments of Se(VI)_5.0 and Se(IV)_5.0 were 54.55% and 43.84%, respectively; the inhibition ratios of weight of sclerotia in treatments of Se(VI)_5.0 and Se(IV)_5.0 were 42.29% and 25.67%, respectively. Results suggested that Se inhibited mycelial growth, severely damaged sclerotial ultrastructure, reduced the capacity of acid production, decreased superoxide dismutase (SOD) and catalase (CAT) activities, increased the content of hydrogen peroxide (H₂O₂) and superoxide anion (O₂^-) in mycelium, and all of these resulted in the reduction in sclerotial formation. Further studies revealed that Se application in medium increased Se concentration in sclerotia and thus inhibited sclerotial germination. Moreover, the pathogenicity of mycelia germinating from sclerotia that pretreated with Se, decreased significantly to rape leaves. These findings broadened our understanding of Se application in plant protection, as well as provided evidences for developing environment-friendly fungicide for S. sclerotiorum control.

Ultra-Structural Alterations in Botrytis cinerea-The Causal Agent of Gray Mold-Treated with Salt Solutions

Potassium bicarbonate (PB), calcium chelate (CCh), and sodium silicate (SSi) have been extensively used as antifungal generally recognized as safe (GRAS) compounds against plant pathogenic fungi. In this research, in in vitro tests, the radial growth, conidial germination, and germ tube elongation of Botrytis cinerea was completely inhibited at 0.3% of PB, SSi, and CCh. In in vivo tests, application of PB, SSi, and CCh completely inhibited the occurrence of gray mold incidence of inoculated 'Italia' grape berries at concentrations of 1.0, 0.8, and 0.8%, respectively. In order to investigate the detailed mechanisms by which salts exhibited antifungal activity, we analyzed their influence on morphological changes by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and also on reactive species of oxygen (ROS), mitochondrial membrane potential (MMP), and adenosine triphosphate (ATP) content. Defects such as malformation and excessive septation were detected on salt-treated hyphae morphology observed by SEM. The internal structure of conidia treated or not with salt solutions was examined by TEM. In treated conidia, most of the conidia were affected and cellular vacuolization and cytoplasmic disorganization was observed. For ROS accumulation, a higher increase was observed in fluorescent conidia in presence of PB, SSi, and CCh by 75, 68, and 70% as compared to control, respectively. MMP was significantly decreased after salt application indicating a loss of mitochondria function. Also, luminescence showed that B. cinerea-conidia treated with salts contained less ATP than the untreated conidia. The results obtained herein are a step towards a comprehensive understanding of the mode of action by which salts act as antifungal agents against B. cinerea.

Boron in soil: The impacts on the biomass, composition and activity of the soil microbial community

The high boron (B) content in desalinated seawater is a concern for crop development. However, in spite of the importance of the soil microbial community in soil fertility, the below-ground impacts of B are still unknown. Here, in a soil-ryegrass model system, the activity, biomass and diversity of the soil microbial community were evaluated in response to irrigation with: i) 0.3 mg B L^-1; ii) 1 mg B L^-1; and iii) 50 mg B L^-1. We assessed two different compounds of boron: boric acid (H₃BO₃) and disodium tetraborate decahydrate (Na₂B₄O₇·10H₂O). Overall, the 1 mg B L^-1 dose was identified as the threshold limit that did not irreversibly harm soil sustainability. In contrast, the highest B dose had a noticeable impact on the nitrogen (N) cycle of the soil, as demonstrated by an increase in the water-soluble N content and a decrease in urease activity. Analysis of the phospholipid fatty acids (PLFAs) revealed that the effect of B on the soil microbial biomass was dependent on the chemical form used. High B doses reduced soil microbial respiration and influenced the composition of the bacterial and fungal communities, with fungal diversity being diminished, as revealed by sequencing approaches.

