Morphological, chemical and molecular differentiation of Fusarium equiseti isolated from Norwegian cereals

Three new species of Fusarium (Nectriaceae, Hypocreales) isolated from Eastern Cape dairy pastures in South Africa

A survey of the fungal diversity associated with mixed pastures from Eastern Cape dairy farms in South Africa led to the isolation of 155 Fusarium strains that belong to the Fusariumincarnatum-equiseti species complex (FIESC). Using single and multigene phylogenies based on partial sequences of the translation elongation factor 1-alpha (TEF), calmodulin (CaM), and the partial RNA polymerase second largest subunit (RPB2) genes, we identified 11 species. They included F.brevicaudatum, F.clavus, F.coffeatum, F.croceum, F.goeppertmayerae, and F.heslopiae, with five species that were found to be new. Based on morphological and phylogenetic data, three new species are formally described here as F.cumulatum, F.mariecurieae, and F.pascuum. We also provided a description for F.goeppertmayerae, as the authors who identified and named this species did not include one. We have chosen to not describe the remaining species, as our cultures lack proper morphological structure development. This study shows that mixed pastures harbour a diverse range of Fusarium species and highlights the need for further studies into their potential to impact animal health.

Species Diversity and Toxigenic Potential of Fusarium incarnatum-equiseti Species Complex Isolates from Rice and Soybean in China

Fusarium incarnatum-equiseti species complex (FIESC) strains are generally considered moderately virulent to many agricultural crops and produce a variety of mycotoxins, which represent a serious threat to food safety and public health. The occurrence of the FIESC strain in agricultural crops has been reported in various climatic regions, but detailed information on the species composition and toxigenic ability is rare in China. In this study, phylogenetic analyses were performed with combined sequences of EF-1a and RPB2 of 186 Fusarium isolates obtained from rice (Oryza sativa) and soybean (Glycine max). Twelve species were identified and 156 of the isolates were resolved within the Incarnatum clade of the FIESC species. Host influenced the population composition: rice isolates belonged to 12 species, among which FIESC 16, 18, and 24 strains were predominant; whereas five species were found among soybean isolates and FIESC 1, 16, and 18 strains dominated. Forty-three isolates were arbitrarily selected and analyzed for their Tri gene sequences and mycotoxigenic potential. Phylogenetic results based on the combined Tri5, Tri7, and Tri13 sequences were coincident with those from housekeeping markers. Type-A and -B trichothecenes were the main metabolites. Diacetoxyscirpenol was detected in all strains at varying concentrations. Nivalenol, 4-acetyl nivalenol, 3-acetyl deoxynivalenol, and neosolaniol were produced in members of the FIESC 1, 3, 7, 8, 15, 16, 17, and 18 strains. Our findings contribute valuable phylogenetic and toxigenic information necessary for the risk evaluation of mycotoxins in agricultural products.

Mycotoxin Production in Fusarium According to Contemporary Species Concepts

Fusarium is one of the most important genera of plant-pathogenic fungi in the world and arguably the world's most important mycotoxin-producing genus. Fusarium species produce a staggering array of toxic metabolites that contribute to plant disease and mycotoxicoses in humans and other animals. A thorough understanding of the mycotoxin potential of individual species is crucial for assessing the toxicological risks associated with Fusarium diseases. There are thousands of reports of mycotoxin production by various species, and there have been numerous attempts to summarize them. These efforts have been complicated by competing classification systems based on morphology, sexual compatibility, and phylogenetic relationships. The current depth of knowledge of Fusarium genomes and mycotoxin biosynthetic pathways provides insights into how mycotoxin production is distributedamong species and multispecies lineages (species complexes) in the genus as well as opportunities to clarify and predict mycotoxin risks connected with known and newly described species. Here, we summarize mycotoxin production in the genus Fusarium and how mycotoxin risk aligns with current phylogenetic species concepts.

