Biogeography of Fusarium graminearum species complex and chemotypes: a review

Potential for the Bio-Detoxification of the Mycotoxins Enniatin B and Deoxynivalenol by Lactic Acid Bacteria and Bacillus spp

Mycotoxins, toxic compounds produced by fungi, pose significant risks to food safety and human health. This study investigates the bio-detoxification potential of 238 strains of lactic acid bacteria (LAB) and Bacillus spp., previously isolated from cereals (including mycotoxin-contaminated grains), against the emerging mycotoxin, enniatin B (ENB), and the prevalent mycotoxin, deoxynivalenol (DON). Out of the tested strains, 26 demonstrated notable mycotoxin reduction capabilities, including 2 Bacillus pumilus and 24 Bacillus licheniformis strains. B. licheniformis strains MA572, MA695, MA696, TR174a, TR284, TR363, and TR466a degraded ENB to levels below the detection limit, and six strains reduced DON by 30-35%; B. licheniformis TR251b and TR374 showed the highest DON reduction with 35.7%. The most promising strains for bio-detoxification were B. licheniformis TR284, which achieved a 100% reduction in ENB and a 28.6% reduction in DON and B. licheniformis TR388 with a 97.5% reduction in ENB and a 31.9% reduction in DON. None of the tested LAB strains significantly reduced either mycotoxin. These findings highlight the promising potential of B. licheniformis strains in bio-detoxifying mycotoxin-contaminated cereal products. Further research into the underlying detoxification mechanisms and safety aspects is essential to develop effective bio-detoxification strategies for enhancing food safety.

Adaptation of Fusarium Head Blight Pathogens to Changes in Agricultural Practices and Human Migration

Fusarium head blight (FHB) is one of the most destructive wheat diseases worldwide. To understand the impact of human migration and changes in agricultural practices on crop pathogens, here population genomic analysis with 245 representative strains from a collection of 4,427 field isolates of Fusarium asiaticum, the causal agent of FHB in Southern China is conducted. Three populations with distinct evolution trajectories are identifies over the last 10,000 years that can be correlated with historically documented changes in agricultural practices due to human migration caused by the Southern Expeditions during the Jin Dynasty. The gradual decrease of 3ADON-producing isolates from north to south along with the population structure and spore dispersal patterns shows the long-distance (>250 km) dispersal of F. asiaticum. These insights into population dynamics and evolutionary history of FHB pathogens are corroborated by a genome-wide analysis with strains originating from Japan, South America, and the USA, confirming the adaptation of FHB pathogens to cropping systems and human migration.

New insights into mycotoxin risk management through fungal population genetics and genomics

Mycotoxin contamination of food and feed is a major global concern. Chronic or acute dietary exposure to contaminated food and feed can negatively affect both human and animal health. Contamination occurs through plant infection by toxigenic fungi, primarily Aspergillus and Fusarium spp., either before or after harvest. Despite the application of various management strategies, controlling these pathogens remains a major challenge primarily because of their ability to adapt to environmental changes and selection pressures. Understanding the genetic structure of plant pathogen populations is pivotal for gaining new insights into their biology and epidemiology, as well as for understanding the mechanisms behind their adaptability. Such deeper understanding is crucial for developing effective and preemptive management strategies tailored to the evolving nature of pathogenic populations. This review focuses on the population-level variations within the two most economically significant toxigenic fungal genera according to space, host, and pathogenicity. Outcomes in terms of migration patterns, gene flow within populations, mating abilities, and the potential for host jumps are examined. We also discuss effective yet often underutilized applications of population genetics and genomics to address practical challenges in the epidemiology and disease control of toxigenic fungi.

Cumin Seed Oil Induces Oxidative Stress-Based Antifungal Activities on Fusarium graminearum

In this study, the antifungal activity of cumin seed oil (CSO) was tested on Fusarium graminearum. (i) Minimum inhibitory concentrations (MICs) and related concentrations (IC75, IC50, and IC25) were detected; (ii) toxicity was evaluated by a water-soluble tetrazolium salt-1 (WST-1) assay; (iii) genomic/epigenomic alterations were evaluated by the coupled restriction enzyme digestion-random amplification (CRED-RA) method; (iv) oxidative stress was investigated by CAT expression, catalase activity, and DCF-DA staining; (v) deoxynivalenol biosynthesis was evaluated by tri6 expression; (vi) and potential effects of CSO on wheat were tested by a water loss rate (WLR) assay. MIC, IC75, IC50 and IC25 values were detected at 0.5, 0.375, 0.25, and 0.125 mg mL-1. In WST-1 assays, significant decreases (p < 0.001) were detected. Genomic template stability (GTS) related to methylation differences ranged from 94.60% to 96.30%. Percentage polymorphism for HapII/MspI values were as 9.1%/15.8%. CAT (oxidative stress-related catalase) and tri6 (zinc finger motif transcription factor) gene expressions were recorded between 5.29 ± 0.74 and 0.46 ± 0.10 (p < 0.05). Increased catalase activity was detected (p < 0.05) by spectrophotometric assays. DCF-DA-stained (oxidative stressed) cells were increased in response to increased concentrations, and there were no significant changes in WLR values. It was concluded that CSO showed strong antifungal activity on F. graminearum via different physiological levels.

