Fusarium Culmorum Strains Research Articles

Pullulan-based films impregnated with silver nanoparticles from the Fusarium culmorum strain JTW1 for potential applications in the food industry and medicine.

Introduction: Biopolymers, such as pullulan, a natural exopolysaccharide from Aureobasidium pullulans, and their nanocomposites are commonly used in the food, pharmaceutical, and medical industries due to their unique physical and chemical properties. Methods: Pullulan was synthesized by the A. pullulans ATCC 201253 strain. Nanocomposite films based on biosynthesized pullulan were prepared and loaded with different concentrations of silver nanoparticles (AgNPs) synthesized by the Fusarium culmorum strain JTW1. AgNPs were characterized by transmission electron microscopy, Zeta potential measurements, and Fourier-transform infrared spectroscopy. In turn, the produced films were subjected to physico-chemical analyses such as goniometry, UV shielding capacity, attenuated total reflection-Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, and their mechanical and degradation properties were assessed. The antibacterial assays of the nanoparticles and the nanocomposite films against both food-borne and reference pathogens, including Listeria monocytogenes, Salmonella infantis, Salmonella enterica, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, were performed using standard methods. Results: AgNPs were small (mean 15.1nm), spherical, and displayed good stability, being coated with protein biomolecules. When used in higher concentrations as an additive to pullulan films, they resulted in reduced hydrophilicity and light transmission for both UV-B and UV-A lights. Moreover, the produced films exhibited a smooth surface. Therefore, it can be concluded that the addition of biogenic AgNPs did not change the morphology and texture of the films compared to the control film. The nanoparticles and nanocomposite films demonstrated remarkable antibacterial activity against both food-borne and reference bacteria. The highest activity of the prepared films was observed against L. monocytogenes. Discussion: The obtained results suggest that the novel nanocomposite films prepared from biosynthesized pullulan and AgNPs can be considered for use in the development of medical products and food packaging. Moreover, this is the first report on pullulan-based nanocomposites with mycogenic AgNPs for such applications.

Biogenic nanosilver bearing antimicrobial and antibiofilm activities and its potential for application in agriculture and industry.