Phylogenetic analysis and growth profiles of Fusarium incarnatum-equiseti species complex strains isolated from Tunisian cereals

The Fusarium incarnatum-equiseti species complex (FIESC) is a phylogenetically rich complex. It includes more than 30 cryptic phylogenetic species, making morphological identification problematic. FIESC has previously been detected in Tunisian cereals, but knowledge on the phylogeny and the ecophysiology of their species is lacking. In this work a phylogenetic analysis was performed using partial sequences of the translation elongation factor 1a gene (EF1a) of three FIESC strains isolated from barley and wheat from Tunisia, situated south in the Mediterranean basin, and additional strains from other countries. The results indicated that all Tunisian strains clustered with FIESC 5 group (F. clavum) together with other Spanish FIESC 5 strains also isolated from cereals. Growth rate profiles of the Tunisian strains were also determined on wheat and sorghum based media at a range of temperatures (15, 20, 25, 30, 35 and 40 °C) and water potential values (-0.7, -2.8, -7.0, and -9.8 MPa, corresponding to 0.995, 0.98, 0.95 and 0.93 aw values). Optimal growth was observed at 20-30 °C and between -0.7 and -7.0 MPa on both substrates (wheat and sorghum). The highest growth rate for the three strains was seen at 25 °C combined with -2.8 MPa. The comparison between the growth profiles of Tunisian and Spanish FIESC 5 strains showed similar trends with some interesting differences regarding temperature and water potential factors. Tunisian strains seem to perform better between 15 and 30 °C and, notably, at even lower water potentials included -9.8 Mpa. This might suggest that tolerance to low water potentials might be for Tunisian strains a more important selective clue than to higher temperatures. These results appeared to be consistent with a population well adapted to the present climatic conditions and predicted scenarios for North Africa.

Wild rice (O. latifolia) from natural ecosystems in the Pantanal region of Brazil: Host to Fusarium incarnatum-equiseti species complex and highly contaminated by zearalenone

We assessed the mycobiota diversity and mycotoxin levels present in wild rice (Oryza latifolia) from the Pantanal region of Brazil; fundamental aspects of which are severely understudied as an edible plant from a natural ecosystem. We found multiple fungal species contaminating the rice samples; the most frequent genera being Fusarium, Nigrospora and Cladosporium (35.9%, 26.1% and 15%, respectively). Within the Fusarium genus, the wild rice samples were mostly contaminated by the Fusarium incarnatum-equiseti species complex (FIESC) (80%) along with Fusarium fujikuroi species complex (20%). Phylogenetic analysis supported multiple FIESC species and gave support to the presence of two putative new groups within the complex (LN1 and LN2). Deoxynivalenol (DON) and zearalenone (ZEN) chemical analysis showed that most of the isolates were DON/ZEN producers and some were defined as high ZEN producers, displaying abundant ZEN levels over DON (over 19 times more). Suggesting that ZEN likely has a key adaptive role for FIESC in wild rice (O. latifolia). Mycotoxin determination in the rice samples revealed high frequency of ZEN, and 85% of rice samples had levels >100 μg/kg; the recommended limit set by regulatory agencies. DON was only detected in 5.2% of the samples. Our data shows that FIESC species are the main source of ZEN contamination in wild rice and the excessive levels of ZEN found in the rice samples raises considerable safety concerns regarding wild rice consumption by humans and animals.

Contamination of Wheat, Barley, and Maize Seeds with Toxigenic Fusarium Species and Their Mycotoxins in Tunisia

Background

Fusarium is a worldwide distributed fungal genus. It includes different species pathogenic to cereals among others crops. Some of these species can also produce toxic compounds toward animals and humans.

Objective

In this work, occurrence of fumonisins B1+B2, zearalenone, type A trichothecenes (T-2 and HT-2 toxins), and type B trichothecenes (deoxynivalenol[DON] and nivalenol[NIV]) was studied in 65 samples of stored and freshly harvested wheat, barley, and maize collected in Tunisia.

Methods

Mycotoxins analyses were performed by using gas chromatography for type B trichothecenes and HPLC for other mycotoxins. Obtained results were compared with the presence of mycotoxigenic species considered responsible for their synthesis by using species-specific polymerase chain reaction (PCR).

