Delfina Popiel

Wheat-infectingFusarium species in Poland — their chemotypes and frequencies revealed by PCR assay

ThreeFusarium species:F. graminearum, F. culmorum andF. cerealis were identified in laboratory cultures and in sporodochia from spikelets of scabby wheat. SCAR (sequence characterized amplified region) primers were used to identifyFusarium species and nivalenol (NIV) and deoxynivalenol (DON) chemotypes within species in laboratory cultures and field collected heads harvested in 2006. Results from PCR analyses confirmed preliminary identifications of species on the basis of examination of macroconidia under a light microscope and identification of cultures on agar media. NIV and DON (3Ac-DON and 15Ac-DON) chemotypes were identified using PCR assay. Among samples and isolates ofF. graminearum, the 15Ac-DON chemotype dominated, and among those whereF. culmorum was identified, the 3Ac-DON chemotype prevailed. Only 5 of the 41 isolates ofF. graminearum tested, displayed the NIV chemotype. An increase in the frequency ofF. graminearum and a decrease in the frequency ofF. culmorum were found during 1998 to 2006.

Species diversity of Trichoderma in Poland

In the present study, we reinvestigate the diversity of Trichoderma in Poland utilizing a combination of morphological and molecular/phylogenetic methods. A total of 170 isolates were collected from six different substrata at 49 sites in Poland. These were divided among 14 taxa as follows: 110 of 170 Trichoderma isolates were identified to the species level by the analysis of their ITS1, ITS2 rDNA sequences as: T. harzianum (43 isolates), T. aggressivum (35), T. citrinoviride (11), T. hamatum (9), T. virens (6), T. longibrachiatum (4), T. polysporum (1), and T. tomentosum (1); 60 isolates belonging to the Viride clade were identified based on a fragment of the translation-elongation factor 1-alpha (tef1) gene as: T. atroviride (20 isolates), T. gamsii (2), T. koningii (17), T. viridescens (13), T. viride (7), and T. koningiopsis (1). Identifications were made using the BLAST interface in TrichOKEY and TrichoBLAST (http://www.isth.info). The most diverse substrata were soil (nine species per 22 isolates) and decaying wood (nine species per 75 isolates). The most abundant species (25%) isolated from all substrata was T. harzianum.

Zearalenone lactonohydrolase activity in Hypocreales and its evolutionary relationships within the epoxide hydrolase subset of a/b-hydrolases

AbstractBackgroundZearalenone is a mycotoxin produced by several species of Fusarium genus, most notably Fusarium graminearum and Fusarium culmorum. This resorcylic acid lactone is one of the most important toxins causing serious animal and human diseases. For over two decades it has been known that the mycoparasitic fungus Clonostachys rosea (synonym: Gliocladium roseum, teleomorph: Bionectria ochroleuca) can detoxify zearalenone, however no such attributes have been described within the Trichoderma genus.ResultsWe screened for the presence of zearalenone lactonohydrolase homologs in isolates of Clonostachys and Trichoderma genera. We report first finding of expressed zearalenone lactonohydrolase in Trichoderma aggressivum. For three isolates (T. aggressivum, C. rosea and Clonostachys catenulatum isolates), we were able to reconstruct full coding sequence and verify the biotransformation ability potential. Additionally, we assessed progression of the detoxification process (in terms of transcript accumulation and mycotoxin decomposition in vitro). In silico, search for origins of zearalenone lactonohydrolase activity in model fungal and bacterial genomes has shown that zearalenone lactonohydrolase homologs form a monophyletic fungal clade among the a/b hydrolase superfamily representatives. We corroborated the finding of functional enzyme homologs by investigating the functional sites (active site pocket with postulated, noncanonical Ser-Glu-His catalytic triad) conserved in both multiple sequence alignment and in homology-based structural models.ConclusionsOur research shows the first finding of a functional zearalenone lactonohydrolase in mycoparasitic Trichoderma aggressivum (an activity earlier characterised in the Clonostachys rosea strains). The supporting evidence for presence and activity of functional enzyme homologs is based on the chemical analyses, gene expression patterns, homology models showing conservation of key structural features and marked reduction of zearalenone content in cultured samples (containing both medium and mycelium). Our findings also show divergent strategies of zearalenone biotransformation ability (rapid induced expression and detoxification vs. gradual detoxification) present in several members of Hypocreales order (Trichoderma and Clonostachys genera). The potential for lactonhydrolase activity directed towards zearalenone and/or similar compounds is likely ancient, with homologs present in several divergent filamentous fungi among both Sordariomycetes (Bionectria sp., Trichoderma sp., Apiospora montagnei) and Leotiomycetes (Marssonina brunnea f. sp. ‘multigermtubi’).

Molecular diagnostics on the toxigenic potential of Fusarium spp. plant pathogens

We propose and test an efficient and rapid protocol for the detection of toxigenic Fusarium isolates producing three main types of Fusarium‐associated mycotoxins (fumonisins, trichothecenes and zearelanone).