The role of JAK2/STAT3 pathway in non-cytotoxic concentrations of DON-induced aggravation of inflammatory response in IL-10 deficient RAW264.7 cells

Deoxynivalenol (DON) as a mycotoxin was commonly found in food and cereals which can affect immune function and inflammatory response. The majority of foods contain DON at levels below the official limit. This study aimed to evaluate the effects of non-cytotoxic concentration of DON on inflammation and its mechanisms using the IL-10 gene-silenced RAW264.7 cell model. The results showed that a non-cytotoxic concentration of DON at 25 ng/ml aggravated IL-10 knockdown-induced inflammation, which was manifested by increasing IL-1β and TNF-α mRNA expression, migration and phagocytosis, decreasing IL-10 mRNA expression, and enhancing JAK2/STAT3 phosphorylation. Adding JAK2 inhibitor AG490 attenuated the aggravating effect of DON on IL-10 knockdown-induced inflammation. In conclusion, a non-cytotoxic concentration of DON enhances the inflammatory response through the JAK2/STAT3 signaling pathway when inflammation occurs in the body. These results indicated that non-cytotoxic concentrations of DON could aggravate inflammation when inflammation was induced by IL-10 knockdown, which increases vigilance against DON contamination at low concentration especially when an animal's body has inflammation.

Antifungal Effect of Metabolites from Bacterial Symbionts of Entomopathogenic Nematodes on Fusarium Head Blight of Wheat

Fungal diseases such as Fusarium head blight (FHB) are significant biotic stressors, negatively affecting wheat production and quality. This study explored the antifungal activity of the metabolites produced by the bacterial symbionts of entomopathogenic nematodes (EPNs) against FHB-causing Fusarium sp. Fusarium graminearum. To achieve this, the symbiotic bacteria of nine EPN isolates from the EPN collection at the Agricultural Research Council-Small Grains (ARC-SG) were isolated from the cadavers of Galleria mellonella (Lepidoptera: Pyralidae) larvae after infection with EPNs. Broth cultures (crude) and their supernatants (filtered and autoclaved) of each bacterial isolate were used as bacterial metabolite treatments to test their inhibitory effect on the mycelial growth and spore germination of F. graminearum. Mycelial growth inhibition rates varied among both bacterial isolates and treatments. Crude metabolite treatments proved to be more effective than filtered and autoclaved metabolite treatments, with an overall inhibition rate of 75.25% compared to 23.93% and 13.32%, respectively. From the crude metabolite treatments, the Xenorhabdus khoisanae SGI 197 bacterial isolate from Steinernema beitlechemi SGI 197 had the highest mean inhibition rate of 96.25%, followed by Photorhabdus luminescens SGI 170 bacteria isolated from Heterorhabditis bacteriophora SGI 170 with a 95.79% mean inhibition rate. The filtered metabolite treatments of all bacterial isolates were tested for their inhibitory activity against Fusarium graminearum spore germination. Mean spore germination inhibition rates from Xenorhabdus spp. bacterial isolates were higher (83.91 to 96.29%) than those from Photorhabdus spp. (6.05 to 14.74%). The results obtained from this study suggest that EPN symbiotic bacterial metabolites have potential use as biological control agents of FHB. Although field efficacy against FHB was not studied, the significant inhibition of mycelial growth and spore germination suggest that the application of these metabolites at the flowering stage may provide protection to plants against infection with or spread of F. graminearum. These metabolites have the potential to be employed as part of integrated pest management (IPM) to inhibit/delay conidia germination until the anthesis (flowering stage) of wheat seedlings has passed.

Fungal Species and Mycotoxins Associated with Maize Ear Rots Collected from the Eastern Cape in South Africa

Maize production in South Africa is concentrated in its central provinces. The Eastern Cape contributes less than 1% of total production, but is steadily increasing its production and has been identified as a priority region for future growth. In this study, we surveyed ear rots at maize farms in the Eastern Cape, and mycotoxins were determined to be present in collected samples. Fungal isolations were made from mouldy ears and species identified using morphology and DNA sequences. Cladosporium, Diplodia, Fusarium and Gibberella ear rots were observed during field work, and of these, we collected 78 samples and isolated 83 fungal strains. Fusarium was identified from Fusarium ear rot (FER) and Gibberella ear rot (GER) and Stenocarpella from Diplodia ear rot (DER) samples, respectively. Using LC-MS/MS multi-mycotoxin analysis, it was revealed that 83% of the collected samples contained mycotoxins, and 17% contained no mycotoxins. Fifty percent of samples contained multiple mycotoxins (deoxynivalenol, 15-acetyl-deoxynivalenol, diplodiatoxin and zearalenone) and 33% contained a single mycotoxin. Fusarium verticillioides was not isolated and fumonisins not detected during this survey. This study revealed that ear rots in the Eastern Cape are caused by a wide range of species that may produce various mycotoxins.