Results

Fumonisins occurred in 20.83% of wheat, 40% of barley, and 57.14% of maize samples, at levels exceeding European limits and suggesting a risk in Tunisian cereals, especially maize. Zearalenone, DON, NIV, and T-2+HT-2 toxins were detected at lower values in only wheat and barley samples. PCR protocols showed the predominance of F. verticillioides especially in maize, and occurrence of F. equiseti and F. graminearum in wheat and barley, and F. proliferatum in only two maize samples. A very consistent correlation was found between the detection of F. verticillioides and the contamination by fumonisins, as well as between the presence of F. graminearum and the contamination by zearalenone, DON, and NIV in the analyzed cereals.

Conclusions

Consequently, the detection of Fusarium species with the current PCR assays strategy in wheat, barley, and maize grains may be considered predictive of their potential mycotoxin risk in these matrices.

Highlights

This work is the first to report information on the occurrence of fumonisins, trichothecene, and ZEN, together with their potentially producing Fusarium species in wheat, barley, and maize in Tunisia. The high level of fumonisins in cereals, especially maize, stresses the importance of the control and the regularization of these mycotoxins for food safety.

Fusarium Head Blight, Mycotoxins and Strategies for Their Reduction

Mycotoxins are secondary metabolites of microscopic fungi, which commonly contaminate cereal grains. Contamination of small-grain cereals and maize with toxic metabolites of fungi, both pathogenic and saprotrophic, is one of the particularly important problems in global agriculture. Fusarium species are among the dangerous cereal pathogens with a high toxicity potential. Secondary metabolites of these fungi, such as deoxynivalenol, zearalenone and fumonisin B1 are among five most important mycotoxins on a European and world scale. The use of various methods to limit the development of Fusarium cereal head diseases and grain contamination with mycotoxins, before and after harvest, is an important element of sustainable agriculture and production of safe food. The applied strategies utilize chemical and non-chemical methods, including agronomic, physical and biological treatments. Biological methods now occupy a special place in plant protection as an element of biocontrol of fungal pathogens by inhibiting their development and reducing mycotoxins in grain. According to the literature, Good Agricultural Practices are the best line of defense for controlling Fusarium toxin contamination of cereal and maize grains. However, fluctuations in weather conditions can significantly reduce the effectiveness of plants protection methods against infection with Fusarium spp. and grain accumulation of mycotoxins.

Identification of fungi associated with soybeans and effective seed disinfection treatments

Sprouts can be a vehicle for the transmission of several pathogens capable of causing human illness, and the potential source of contamination is seed used for sprouting. The limited information about seed-borne pathogens as well as their incidence on soybean seeds for soybean sprout industry led the objectives of this study that were to identify seed-borne pathogens on commercial sprout soybean seeds and to evaluate different decontamination treatments on disinfection effectiveness and sprout quality. Seeds of "MFS-561," a sprout soybean cultivar, from three production regions were used in this study. The internal transcribed spacer (ITS1 and ITS2) DNA sequences of the isolated fungi from MFS-561 seeds were used for species identification. Seven disinfection treatments were evaluated on their effectiveness on reducing fungal incidence and impact on sprout characteristics. Out of 55 fungal isolates obtained from the soybean seeds, seven species and six genera were identified. The most frequent genera across regions were Alternaria, Diaphorte, and Fusarium. The treatment of soaking seeds in 2% calcium hypochlorite for 10 min and 5% acetic acid for 2 min before sprouting were promising seed disinfection treatments as they significantly reduced fungi incidence without any negative effects on sprout quality.