Antifungal activity of thymol and carvacrol against postharvest pathogens Botrytis cinerea

Botrytis cinerea is a primary pathogen causing stem and fruit rot during pre- and post-harvest. In the present study, the main purpose was to inquire into the antifungal activity and potential mechanisms of thymol and carvacrol against B. cinerea. During the experiment, the effects of thymol and carvacrol on physical and biochemical parameters of B. cinerea were evaluated. Results indicated that thymol and carvacrol exhibited strong antifungal activity against the targeted pathogen, with minimum inhibitory concentration and minimum fungicidal concentration of 65 mg/L and 100 mg/L for thymol, and 120 μL/L and 140 μL/L for carvacrol. Thymol and carvacrol changed obviously the morphology of B. cinerea hyphae by disrupting and distorting the mycelia through scanning electron microscopy. The membrane permeability of B. cinerea hyphae was prompted with the increment of two chemical agents' concentration, as evidenced by extracellular conductivity increase, the release of cell constituent, and the decrease of extracellular pH. Furthermore, a marked decline in total lipid content of B. cinerea cells was induced by the two chemical agents, suggesting that the cell membrane structures were destructed. Therefore, present results indicated that thymol and carvacrol may be used as a good alternative to conventional fungicides against B. cinerea in controlling grey molds in horticultural products.

Cytosporone B as a Biological Preservative: Purification, Fungicidal Activity and Mechanism of Action against Geotrichum citri-aurantii

To prevent citrus decay caused by Geotrichum citri-aurantii, 12 natural products were isolated from two endophytic fungi, in which cytosporone B was shown to have excellent bioactivity for control of G. citri-aurantii with median effect concentration (EC₅₀) of 26.11 μg/mL and minimum inhibitory concentration (MIC) of 105 μg/mL, and also significantly reduced the decay of sugar orange during the in vivo trials. In addition, cytosporone B could alter the morphology of G. citri-aurantii by causing distortion of the mycelia and loss of membrane integrity. Differentially expressed genes (DEGs) between cytosporone B-treated and -untreated samples were revealed by Illumina sequencing, including 3540 unigenes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that most DEGs were related to metabolic production and cell membrane. These findings suggest cytosporone B is a promising biological preservative to control citrus decay and reveal the action mechanism of cytosporone B in relation to the destruction of the fungal cell membrane at both morphological and molecular levels.

Development of antimicrobial gelatin films with boron derivatives

Food packaging technology has been advancing to provide safe and high quality food products and to minimize food waste. Moreover, there is a dire need to replace plastic materials in order to reduce environmental pollution. The aim of this study was to prepare biodegradable antimicrobial packaging films from gelatin. Boric acid, disodium octaborate tetrahydrate, and sodium pentaborate were incorporated as the antimicrobial agents. Films containing boric acid and its salts showed antibacterial effect against Staphylococcus aureus and Pseudomonas aeruginosa, as well as antifungal and anticandidal effects against Aspergillus niger and Candida albicans. The mechanical strength of the films was mostly enhanced by the addition of boron derivatives. The rheological measurements and Fourier-transform infrared spectroscopy results suggest that boron derivatives did not interfere with the network formation during gelling. The morphology of boron-added antimicrobial films was found to be similar to the morphology of the control . In conclusion, the newly developed gelatin films containing 10% or 15% disodium octaborate (g/g gelatin) might be good candidates for biodegradable antimicrobial packaging materials.

In vitro drug release behavior of Ce-doped nano-bioactive glass carriers under oxidative stress

Ce-containing bioactive glasses are known to decrease reactive oxygen activities inside the body. That is because of their excellent catalytic activities which come from the fast interchange of Ce³⁺/Ce⁴⁺ oxidation states. This research was mainly aimed at preparing new Ce-doped nano-bioactive glasses based on 60SiO₂-(10-x)B₂O₃-25CaO-5P₂O₅-xCeO₂, in mole% (x = 0 and 5 mol%) as multifunctional bone fillings. Moreover, the glasses were used as a delivery system for ciprofloxacin to intensely solve the bone infection complications. Nevertheless, there were no previous works studied of the nature immersing solution effect on the drug release behavior from Ce-doped nano-bioactive glass carriers. Therefore, phosphate-free and phosphate-containing buffer solutions with/without superoxide species (H₂O₂) were used to investigate the efficacy of this drug delivery system in different environment. The results showed that Ce addition enhanced the formation of apatite layer and cell viability. Moreover, the percentage of released drug was apparently affected by the glass composition and nature of soaking fluid, specifically, in the media containing superoxide species (H₂O₂). In conclusion, the prepared Ce-doped glass nanoparticles illustrated multifunctional bone filling material, but when it intended to be utilized as a drug delivery system, the nature of surrounding medium have to be taken into consideration.