Due to the increasing resistance of bacteria and fungi to antimicrobials, it is necessary to search for effective alternatives to prevent and treat pathogens causing diseases in humans, animals, and plants. In this context, the mycosynthesized silver nanoparticles (AgNPs) are considered as a potential tool to combat such pathogenic microorganisms. AgNPs were synthesized from Fusarium culmorum strain JTW1 and characterized by Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Nanoparticle Tracking Analysis (NTA), Dynamic Light Scattering (DLS) and Zeta potential measurement. The minimum inhibitory (MIC) and biocidal concentrations (MBC) were determined against 13 bacterial strains. Moreover, the combined effect of AgNPs with antibiotics (streptomycin, kanamycin, ampicillin, tetracycline) was also studied by determining the Fractional Inhibitory Concentration (FIC) index. The anti-biofilm activity was examined by crystal violet and fluorescein diacetate (FDA) assays. Furthermore, antifungal activity of AgNPs was evaluated against a panel of phytopathogenic fungi viz., Botrytis, Colletotrichum, Fusarium, Phoma, Sclerotinia, and an oomycete pathogen Phytophthora by agar well-diffusion and micro-broth dilution method to evaluate the minimal AgNPs concentrations that inhibit fungal spore germination. Fungi-mediated synthesis resulted in the formation of small (15.56 ± 9.22 nm), spherical and stable (zeta potential of - 38.43 mV) AgNPs with good crystallinity. The results of FTIR spectroscopy indicated the presence of various functional groups, namely hydroxyl, amino, and carboxyl ones, from the biomolecules on the surface of AgNPs. The AgNPs showed antimicrobial and antibiofilm formation activities against Gram-positive and Gram-negative bacteria. The values of MIC and MBC ranged between 16-64 and 32-512 μg mL-1, respectively. The enhanced effect of AgNPs in combination with antibiotics was confirmed against human pathogens. The highest synergistic effect (FIC = 0.0625) was demonstrated by the combination of AgNPs with streptomycin against two strains of Escherichia coli (ATCC 25922 and ATCC 8739), followed by Klebsiella pneumoniae and Pseudomonas aeruginosa (FIC = 0.125). Enhanced effects of AgNPs with ampicillin were also shown against Staphylococcus aureus ATCC 25923 (FIC = 0.125) and P. aeruginosa (FIC = 0.25), as well as kanamycin against S. aureus ATCC 6538 (FIC = 0.25). The crystal violet assay revealed that the lowest concentration of AgNPs (0.125 μg mL-1) reduced the development of biofilms of Listeria monocytogenes and Salmonella enterica, while the maximum resistance was shown by Salmonella infantis, its biofilm was reduced after exposure to a concentration of 512 μg mL-1. A high inhibitory effect on the activity of bacterial hydrolases was observed by the FDA assay. AgNPs at a concentration of 0.125 μg mL-1 reduced the hydrolytic activity of all biofilms formed by the tested pathogens, except E. coli ATCC 25922, P. aeruginosa, and Pectobacterium carotovorum (efficient concentration was 2-fold higher, at 0.25 μg mL-1), while the hydrolytic activity of E. coli ATCC 8739, Salmonella infantis and S. aureus ATCC 6538 was suppressed after treatment with AgNPs at concentrations of 0.5, 2 and 8 μg mL-1, respectively. Moreover, AgNPs inhibited fungal growth and spore germination of Botrytis cinerea, Phoma lingam, and Sclerotinia sclerotiorum. MIC and MFC values of AgNPs against spores of these fungal strains were determined at 64, 256, and 32 μg mL-1, and zones of growth inhibition were 4.93, 9.54, and 3.41 mm, respectively. Fusarium culmorum strain JTW1 was found to be an eco-friendly biological system for an easy, efficient and inexpensive synthesis of AgNPs. In our study, the mycosynthesised AgNPs demonstrated remarkable antimicrobial (antibacterial and antifungal) and antibiofilm activities against a wide range of human and plant pathogenic bacteria and fungi singly and in combination with antibiotics. These AgNPs could be applied in medicine, agriculture, and food industry to control such pathogens that cause numerous human diseases and crop losses. However, before using them extensive animal studies are required to evaluate the toxicity, if any.

Varietal resistance of Algerian bread wheat against Fusarium culmorum, the main agent of crown rot on wheat

Fusarium crown rot (FCR) is one of the serious wheat diseases. FC11 is one strain among 34 isolates obtained in a previous study, and identified as Fusarium culmorum strain highly pathogenic. FC11 was assigned the accession number MW151664 by NCBI GenBank. Two resistance/sensitivity tests were conducted on 9 cultivars (cv) of bread wheat. The In vitro test in the oven with the parameters; percentage of germination inhibition (%GI), to determine the tolerance of seedlings germination, and the Area Under the Disease Progress Curve (AUDPC) to test the tolerance to the initial infection of germinated coleoptiles. In in-vivo test in the growth chamber, the disease severity (DS) parameter used to test the cultivars ability to tolerate FCR induced by F. culmorum. The results showed that all cultivars were susceptible to FC11 with a significant decrease in germination and coleoptile emergence rate with GI% and AUDPC values reached up to 68.35, and 68.98% for cv. Boumerzoug and Hidhab, respectively. The cv. Bordj Mehis and Ain Abid showed significant susceptibility to F. culmorum, where length of the vegetative system and fresh weight (RCL% and RCW%) were negatively affected up to 28.66 and 56.66%, respectively. In this work, the cv. Akhamokh showed an interesting level of FCR tolerance among other cultivars tested.