Maize pollen carry bacteria that suppress a fungal pathogen that enters through the male gamete fertilization route

In flowering plants, after being released from pollen grains, the male gametes use the style channel to migrate towards the ovary where they fertilize awaiting eggs. Environmental pathogens exploit the style passage, resulting in diseased progeny seed. The belief is that pollen also transmits pathogens into the style. By contrast, we hypothesized that pollen carries beneficial microbes that suppress environmental pathogens on the style passage. No prior studies have reported pollen-associated bacterial functions in any plant species. Here, bacteria were cultured from maize (corn) pollen encompassing wild ancestors and farmer-selected landraces from across the Americas, grown in a common field in Canada for one season. In total, 298 bacterial isolates were cultured, spanning 45 genera, 103 species, and 88 OTUs, dominated by Pantoea, Bacillus, Pseudomonas, Erwinia, and Microbacterium. Full-length 16S DNA-based taxonomic profiling showed that 78% of bacterial taxa from the major wild ancestor of maize (Parviglumis teosinte) were present in at least one cultivated landrace. The species names of the bacterial isolates were used to search the pathogen literature systematically; this preliminary evidence predicted that the vast majority of the pollen-associated bacteria analyzed are not maize pathogens. The pollen-associated bacteria were tested in vitro against a style-invading Fusarium pathogen shown to cause Gibberella ear rot (GER): 14 isolates inhibited this pathogen. Genome mining showed that all the anti-Fusarium bacterial species encode phzF, associated with biosynthesis of the natural fungicide, phenazine. To mimic the male gamete migration route, three pollen-associated bacterial strains were sprayed onto styles (silks), followed by Fusarium inoculation; these bacteria reduced GER symptoms and mycotoxin accumulation in progeny seed. Confocal microscopy was used to search for direct evidence that pollen-associated bacteria can defend living silks against Fusarium graminearum (Fg); bacterial strain AS541 (Kluyvera intermedia), isolated from pollen of ancestral Parviglumis, was observed to colonize the susceptible style/silk entry points of Fg (silk epidermis, trichomes, wounds). Furthermore, on style/silk tissue, AS541 colonized/aggregated on Fg hyphae, and was associated with Fg hyphal breaks. These results suggest that pollen has the potential to carry bacteria that can defend the style/silk passage against an environmental pathogen - a novel observation.

What Is Fusarium Head Blight (FHB) Resistance and What Are Its Food Safety Risks in Wheat? Problems and Solutions-A Review

The term "Fusarium Head Blight" (FHB) resistance supposedly covers common resistances to different Fusarium spp. without any generally accepted evidence. For food safety, all should be considered with their toxins, except for deoxynivalenol (DON). Disease index (DI), scabby kernels (FDK), and DON steadily result from FHB, and even the genetic regulation of Fusarium spp. may differ; therefore, multitoxin contamination is common. The resistance types of FHB form a rather complex syndrome that has been the subject of debate for decades. It seems that resistance types are not independent variables but rather a series of components that follow disease and epidemic development; their genetic regulation may differ. Spraying inoculation (Type 1 resistance) includes the phase where spores land on palea and lemma and spread to the ovarium and also includes the spread-inhibiting resistance factor; therefore, it provides the overall resistance that is needed. A significant part of Type 1-resistant QTLs could, therefore, be Type 2, requiring the retesting of the QTLs; this is, at least, the case for the most effective ones. The updated resistance components are as follows: Component 1 is overall resistance, as discussed above; Component 2 includes spreading from the ovarium through the head, which is a part of Component 1; Component 3 includes factors from grain development to ripening (FDK); Component 4 includes factors influencing DON contamination, decrease, overproduction, and relative toxin resistance; and for Component 5, the tolerance has a low significance without new results. Independent QTLs with different functions can be identified for one or more traits. Resistance to different Fusarium spp. seems to be connected; it is species non-specific, but further research is necessary. Their toxin relations are unknown. DI, FDK, and DON should be checked as they serve as the basic data for the risk analysis of cultivars. A better understanding of the multitoxin risk is needed regarding resistance to the main Fusarium spp.; therefore, an updated testing methodology is suggested. This will provide more precise data for research, genetics, and variety registration. In winter and spring wheat, the existing resistance level is very high, close to Sumai 3, and provides much greater food safety combined with sophisticated fungicide preventive control and other practices in commercial production.

