Phytopathogenic Fungus Fusarium Culmorum Research Articles

The Effect of Nitrogen Fertilization and Fusarium culmorum Inoculation on the Biomarkers of Oxidative Stress in Wheat Flag Leaves

During cultivation, wheat is exposed to several abiotic and/or biotic stress conditions that may adversely impact the wheat yield and quality. The impact of abiotic stress caused by nitrogen deficiency and biotic stress caused by phytopathogenic fungus Fusarium culmorum on biomarkers of oxidative stress in the flag leaf of nine winter wheat varieties (Ficko, U-1, Galloper, BC Mandica, BC Opsesija, Ingenio, Isengrain, Felix, and Bezostaya-1) was analyzed in this study. Hydrogen peroxide concentration and lipid peroxidation level were measured as indicators of oxidative stress, while the antioxidant response was determined by measuring the concentration of phenolic compounds and activities of antioxidant enzymes. Wheat variety and nitrogen treatment had a significant effect on all examined biomarkers of oxidative stress in the flag leaf, while the impact of Fusarium treatment was less pronounced. The most significant impact on the measured stress biomarkers had a low nitrogen level, which mainly increased hydrogen peroxide concentration and lipid peroxidation level and decreased activities of antioxidant enzymes in most varieties. The obtained results were discussed and compared with the previous study in which biochemical analyzes were performed on the wheat spike. There was no significant strong correlation between flag leaf and spike response in the measured parameters, which, in addition to the variety-specific response, also indicates a tissue-specific antioxidant response.

Aromatic Carboxylic Acids in Barley-Root Exudates and Their Influence on the Growth of Fusarium culmorum and Pseudomonas fluorescens

An ultraperformance liquid chromatography system was used to establish the presence of seven aromatic carboxylic acids, known as antimicrobial substances, in root exudates of barley colonized by the phytopathogenic fungus Fusarium culmorum and the antagonistic bacterium Pseudomonas fluorescens. It was established that barley produced fewer antimicrobial components in exudates in response to the colonization of P. fluorescens than after colonization by F. culmorum. All aromatic carboxylic acids inhibited the growth of F. culmorum, but only two of them inhibited the growth of P. fluorescens and only at the highest concentration. The obtained data demonstrate the ability of the plant to create favorable conditions for the development of beneficial rhizobacteria and to create unfavorable conditions for the growth of the phytopathogenic fungus via the composition of root exudates. In the future, it will be possible to select varieties of grain crops with a specific composition of antimicrobial components in root exudates.

Low-temperature plasma applications in chemical fungicide treatment reduction

Abstract In order to reduce the environmental burden of chemicals, various new alternatives to seed protection are being sought. Our aim was to find an environmentally acceptable solution leading to the inactivation of seed-borne phytopathogenic fungi Fusarium culmorum on the surface of wheat and barley seeds with a positive effect on their germination. As a low-temperature plasma (LTP) source, a Diffuse Coplanar Surface Barrier Discharge (DCSBD) was used. Plasma generated by DCSBD is non-equilibrium, cold, diffuse, macroscopically homogeneous even in ambient air at atmospheric pressure. Experimental results showed that LTP treatment in the range of 120—300 s significantly inhibits the growth of F. culmorum on the surface of the seeds. The efficiency of LTP treatment was compared with traditional seed protection processes using chemical fungicide and also with combined seed pretreatment by plasma and subsequent application of chemical fungicide. No growth of F. culmorum was observed after the combination of Vitavax 2000 fungicide application in the dose of 10 % and 60 s of LTP treatment even on the 5th day of incubation. Better wettability of seeds with the chemical fungicide was related to the change on seed surface, which becomes hydrophilic after 10 s of LTP application. Short LTP exposure times did not affect germination and improved the growth parameter of cereal seeds. By combining physical (LTP) and chemical (Vitavax 2000) treatments of cereal seeds, it is possible to effectively reduce the required amount of chemical fungicide and to stimulate germination and early growth seed parameters.

The Role of Root Exudates of Barley Colonized by Pseudomonas fluorescens in Enhancing Root Colonization by Fusarium culmorum.