Variation in secondary metabolite production potential in the Fusarium incarnatum-equiseti species complex revealed by comparative analysis of 13 genomes

Background

The Fusarium incarnatum-equiseti species complex (FIESC) comprises 33 phylogenetically distinct species that have been recovered from diverse biological sources, but have been most often isolated from agricultural plants and soils. Collectively, members of FIESC can produce diverse mycotoxins. However, because the species diversity of FIESC has been recognized only recently, the potential of species to cause mycotoxin contamination of crop plants is unclear. In this study, therefore, we used comparative genomics to investigate the distribution of and variation in genes and gene clusters responsible for the synthesis of mycotoxins and other secondary metabolites (SMs) in FIESC.

Results

We examined genomes of 13 members of FIESC that were selected based primarily on their phylogenetic diversity and/or occurrence on crops. The presence and absence of SM biosynthetic gene clusters varied markedly among the genomes. For example, the trichothecene mycotoxin as well as the carotenoid and fusarubin pigment clusters were present in all genomes examined, whereas the enniatin, fusarin, and zearalenone mycotoxin clusters were present in only some genomes. Some clusters exhibited discontinuous patterns of distribution in that their presence and absence was not correlated with the phylogenetic relationships of species. We also found evidence that cluster loss and horizontal gene transfer have contributed to such distribution patterns. For example, a combination of multiple phylogenetic analyses suggest that five NRPS and seven PKS genes were introduced into FIESC from other Fusarium lineages.

Conclusion

Our results suggest that although the portion of the genome devoted to SM biosynthesis has remained similar during the evolutionary diversification of FIESC, the ability to produce SMs could be affected by the different distribution of related functional and complete gene clusters.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5567-7) contains supplementary material, which is available to authorized users.

Cinnamic Acid Inhibited Growth of Faba Bean and Promoted the Incidence of Fusarium Wilt

To ascertain the role and mechanism of cinnamic acid in the process of soil-borne Fusarium wilt infection with fava bean, we studied the effect of cinnamic acid on the faba bean and Fusarium oxysporum f. fabae (FOF). Our results showed that cinnamic acid treatment affected the physiological resistance of faba bean to FOF after inoculation with the pathogen and enhanced the pathogenicity of the pathogen, which may have led to aggravation of infection by the pathogen and increases in the incidence rates of Fusarium wilt and disease.

Mycoflora isolation and molecular characterization of Aspergillus and Fusarium species in Tunisian cereals

Wheat, barley and maize are the mainly consumed cereals in Tunisia. This study aimed to determine the mycoflora of these cereals with special focus on the mycotoxigenic Aspergillus and Fusarium species. Freshly harvested samples and other stored samples of each type of cereal (31 and 34 samples, respectively) were collected in Tunisia and cultured for fungal isolation and identification. Identification of fungal genera was based on morphological features. Aspergillus and Fusarium species were identified by species specific PCR assays complemented with DNA sequencing. Alternaria (70.83%), Eurotium (62.50%), Aspergillus (54.17%) and Penicillium (41.67%) were the most frequent fungi isolated from wheat. Penicillium (75%), Aspergillus (70%), Eurotium (65%) and Alternaria (65%) were the most frequently recovered genera from barley. The predominant genera in maize were Aspergillus (76.19%), Eurotium (42.86%), and Penicillium (38.09%). Aspergilllus, Penicillium, Fusarium and Alternaria were detected in both stored and freshly harvested grain samples. The frequencies of contamination with Aspergillus, Fusarium and Alternaria were higher in freshly harvested samples, whereas Penicillium species were more frequent in stored samples. The predominant Aspergillus species detected were A. flavus and A. niger. The Fusarium species detected were F. equiseti, F. verticillioides, F. nygamai, and F. oxysporum. This study suggested the potential risk for Aflatoxins and, to a lesser extent, for Ochratoxin A in Tunisian cereals. This is the first survey about mycoflora associated with wheat, barley and maize in Tunisia.

