Phytopathogenic Fungus Alternaria Research Articles

Novel Aminocoumarin-Based Schiff Bases: High Antifungal Activity in Agriculture.

Structural modification is an effective way to improve the antifungal activity of natural products and has been widely used in the development of novel fungicides. In this work, a series of aminocoumarin-based Schiff bases were synthesized and characterized by 1H-NMR, 13C NMR and HR-MS spectra. The in vitro inhibition activity of all compounds was tested against four phytopathogenic fungi (Alternaria solani, Fusarium oxysporum, Botrytis cinerea, and Alternaria alternata) using the mycelial growth rate method. The results showed that most of the target compounds exhibited significant antifungal activities. In particular, compounds 5b, 5c, 5d, 5h, 5n, 7c, 7n, and 7p exhibited more effective antifungal activity than commercially available fungicides, chlorothalonil and azoxystrobin. The structure-activity relationship revealed that the electron-withdrawing groups with more electronegativity introduced at the C-3 position were effective in improving the inhibitory activity and that halogenated benzaldehydes would be necessary in the preparation of Schiff bases. The compound 5n against Fusarium oxysporum (EC50=8.73 μg/mL) and the compound 7p against Alternaria alternata (EC50=26.25 μg/mL) were much better than the positive controls (chlorothalonil and azoxystrobin). Therefore, compounds 5n and 7p could serve as promising lead compounds for the development of novel broad-spectrum fungicides, which could be useful for applications in the agriculture.

Complete genome sequence of a novel mitovirus identified in the phytopathogenic fungus Alternaria tenuissima.

In this study, a novel positive-sense single-stranded RNA (+ ssRNA) mycovirus, Alternaria tenuissima mitovirus 1 (AtMV1), was identified in Alternaria tenuissima strain YQ-2-1, a phytopathogenic fungus causing leaf blight on muskmelon. The genome of AtMV1 is a single RNA molecule that is 3013 nt in length with an A + U content of 66.58% and contains a single open reading frame (ORF) using the fungal mitochondrial genetic code. The ORF was predicted to encode a 313-amino-acid RNA-dependent RNA polymerase (RdRp) with a molecular mass of 35.48 kDa, which contains six conserved motifs with the highly conserved GDD tripeptide in motif IV. The 5' and 3' untranslated regions were predicted to fold into stem-loop and panhandle secondary structures. The results of a BLASTp search revealed that the amino acid (aa) sequence of RdRp of AtMV1 shared the highest sequence similarity (51.04% identity) with that of Sichuan mito-like virus 30, a member of the genus Duamitovirus within the family Mitoviridae. Phylogenetic analysis based on the aa sequence of the RdRp suggested that AtMV1 is a novel member of the genus Duamitovirus. To our knowledge, this is the first report of the complete genome sequence of a new mitovirus infecting A. tenuissima.

Complete genome sequence of a novel mitovirus isolated from the phytopathogenic fungus Alternaria alternata causing apple leaf blotch.

In this study, a novel mitovirus, tentatively designated as "Alternaria alternata mitovirus 2" (AaMV2), was isolated from the fungus Alternaria alternata f. sp. mali causing apple leaf blotch disease. The complete genome of AaMV2 is 3,157 nucleotides in length, with an A+U content of 68.10%. The genome has a single large open reading frame (ORF) encoding an RNA-dependent RNA polymerase (RdRp) protein with a molecular mass of 98.10 kDa. BLAST analysis revealed that AaMV2 has the highest sequence identity to Leptosphaeria biglobosa mitovirus 6, with 79.76% and 82.86% identity at the amino acid and nucleotide level, respectively. Phylogenetic analysis suggested that AaMV2 is a new member of the genus Duamitovirus within the family Mitoviridae. This is the first report of the complete genome sequence analysis of a mitovirus in A. alternata.

Determination of antifungal efficacy and phytotoxicity of a unique silica coated porous zinc oxide nanocomposite medium for slow-release agrochemicals.