Notopterygium incisum extract and associated secondary metabolites inhibit apple fruit fungal pathogens

In the search for antifungal lead compounds from natural resources, Notopterygium incisum, a medicine plant only distributed in China, showed antifungal potential against apple fruit pathogens. Based on the bioassay-guided isolation, chromatography fraction 6 of the ethyl acetate partition exhibited significant in vitro and in vivo antifungal activities against apple fruit pathogens. Furthermore, nine antifungal secondary metabolites, including five linear furocoumarins (1-5), two phenylethyl esters (6-7), one falcarindiol (8), and one sesquiterpenoid (9), were isolated and elucidated from fraction 6. Compound 5 is a new metabolite, and 9 isolated from the genus Notopterygium for the first time. The purified compounds (1-9) were firstly reported to exhibit antifungal activities against apple fruit pathogens of Colletotrichum gloeosporioides and Botryosphaeria dothidea with the MIC values ranging from 8 to 250 mg L^-1, especially 8 of 16 and 8 mg L^-1, respectively. Moreover, 8 could inhibit the spore germination and new sporulation of B. dothidea, as well as enhance the membrane permeabilization of B. dothidea spores. This was the first investigation for the antifungal components against apple fruit pathogens from Notopterygium incisum, which has great potential to be developed into bio-fungicides.

Inhibitory effect of resin composite containing S-PRG filler on Streptococcus mutans glucose metabolism

OBJECTIVES

Resin composites containing surface pre-reacted glass-ionomer (S-PRG) fillers have been reported to inhibit Streptococcus mutans growth on their surfaces, and their inhibitory effects were attributed to BO₃^3- and F^- ions. The aim of this study was to evaluate S. mutans acid production through glucose metabolism on resin composite containing S-PRG fillers and assess inhibitory effects of BO₃^3- and F^- on S. mutans metabolic activities.

METHODS

The pH change through S. mutans acid production on experimental resin composite was periodically measured after the addition of glucose. Inhibitory effects of BO₃^3- or F^- solutions on S. mutans metabolism were evaluated by XTT assays and measurement of the acid production rate.

RESULTS

The pH of experimental resin containing S-PRG fillers was significantly higher than that of control resin containing silica fillers (p < 0.05). OD₄₅₀ values by XTT assays and S. mutans acid production rates significantly decreased in the presence of BO₃^3- and F^- compared with the absence of these ions (p < 0.05).

CONCLUSIONS

pH reduction by S. mutans acid production was inhibited on resin composite containing S-PRG fillers. Moreover, S. mutans glucose metabolism and acid production were inhibited in the presence of low concentrations of BO₃^3- or F^-.

CLINICAL SIGNIFICANCE

BO₃^3- or F^- released from resin composite containing S-PRG fillers exhibits inhibitory effects on S. mutans metabolism at concentrations lower than those which inhibit bacterial growth.

Activity of the pterophyllins 2 and 4 against postharvest fruit pathogenic fungi. Comparison with a synthetic analog and related intermediates

The antifungal activity of pterophyllin 2, pterophyllin 4, a 5-desmethyl analog of the latter and some of their synthetic intermediates, against three postharvest phytopathogenic fungi, was evaluated. The target fungi were Rhizopus stolonifer, Botrytis cinerea and Monilinia fructicola, which affect fruits worldwide, causing important economic losses. The tests were carried out with imazalil and carbendazim as positive controls. Minimum inhibitory concentrations and minimum fungicidal concentrations were determined, and the morphology of the colonies was examined microscopically. In liquid medium, it was found that pterophyllin 4 exhibited selective fungicidal activity toward M. fructicola, whereas its congener pterophyllin 2 proved to be less potent and not selective and the 5-desmethyl analog of pterophyllin 4 displayed a different activity profile. Morphological changes were observed in the colonies exposed to pterophyllin 4. The results highlighted the importance of small structural features for the antifungal behavior and also suggested that, in Nature, the pterophyllins may act as plant defenses against pathogens.