ToxGen: an improved reference database for the identification of type B-trichothecene genotypes in Fusarium

Type B trichothecenes, which pose a serious hazard to consumer health, occur worldwide in grains. These mycotoxins are produced mainly by three different trichothecene genotypes/chemotypes: 3ADON (3-acetyldeoxynivalenol), 15ADON (15-acetyldeoxynivalenol) and NIV (nivalenol), named after these three major mycotoxin compounds. Correct identification of these genotypes is elementary for all studies relating to population surveys, fungal ecology and mycotoxicology. Trichothecene producers exhibit enormous strain-dependent chemical diversity, which may result in variation in levels of the genotype's determining toxin and in the production of low to high amounts of atypical compounds. New high-throughput DNA-sequencing technologies promise to boost the diagnostics of mycotoxin genotypes. However, this requires a reference database containing a satisfactory taxonomic sampling of sequences showing high correlation to actually produced chemotypes. We believe that one of the most pressing current challenges of such a database is the linking of molecular identification with chemical diversity of the strains, as well as other metadata. In this study, we use the Tri12 gene involved in mycotoxin biosynthesis for identification of Tri genotypes through sequence comparison. Tri12 sequences from a range of geographically diverse fungal strains comprising 22 Fusarium species were stored in the ToxGen database, which covers descriptive and up-to-date annotations such as indication on Tri genotype and chemotype of the strains, chemical diversity, information on trichothecene-inducing host, substrate or media, geographical locality, and most recent taxonomic affiliations. The present initiative bridges the gap between the demands of comprehensive studies on trichothecene producers and the existing nucleotide sequence databases, which lack toxicological and other auxiliary data. We invite researchers working in the fields of fungal taxonomy, epidemiology and mycotoxicology to join the freely available annotation effort.

Influence of temperature, water activity and incubation time on fungal growth and production of ochratoxin A and zearalenone by toxigenic Aspergillus tubingensis and Fusarium incarnatum isolates in sorghum seeds

The major objective of this study was to describe the effect of water activity and temperature on radial growth and production of ochratoxin A (OTA) and zearalenone (ZEA) on sorghum grains of three Aspergillus tubingensis and three Fusarium incarnatum isolates. The water activity range was 0.91-0.99 a_w for F. incarnatum isolates and 0.88-0.99 a_w for A. tubingensis isolates. Temperatures of incubation were 15, 25 and 37°C for both species. Mycotoxin production was determined after 7, 14, 21 and 28days depending on the growth rate of the six isolates. Maximum growth rates (mm/day) were observed at 37°C and 0.99 a_w for A. tubingensis isolates and at 0.99 a_w and 25°C for F. incarnatum isolates. A. tubingensis was able to grow at 15°C only at the highest a_w levels (0.97 and 0.99 a_w). However, at this temperature F. incarnatum grew at 0.94 a_w. Optimum ochratoxin A production was observed at 0.97 a_w×37°C whereas optimal conditions for ZEA production varied from one isolate to another. Moreover, isolates of F. incarnatum from Tunisia do not require high a_w and temperature levels to yield maximum levels of ZEA. In general, our results showed that there is no correlation between the growth and production of ZEA in the case of F. incarnatum. This is the first study on the water activity and temperature effect on growth rate and ZEA production of F. incarnatum. Our results show that sorghum grains not only support growth but also OTA and ZEA production by A. tubingensis and F. incarnatum, respectively.

Trichothecenes and zearalenone production by Fusarium equiseti and Fusarium semitectum species isolated from Argentinean soybean

Fusarium equiseti and Fusarium semitectum represent the most abundant species in the Fusarium complex isolated from flowers, soybean pods and seeds in Argentina. The aim of the present study was to assess the production of major type A and type B trichothecenes (diacetoxyscirpenol, neosolaniol, T-2 toxin and HT-2 toxin, nivalenol, deoxynivalenol) and zearalenone by 40 F. equiseti and 22 F. semitectum isolates on rice culture. Mycotoxins were determined by HPLC with fluorescence detection after derivatisation with 1-anthronylnitrile for type A trichothecenes (i.e. diacetoxyscirpenol, neosolaniol, T-2 toxin and HT-2 toxin), by HPLC with UV detection for type B trichothecenes (i.e. nivalenol and deoxynivalenol), and by TLC for zearalenone. A total of 22 of 40 F. equiseti isolates produced diacetoxyscirpenol, nivalenol and ZEA alone or in combination, whereas only two of 20 F. semitectum isolates were nivalenol and ZEA producers. Both Fusarium species did not produce any deoxynivalenol, neosolaniol, T-2 toxin and HT-2 toxin. The variable retention in toxigenicity displayed by both fungal species suggests that these species have a saprophytic lifestyle in the soybean agroecosystem in Argentina.