Fusarium biocontrol: antagonism and mycotoxin elimination by lactic acid bacteria

Mycotoxins produced by Fusarium species are secondary metabolites with low molecular weight formed by filamentous fungi generally resistant to different environmental factors and, therefore, undergo slow degradation. Contamination by Fusarium mycotoxins in cereals and millets is the foremost quality challenge the food and feed industry faces across the globe. Several types of chemical preservatives are employed in the mitigation process of these mycotoxins, and they help in long-term storage; however, chemical preservatives can be used only to some extent, so the complete elimination of toxins from foods is still a herculean task. The growing demand for green-labeled food drives to evade the use of chemicals in the production processes is getting much demand. Thus, the biocontrol of food toxins is important in the developing food sector. Fusarium mycotoxins are world-spread contaminants naturally occurring in commodities, food, and feed. The major mycotoxins Fusarium species produce are deoxynivalenol, fumonisins, zearalenone, and T2/HT2 toxins. Lactic acid bacteria (LAB), generally regarded as safe (GRAS), is a well-explored bacterial community in food preparations and preservation for ages. Recent research suggests that LAB are the best choice for extenuating Fusarium mycotoxins. Apart from Fusarium mycotoxins, this review focuses on the latest studies on the mechanisms of how LAB effectively detoxify and remove these mycotoxins through their various bioactive molecules and background information of these molecules.

Rapid and Sensitive Detection of Toxigenic Fusarium asiaticum Integrating Recombinase Polymerase Amplification, CRISPR/Cas12a, and Lateral Flow Techniques

Fusarium head blight (FHB) is a global cereal disease caused by a complex of Fusarium species. Both Fusarium graminearum and F. asiaticum are the causal agents of FHB in China. F. asiaticum is the predominant species in the Middle-Lower Reaches of the Yangtze River (MLRYR) and southwest China. Therefore, detecting F. asiaticum in a timely manner is crucial for controlling the disease and preventing mycotoxins from entering the food chain. Here, we combined rapid genomic DNA extraction, recombinase polymerase amplification, Cas12a cleavage, and lateral flow detection techniques to develop a method for the rapid detection of F. asiaticum. The reaction conditions were optimized to provide a rapid, sensitive, and cost-effective method for F. asiaticum detection. The optimized method demonstrated exceptional specificity in detecting F. asiaticum while not detecting any of the 14 other Fusarium strains and 3 non-Fusarium species. Additionally, it could detect F. asiaticum DNA at concentrations as low as 20 ag/μL, allowing for the diagnosis of F. asiaticum infection in maize and wheat kernels even after 3 days of inoculation. The developed assay will provide an efficient and robust detection platform to accelerate plant pathogen detection.

Infectivity and stress tolerance traits affect community assembly of plant pathogenic fungi

Understanding how ecological communities assemble is an urgent research priority. In this study, we used a community ecology approach to examine how ecological and evolutionary processes shape biodiversity patterns of plant pathogenic fungi, Fusarium graminearum and F. asiaticum. High-throughput screening revealed that the isolates had a wide range of phenotypic variation in stress tolerance traits. Net Relatedness Index (NRI) and Nearest Taxon Index (NTI) values were computed based on stress-tolerant distance matrices. Certain local regions exhibited positive values of NRI and NTI, indicating phenotypic clustering within the fungal communities. Competition assays of the pooled strains were conducted to investigate the cause of clustering. During stress conditions and wheat colonization, only a few strains dominated the fungal communities, resulting in reduced diversity. Overall, our findings support the modern coexistence theory that abiotic stress and competition lead to phenotypic similarities among coexisting organisms by excluding large, low-competitive clades. We suggest that agricultural environments and competition for host infection lead to locally clustered communities of plant pathogenic fungi in the field.

Population structure and genetic diversity of Fusarium graminearum from southwestern Russia and the Russian Far East as compared with northern Europe and North America

Genetic variation at variable number tandem repeat (VNTR) markers was used to assess population structure and diversity among 296 Fusarium graminearum isolates from northern Europe (Finland, northwestern Russia, and Norway), southern Europe (southwestern and western Russia), and Asia (Siberia and the Russian Far East). We identified at least two highly differentiated and geographically structured genetic populations (E1 and E2) in Eurasia (Φ_PT = 0.35). Isolates from northern Europe were almost exclusively from the E1 population (95.6%) and had the 3ADON (3-acetyldeoxynivalenol) trichothecene genotype (97.3%). In contrast, all isolates from southern Europe were from the E2 population and 94.4% had the 15ADON (15-acetyldeoxynivalenol) genotype. The E2 population also predominated in the Asian sampling locations (92.7%) where 3ADON and 15ADON genotypes occurred at nearly equal frequencies. Southern European isolates were more closely related to those from Asia (Φ_PT = 0.06) than to geographically closer populations from northern Europe (Φ_PT ≥ 0.31). Northern European populations also harbored substantially less genetic diversity (Ne ≤ 2.1) than populations in southern Europe or Asia (Ne ≥ 3.4), indicative of a selective sweep or recent introduction and subsequent range expansion in northern Europe. Bayesian analyses incorporating previously described genetic populations from North America (NA1 and NA2) surprisingly identified NA2 and E2 as a single genetic population, consistent with hypotheses of a recent Eurasian origin for NA2. Additionally, more than 10% of the isolates from Asia and southern Europe were assigned to the NA1 population, indicating recent introductions of NA1 into parts of Eurasia. Collectively, these results demonstrate that there are at least three genetic populations of F. graminearum in the Northern Hemisphere and indicate that population-level diversity in Eurasia and North America has been shaped by recent transcontinental introductions.