In this study the antifungal efficacy and phytotoxicity of silica coated porous zinc oxide nanoparticle (SZNP) was analyzed as this nanocomposite was observed to be a suitable platform for slow release fungicides and has the promise to bring down the dosage of other agrochemicals as well. Loading and release kinetics of tricyclazole, a potent fungicide was analyzed by measuring surface area (SBET) using Brunauer-Emmett-Teller (BET) isotherm and LC-MS/MS respectively. The antifungal efficacy of ZnO nanoparticle (ZNP) and SZNP was investigated on two phytopathogenic fungi (Alternaria solani and Aspergillus niger). The morphological changes to the fungal structure due to ZNP and SZNP treatment were studied by field emission-scanning electron microscopy (FESEM). Nanoparticle mediated elevation of reactive oxygen species in fungal samples was detected by analyzing the level of superoxide dismutase, catalase, thiol content, lipid peroxidation and by 2,7-dichlorofluorescin diacetate (DCFH-DA) assay. The phytotoxicity of these two nanostructures was assessed in rice plants by measuring primary plant growth parameters. Further, the translocation of the nanocomposite in the same plant model system was examined by checking the presence of Fluorescein isothiocyanate (FITC) tagged SZNP within the plant tissue. ZNP had superior antifungal efficacy than SZNP and caused generation of more reactive oxygen species (ROS) in the fungal samples. Even then SZNP was preferred as an agrochemical delivery vehicle because unlike ZNP alone it was not toxic to plant system. Moreover, as silica in nano form is entomotoxic in nature and nano ZnO has antifungal property, both the cargo (agrochemical) and the carrier system (silica coated porous nano zinc oxide) will have a synergistic effect in crop protection.

Revealing the diversity of Jojoba-associated fungi using amplicon metagenome approach and assessing the in vitro biocontrol activity of its cultivable community.

Jojoba shrubs are wild plants cultivated in arid and semiarid lands and characterized by tolerance to drought, salinity, and high temperatures. Fungi associated with such plants may be attributed to the tolerance of host plants against biotic stress in addition to the promotion of plant growth. Previous studies showed the importance of jojoba as jojoba oil in the agricultural field; however, no prior study discussed the role of jojoba-associated fungi (JAF) in reflecting plant health and the possibility of using JAF in biocontrol. Here, the culture-independent and culture-dependent approaches were performed to study the diversity of the jojoba-associated fungi. Then, the cultivable fungi were evaluated for in-vitro antagonistic activity and in vitro plant growth promotion assays. The metagenome analysis revealed the existence of four fungal phyla: Ascomycota, Aphelidiomycota, Basidiomycota, and Mortierellomycota. The phylum Ascomycota was the most common and had the highest relative abundance in soil, root, branch, and fruit samples (59.7%, 50.7%, 49.8%, and 52.4%, respectively). Alternaria was the most abundant genus in aboveground tissues: branch (43.7%) and fruit (32.1%), while the genus Discosia had the highest abundance in the underground samples: soil (24%) and root (30.7%). For the culture-dependent method, a total of 14 fungi were isolated, identified, and screened for their chitinolytic and antagonist activity against three phytopathogenic fungi (Fusarium oxysporum, Alternaria alternata and Rhizoctonia solani) as well as their in vitro plant growth promotion (PGP) activity. Based on ITS sequence analysis, the selected potent isolates were identified as AspergillusstellatusEJ-JFF3, Aspergillusflavus EJ-JFF4, Stilbocreasp. EJ-JLF1, Fusariumsolani EJ-JRF3, and AmesiaatrobrunneaEJ-JSF4. The endophyte strain A. flavus EJ-JFF4 exhibited the highest chitinolytic activity (9 Enzyme Index) and antagonistic potential against Fusarium oxysporum, Alternaria alternata, and Rhizoctonia solani phytopathogens with inhibitory percentages of 72, 70, and 80 respectively. Also, A. flavus EJ-JFF4 had significant multiple PGP properties, including siderophore production (69.3%), phosphate solubilization (95.4 µg ml-1). The greatest production of Indol-3-Acetic Acid was belonged to A.atrobrunnea EJ-JSF4 (114.5 µg ml-1). The analysis of FUNGuild revealed the abundance of symbiotrophs over other trophic modes, and the guild of endophytes was commonly assigned in all samples. For the first time, this study uncovered fungal diversity associated with jojoba plants using a culture-independent approach and in-vitro assessed the roles of cultivable fungal strains in promoting plant growth and biocontrol. The present study indicated the significance of jojoba shrubs as a potential source of diverse fungi with high biocontrol and PGP activities.