Antibacterial Effect of Potassium Tetraborate Tetrahydrate against Soft Rot Disease Agent Pectobacterium carotovorum in Tomato

Soft rot caused by Pectobacterium carotovorum is one of most common bacterial diseases occurring in fruits and vegetables worldwide, yet consumer-acceptable options for post-harvest disease management are still insufficient. We evaluated the effect of potassium tetraborate tetrahydrate (B4K2O7.4H2O) (PTB) on the growth of P. carotovorum using strain BA17 as a representative of high virulence. Complete inhibition of bacterial growth was achieved by treatment with PTB at 100 mM both at pH 9.2 and after adjustment to pH 7.0. Bactericidal activity was quantified and validated by counting fluorescently labeled live and dead bacterial cells using flow cytometry, and reconfirmed using qPCR with high-affinity photoreactive DNA binding dye propidium monoazide (PMA). The results of flow cytometry, qPCR, and culturing confirmed that bacterial cells were killed following exposure to PTB at 100 mM. Bacterial cell membranes were damaged following a 5-min treatment and extrusion of cytoplasmic material from bacterial cells was observed using electronic transmission microscopy. Soft rot incidence on inoculated tomato fruit was significantly reduced by dipping infected fruits in PTB at 100 mM for 5 min and no lesions developed following a 10-min treatment. PTB does not pose a hazard to human health and is an effective alternative to other bactericides and antibiotics for controlling soft rot disease of tomato caused by P. carotovorum.

Involvement of BcElp4 in vegetative development, various environmental stress response and virulence of Botrytis cinerea

The Saccharomyces cerevisiae Elongator complex consisting of the six Elp1-Elp6 proteins has been proposed to participate in three distinct cellular processes: transcriptional elongation, polarized exocytosis and formation of modified wobble uridines in tRNA. In this study, we investigated the function of BcElp4 in Botrytis cinerea, which is homologous to S. cerevisiae Elp4. A bcelp4 deletion mutant was significantly impaired in vegetative growth, sclerotia formation and melanin biosynthesis. This mutant exhibited decreased sensitivity to osmotic and oxidative stresses as well as cell way-damaging agent. Pathogenicity assays revealed that BcElp4 is involved in the virulence of B. cinerea. In addition, the deletion of bcelp4 led to increased aerial mycelia development. All these defects were restored by genetic complementation of the bcelp4 deletion mutant with the wild-type bcelp4 gene. The results of this study indicated that BcElp4 is involved in regulation of vegetative development, various environmental stress response and virulence in B. cinerea.

Edible coating composed of chitosan and Salvia fruticosa Mill. extract for the control of grey mould of table grapes

BACKGROUND

Consumer concerns regarding high-quality produce, free of pesticide residues, direct research towards disease management strategies that minimise or even exclude the use of synthetic chemistries in crop production. The efficacy of a chitosan-based edible coating combined with the acetonic extract of Salvia fruticosa Mill. (ASF) was assessed against the grey mould of table grapes.

RESULTS

HPLC-SPE-NMR and q-NMR analyses defined major constituents of ASF to be the flavonoids hispidulin, salvigenin and cirsimaritin and the diterpenes carnosic acid, carnosol and the 12-methoxycarnosic acid. The extract was found to be efficacious in reducing spore germination and mycelial growth of Botrytis cinerea in vitro at 10 and 25 °C. However, the combination of the ASF with chitosan 1% (w/v; CHIT) significantly improved fungal inhibition. Similarly, in fruit inoculation trials at 10 °C, the efficacy of the combined application of the ASF at 500 mg L^-1 with CHIT against grey mould was statistically equal to the synthetic fungicide thiabendazole, ranging from 98.4% to 92.7% at 12 and 21 days post-inoculation, respectively. Furthermore, chitosan coating alone and in combination with ASF decreased the rate of fruit weight loss during cold storage, while preserved soluble solids content and titratable acidity. Chitosan-based coatings did not affect quality attributes and the bioactive compounds in table grapes.

CONCLUSION

The combined application of the ASF in the form of an edible coating with chitosan could effectively control B. cinerea without deteriorating quality and physico-chemical properties of grapes. © 2016 Society of Chemical Industry.