Trichoderma versus Fusarium—Inhibition of Pathogen Growth and Mycotoxin Biosynthesis

This study evaluated the ability of selected strains of Trichoderma viride, T. viridescens, and T. atroviride to inhibit mycelium growth and the biosynthesis of mycotoxins deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEN), α-(α-ZOL) and β-zearalenol (β-ZOL) by selected strains of Fusarium culmorum and F. cerealis. For this purpose, an in vitro experiment was carried out on solid substrates (PDA and rice). After 5 days of co-culture, it was found that all Trichoderma strains used in the experiment significantly inhibited the growth of Fusarium mycelium. Qualitative assessment of pathogen-antagonist interactions showed that Trichoderma colonized 75% to 100% of the medium surface (depending on the species and strain of the antagonist and the pathogen) and was also able to grow over the mycelium of the pathogen and sporulate. The rate of inhibition of Fusarium mycelium growth by Trichoderma ranged from approximately 24% to 66%. When Fusarium and Trichoderma were co-cultured on rice, Trichoderma strains were found to inhibit DON biosynthesis by about 73% to 98%, NIV by about 87% to 100%, and ZEN by about 12% to 100%, depending on the pathogen and antagonist strain. A glycosylated form of DON was detected in the co-culture of F. culmorum and Trichoderma, whereas it was absent in cultures of the pathogen alone, thus suggesting that Trichoderma is able to glycosylate DON. The results also suggest that a strain of T. viride is able to convert ZEN into its hydroxylated derivative, β-ZOL.

On the biocontrol by Trichoderma afroharzianum against Fusarium culmorum responsible of fusarium head blight and crown rot of wheat in Algeria

BackgroundDurum wheat (Triticum durum Desf.) is one of the most important cereals in the world. Unfortunately, the wheat plant is a target of several species of the genus Fusarium. This genus causes two serious diseases: fusarium crown rot (FCR) and fusarium head blight (FHB). The search for new indigenous strains of Trichoderma with a high potential for biocontrol against these two diseases was the purpose of this study.ResultsBiocontrol potential of 15 isolates of Trichoderma (T1 to T15), isolated from different rhizosphere soils and Algerian ecosystems, was evaluated against 4 strains of Fusarium culmorum (FC11, FC2, FC4, and FC20); the main causative agent of FCR and FHB. The efficacy of biological control by Trichoderma spp., evaluated by in vitro tests (direct and indirect confrontation), was confirmed by in vivo bioassays. The in vitro results showed a significant inhibition of mycelial growth of F. culmorum species than the control. The highest percentages of inhibition were obtained by T9, T12, and T14 isolates causing a maximum inhibition percentage of 81.81, 77.27, and 80.68%, respectively. T14 was selected for biocontrol in in vivo testing. A tube and pot experiments for FCR against F. culmorum showed that T14 decreased the disease severity with 50 and 63.63% reduction, respectively. FHB infection was significantly reduced by T14 in all durum wheat cultivars tested, where %AUDPC (area under the disease progress curve) reduction was 49.77, 43.43, 48.25, and 74.60% for Simeto, Waha, Bousselem, and Setifis genotypes, respectively. Yields also increased significantly for almost all cultivars. The antagonistic T14 was characterized based on molecular tools, using translation elongation factor1-alpha (TEF1-α) and internal transcribed spacers rDNA (ITS1). The results identified T14 as T. afroharzianum with accession numbers attributed by NCBI GenBank as MW171248 and MW159753.ConclusionsTrichoderma afroharzianum, evaluated for the first time in Algeria as biocontrol agent, is a promising biocontrol approach against FCR and FHB.

Highly Regioselective and Stereoselective Biohydroxylations of Oxandrolone

Microbially catalyzed reactions are a powerful and valuable tool for organic synthesis of many compounds with potential biological activity. Herein, we report efficient hydroxylations of the steroidal anabolic-androgenic lactone, oxandrolone, in the cultures of three strains of fungi, Fusarium culmorum, Mortierella isabellina, and Laetiporus sulphureus. These reactions resulted in the production of four metabolites identified as 12β-hydroxyoxandrolone (2), 9α-hydroxyoxandrolone (3), 6α-hydroxyoxandrolone (4), and 15α-hydroxyoxandrolone (5), the latter being a new compound. The high substrate conversion rates and the product yields achieved indicate that these strains offer a new way to generate steroidal hydroxylactones with potential pharmaceutical interest. The structures of the isolated derivatives were characterized on the basis of spectroscopic data. The effect of modification of the A-ring structure of the steroid by the lactone group on the selectivity of hydroxylation in cultures of the tested fungi is also discussed.