Cynara cardunculus L. var. scolymus L. Landrace "Carciofo Ortano" as a Source of Bioactive Compounds.

The preservation of agricultural biodiversity and socioeconomic development are relevant both to enhance domestic production and to support innovation. In the search for new biomolecules, we have focused on the "Carciofo Ortano" landrace, growth in the northern part of the Lazio region. Artichoke cultivation generates substantial by-products, including leaves, stems, and roots, which could serve as valuable sources of biomolecules and prebiotic dietary fiber. To valorize the leaf waste of the "Carciofo Ortano" landrace, a multidisciplinary approach was applied. Chemical analysis using HPLC-DAD identified mono-O- and di-O-caffeoylquinic acids and the sesquiterpene cynaropicrin in all artichoke leaf extracts. SPME-GC/MS analyses detected aliphatic alcohols in the fresh leaf samples. Antiproliferative and cytotoxic studies on cancer (SH-SY5Y, MCF-7, MDA) and normal (MCF-10A) human cell lines revealed that leaf extracts induced a selective dose and time-dependent biological effect. While showing slight activity against environmental bacterial strains, artichoke leaf extracts exhibited significant antifungal activity against the phytopathogenic fungus Alternaria alternata. Overall, the results highlight the potential of "Carciofo Ortano" cultivation by-products as a rich source of biomolecules with versatile applications in humans, animals, and the environment.

Curcumin: An innovative approach for postharvest control of Alternaria alternata induced black rot in cherry tomatoes

Curcumin, a natural bioactive compound derived from Curcuma longa, has been widely recognized for its antifungal properties. In this study, we investigated the effects of curcumin on the phytopathogenic fungus Alternaria alternata and its pathogenicity in cherry tomato fruit. The results demonstrated that curcumin treatment significantly inhibited mycelial growth and spore germination of A. alternata in a dose-dependent manner. Scanning electron microscopy revealed alterations in the morphology of A. alternata mycelia treated with curcumin. Furthermore, curcumin treatment led to an increase in malondialdehyde and hydrogen peroxide contents, indicating cell membrane damage in A. alternata. Moreover, curcumin exhibited a remarkable inhibitory effect on the incidence and lesion diameters of black rot caused by A. alternata in cherry tomato fruit. Gene expression analysis revealed upregulation of defense-related genes (POD, SOD, and CAT) in tomato fruit treated with curcumin. Additionally, curcumin treatment resulted in decreased activity of exocellular pathogenic enzymes (polygalacturonase, pectin lyase, and endo-1,4-β-d-glucanase) in A. alternata. Overall, our findings highlight the potential of curcumin as an effective antifungal agent against A. alternata, providing insights into its inhibitory mechanisms on mycelial growth, spore germination, and pathogenicity in cherry tomato fruit.

Antifungal Activity of Streptomyces hygroscopicus JY-22 against Alternaria alternata and Its Potential Application as a Biopesticide to Control Tobacco Brown Spot

