Changes in soil microbial communities as a result of growing Brassicaceae crops

The study was conducted in 2006 - 2008 at the Production and Experimental Station of the University of Warmia and Mazury in Olsztyn, located in Bałcyny (NE Poland). The objective of this study was to determine the microbial quality of soil after Brassicaceae grown as forecrops for winter wheat. A field experiment was established on grey-brown podsolic soil, and it involved the following forecrops: winter rapeseed, spring rapeseed, white mustard, Chinese mustard, and winter wheat as control. Soil samples for microbiological analyses were collected in the spring, before the sowing of forecrops, and in the autumn, after the harvest of Brassicaceae and ploughing-in crop residues. Bacterial and fungal communities isolated from soil sown with Brassicaceae as forecrops were generally more abundant and diverse. These communities exerted an inhibitory effect on the growth of soil pathogens. Forecrops with the greatest microbiological potential were white mustard and winter rapeseed

THE EFFECT OF IMPROPER DISPOSAL OF THE RESIDUES OF PLANT PROTECTION PRODUCTS ON SOIL MICROORGANISMS

New legislation emphasizes the importance of proper disposal of the residues of plant protection products in farms in the agricultural and horticultural sector, because some of those residues may remain in soil in unchanged form for several years, thus affecting the biodiversity of soil microorganisms. A questionnaire survey was conducted to determine the methods of application and disposal of plant protection products by professional users. Biodiversity of microbial communities in soil at sites contaminated by xenobiotics from point sources was evaluated in a laboratory experiment. The awareness of the users of plant protection products regarding responsible and safe use of approved sprayers and the need to train persons performing protective treatments was satisfactory. However, the respondents demonstrated a low level of environmental awareness, and they often declared that in their farms the residues of plant protection products are disposed of in the same place repeatedly. Such practices reduce the biodiversity of soil-dwelling microbes, in particular, the counts of nitrogen-fixing bacteria. In most cases, fungi of the genus Mucor and the species of Fusarium culmorum and Gliocladium roseum did not respond to the presence of the residues of plant protection products in soil

Zbiorowiska grzybów ziarna różnych rozmnożeń pszenżyta w latach 1993 i 1994 [Communities of fungi in grain from several generations of triticale]

An assessment of health status of winter triticale grain obtained from a longterm reproduction experiment was performed in 1993-1994. Grain from six generations of triticale was examined each year. In both years of the study, the most frequently isolated fungus was Alternaria alternata. The number of isolated pathogens as well as the total extent of grain infestation by fungi depended on the weather conditions during the vegetative growth of triticale plants. There was no correlation between the generations of triticale and fungal infestation of triticale grain

Immunological aspects of antitumor photodynamic therapy outcome

Abstract Photodynamic therapy (PDt

Alternaria alternata as a Seed-Transmitted Pathogen of Sida hermaphrodita (Malvaceae) and Its Suppression by Aureobasidium pullulans

Background: Sida hermaphrodita (Virginia fanpetals) was introduced to Poland nearly 70 years ago as a potential fodder plant, and it is gaining importance as an energy crop. Alternaria alternata transmitted by seeds may exert a negative effect on the health of Virginia fanpetals plants. Methods: The virulence of the A. alternata pathogen, isolated from Virginia fanpetals seeds, was tested on detached leaves of Virginia fanpetals plants. The isolates were identified as A. alternata based on partial sequence analysis of Alta1, TEF1a and gdp genes and the ITS 1–5.8SrDNA–ITS 2 region. Pathogen transmission from seeds to seedlings and the influence of seed dressing with a suspension of Aureobasidium pullulans on seedling health were analyzed in a greenhouse experiment. Results: Three of the nine analyzed A. alternata isolates were highly pathogenic for S. hermaphrodita. The initial symptoms of leaf infection were small, round dark brown or black spots which grew into larger dark brown spots surrounded by a chlorotic halo. Alternaria alternata was re-isolated from inoculated plants and was identified as the causal agent of Alternaria leaf spot disease. In the greenhouse experiment, S. hermaphrodita seeds dressed with a suspension of A. pullulans and inoculated with A. alternata produced a higher number of seedlings with a higher health status than non-dressed seeds. Conclusions: The study demonstrated that A. alternata is transmitted from infected S. hermaphrodita seeds to developing plants and biological control limits this phenomenon