In silico assessment of Rhanterium adpressum sesquiterpenes inhibitory effect on 3 and 15-O-trichothecene acetyltransferases

Essential oils (EO) from leaves and flowers of Rhanterium adpressum have shown to inhibit the mycelial growth and type B trichothecenes production. The four strains of Fusarium culmorum and Fusarium graminearum were inhibited with 0.25 μL.mL-1 of each oil. The inhibitory activity of 11 sesquiterpenes identified in these oils was here examined in silico against two key enzymes in the biosynthesis pathway of trichotecenes namely: 15-O-trichothecene acetyltransferase and 3-O-trichothecene acetyltransferase. In sesquiterpene composition, T-Muurolol and α-Eudesmol have the highest percentages ranging from 1.4 to 2.75 %. Three-dimensional structures of these two enzymes were modeled using SWISS-MODEL with GMQE = 0.93 and QMEAN = -0.45 for 3-O-trichothecene acetyltransferase and GMQE = 0.93, QMEAN = -0.58 for 15-O-trichothecene acetyltransferase. By the results of docking, T-Muurolol and α-Eudesmol showed high affinity compared to 15-Decalonectrin and Deoxynivalenol. These molecules are all sesquiterpenes with no major conformational difference with an RMSD of 3.7 Å and 3.5 Å between 15-decalonectrin and α-Eudesmol, T-Muurolol respectively. The results of docking prove the inhibitory effect of R. adpressum EO sesquiterpenes on the enzymes of mycotoxins biosynthesis pathway of F. culmorum and F. graminearum.

Description of a Novel Mycovirus in the Phytopathogen Fusarium culmorum and a Related EVE in the Yeast Lipomyces starkeyi.

A new mycovirus was found in the Fusarium culmorum strain A104-1 originally sampled on wheat in Belgium. This novel virus, for which the name Fusarium culmorum virus 1 (FcV1) is suggested, is phylogenetically related to members of the previously proposed family ‘’Unirnaviridae’’. FcV1 has a monopartite dsRNA genome of 2898 bp that harbors two large non-overlapping ORFs. A typical -1 slippery motif is found at the end of ORF1, advocating that ORF2 is translated by programmed ribosomal frameshifting. While ORF2 exhibits a conserved replicase domain, ORF1 encodes for an undetermined protein. Interestingly, a hypothetically transcribed gene similar to unirnaviruses ORF1 was found in the genome of Lipomyces starkeyi, presumably resulting from a viral endogenization in this yeast. Conidial isolation and chemical treatment were unsuccessful to obtain a virus-free isogenic line of the fungal host, highlighting a high retention rate for FcV1 but hindering its biological characterization. In parallel, attempt to horizontally transfer FcV1 to another strain of F. culmorum by dual culture failed. Eventually, a screening of other strains of the same fungal species suggests the presence of FcV1 in two other strains from Europe.

Differences in Production, Composition, and Antioxidant Activities of Exopolymeric Substances (EPS) Obtained from Cultures of Endophytic Fusarium culmorum Strains with Different Effects on Cereals.