Antibacterial activity of resin composites containing surface pre-reacted glass-ionomer (S-PRG) filler

OBJECTIVE

A surface pre-reacted glass-ionomer (S-PRG) filler is a technology of interest for providing bio-functions to restorative materials. Resin composites containing S-PRG filler have been reported to show less plaque accumulation and reduced bacterial attachment. In this study, experimental resin composites containing S-PRG filler at various concentrations were fabricated, and the inhibitory effects on bacterial growth on their surface and the association of ions released from S-PRG filler with antibacterial activity were evaluated.

METHODS

Five kinds of experimental resin composites containing S-PRG filler at 0, 13.9, 27.3, 41.8, or 55.9 (vol.%) were fabricated. Streptococcus mutans was cultured on the cured discs for 18h to examine the growth of bacteria in contact with the surface of the experimental resins. The concentrations of Al(3+), BO3(3-), F(-), Na(+), SiO3(2-), or Sr(2+) released from each experimental resin into water were measured. The standardized solutions of each ion were prepared at the concentrations determined to be released from the experimental resin, and their inhibitory effects of single ion species on S. mutans growth were evaluated by using each standardized solution.

RESULTS

Resin composites containing S-PRG filler at 13.9 (vol.%) or greater inhibited S. mutans growth on their surface. When S. mutans was incubated in the presence of six kinds of ions at the concentrations released from the resin composite containing S-PRG filler at 55.9 (vol.%), a significant reduction in bacterial number was observed for BO3(3-), F(-), Al(3+), and SiO3(2-). Among these four ions, BO3(3-) and F(-) demonstrated the strongest inhibitory effect on S. mutans growth.

SIGNIFICANCE

Our findings suggest that resin composites containing S-PRG filler inhibit the growth of S. mutans on their surface. BO3(3-), F(-), Al(3+) and SiO3(2-) released from S-PRG filler have the ability to inhibit S. mutans growth, and the inhibitory effects are mainly attributed to release of BO3(3-) and F(-).

Induction of Direct or Priming Resistance against Botrytis cinerea in Strawberries by β-Aminobutyric Acid and Their Effects on Sucrose Metabolism

The specific forms of disease resistance induced by β-aminobutyric acid (BABA) and their impacts on sucrose metabolism of postharvest strawberries were determined in the present research. Treatment with 10-500 mmol L(-1) BABA inhibited the Botrytis cinerea infection, possibly directly by suppressing the fungus growth and indirectly by triggering disease resistance. Moreover, BABA-induced resistance against B. cinerea infection in strawberries was associated with either one of two mechanisms, depending upon the concentration used: BABA at concentrations higher than 100 mmol L(-1) directly induced the defense response, including a H2O2 burst, modulation of the expression of PR genes, including FaPR1, FaChi3, Faβglu, and FaPAL, and increased activities of chitinase, β-1,3-glucanase, and PAL, whereas BABA at 10 mmol L(-1) activated a priming response because the BABA-treated fruits exhibited an increased capacity to express molecular defense only when the fruits were inoculated with B. cinerea. Activation of the priming defense appeared almost as effective against B. cinerea as inducing direct defense. However, the primed strawberries maintained higher activities of SS synthesis and SPS and SPP enzymes) and lower level of SS cleavage during the incubation; these activities contributed to higher sucrose, fructose, and glucose contents, sweetness index, and sensory scores compared to fruits exhibiting the direct defense. Thus, it is plausible that the priming defense, which can be activated by BABA at relatively low concentrations, represents an optimal strategy for combining the advantages of enhanced disease protection and soluble sugar accumulation.