Tobacco brown spot caused by Alternaria alternata is a devastating fungal disease endangering plant production. To effectively control brown spot disease, an antagonistic Actinomyces strain, Streptomyces hygroscopicus JY-22, was isolated from rhizospheric soil, which remarkably restrains the growth of phytopathogenic fungus Alternaria alternata. This antagonistic strain and its culture filtrate showed significant antifungal activity against Alternaria alternata. Firstly, the confrontation culture method of strains JY-22 and Alternaria alternata showed that Streptomyces hygroscopicus JY-22 had noticeable antifungal activity against Alternaria alternata, including inhibition of mycelial growth and mycelial morphological changes, compared with the control group. Furthermore, the culture filtrate of Streptomyces hygroscopicus JY-22 showed substantial inhibition of the mycelial growth and spore germination of Alternaria alternata in a dose-dependent manner. Additional studies revealed that these antifungal actions were mainly related to membrane-active mechanisms that increased membrane permeability and damaged the cell membrane, leading to changes in certain cytoplasmic properties, such as extracellular conductivity and ergosterol, MDA and soluble protein content. In detached-leaf and field experiments, foliar spraying with culture filtrate resulted in smaller lesions and a lower disease index than the control group. Taken together, these results suggest that Streptomyces hygroscopicus JY-22 and its culture filtrate have the potential to be a safe biopesticide for the bio-control of tobacco brown spot.

Evaluation of hydrolytic enzymes and antifungal activity of extracellular bioactive compounds of Desmonostoc alborizicum and Neowestiellopsis persica against Plant Pathogenic Fungi

Agriculture requires the extensive use of chemical pesticides to protect crops against pests and diseases. An important mechanism for the biological control of pathogenic fungi is the breakdown of their cell walls. Cyanobacteria are found commonly growing as blooms which provides a competitive advantage to these organisms. This is one of the critical factors responsible for the production of several hydrolytic enzymes with antifungal activity. However, the role of the hydrolytic enzymes of Neowestiellopsis and Desmonostoc, which are implicated in the fungicidal activity of several biocontrol strains, has not been explored. Therefore in this study, hydrolytic enzymes (chitosanase, protease, FPase, carboxymethyl cellulose, xylanase, cellobiohydrolases and cellobiase) of two cyanobacteria strains were evaluated against a set of phytopathogenic fungi (Alternaria alternata, Fusarium solani, Fusarium oxysporum, Macrophomina phaseolina, Verticillium dahliae and Phytophthora). The results of statistical analysis showed that the level of protease, FPase and xylanase activity in Desmonostoc alborizicum cyanobacterial extract has been significantly higher than in Neowestiellopsis. Moreover, IAA hormone activity and soluble protein content were significantly higher in Desmonostoc alborizicum cyanobacterial extract. While CMCase, cellobiohydrolases, cellobiase, and chitosanase activity was significantly higher in Neowestiellopsis persica A1387 cyanobacterial extract in comparison to Desmonostoc alborizicum. Moreover, Neowestiellopsis persica was observed to be highly potent in terms of its fungicidal activity. Comparative evaluation of the activity of hydrolytic enzymes and antifungal activity revealed that such enzymes might contribute to the fungicidal activity of the cyanobacterial strains, besides other bioactive compounds, including IAA, which are established promising traits for biocontrol agents. This study is a first-time report on the production of hydrolytic enzymes by these two cyanobacteria strains, which can be potential candidates for the development of biocontrol agent(s) against selected phytopathogenic fungi.

Synthesis and biological activities of some new antimicrobial and cytotoxic 5-/7-/8-phenylphenalenone derivatives

Utilizing a facile method, sixty-three analogs of the 5-/7-/8-phenylphenalenone core were synthesized, of which sixty compounds are new. These compounds were systematically evaluated for their biological activities against phytopathogenic fungi (Alternaria solani, Cercospora arachidicola, Fusarium oxysporum, Gibberella zeae and Physalospora piricola), the tobacco mosaic virus (TMV), as well as human cancer cell lines (p53-wild-type HCT-116 colon cancer cells, p53-mutated HT-29 colon cancer cells, PANC-1 pancreatic cancer cells, and PC-3 prostate cancer cells). 5p and 8m showed a broader fungicidal spectrum of activity among all of the target compounds and are worthy of further structural optimization to develop more potent fungicidal agents. Some of the effects of 7c and 8m (inactivation, curing, or protection) against TMV infection were more efficient than the commercial antiviral agents' ribavirin and ningnanmycin. These analogs could be selected as potential antiviral hit compounds. Cytotoxic compound 7c (IC50 1.8 μM in HT-29 cells) is worth pursuing for further structural modification to achieve a higher antitumor potency.