Exopolymeric substances (EPS) can determine plant-microorganism interactions and have great potential as bioactive compounds. The different amounts of EPS obtained from cultures of three endophytic Fusarium culmorum strains with different aggressiveness—growth promoting (PGPF), deleterious (DRMO), and pathogenic towards cereal plants—depended on growth conditions. The EPS concentrations (under optimized culture conditions) were the lowest (0.2 g/L) in the PGPF, about three times higher in the DRMO, and five times higher in the pathogen culture. The EPS of these strains differed in the content of proteins, phenolic components, total sugars, glycosidic linkages, and sugar composition (glucose, mannose, galactose, and smaller quantities of arabinose, galactosamine, and glucosamine). The pathogen EPS exhibited the highest total sugar and mannose concentration. FTIR analysis confirmed the β configuration of the sugars. The EPS differed in the number and weight of polysaccharidic subfractions. The EPS of PGPF and DRMO had two subfractions and the pathogen EPS exhibited a subfraction with the lowest weight (5 kDa). The three EPS preparations (ethanol-precipitated EP, crude C, and proteolysed P) had antioxidant activity (particularly high for the EP-EPS soluble in high concentrations). The EP-EPS of the PGPF strain had the highest antioxidant activity, most likely associated with the highest content of phenolic compounds in this EPS.

Rearrangement of cell wall polymers in flax infected with a pathogenic strain of Fusarium culmorum

A pathogenic strain of Fusarium culmorum caused flax disease whose first visible symptom was pigmentation and possible necrosis of the root tip. To better understand the process of infection we tried to determine the role of cell wall polymers in flax treated with F. culmorum. F. culmorum infection caused cell wall rearrangement which was associated with changes in the cell wall structure without changes in the amount of polymers. Moreover, pathogenic fungi strongly induced chitinase, β-1,3-glucanase, cellulase2, α-galactosidase and lignin-related genes, while mRNA levels of the majority of genes involved in metabolism of cell wall polysaccharide polymers decreased in time.

Structural Variations in LysM Domains of LysM-RLK PsK1 May Result in a Different Effect on Pea⁻Rhizobial Symbiosis Development.

Lysin-motif receptor-like kinase PsK1 is involved in symbiosis initiation and the maintenance of infection thread (IT) growth and bacterial release in pea. We verified PsK1 specificity in relation to the Nod factor structure using k1 and rhizobial mutants. Inoculation with nodO and nodE nodO mutants significantly reduced root hair deformations, curling, and the number of ITs in k1-1 and k1-2 mutants. These results indicated that PsK1 function may depend on Nod factor structures. PsK1 with replacement in kinase domain and PsSYM10 co-production in Nicotiana benthamiana leaves did not induce a hypersensitive response (HR) because of the impossibility of signal transduction into the cell. Replacement of P169S in LysM3 domain of PsK1 disturbed the extracellular domain (ECD) interaction with PsSYM10′s ECD in Y2H system and reduced HR during the co-production of full-length PsK1 and PsSYM0 in N. benthamiana. Lastly, we explored the role of PsK1 in symbiosis with arbuscular mycorrhizal (AM) fungi; no significant differences between wild-type plants and k1 mutants were found, suggesting a specific role of PsK1 in legume–rhizobial symbiosis. However, increased sensitivity to a highly aggressive Fusarium culmorum strain was found in k1 mutants compared with the wild type, which requires the further study of the role of PsK1 in immune response regulation.

Changes in Phenylpropanoid and Trichothecene Production by Fusarium culmorum and F. graminearum Sensu Stricto via Exposure to Flavonoids.

Flavonoids are a group of hydroxylated polyphenolic compounds widely distributed in the plant kingdom. Biosynthesis of these compounds involves type III PKSs, whose presence has been recently predicted in some fungal species through genome sequencing efforts. In this study, for the first time it was found that Fusaria produce flavonoids on solid YES medium. Naringenin, as the central precursor of all flavonoids, was produced at highest quantities, followed by quercetin, kaempferol, apigenin and luteolin. In plants, flavonoids are involved in the protection of cereals to a wide range of stresses, including host defense against Fusaria. Under in vitro conditions, strains of Fusarium culmorum and F. graminearum sensu stricto were incubated at levels of flavonoids close to amounts produced by cereals in response to fungal infection. The amounts of exogenous naringenin, apigenin, luteolin, kaempferol and quercetin were reduced and converted by fungi to the other flavonoid derivatives. Treatment of fungi with naringenin derivatives led to the inhibition of naringenin production. Correspondingly, the production of fungal-derived phenolic acids decreased in flavonoid treated samples, although this effect appeared to be dependent on the strain, flavonoid molecule and its concentration. Fusaria showed high variability in trichothecene production in response to flavonoids. With emphasis on quercetin, mycotoxin accumulation in the media was significantly decreased by luteolin, kaempferol, naringenin and apigenin. However, in some cases, apigenin led to the increase of mycotoxin content in the media. Gene expression experiments of Tri genes responsible for trichothecene biosynthesis (Tri4, Tri5 and Tri10) proved that the inhibition of mycotoxin production by flavonoids occurred at the transcriptional level. However, the changes in Tri transcript levels were not significant in most apigenin and all kaempferol-treated cultures. In this study, a link was established between antioxidant and antiradical properties of flavonoids and their effects on fungi.