Untargeted Metabolomics Reveals a Multi-Faceted Resistance Response to Fusarium Head Blight Mediated by the Thinopyrum elongatum Fhb7E Locus Transferred via Chromosome Engineering into Wheat

The Thinopyrum elongatum Fhb7E locus has been proven to confer outstanding resistance to Fusarium Head Blight (FHB) when transferred into wheat, minimizing yield loss and mycotoxin accumulation in grains. Despite their biological relevance and breeding implications, the molecular mechanisms underlying the resistant phenotype associated with Fhb7E have not been fully uncovered. To gain a broader understanding of processes involved in this complex plant-pathogen interaction, we analysed via untargeted metabolomics durum wheat (DW) rachises and grains upon spike inoculation with Fusarium graminearum (Fg) and water. The employment of DW near-isogenic recombinant lines carrying or lacking the Th. elongatum chromosome 7E region including Fhb7E on their 7AL arm, allowed clear-cut distinction between differentially accumulated disease-related metabolites. Besides confirming the rachis as key site of the main metabolic shift in plant response to FHB, and the upregulation of defence pathways (aromatic amino acid, phenylpropanoid, terpenoid) leading to antioxidants and lignin accumulation, novel insights were revealed. Fhb7E conferred constitutive and early-induced defence response, in which specific importance of polyamine biosynthesis, glutathione and vitamin B6 metabolisms, along with presence of multiple routes for deoxynivalenol detoxification, was highlighted. The results suggested Fhb7E to correspond to a compound locus, triggering a multi-faceted plant response to Fg, effectively limiting Fg growth and mycotoxin production.

Deoxynivalenol at No-Observed Adverse-Effect Levels Aggravates DSS-Induced Colitis through the JAK2/STAT3 Signaling Pathway in Mice

The etiology of inflammatory bowel diseases (IBDs) involves complex genetic and environmental factors such as mycotoxin contamination. Deoxynivalenol (DON), a well-known mycotoxin, contaminates food and feed and can induce intestinal injury and inflammatory response. The dose of DON in many foods is also below the limit, although the dose of DON exceeds the limit. The present study aims to evaluate the effects of the nontoxic dose of DON on colitis induced by dextran sodium sulfate (DSS) and the mechanism in mice. The results showed a nontoxic dose of DON at 50 μg/kg bw per day exacerbated DSS-induced colitis in mice as demonstrated by increased disease activity index, decreased colon length, increased morphological damage, decreased occludin and mucoprotein 2 expression, increased IL-1β and TNF-α expression, and decreased IL-10 expression. DON at 50 μg/kg bw per day enhanced JAK2/STAT3 phosphorylation induced by DSS. Adding JAK2 inhibitor AG490 attenuated the aggravating effects of DON on DSS-induced colitis by reversing the morphological damage, occludin and mucoprotein 2 expression increased, IL-1β and TNF-α expression increased, and IL-10 expression decreased. Taken together, a nontoxic dose of DON could aggravate DSS-induced colitis via the JAK2/STAT3 signaling pathway. This suggests that DON, below the standard limit dose, is also a risk for IBD and may be harmful to the health of humans and animals, which could provide the basis for establishing limits for DON.

Inter-laboratory study on simultaneous quantification of ten trichothecenes in feed

An inter-laboratory study was performed in eight laboratories to evaluate the simultaneous quantification method for HT-2 toxin (HT-2), T-2 toxin (T-2), diacetoxyscirpenol (DAS), neosolaniol (NES), 3-acetyldeoxynivalenol (3-AcDON), 15-acetyldeoxynivalenol (15-AcDON), deoxynivalenol (DON), deoxynivalenol-3-glucoside (D3G), nivalenol (NIV), and fusarenon-X (FUS-X) in feed. The mycotoxins in the samples were extracted with hydrous acetonitrile, purified using a multifunctional column (InertSep^® VRA-3) and a phospholipid removal column (Hybrid SPE^®-Phospholipid), and then quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with atmospheric pressure chemical ionisation mode. The mean recovery, repeatability, reproducibility, and Horwitz ratio from the inter-laboratory validation study were 99.8-109%, 3.1-9.8%, 4.3-9.8%, and 0.19-0.45, respectively, for type A trichothecenes (HT-2, T-2, DAS, and NES). Those values for type B trichothecenes (3-AcDON, 15-AcDON, DON, NIV, and FUS-X) were 89.9-116%, 3.4-9.1%, 5.6-14%, and 0.25-0.70, and the values for modified mycotoxin (D3G) were 78.2-96.7%, 3.5-6.4%, and 13-22%, respectively.