Phylogenetic analyses and toxigenic profiles of Fusarium equiseti and Fusarium acuminatum isolated from cereals from Southern Europe

Fusarium equiseti and Fusarium acuminatum are toxigenic species that contaminate cereal crops from diverse climatic regions. They are common in Spanish cereals. The information available on their phylogenetics and toxigenic profiles is, however, insufficient to assist risk evaluation. In this work, phylogenetic analyses were performed using partial sequences of the translation elongation factor gene (EF-1α) of F. equiseti and F. acuminatum strains isolated from barley and wheat from Spain and other countries. The Northern and Southern European F. equiseti strains largely separated into two phylogenetically distinct clusters. This suggests the existence of two distinct populations within this species, explaining its presence in these regions of markedly different climate. Production of type A and B trichothecenes by the Spanish strains, examined in wheat cultures using a multitoxin analytical method, indicated that F. equiseti could produce deoxynivalenol and nivalenol and other trichothecenes, at concentrations that might represent a significant risk of toxin contamination for Southern European cereals. F. acuminatum showed low intraspecific genetic variability and 58% of the strains could produce deoxynivalenol at low level. Neither species was found to produce T-2 or HT-2 toxins. The present results provide important phylogenetic and toxigenic information essential for the accurate prediction of toxigenic risk.

Polymorphism of mycotoxin biosynthetic genes among Fusarium equiseti isolates from Italy and Poland

Fusarium equiseti (Corda) Saccardo is a soil saprophyte and a weak pathogen, associated with several diseases of fruit and other crops in subtropical and tropical areas, but also in countries with temperate climate. A wide range of secondary metabolites has been identified among natural F. equiseti populations, with zearalenone (ZEA), fusarochromanone and fusarenon-X being the most common. In present study, the genetic diversity of strains from two populations (from Italy and Poland) was evaluated by analysing the translation elongation factor 1α (tef-1α) sequences, two polyketide synthases from the ZEA biosynthetic pathway (PKS13 and PKS4) and the TRI5 gene from the trichothecene biosynthetic pathway. ZEA was produced in rice cultures by 20 of the 27 tested isolates in concentrations ranging from 1.34 ng/g to 34,000 ng/g). The ability to produce enniatins and trichothecenes was evaluated in all strains by identifying esyn1, TRI13 and TRI4 genes. The presence of PKS4 and PKS13 genes was confirmed by polymerase chain reaction (PCR) in only some ZEA-producing isolates. Similarly, the TRI5 gene was found in 14 of the 27 isolates tested. This is likely to have been caused by the divergence of those genes between F. equiseti and F. graminearum (the latter species was used for the primers design) and can be exploited in phylogenetic studies. The analysis of the mycotoxin biosynthetic gene sequences can be used to differentiate the studied genotypes even more precisely than the analysis of the non-coding regions (like tef-1α).

Alteration in lignin biosynthesis restricts growth of Fusarium spp. in brown midrib sorghum