Diversity of Avena Species by Morphological Traits and Resistance to Fusarium Head Blight

Sixty-six genotypes of 19 Avena species of different ploidy from VIR collection are analyzed for resistance to Fusarium head blight. The plants were infected in the field with Fusarium culmorum strains. For the first time in the world a representative set of the wild Avena species is assessed. The DNA content of trichothecene-producing Fusarium fungi was identified by a quantitative polymerase chain reaction (qPCR) method. The amount of mycotoxins in the grain was determined by an enzyme-linked immunosorbent assay (ELISA) method. The smallest amounts of Fusarium DNA and deoxynivalenol (DON) were detected in seven genotypes of hexaploid species: A. byzantina, A. sterilis, A. sativa and A. fatua and one diploid species A. wiestii. Statistically significant connections were demonstrated between the morphological traits of the genotypes, the Fusarium DNA content and amount of DON.

Development of two strains of Fusarium culmorum with a different aggressiveness in the soil and on the roots of barley of two genotypes

Fusarium culmorum can affect plants including cereals or develop saprophytically in the soil. It is unknown whether its saprophytic ability is different in strains with a different aggressiveness. This knowledge could be used for effective breeding of resistant cultivars. Here, we aimed to study the development of two F. culmorum strains with a different aggressiveness in the soil under barley, to compare their saprophytic ability and to reveal the influence, if any, of the host plant on the development of strains in the soil and on the roots. Saprophytic development of the strains was studied on membranes inoculated with macroconidia and placed into non-sterile soil under barley of two genotypes. The fungus was identified on the membranes and on barley roots by indirect immunofluorescent method. Both strains could develop saprophytically. The more aggressive strain (Fc538) showed a lesser saprophytic fitness than the less aggressive strain (Fc885): its mycelial density was lower and the number of chlamydospores was greater. Barley genotypes influenced the development of the fungal strains. Interestingly, conditions for saprophytic development of both strains were more favourable in the soil under barley of the resistant genotype. The more aggressive strain colonized barley of the resistant genotype more actively. Rot symptoms appeared earlier in the barley of the resistant genotype, but the number of diseased plants was greater in the barley of the susceptible genotype. The presence of a saprophytic stage in life cycle should slow down the accumulation of aggressive races in field populations of F. culmorum. Possible interactions between F. culmorum strains and barley plants are discussed.

Phenotypic and biochemical characterization of new advanced durum wheat breeding lines from Algeria that show resistance to fusarium head blight and to mycotoxin accumulation

Durum wheat (Triticum turgidum L. var. durum) is a crop highly susceptible to Fusarium head blight (FHB), which results in yield losses and downgrades the quality of grains mostly due to mycotoxin contamination. Although breeding for resistance to FHB is one of the most promising strategy for minimizing crop damage, the attempts to obtain durum wheat resistant lines have been limited so far. Two potentially interesting lines were recently delivered by a breeding program based on crosses involving cultivars from Europe and Syria. Using a field experiment in Algeria with four different Fusarium culmorum strains and a spray inoculation method, we demonstrated that the two breeding lines were significantly less affected than a set of commercial cultivars. The two breeding lines were shown to exhibit a higher resistance to both initial fungal infection and disease spread , and to mycotoxin contamination. In addition, a detailed analysis of 2 phenolic acid composition of grains indicates significant differences in p-coumaric acid between the FHB-resistant breeding lines and the sensitive genotypes. Our results corroborate the importance of cell wall composition in preventing the diffusion of F. culmorum and therefore contributing to the resistance of cereals to FHB.