Evaluation of Magonia pubescens A. St.-Hill. Roots Extract against Phytopathogens: Searching for Eco-Friendly Crop Protection Products

Botanical biopesticides have emerged as sustainable and eco-friendly alternatives to synthetic pesticides, whose indiscriminate use leads to several drawbacks to human and environmental health. To the best of our knowledge, there have been no reports on M. pubescens’ bioactivity on phytopathogens affecting crops as a potential fungicide or antifeedant. This has encouraged us to investigate the potential of the roots of this plant as a source of biopesticides. The present study reports on the evaluation of the roots extract from Magonia pubescens A. St.-Hill., a species from the Cerrado (Brazilian savannah), on the phytopathogenic fungi Botrytis cinerea, Fusarium oxysporum, and Alternaria alternata. In addition, its insect antifeedant effect was assayed against Chrysodeixis chalcites. Thus, an in vitro test-assay was used to determine the fungicide potential (percentage growth inhibition, % GI) of the ethanolic extract of this plant species, whereas a leaf-disk bioassay on the 5th instar larvae of C. chalcites was performed to evaluate its insecticidal potential. The ethanolic extract was further fractionated by liquid–liquid partition using solvents of increasing polarity. The hexane/dichloromethane fraction exhibited a moderated potency and was similar to the ethanolic extract on the three assayed fungi (around % GI 30 at 1 mg/mL), whereas the n-butanol fraction showed a slight improvement of the fungicide effect against B. cinerea (% GI 39.18 at 1 mg/mL). Moreover, the ethanolic extract exhibited a strong antifeedant activity, with a refusal rate (FR) higher than 90% in both choice and non-choice assays against C. chalcites, while the ethyl acetate and n-butanol fractions behaved as appetite suppressors. These results highlight M. pubescens as a promising source of biopesticides and deserve further investigations to optimize extraction procedures.

The Regulatory Hub of Siderophore Biosynthesis in the Phytopathogenic Fungus Alternaria alternata.

A GATA zinc finger-containing repressor (AaSreA) suppresses siderophore biosynthesis in the phytopathogenic fungus Alternaria alternata under iron-replete conditions. In this study, targeted gene deletion revealed two bZIP-containing transcription factors (AaHapX and AaAtf1) and three CCAAT-binding proteins (AaHapB, AaHapC, and AaHapE) that positively regulate gene expression in siderophore production. This is a novel phenotype regarding Atf1 and siderophore biosynthesis. Quantitative RT-PCR analyses revealed that only AaHapX and AaSreA were regulated by iron. AaSreA and AaHapX form a transcriptional feedback negative loop to regulate iron acquisition in response to the availability of environmental iron. Under iron-limited conditions, AaAtf1 enhanced the expression of AaNps6, thus playing a positive role in siderophore production. However, under nutrient-rich conditions, AaAtf1 plays a negative role in resistance to sugar-induced osmotic stress, and AaHapX plays a negative role in resistance to salt-induced osmotic stress. Virulence assays performed on detached citrus leaves revealed that AaHapX and AaAtf1 play no role in fungal pathogenicity. However, fungal strains carrying the AaHapB, AaHapC, or AaHapE deletion failed to incite necrotic lesions, likely due to severe growth deficiency. Our results revealed that siderophore biosynthesis and iron homeostasis are regulated by a well-organized network in A. alternata.