To improve sorghum for bioenergy and forage uses, brown midrib (bmr)6 and -12 near-isogenic genotypes were developed in different sorghum backgrounds. The bmr6 and bmr12 grain had significantly reduced colonization by members of the Gibberella fujikuroi species complex compared with the wild type, as detected on two semiselective media. Fusarium spp. were identified using sequence analysis of a portion of the translation elongation factor (TEF) 1-alpha gene. The pathogens Fusarium thapsinum, F. proliferatum, and F. verticillioides, G. fujikuroi members, were commonly recovered. Other frequently isolated Fusarium spp. likely colonize sorghum asymptomatically. The chi(2) analyses showed that the ratios of Fusarium spp. colonizing bmr12 grain were significantly different from the wild type, indicating that bmr12 affects colonization by Fusarium spp. One F. incarnatum-F. equiseti species complex (FIESC) genotype, commonly isolated from wild-type and bmr6 grain, was not detected in bmr12 grain. Phylogenetic analysis suggested that this FIESC genotype represents a previously unreported TEF haplotype. When peduncles of wild-type and near-isogenic bmr plants were inoculated with F. thapsinum, F. verticillioides, or Alternaria alternata, the resulting mean lesion lengths were significantly reduced relative to the wild type in one or both bmr mutants. This indicates that impairing lignin biosynthesis results in reduced colonization by Fusarium spp. and A. alternata.

Novel multilocus sequence typing scheme reveals high genetic diversity of human pathogenic members of the Fusarium incarnatum-F. equiseti and F. chlamydosporum species complexes within the United States

Species limits within the clinically important Fusarium incarnatum-F. equiseti and F. chlamydosporum species complexes (FIESC and FCSC, respectively) were investigated using multilocus DNA sequence data. Maximum-parsimony and maximum-likelihood analyses of aligned DNA sequences from four loci resolved 28 species within the FIESC, within which the species were evenly divided among two clades designated Incarnatum and Equiseti, and four species within the FCSC. Sequence data from a fifth locus, beta-tubulin, was excluded from the study due to the presence of highly divergent paralogs or xenologs. The multilocus haplotype nomenclature adopted in a previous study (K. O'Donnell, D. A. Sutton, A. Fothergill, D. McCarthy, M. G. Rinaldi, M. E. Brandt, N. Zhang, and D. M. Geiser, J. Clin. Microbiol. 46:2477-2490, 2008) was expanded to all of the species within the FIESC and FCSC to provide the first DNA sequence-based typing schemes for these fusaria, thereby facilitating future epidemiological investigations. Multilocus DNA typing identified sixty-two sequence types (STs) among 88 FIESC isolates and 20 STs among 26 FCSC isolates. This result corresponds to indices of discrimination of 0.985 and 0.966, respectively, for the FIESC and FCSC four-locus typing scheme using Simpson's index of discrimination. Lastly, four human and two veterinary isolates, received as members of the FIESC or FCSC, were resolved as five phylogenetically distinct species nested outside these species complexes. To our knowledge, these five species heretofore have not been reported to cause mycotic infections (i.e., F. armeniacum, F. brachygibbosum, F. flocciferum, and two unnamed Fusarium species within the F. tricinctum species complex).

Community ecology of fungal pathogens causing wheat head blight

Research on the pathogen components involved in Fusarium head blight (FHB) along with the effects of their interactions on disease development and mycotoxin accumulation is reviewed. The fungal components within the FHB complex differ significantly in different environments. Individual species may respond differently to, and be differentially influenced by, particular disease control measures. Almost all published co-inoculation studies on wheat spikes or grains show that competitive interactions among FHB pathogens are the rule when fungal/disease development is considered. However, the fungi with the competitive advantage do not usually gain any advantage from the presence of other weaker competing fungi. Total mycotoxin production in mixed inoculations may decrease, increase, or remain unchanged compared with single-isolate inoculations, depending on the fungal species concerned and environmental conditions. A few recent studies, where each individual fungal component was quantified using molecular methods, suggest that mycotoxin productivity in mixed inoculations generally increases.

DNA microarray to detect and identify trichothecene- and moniliformin-producing Fusarium species

AIMS

To develop a DNA microarray for easy and fast detection of trichothecene- and moniliformin-producing Fusarium species.