Sinapic Acid Affects Phenolic and Trichothecene Profiles of F. culmorum and F. graminearum Sensu Stricto.

Plant-derived compounds for reducing the mycotoxin load in food and feed have become a rapidly developing research field of importance for plant breeding efforts and in the search for natural fungicides. In this study, toxigenic strains of Fusarium culmorum and F. graminearum sensu stricto were exposed to sinapic acid on solid YES media at levels close to those reported in wheat bran. Fusaria produced phenolic acids, whose accumulation was decreased by exogenous sinapic acid. Strains exposed to the lowest doses of sinapic acid showed more efficient reduction of phenolic acid production than fungi kept at higher concentrations of this compound. Fungi reduced exogenous sinapic acid, leading to the formation of syringic aldehyde. Treatment with sinapic acid led to a dramatic accumulation of its parent compound ferulic acid, presumably due to inhibition of the further conversion of this phenolic compound. Exogenous sinapic acid decreased the production of trichothecenes by fungi. Higher doses of sinapic acid resulted in more efficient reduction of mycotoxin accumulation in the media. Gene expression studies of Tri genes responsible for trichothecene biosynthesis (Tri4, Tri5 and Tri10) proved that the inhibition of mycotoxin production by sinapic acid occurred at the transcriptional level. Fusaria respond to sinapic acid by stimulation of ergosterol biosynthesis.

The bean rhizosphere Pseudomonas aeruginosa strain RZ9 strongly reduces Fusarium culmorum growth and infectiveness of plant roots

A faba bean rhizospheric Pseudomonas aeruginosa isolate RZ9 was used for studying its antifungal activity and protecting effects of faba bean and common bean against the root pathogen Fusarium culmorum strain MZB47. The dual culture tests showed that RZ9 inhibits MZB47 in vitro growth by 56%. When mixing RZ9 cell suspension with MZB47 macroconidia at equal proportion, the macroconidia viability was reduced with 70%. Pathogenicity tests conducted in sterile conditions showed that MZB47 caused an intense root rotting in faba bean ‘Aquadulce’ plantlets and a slight level in common bean ‘Coco blanc’. This was associated to significant decreases in plant growth only in ‘Aquadulce’, reducing shoot dry weight (DW) by 82% and root DW by 70%. In soil samples, MZB47 caused severe root rotting and induced significant decreases in shoot DW (up to 51%) and root DW (up to 60%) for both beans. It was associated to a decrease in nodule number by 73% and 52% for faba bean and common bean, respectively. Biocontrol assays revealed that the inoculation of RZ9 to MZB47-treated plantlets enhanced shoot DWs (25% and 110%) and root DWs (29% and 67%), in faba bean and common bean, respectively. Moreover, root rotting levels decreased and nodule number increased in treated compared to untreated plantlets. Collected data highlighted the disease severity of F. culmorum and demonstrated the potential of using RZ9 in controlling Fusaria root diseases in beans. Thereby, the current study represents the first report on the biocontrol effectiveness of P. aeruginosa against F. culmorum in beans.

Trans-Cinnamic and Chlorogenic Acids Affect the Secondary Metabolic Profiles and Ergosterol Biosynthesis by Fusarium culmorum and F. graminearum Sensu Stricto.