Влияние депонированной формы комплексного пестицидного препарата на структуру урожая зерновых культур и заболеваемость корневыми гнилями

The use of chemical plant protection products is essential to obtain a quality crop, but entails the risks of spreading pesticides in the biosphere and causing damage to beneficial biota. Therefore, the development of new approaches to the delivery of pesticides, which reduce the negative impact on agroecosystems, is an important direction for sustainable agriculture development. The effect of a complex preparation containing the fungicide tebuconazole and the herbicide tribunuron-methyl, embedded in a biodegradable polymer base of poly(3-hydroxybutyrate) and birch sawdust, on the several indicators was studied: the number of rhizospheric micromycetes of spring wheat cv. Novosibirskaya 15 and spring barley cv. Biom, the effectiveness of root pathogens control, and the structure and quality of the crop. In field experiments, a prolonged fungicidal action of the complex embedded preparation was demonstrated, which was superior in duration and efficiency to the traditional pre-sowing seed dressing. During the growing season, there was a significant (p <0.05) decrease in the number of micromycetes in the rhizosphere of wheat and barley by 1.5-2 times in comparison with the control, as well as a decrease in the prevalence of root phytopathogenic fungi (Alternaria, Bipolaris, and Fusarium). A high level of biological efficiency of the embedded fungicide was demonstrated in different phases of plant development - from 73.4 to 100% on wheat and from 68 to 100% on barley. As a result, the use of a complex embedded preparation increased the yield of spring wheat and barley, respectively, by 10.8 and 4.4 c/ha compared to the control and contributed to the improvement of the grain quality of crops. Keywords: PESTICIDES, EMBEDDING, TEBUCONAZOL, TRIBUNURON-METHYL, POLY(3-HYDROXYBUTYRATE), ROOT ROTS, YIELD, WHEAT, BARLEY

Biosynthesis of Novel Tellurium Nanorods by Gayadomonas sp. TNPM15 Isolated from Mangrove Sediments and Assessment of Their Impact on Spore Germination and Ultrastructure of Phytopathogenic Fungi

The biosynthesis of nanoparticles using green technology is emerging as a cost-efficient, eco-friendly and risk-free strategy in nanotechnology. Recently, tellurium nanoparticles (TeNPs) have attracted growing attention due to their unique properties in biomedicine, electronics, and other industrial applications. The current investigation addresses the green synthesis of TeNPs using a newly isolated mangrove-associated bacterium, Gayadomonas sp. TNPM15, and their impact on the phytopathogenic fungi Fusarium oxysporum and Alternaria alternata. The biogenic TeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR). The results of TEM revealed the intracellular biosynthesis of rod-shaped nanostructures with a diameter range from 15 to 23 nm and different lengths reaching up to 243 nm. Furthermore, the successful formation of tellurium nanorods was verified by SEM-EDX, and the XRD pattern revealed their crystallinity. In addition, the FTIR spectrum provided evidence for the presence of proteinaceous capping agents. The bioinspired TeNPs exhibited obvious inhibitory effect on the spores of both investigated phytopathogens accomplished with prominent ultrastructure alternations, as evidenced by TEM observations. The biogenic TeNPs impeded spore germination of F. oxysporum and A. alternata completely at 48.1 and 27.6 µg/mL, respectively. Furthermore, an increase in DNA and protein leakage was observed upon exposure of fungal spores to the biogenic TeNPs, indicating the disruption of membrane permeability and integrity. Besides their potent influence on fungal spores, the biogenic TeNPs demonstrated remarkable inhibitory effects on the production of various plant cell wall-degrading enzymes. Moreover, the cytotoxicity investigations revealed the biocompatibility of the as-prepared biogenic TeNPs and their low toxicity against the human skin fibroblast (HSF) cell line. The biogenic TeNPs showed no significant cytotoxic effect towards HSF cells at concentrations up to 80 μg/mL, with a half-maximal inhibitory concentration (IC50) value of 125 μg/mL. The present work spotlights the antifungal potential of the biogenic TeNPs produced by marine bacterium against phytopathogenic fungi as a promising candidate to combat fungal infections.