The aim of this study was to find out why after joint inoculation of the substrate with the phytopathogenic fungus Fusarium culmorum and the antagonistic bacterium Pseudomonas fluorescens the amount of the fungus on the root surface in the beginning of the colonization was greater on the roots colonized by the bacterium than on control roots. This phenomenon is especially interesting because joint inoculation with P. fluorescens was always followed by a considerable decrease in the incidence of Fusarium root rot. In two experiments barley was grown in sterile vermiculite inoculated only with F. culmorum, only with P. fluorescens and jointly with the fungus and the bacterium. In the control, vermiculite was not inoculated with any microorganisms. After the removal from the vermiculite, barley plants were transferred into deionized water for the collection of root exudates. The duration of barley growth in the vermiculite and in the water was different in the two experiments. The exudates were tested for their ability to elicit chemotropism in F. culmorum and influence its growth. We did not observe any chemotropism of F. culmorum towards barley root exudates. However, the exudates of the barley colonized by the bacterium stimulated the growth of fungal germ tubes. Using an ultra-performance liquid chromatography system, we found that experimental conditions influenced the quantitative composition of the exudates. The amount of amino acids in the solution of exudates decreased considerably after a prolonged growth of control barley in water, while the presence of P. fluorescens resulted in a considerably increase of the amount of amino acids in the exudates. The exudates of barley colonized by P. fluorescens contained much more glucose, lactic acid and several amino acids than the exudates of control barley. These components are known to be necessary for the growth of F. culmorum. Their presence in the exudates of barley colonized by P. fluorescens seems to be the reason of a more active colonization by the fungus of barley roots colonized by the bacterium.

Biocontrol of the toxigenic plant pathogen Fusarium culmorum by soil fauna in an agroecosystem.

In 2011 and 2013, a field experiment was conducted in a winter wheat field at Adenstedt (northern Germany) to investigate biocontrol and interaction effects of important members of the soil food web (Lumbricus terrestris, Annelida; Folsomia candida, Collembola and Aphelenchoides saprophilus, Nematoda) on the phytopathogenic fungus Fusarium culmorum in wheat straw. Therefore, soil fauna was introduced in mesocosms in defined numbers and combinations and exposed to either Fusarium-infected or non-infected wheat straw. L. terrestris was introduced in all faunal treatments and combined either with F. candida or A. saprophilus or both. Mesocosms filled with a Luvisol soil, a cover of different types of wheat straw and respective combinations of faunal species were established outdoors in the topsoil of a winter wheat field after harvest of the crop. After a time span of 4 and 8weeks, the degree of wheat straw coverage of mesocosms was quantified to assess its attractiveness for the soil fauna. The content of Fusarium biomass in residual wheat straw and soil was determined using a double-antibody sandwich (DAS)-ELISA method. In both experimental years, the infected wheat straw was incorporated more efficiently into the soil than the non-infected control straw due to the presence of L. terrestris in all faunal treatments than the non-infected control straw. In addition, Fusarium biomass was reduced significantly in all treatments after 4weeks (2011: 95-99%; 2013:15-54%), whereupon the decline of fungal biomass was higher in faunal treatments than in non-faunal treatments and differed significantly from them. In 2011, Fusarium biomass of the faunal treatments was below the quantification limit after 8weeks. In 2013, a decline of Fusarium biomass was observed, but the highest content of Fusarium biomass was still found in the non-faunal treatments after 8weeks. In the soil of all treatments, Fusarium biomass was below the quantification limit. The earthworm species L. terrestris revealed a considerable potential as an effective biocontrol agent contributing to a sustainable control of a Fusarium plant pathogen in wheat straw, thus reducing the infection risk for specific plant diseases in arable fields.

The influence of soils with different textures on development, colonization capacity and interactions between Fusarium culmorum and Pseudomonas fluorescens in soil and on barley roots

Backgrounds and aims Soils are known to influence the survival and the biocontrol activity of Pseudomonas bacteria. However, few studies have focused on the development of the phytopathogenic fungus Fusarium culmorum under various soil conditions and its interactions with the antagonistic microflora. The aims of our research were to study the development of Fusarium culmorum and Pseudomonas fluorescens in two soils with different textures and on barley roots and to assess the influence of these soils in the growth, colonization capacity and interactions between the phytopathogen and the antagonist.