The distant siblings – a phylogenomic roadmap illuminates the origins of extant diversity in fungal aromatic polyketide biosynthesis

Abstract In recent years, the influx of newly sequenced fungal genomes has enabled sampling of secondary metabolite biosynthesis on an unprecedented scale. However, explanations of extant diversity which take into account both large-scale phylogeny reconstructions and knowledge gained from multiple genome projects are still lacking. We analyzed the evolutionary sources of genetic diversity in aromatic polyketide biosynthesis in over 100 model fungal genomes. By reconciling the history of over 400 nonreducing polyketide synthases (NR-PKSs) with corresponding species history, we demonstrate that extant fungal NR-PKSs are clades of distant siblings, originating from a burst of duplications in early Pezizomycotina and thinned by extensive losses. The capability of higher fungi to biosynthesize the simplest precursor molecule (orsellinic acid) is highlighted as an ancestral trait underlying biosynthesis of aromatic compounds. This base activity was modified during early evolution of filamentous fungi, toward divergent reaction schemes associated with biosynthesis of, for example, aflatoxins and fusarubins (C4–C9 cyclization) or various anthraquinone derivatives (C6–C11 cyclization). The functional plasticity is further shown to have been supplemented by modularization of domain architecture into discrete pieces (conserved splice junctions within product template domain), as well as tight linkage of key accessory enzyme families and divergence in employed transcriptional factors. Although the majority of discord between species and gene history is explained by ancient duplications, this landscape has been altered by more recent duplications, as well as multiple horizontal gene transfers. The 25 detected transfers include previously undescribed events leading to emergence of, for example, fusarubin biosynthesis in Fusarium genus. Both the underlying data and the results of present analysis (including alternative scenarios revealed by sampling multiple reconciliation optima) are maintained as a freely available web-based resource: http://cropnet.pl/metasites/sekmet/nrpks_2014.

Optimal Trichoderma strains for control of stem canker of brassicas: molecular basis of biocontrol properties and azole resistance

Genus Trichoderma contains the most powerful agents used in biocontrol. Our study demonstrated that T. harzianum, T. hamatum and T. longibrachiatum can effectively control phytopathogenic fungi Leptosphaeria maculans and L. biglobosa. The effects of Trichoderma on pathogens’ growth (in dual cultures on agar media) and on disease severity (on seedlings in controlled conditions) were also confirmed by field experiments. Additionally, spraying with conidiospores in the autumn was helpful in reducing the incidence and severity of phoma leaf spots. It has also accelerated the degradation of plant stubble and the decomposition of pathogens’ fruiting bodies. Furthermore, all Trichoderma isolates showed higher cellulolytic activity and enhanced resistance to flusilazole treatments as compared to Leptosphaeria spp., which coincided with upregulation of 14α-sterol demethylases and an AbcG5 transporter. The effects we observed justify the use of Trichoderma to enhance the resistance of oilseed rape against pathogens, which in turn may lead to a decrease in the use of pesticides.

Suppressive Effect of Trichoderma spp. on Toxigenic Fusarium Species

The aim of the present study was to examine the abilities of twenty-four isolates belonging to ten different Trichoderma species (i.e., Trichoderma atroviride, Trichoderma citrinoviride, Trichoderma cremeum, Trichoderma hamatum, Trichoderma harzianum, Trichoderma koningiopsis, Trichoderma longibrachiatum, Trichoderma longipile, Trichoderma viride and Trichoderma viridescens) to inhibit the mycelial growth and mycotoxin production by five Fusarium strains (i.e., Fusarium avenaceum, Fusarium cerealis, Fusarium culmorum, Fusarium graminearum and Fusarium temperatum). Dual-culture bioassay on potato dextrose agar (PDA) medium clearly documented that all of the Trichoderma strains used in the study were capable of influencing the mycelial growth of at least four of all five Fusarium species on the fourth day after co-inoculation, when there was the first apparent physical contact between antagonist and pathogen. The qualitative evaluation of the interaction between the colonies after 14 days of co-culturing on PDA medium showed that ten Trichoderma strains completely overgrew and sporulated on the colony at least one of the tested Fusarium species. Whereas, the microscopic assay provided evidence that only T. atroviride AN240 and T. viride AN255 formed dense coils around the hyphae of the pathogen from where penetration took place. Of all screened Trichoderma strains, T. atroviride AN240 was also found to be the most efficient (69-100% toxin reduction) suppressors of mycotoxins (deoxynivalenol, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, nivalenol, zearalenone, beauvericin, moniliformin) production by all five Fusarium species on solid substrates. This research suggests that T. atroviride AN240 can be a promising candidate for the biological control of toxigenic Fusarium species.

Adaptation and response to mycotoxin presence in pathogen-pathogen interactions within the Fusarium genus

The ability of fungal plant pathogens to exude bioactive compounds is an important element of competition in a changing environment. The filamentous fungi usually retain a number of adaptations related not only to the production of toxic compounds by themselves but also to the mitigation of exogenous influences by toxins present in the environment. We examined a distinct effect of toxins on morphology, growth patterns and gene expression after stimulation in mycotoxin-producing and nonproducing isolates representing four evolutionarily divergent species (and chemotypes) within the Fusarium genus (Fusarium graminearum, Fusarium oxysporum, Fusarium proliferatum and Fusarium verticillioides). The aim of our work was to investigate the influence of mycotoxins present in the environment on fungal isolates belonging to evolutionarily divergent complexes within Fusarium genus. The results point to retention of resistance mechanisms in non-producer isolates (F. oxysporum) and specific dose-dependent differences i...