Plant-derived compounds limiting mycotoxin contamination are currently of major interest in food and feed production. However, their potential application requires an evaluation of their effects on fungal secondary metabolism and membrane effects. In this study, different strains of Fusarium culmorum and F. graminearum sensu stricto were exposed to trans-cinnamic and chlorogenic acids on solid YES media. Fusaria produced phenolic acids, whose accumulation was lowered by exogenous phenolic compounds. In addition, fungi reduced exogenous phenolic acids, leading either to their conversion or degradation. trans-Cinnamic acid was converted to caffeic and ferulic acids, while chlorogenic acid was degraded to caffeic acid. The latter underwent further degradation to protocatechuic acid. Fungal-derived trans-cinnamic acid, as the first intermediate of the shikimate pathway, increased after chlorogenic acid treatment, presumably due to the further inhibition of the conversion of trans-cinnamic acid. Exogenous trans-cinnamic and chlorogenic acid displayed the inhibition of mycotoxin production by Fusaria, which appeared to be largely dependent on the phenolic compound and its concentration and the assayed strain. Exogenous phenolic acids showed different effects on ergosterol biosynthesis by fungi. It was found that the production of this membrane sterol was stimulated by trans-cinnamic acid, while chlorogenic acid negatively impacted ergosterol biosynthesis, suggesting that phenolic acids with stronger antifungal activities may upregulate ergosterol biosynthesis by Fusaria. This paper reports on the production of phenolic acids by Fusaria for the first time.

Population genetic structure and mycotoxin potential of the wheat crown rot and head blight pathogen Fusarium culmorum in Algeria

Surveys for crown rot (FCR) and head blight (FHB) of Algerian wheat conducted during 2014 and 2015 revealed that Fusarium culmorum strains producing 3-acetyl-deoxynivalenol (3ADON) or nivalenol (NIV) were the causal agents of these important diseases. Morphological identification of the isolates (n FCR=110, n FHB=30) was confirmed by sequencing a portion of TEF1. To assess mating type idiomorph, trichothecene chemotype potential and global population structure, the Algerian strains were compared with preliminary sample of F. culmorum from Italy (n=27), Australia (n=30) and the United States (n=28). A PCR assay for MAT idiomorph revealed that MAT1-1 and MAT1-2 strains were segregating in nearly equal proportions, except within Algeria where two-thirds of the strains were MAT1-2. An allele-specific PCR assay indicated that the 3ADON trichothecene genotype was predominant globally (83.8% 3ADON) and in each of the four countries sampled. In vitro toxin analyses confirmed trichothecene genotype PCR data and demonstrated that most of the strains tested (77%) produced culmorin. Global population genetic structure of 191 strains was assessed using nine microsatellite markers (SSRs). AMOVA of the clone corrected data indicated that 89% of the variation was within populations. Bayesian analysis of the SSR data identified two globally distributed, sympatric populations within which both trichothecene chemotypes and mating types were represented.

Pathogenicity and trichothecenes production of Fusarium culmorum strains causing head blight on wheat and evaluation of resistance of the varieties cultivated in Algeria

Fusarium head blight (FHB) is a major disease of wheat that has been studied worldwide but never in Algeria where high quantities of both durum wheat and common soft wheat are grown and traditionally consumed as semolina and bread. Fusarium root rot has also been observed in this country. Here we show that Fusarium culmorum seems to be the major pathogen associated with these diseases in Algeria. The type of mycotoxins produced by four F. culmorum isolates and their capacity to confer the disease on spike and accumulate type B trichothecenes in the grain was evaluated. Two strains produced deoxynivalenol, 3-acetyldeoxynivalenol and zearalenone in vitro. The two other strains produced nivalenol and fusarenone X. The four strains were used for artificial spray inoculations on wheat spikes to determine their potential in generating FHB symptoms and accumulating mycotoxins in local field conditions. A panel constituted of four durum wheat and four soft wheat varieties generally cultivated in Algeria and of two newly created durum wheat lines were evaluated. The results show a correlation between the level of invasion of the grain and the quantity of accumulated toxins with a large diversity depending on the cultivars. Interestingly, two local durum wheat varieties and the two new durum lines showed a promising level of resistance to FHB with significantly lower trichothecene accumulation. The content in phenolic compounds of the different varieties was assessed and evaluated as possible factor of resistance to trichothecene accumulation. This is the first report evaluating the wheat varieties cultivated in Algeria for their susceptibility to Fusarium Head Blight caused by local strains of F. culmorum in semi-arid bioclimatic condition.