Contribution of the endogeic earthworm species Aporrectodea caliginosa to the degradation of deoxynivalenol and Fusarium biomass in wheat straw

In arable fields managed by conservation tillage combined with crop residue mulching, plant pathogen repression is an important ecosystem service to prevent cultivated plants from fungal diseases and mycotoxin contamination. A laboratory microcosm study was conducted to investigate the contribution of the endogeic, geophagous earthworm species Aporrectodea caliginosa as a secondary decomposer to the reduction of the phytopathogenic fungus Fusarium culmorum and its mycotoxin deoxynivalenol (DON) in wheat straw residues. After 5weeks experimental time, the Fusarium biomass and the DON concentration in aboveground straw were reduced considerably to the same extent both in presence and absence of A. caliginosa. Another substantial reduction of Fusarium biomass and DON concentration was found in belowground straw, which A. caliginosa had buried into the soil. Thus, we conclude that the particular contribution of secondary decomposers like A. caliginosa to the degradation of phytopathogenic fungi like Fusarium species and their mycotoxins like DON in the soil systems has to be assessed as minor.

Biological properties of the wild rhizosphere strain Pseudomonas fluorescens 2137 and its derivatives marked with the gusA gene

The natural wild rhizosphere strain P. fluorescens 2137 was marked with the beta-glucuronidase gene gusA. The introduction of this gene influenced the viability of the wild strain, as well as its certain physiological parameters, such as cultural characteristics, biochemical properties, and antagonistic activity against the phytopathogenic fungi Fusarium culmorum, F. oxysporum, F. graminearum, and Verticillum nigrescens. The gusA-marked derivative strains that deviate the least from the wild strain in biological properties can be used to monitor populations of P. fluorescens 2137 cells in the plant rhizosphere.

Extracellular proteinases from the phytopathogenic fungus Fusarium culmorum

The growth of Fusarium culmorum fungus on a medium containing thermostable proteins from potato tubers was accompanied by the production of proteinases, exhibiting activity over a broad pH range (from 6.0-10.0). When studied by SDS-PAGE in the presence of beta-mercaptoethanol, extracellular proteinases were represented by at least five species with a molecular weight of 30-60 kDa. Inhibitor analysis and studies of enzyme activities with synthetic substrates demonstrated that the culture liquid of Fusarium culmorum contained serine proteinases of various classes. The amount of subtilisin-like proteinases was the highest. A near-complete inhibition of the enzymes was caused by proteinaceous proteinase inhibitors from potato tubers. These data suggest that proteinases of the phytopathogen Fusarium culmorum serve as a metabolic target for natural inhibitors of potato proteinases.

Bacillus subtilis and Phenotypically Similar Strains Producing Hexaene Antibiotics

We studied metabolites synthesized by Bacillus subtilis strains, including the type strain of B. atrophaeus and phenotypically similar cultures. These metabolites were presented by polyene antibiotics with conjugated double bonds. Hexaenes from study strains inhibited the growth of phytopathogenic fungi Fusarium culmorum, F. sporotrichiella, F. oxysporum, Botrytis sorokiniana, Alternaria tenuis, and Phytophtora infestans. The degree of growth inhibition depended on the test fungus.

Optimization of growth and hydrolytic enzymes production by Fusarium culmorum using response surface method

Production of hydrolytic enzymes by a phytopathogenic fungus Fusarium culmorum was investigated. The proteolytic activity was observed when the fungus was grown in the medium containing starch or soybean meal as a carbon source. The amylolytic and lipolytic activities were not found. Response surface modeling was applied to shake-flask culture of the fungus to determine the optimum concentration of carbon source and optimal culture time for growth and protease production. The results indicated that the maximum yield of protease production corresponded to the concentration of soybean meal of 1.4 g/ml and culture time of 4.5 days.