In vitro efficacy of herbal plant extracts on some phytopathogenic fungi

Crops are subject to yield losses caused by the presence of pests whose species and population diversity are changing with climate warming. The use of agrochemicals is still the most effective method of plant protection against diseases and pests. However, the intensive use of pesticides in some EU countries makes it necessary to search for alternative methods that can be applied in plant protection for consumer and environmental safety. The aim of the study was the laboratory evaluation of the fungistatic effect of extracts of herbal plants occurring in natural state in Poland: horseradish (Armoracia rusticana L.), yarrow (Achillea millefolium L.) and tansy (Tanacetum vulgare L.) on selected polyphagic phytopathogenic fungi (Alternaria alternata, Botrytis cinerea, Colletotrichum coccodes and Fusarium oxysporum). In this study, 5%, 10% and 20% concentrations of herbal water-extract extracts were applied to evaluate their effects on linear growth of fungi and inhibition of their growth relative to control. Total content of polyphenols and flavonoids was assessed in the extracts using spectrophotometry, and their antioxidant activity by applying the synthetic DPPH radical. The plant extracts of tansy and yarrow leaves were characterized by a higher content of polyphenols and flavonoids compared to horseradish leaf extracts; they also had a higher antioxidant activity. Plant extracts inhibited the growth of fungi to a different extent, depending on the species of fungus, type of extract, its concentration and duration of action. The strongest fungistatic effect was recorded for tansy and yarrow extracts, while the weakest for the extract of horseradish leaves. Plant extracts showed the weakest effect against Botrytis cinerea, inhibiting the development of this fungus only during the first days of the experiment. The present research is a preliminary study that will be used in the further to develop a biological preparation for the protection of agricultural and horticultural plants against fungal pathogens.

Synthesis and Biological Activities Assessment of 4‐, 6‐, and 9‐Phenylphenalenone Derivatives

AbstractBy means of a facile method, sixty analogs of 4‐, 6‐, and 9‐phenylphenalenone were synthesized, of which forty‐nine compounds are novel. These synthesized compounds were first evaluated for their biological activities against phytopathogenic fungi(Alternaria solani,Cercospora arachidicola,Fusarium omysporum,Gibberella zeae, andPhysalospora piricola), tobacco mosaic virus (TMV), as well as human cancer cells (p53‐wild‐type HCT‐116 colon cancer cells, p53‐mutated HT‐29 colon cancer cells, PANC‐1 pancreatic cancer cells, and PC‐3 prostate cancer cells) systematically.9 owas sufficiently effective against all the tested phytofungal strains and is worth further structural optimization for developing into a more potent fungicidal agent. Some effects of6 oand9 d(inactivation, curing, or protection) against TMV infection were more efficient than the commercial antiviral agents ribavirin and ningnanmycin. These could be selected as potential antiviral lead compounds. With regards to cytotoxicity, the cytotoxic compounds6 p(IC501.6 μM in HCT‐116 cells) and9 c(IC502.6 μM in PC‐3 cells) are worth further structural modification to achieve a higher antitumor potency.

Evaluation of The Spirulina (Arthrospira platensis Gomont) Antimicrobial Activity

The present work was carried out to enhance biomass production of Spirulina (Arthrospira platensis Gomont) in a modified medium and to investigate “in vitro” its ability to produce antimicrobial substances against pathogenic bacteria and phytopathogenic fungi. The antibacterial activity was evaluated by the solid medium diffusion method on two pathogenic bacteria (Bacillus cereus & Klebsiella sp.), And the antifungal activity was evaluated on three phytopathogenic fungi (Alternaria solani, Cladosporium sp., Fusarium culmorum). The antibacterial test showed that the aqueous extract produced by S. platensis was more active against Gram-positive than on Gram-negative bacteria, the highest antibacterial activity was recorded against Bacillus cereus. Moreover, the Antifungal test showed that the aqueous extract was active against all three tested fungi and the highest antifungal activity was recorded against F. culmorum with over 90% inhibition of mycelial growth. The results of this research proved that cyanobacteria could be a good source for the production of antimicrobial agents which could be effective when compared with contemporary antimicrobial compounds and it can be used in the Biocontrol of several plant fungal diseases.

Antifungal Potential of Canarian Plant Extracts against High-Risk Phytopathogens.