Microbial Inhibition of Fusarium Pathogens and Biological Modification of Trichothecenes in Cereal Grains

Fungi of the genus Fusarium infect cereal crops during the growing season and cause head blight and other diseases. Their toxic secondary metabolites (mycotoxins) contaminate grains. Several dozen toxic compounds produced by fungal pathogens have been identified to date. Type B trichothecenes—deoxynivalenol, its acetyl derivatives and nivalenol (produced mainly by F. graminearum and F. culmorum)—are most commonly detected in cereal grains. “T-2 toxin” (produced by, among others, F. sporotrichioides) belongs to type-A trichothecenes which are more toxic than other trichothecenes. Antagonistic bacteria and fungi can affect pathogens of the genus Fusarium via different modes of action: direct (mycoparasitism or hyperparasitism), mixed-path (antibiotic secretion, production of lytic enzymes) and indirect (induction of host defense responses). Microbial modification of trichothecenes involves acetylation, deacetylation, oxidation, de-epoxidation, and epimerization, and it lowers the pathogenic potential of fungi of the genus Fusarium. Other modifing mechanisms described in the paper involve the physical adsorption of mycotoxins in bacterial cells and the conjugation of mycotoxins to glucose and other compounds in plant and fungal cells. The development of several patents supports the commercialization and wider application of microorganisms biodegrading mycotoxins in grains and, consequently, in feed additives

ECOTOXICITY AND PHYTOTOXICITY OF PLANT PROTECTION PRODUCTS TO RHIZOSPHERE FUNGI AND WINTER WHEAT SEEDLINGS

Registration of plant protection products involves the analysis of their effects on soil microorganisms. The residues of plant protection products penetrate the soil, but their impact on fungi remains scarcely researched. In this study, the influence of selected plant protection products on the abundance of rhizosphere-dwelling fungi and the growth of winter wheat seedlings was evaluated under greenhouse conditions. The analysed plant protection products had an inhibitory effect on the growth of filamentous fungi in the rhizosphere, whereas yeasts were resistant to those products applied to soil. Tebuconazole exerted the strongest suppressive effect on the growth of filamentous fungi, and propiconazole was characterized by the greatest phytotoxic activity against winter wheat seedlings. Azoxystrobin had the weakest ecotoxic and phytotoxic effects, and its application to soil usually led to a rapid increase in the counts of fungi of the genus Acremonium

A Review of the Interactions between Wheat and Wheat Pathogens: Zymoseptoria tritici, Fusarium spp. and Parastagonospora nodorum

Zymoseptoria tritici is a hemibiotrophic pathogen which causes Septoria leaf blotch in wheat. The pathogenesis of the disease consists of a biotrophic phase and a necrotrophic phase. The pathogen infects the host plant by suppressing its immune response in the first stage of infection. Hemibiotrophic pathogens of the genus Fusarium cause Fusarium head blight, and the necrotrophic Parastagonospora nodorum is responsible for Septoria nodorum blotch in wheat. Cell wall-degrading enzymes in plants promote infections by necrotrophic and hemibiotrophic pathogens, and trichothecenes, secondary fungal metabolites, facilitate infections caused by fungi of the genus Fusarium. There are no sources of complete resistance to the above pathogens in wheat. Defense mechanisms in wheat are controlled by many genes encoding resistance traits. In the wheat genome, the characteristic features of loci responsible for resistance to pathogenic infections indicate that at least several dozen genes encode resistance to pathogens. The molecular interactions between wheat and Z. tritici, P. nodorum and Fusarium spp. pathogens have been insufficiently investigated. Most studies focus on the mechanisms by which the hemibiotrophic Z. tritici suppresses immune responses in plants and the role of mycotoxins and effector proteins in infections caused by P. nodorum and Fusarium spp. fungi. Trichothecene glycosylation and effector proteins, which are involved in defense responses in wheat, have been described at the molecular level. Recent advances in molecular biology have produced interesting findings which should be further elucidated in studies of molecular interactions between wheat and fungal pathogens. The Clustered Regularly-Interspaced Short Palindromic Repeats/ CRISPR associated (CRISPR/Cas) system can be used to introduce targeted mutations into the wheat genome and confer resistance to selected fungal diseases. Host-induced gene silencing and spray-induced gene silencing are also useful tools for analyzing wheat–pathogens interactions which can be used to develop new strategies for controlling fungal diseases