METHOD AND RESULTS

A DNA microarray was developed for detection and identification of 14 trichothecene- and moniliformin-producing species of the fungal genus Fusarium. The array could also differentiate between four species groups. Capture probes were designed based on recent phylogenetic analyses of translation elongation factor-1 alpha (TEF-1alpha) sequences. Particular emphasis was put on designing capture probes corresponding to groups or species with particular mycotoxigenic synthetic abilities. A consensus PCR amplification of a part of the TEF-1alpha is followed by hybridization to the Fusarium chip and the results are visualized by a colorimetric Silverquant detection method. We validated the Fusarium chip against five naturally infected cereal samples for which we also have morphological and chemical data. The limit of detection was estimated to be less than 16 copies of genomic DNA in spiked commercial wheat flour.

CONCLUSIONS

The current Fusarium chip proved to be a highly sensitive and fast microarray for detection and identification of Fusarium species. We postulate that the method also has potential for (semi-)quantification.

SIGNIFICANCE AND IMPACT OF THE STUDY

The Fusarium chip may prove to be a very valuable tool for screening of cereal samples in the food and feed production chain, and may facilitate detection of new or introduced Fusarium spp.

Fusarium toxins of the scirpentriol subgroup: a review

Scirpentriol and its seven acetylated derivatives comprise a family of type-A trichothecene toxins produced by several species of Fusarium fungi. Out of this group 4,15-diacetoxyscirpenol has attracted most attention. It elicits toxic responses in several species and was detected in a variety of substrates. Out of the three possible monoacetylated derivatives 15-monoacetoxyscirpenol and the parent alcohol scirpentriol received some attention, whereas the remaining members of the family were mentioned in few reports. The present review deals with the structure, biosynthesis, analysis and toxicity of scirpentriol toxins. Formation by Fusarium species as well as culture conditions used for toxigenicity studies are reviewed; data about the natural occurrence of scirpentriol toxins in different cereal types, cereal associated products as well as in non-grain matrices including potato and soya bean are reported. Basing on literature reports about the toxicity of scirpentriol toxins an attempt is made to summarise the state of knowledge for risk evaluation for human and animal health.

Toxigenic Fusarium spp. as determinants of trichothecene mycotoxins in settled grain dust

Trichothecenes are immunosuppressive mycotoxins produced mainly by Fusarium spp. and often are detected as natural contaminants of grain and other agricultural products. Exposure to trichothecenes through inhalation during grain work may represent possible health risks for grain farmers. We aimed, therefore, to investigate the level of Fusarium spp. and trichothecenes in settled grain dust collected during work on 92 Norwegian farms. Mycotoxins were determined by gas chromatography-mass spectrometry, whereas the Fusarium spp. were identified and quantified both by species-specific semiquantitative polymerase chain reaction (PCR) and by cultivation. All potential trichothecene-producing molds in the grain dust were quantified using a PCR assay specific for tri5, the gene coding for trichodiene synthase that catalyzes the first step in the trichothecene biosynthesis. We performed correlation analysis between mold-DNA and mycotoxins to assess whether the PCR-detected DNA could be used as indicators of the mycotoxins. The methodological problem of detecting small amounts of airborne mycotoxins during grain work may then be avoided. Whereas the trichothecene-producing Fusarium species in grain dust could not be identified or quantified to a sufficient extent by cultivation, all investigated Fusarium spp. could be specifically detected by PCR and quantified from the DNA agarose gel band intensities. Furthermore, we observed a strong correlation between the trichothecenes HT-2 toxin (HT-2) or T-2 toxin (T-2) and DNA specific for tri5 (r = 0.68 for HT-2 and r = 0.50 for T-2; p < 0.001), F. langsethiae (r = 0.77 for HT-2 and r = 0.59 for T-2; p < 0.001), or F. poae (r = 0.41 for HT-2 and r = 0.35 for T-2; p < 0.001). However, only a moderate correlation was observed between the trichothecene deoxynivalenol (DON) and the combination of its producers, F. culmorum and F. graminearum (r = 0.24, p = 0.02), and no significant correlation was observed between DON and tri5. PCR clearly improved the detection of toxigenic Fusaria as potential sources of health risks for farmers inhaling grain dust during work, but the use of Fusarium-DNA as indicators for trichothecenes should be used cautiously.