Transcriptome Dynamic Analysis Reveals New Candidate Genes Associated with Resistance to Fusarium Head Blight in Two Chinese Contrasting Wheat Genotypes

In recent years, Fusarium head blight (FHB) has developed into a global disease that seriously affects the yield and quality of wheat. Effective measures to solve this problem include exploring disease-resistant genes and breeding disease-resistant varieties. In this study, we conducted a comparative transcriptome analysis to identify the important genes that are differentially expressed in FHB medium-resistant (Nankang 1) and FHB medium-susceptible (Shannong 102) wheat varieties for various periods after Fusarium graminearum infection using RNA-seq technology. In total, 96,628 differentially expressed genes (DEGs) were identified, 42,767 from Shannong 102 and 53,861 from Nankang 1 (FDR < 0.05 and |log2FC| > 1). Of these, 5754 and 6841 genes were found to be shared among the three time points in Shannong 102 and Nankang 1, respectively. After inoculation for 48 h, the number of upregulated genes in Nankang 1 was significantly lower than that of Shannong 102, but at 96 h, the number of DEGs in Nankang 1 was higher than that in Shannong 102. This indicated that Shannong 102 and Nankang 1 had different defensive responses to F. graminearum in the early stages of infection. By comparing the DEGs, there were 2282 genes shared at the three time points between the two strains. GO and KEGG analyses of these DEGs showed that the following pathways were associated with disease resistance genes: response to stimulus pathway in GO, glutathione metabolism, phenylpropanoid biosynthesis, plant hormone signal transduction, and plant-pathogen interaction in KEGG. Among them, 16 upregulated genes were identified in the plant-pathogen interaction pathway. There were five upregulated genes, TraesCS5A02G439700, TraesCS5B02G442900, TraesCS5B02G443300, TraesCS5B02G443400, and TraesCS5D02G446900, with significantly higher expression levels in Nankang 1 than in Shannong 102, and these genes may have an important role in regulating the resistance of Nankang 1 to F. graminearum infection. The PR proteins they encode are PR protein 1-9, PR protein 1-6, PR protein 1-7, PR protein 1-7, and PR protein 1-like. In addition, the number of DEGs in Nankang 1 was higher than that in Shannong 102 on almost all chromosomes, except chromosomes 1A and 3D, but especially on chromosomes 6B, 4B, 3B, and 5A. These results indicate that gene expression and the genetic background must be considered for FHB resistance in wheat breeding.

Quantitative PCR assays for the species-specific detection of Fusarium graminearum sensu stricto and Fusarium asiaticum in winter wheat growing regions in China

Fusarium graminearum species complex (FGSC) is one of the most devastating fungal plant pathogens of cereal crops worldwide, resulting in a corresponding mycotoxins contamination in cereal-based food. The detection of FGSC to study its population structure and species distribution is of great concern for the integrated control of mycotoxins contamination in grains entering food supply chains. In this study, real time quantitative PCR (RT-qPCR) and droplet digital PCR (ddPCR) methods were developed for the species-specific detection of Fusarium graminearum species complex in winter wheat growing regions in China. Primers and probes were designed basing the on the sequence of Fg-16 SCAR fragment (sequence characterized amplified regions analysis) and confirmed to make a distinguishment between the two prevailing species including Fusarium graminearum sensu stricto and Fusarium asiaticum. The assay specificity was tested against 24 isolates of target Fusarium species and several non-target Fusarium species that were frequently isolated from wheat in China. Consistent results could be obtained by the developed RT-qPCR and ddPCR assays, and both of them were sensitive enough for the detection of FGSC in these regions. Population structure and species distribution of FGSC in North China plain and Yangtze River plain by the developed qPCR assays accorded with previous results obtained by fungal isolation method. The newly developed qPCR assays are time-saving and will provide new insights during the routine surveillance of FGSC in winter wheat growing regions in China and possibly other countries.