Aquaporin8 regulates cellular development and reactive oxygen species production, a critical component of virulence in Botrytis cinerea

Aquaporins (AQPs) are ubiquitous in nearly all organisms, mediating selective and rapid flux of water across biological membranes. The role of AQPs in phytopathogenic fungi is poorly understood. Orthologs of AQP genes in Botrytis cinerea were identified and knocked out. The effects of AQPs on hyphal growth and conidiation, formation of infection structures and virulence on plant hosts were examined. The role of AQP8 in reactive oxygen species (ROS) production, distribution and transport were further determined. Among eight AQPs, only AQP8 was essential for the ability of B. cinerea to infect plants. AQP8 was demonstrated to be an intrinsic plasma membrane protein, which may function as a channel and mediate hydrogen peroxide uptake. Deletion of AQP8 in B. cinerea completely inhibited the development of conidia and infection structures, and significantly affected noxR expression. Further observations revealed that both AQP8 and noxR impacted ROS distribution in the hyphal tips of B. cinerea. Moreover, AQP8 affected the expression of a mitochondrial protein, NQO1. A knockout mutant of NQO1 was observed to display reduced virulence. These data lead to a better understanding of the important role of AQP8 in the development and pathogenesis of plant pathogens.

Effect of Selenium on Control of Postharvest Gray Mold of Tomato Fruit and the Possible Mechanisms Involved

Selenium (Se) has important benefits for crop growth and stress tolerance at low concentrations. However, there is very little information on antimicrobial effect of Se against the economically important fungus Botrytis cinerea. In the present study, using sodium selenite as Se source, we investigated the effect of Se salts on spore germination and mycelial growth of the fungal pathogen in vitro and gray mold control in harvested tomato fruit. Se treatment at 24 mg/L significantly inhibited spore germination of the fungal pathogen and effectively controlled gray mold in harvested tomato fruit. Se treatment at 24 mg/L seems to induce the generation of intracellular reactive oxygen species in the fungal spores. The membrane integrity damage was observed with fluorescence microscopy following staining with propidium iodide after treatment of the spores with Se. These results suggest that Se has the potential for controlling gray mold rot of tomato fruits and might be useful in integrated control against gray mold disease of postharvest fruits and vegetables caused by B. cinerea. The mechanisms by which Se decreased gray mold decay of tomato fruit may be directly related to the severe damage to the conidia plasma membrane and loss of cytoplasmic materials from the hyphae.

Bis(2,3-dibromo-4,5-dihydroxybenzyl) ether, a marine algae derived bromophenol, inhibits the growth of Botrytis cinerea and interacts with DNA molecules

Bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (BDDE) is a bromophenol isolated from marine algae. Previous reports have shown that BDDE possesses cytotoxic and antibacterial activity. In the present study, we demonstrate that BDDE displays broad-spectrum antifungal activities, especially on Botrytis cinerea. BDDE inhibits the growth of B. cinerea cultured on a solid medium of potato dextrose agar (PDA) as well as on the potato dextrose broth (PDB) medium. Moreover, BDDE decreases the incidence of fruit decay and severity of strawberries infected with B. cinerea. Further studies have revealed that BDDE decreases the germination rate and inhibits the mycelial growth of B. cinerea. The inhibition mechanisms are related to the disruption of the cell membrane integrity in B. cinerea spores and newly formed germ tubes. This study also suggests that BDDE possibly interacts with DNA via intercalation and minor groove binding. The studies provide evidence that BDDE has potential application in the control of gray mold after fruit harvest and the compound could serve as a candidate or lead template for rational drug design and for the development of antifungal agents.

Boric acid inhibits germination and colonization of Saprolegnia spores in vitro and in vivo

Saprolegnia infections cause severe economic losses among freshwater fish and their eggs. The banning of malachite green increased the demand for finding effective alternative treatments to control the disease. In the present study, we investigated the ability of boric acid to control saprolegniosis in salmon eggs and yolk sac fry. Under in vitro conditions, boric acid was able to decrease Saprolegnia spore activity and mycelial growth in all tested concentrations above 0.2 g/L, while complete inhibition of germination and growth was observed at a concentration of 0.8 g/L. In in vivo experiments using Atlantic salmon eyed eggs, saprolegniosis was controlled by boric acid at concentrations ranging from 0.2-1.4 g/L during continuous exposure, and at 1.0-4.0 g/L during intermittent exposure. The same effect was observed on salmon yolk sac fry exposed continuously to 0.5 g/L boric acid during the natural outbreak of saprolegniosis. During the experiments no negative impact with regard to hatchability and viability was observed in either eggs or fry, which indicate safety of use at all tested concentrations. The high hatchability and survival rates recorded following the in vivo testing suggest that boric acid is a candidate for prophylaxis and control of saprolegniosis.