Phytopathogens are responsible for great losses in agriculture. In particular, Fusarium, Alternaria and Botrytis are fungal diseases that affect crops worldwide. In the search for eco-friendly solutions to pest control, plants and their chemo-biodiversity are promising sources of biopesticides for integrated pest management. The aim of the present study is to report the evaluation of sixteen plant species from the Canary Islands Archipelago against the phytopathogenic fungi Botrytis cinerea, Fusarium oxysporum, and Alternaria alternata. The plants were selected on the basis of their traditional uses in medicine and/or pest control, as well as on scientific studies reporting their uses in crop protection. Their growth inhibition (% I), in an in vitro test-assay on mycelium, was used to identify six ethanolic plant extracts displaying activity (% I > 30% at 1 mg/mL) against at least one of the assayed fungi. The most effective plant extracts were further fractionated by liquid-liquid partition, using solvents of increasing polarity. This procedure led to an improvement of the bioactivity against the phytopathogens, even affecting the hexane fraction from S. canariensis and achieving an 83.93% of growth inhibition at 0.5 mg/mL on B. cinerea. These findings identified five plant-derived extracts as potential candidates for the future development of new biofungicides, which could be applied in integrated pest management.

Novel and diverse mycoviruses co-infecting a single strain of the phytopathogenic fungus Alternaria dianthicola.

Alternaria dianthicola is a pathogenic fungus that causes serious leaf or flower blight on some medicinal plants worldwide. In this study, multiple dsRNA bands in the range of 1.2-10 kbp were found in a Alternaria dianthus strain HNSZ-1, and eleven full-length cDNA sequences of these dsRNA were obtained by high-throughput sequencing, RT-PCR detection and conventional Sanger sequencing. Homology search and phylogenetic analyses indicated that the strain HNSZ-1 was infected by at least nine mycoviruses. Among the nine, five viruses were confirmed to represent novel viruses in the families Hypoviridae, Totiviridae, Mymonaviridae and a provisional family Ambiguiviridae. Virus elimination and horizontal transmission indicated that the (-) ssRNA virus, AdNSRV1, might be associated with the slow growth and irregular colony phenotype of the host fungus. As far as we know, this is the first report for virome characterization of A. dianthus, which might provide important insights for screening of mycovirus for biological control and for studying of the interactions between viruses or viruses and their host.

Histone Methylation Is Required for Virulence, Conidiation, and Multi-Stress Resistance of Alternaria alternata

Histone methylation, which is critical for transcriptional regulation and various biological processes in eukaryotes, is a reversible dynamic process regulated by histone methyltransferases (HMTs) and histone demethylases (HDMs). This study determined the function of 5 HMTs (AaDot1, AaHMT1, AaHnrnp, AaSet1, and AaSet2) and 1 HDMs (AaGhd2) in the phytopathogenic fungus Alternaria alternata by analyzing targeted gene deletion mutants. The vegetative growth, conidiation, and pathogenicity of ∆AaSet1 and ∆AaSet2 were severely inhibited indicating that AaSet1 and AaSet2 play critical roles in cell development in A. alternata. Multiple stresses analysis revealed that both AaSet1 and AaSet2 were involved in the adaptation to cell wall interference agents and osmotic stress. Meanwhile, ∆AaSet1 and ∆AaSet2 displayed serious vegetative growth defects in sole carbon source medium, indicating that AaSet1 and AaSet2 play an important role in carbon source utilization. In addition, ∆AaSet2 colony displayed white in color, while the wild-type colony was dark brown, indicating AaSet2 is an essential gene for melanin biosynthesis in A. alternata. AaSet2 was required for the resistance to oxidative stress. On the other hand, all of ∆AaDot1, ∆AaHMT1, and ∆AaGhd2 mutants displayed wild-type phenotype in vegetative growth, multi-stress resistance, pathogenicity, carbon source utilization, and melanin biosynthesis. To explore the regulatory mechanism of AaSet1 and AaSet2, RNA-seq of these mutants and wild-type strain was performed. Phenotypes mentioned above correlated well with the differentially expressed genes in ∆AaSet1 and ∆AaSet2 according to the KEGG and GO enrichment results. Overall, our study provides genetic evidence that defines the central role of HMTs and HDMs in the pathological and biological functions of A. alternata.