Discovery and Characterization of Putative Glycoprotein-Encoding Mycoviruses in the Bunyavirales

Although segmented negative-sense RNA viruses (SNSRVs) have been frequently discovered in various fungi, most SNSRVs reported only the large segments. In this study, we investigated the diversity of the mycoviruses in the phytopathogenic fungus Fusarium asiaticum using the metatranscriptomic technique. We identified 17 fungal single-stranded RNA (ssRNA) viruses including nine viruses within Mitoviridae, one each in Narnaviridae, Botourmiaviridae, Hypoviridae, Fusariviridae, and Narliviridae, two in Mymonaviridae, and one trisegmented virus temporarily named Fusarium asiaticum mycobunyavirus 1 (FaMBV1). The FaMBV1 genome comprises three RNA segments, large (L), medium (M), and small (S) with 6,468, 2,639, and 1,420 nucleotides, respectively. These L, M, and S segments putatively encode the L protein, glycoprotein, and nucleocapsid, respectively. Phylogenetic analysis based on the L protein showed that FaMBV1 is phylogenetically clustered with Alternaria tenuissima negative-stranded RNA virus 2 (AtNSRV2) and Sclerotinia sclerotiorum negative-stranded RNA virus 5 (SsNSRV5) but distantly related to the members of the family Phenuiviridae. FaMBV1 could be vertically transmitted by asexual spores with lower efficiency (16.7%, 2/42). Comparison between FaMBV1-free and -infected fungal strains revealed that FaMBV1 has little effect on hyphal growth, pathogenicity, and conidium production, and its M segment is dispensable for viral replication and lost during subculture and asexual conidiation. The M and S segments of AtNSRV2 and SsNSRV5 were found using bioinformatics methods, indicating that the two fungal NSRVs harbor trisegmented genomes. Our results provide a new example of the existence and evolution of the segmented negative-sense RNA viruses in fungi. IMPORTANCE Fungal segmented negative-sense RNA viruses (SNSRVs) have been frequently found. Only the large segment encoding RNA-dependent RNA polymerase (RdRp) has been reported in most fungal SNSRVs, except for a few fungal SNSRVs reported to encode nucleocapsids, nonstructural proteins, or movement proteins. Virome analysis of the Fusarium spp. that cause Fusarium head blight discovered a novel virus, Fusarium asiaticum mycobunyavirus 1 (FaMBV1), representing a novel lineage of the family Phenuiviridae. FaMBV1 harbors a trisegmented genome that putatively encodes RdRp, glycoproteins, and nucleocapsids. The putative glycoprotein was first described in fungal SNSRVs and shared homology with glycoprotein of animal phenuivirus but was dispensable for its replication in F. asiaticum. Two other trisegmented fungal SNSRVs that also encode glycoproteins were discovered, implying that three-segment bunyavirus infections may be common in fungi. These findings provide new insights into the ecology and evolution of SNSRVs, particularly those infecting fungi.

Evaluation of Barley and Wheat Germplasm for Resistance to Head Blight and Mycotoxin Production by Fusarium asiaticum and F. graminearum

Fusarium head blight (FHB) is one of the most serious diseases in barley and wheat, as it is usually accompanied by the production of harmful mycotoxins in the grains. To identify FHB-resistant breeding resources, we evaluated 60 elite germplasm accessions of barley (24) and wheat (36) for FHB and mycotoxin accumulation. Assessments were performed in a greenhouse and five heads per accession were inoculated with both Fusarium asiaticum (Fa73, nivalenol producer) and F. graminearum (Fg39, deoxynivalenol producer) strains. While the accessions varied in disease severity and mycotoxin production, four wheat and one barley showed <20% FHB severity repeatedly by both strains. Mycotoxin levels in these accessions ranged up to 3.9 mg/kg. FHB severity was generally higher in barley than in wheat, and Fa73 was more aggressive in both crops than Fg39. Fg39 itself, however, was more aggressive toward wheat and produced more mycotoxin in wheat than in barley. FHB severity by Fa73 and Fg39 were moderately correlated in both crops (r = 0.57/0.60 in barley and 0.42/0.58 in wheat). FHB severity and toxin production were also correlated in both crops, with a stronger correlation for Fa73 (r = 0.42/0.82 in barley, 0.70 in wheat) than for Fg39.

Physiological and metabolic analyses provide insight into soybean seed resistance to fusarium fujikuroi causing seed decay

Seed-borne pathogens cause diverse diseases at the growth, pre- and post-harvest stage of soybean resulting in a large reduction in yield and quality. The physiological and metabolic aspects of seeds are closely related to their defense against pathogens. Recently, Fusarium fujikuroi has been identified as the dominant seed-borne fungi of soybean seed decay, but little information on the responses of soybean seeds induced by F. fujikuroi is available. In this study, a time-course symptom development of seed decay was observed after F. fujikuroi inoculation through spore suspension soaking. The germination rate and the contents of soluble sugar and soluble protein were significantly altered over time. Both chitinase and β-1,3-glucanase as important fungal cell wall-degrading enzymes of soybean seeds were also rapidly and transiently activated upon the early infection of F. fujikuroi. Metabolic profile analysis showed that the metabolites in glycine, serine, and threonine metabolism and tryptophan metabolism were clearly induced by F. fujikuroi, but different metabolites were mostly enriched in isoflavone biosynthesis, flavone biosynthesis, and galactose pathways. Interestingly, glycitein and glycitin were dramatically upregulated while daidzein, genistein, genistin, and daidzin were largely downregulated. These results indicate a combination of physiological responses, cell wall-related defense, and the complicated metabolites of soybean seeds contributes to soybean seed resistance against F. fujikuroi, which are useful for soybean resistance breeding.

Genetic sources and loci for Fusarium head blight resistance in bread wheat

Fusarium head blight (FHB) of wheat is an important disease worldwide, affecting the yield, end-use quality and threatening food safety. Genetic resources or stable loci for FHB resistance are still limited in breeding programs. A panel of 265 bread wheat accessions from China, CIMMYT-Mexico and other countries was screened for FHB resistance under 5 field experiments in Mexico and China, and a genome-wide association analysis was performed to identify QTLs associated with FHB resistance. The major locus Fhb1 was significantly associated with FHB severity and Deoxynivalenol content in grains. FHB screening experiments in multiple environments showed that Fhb1-harbouring accessions Sumai3, Sumai5, Ningmai9, Yangmai18 and Tokai66 had low FHB index, disease severity and DON content in grains in response to different Fusarium species and ecological conditions in Mexico and China. Accessions Klein Don Enrique, Chuko and Yumai34 did not have Fhb1 but still showed good FHB resistance and low mycotoxin accumulation. Sixteen loci associated with FHB resistance or DON content in grains were identified on chromosomes 1A, 1B, 2B, 3A, 3D, 4B, 4D, 5A, 5B, 7A, and 7B in multiple environments, explaining phenotypic variation of 4.43–10.49%. The sources with good FHB resistance reported here could be used in breeding programs for resistance improvement in Mexico and China, and the significant loci could be further studied and introgressed for resistance improvement against FHB and mycotoxin accumulation in grains.

Whole-genome single nucleotide polymorphism analysis for typing the pandemic pathogen Fusarium graminearum sensu stricto

Recent improvements in microbiology and molecular epidemiology were largely stimulated by whole- genome sequencing (WGS), which provides an unprecedented resolution in discriminating highly related genetic backgrounds. WGS is becoming the method of choice in epidemiology of fungal diseases, but its application is still in a pioneer stage, mainly due to the limited number of available genomes. Fungal pathogens often belong to complexes composed of numerous cryptic species. Detecting cryptic diversity is fundamental to understand the dynamics and the evolutionary relationships underlying disease outbreaks. In this study, we explore the value of whole-genome SNP analyses in identification of the pandemic pathogen Fusarium graminearum sensu stricto (F.g.). This species is responsible for cereal diseases and negatively impacts grain production worldwide. The fungus belongs to the monophyletic fungal complex referred to as F. graminearum species complex including at least sixteen cryptic species, a few among them may be involved in cereal diseases in certain agricultural areas. We analyzed WGS data from a collection of 99 F.g. strains and 33 strains representing all known cryptic species belonging to the FGSC complex. As a first step, we performed a phylogenomic analysis to reveal species-specific clustering. A RAxML maximum likelihood tree grouped all analyzed strains of F.g. into a single clade, supporting the clustering-based identification approach. Although, phylogenetic reconstructions are essential in detecting cryptic species, a phylogenomic tree does not fulfill the criteria for rapid and cost-effective approach for identification of fungi, due to the time-consuming nature of the analysis. As an alternative, analysis of WGS information by mapping sequence data from individual strains against reference genomes may provide useful markers for the rapid identification of fungi. We provide a robust framework for typing F.g. through the web-based PhaME workflow available at EDGE bioinformatics. The method was validated through multiple comparisons of assembly genomes to F.g. reference strain PH-1. We showed that the difference between intra- and interspecies variability was at least two times higher than intraspecific variation facilitating successful typing of F.g. This is the first study which employs WGS data for typing plant pathogenic fusaria.

Bambara Groundnut Rhizobacteria Antimicrobial and Biofertilization Potential

Bambara groundnut, an underutilized crop has been proved to be an indigenous crop in Africa with the potential for food security. The rhizosphere of Bambara groundnut contains Rhizobacteria, with the ability to grow, adapt, and colonize their surroundings even in unfavorable conditions and have not been explored for their plant growth-promoting properties. The aim of this research was to determine the potential of rhizobacteria from Bambara groundnut soil samples as either biofertilizers or biocontrol agents or both to help provide sustainable agriculture in Africa and globally. Bambara groundnut rhizospheric soil samples were collected and analyzed for their chemical composition. Rhizobacteria isolates were cultured from the soil samples. Plant growth-promoting, antifungal activities and phylogenetic analysis using 16S rRNA were carried out on the isolates to identify the rhizobacteria. A 2-year field study planting was carried out to determine the effect of these rhizobacteria as biofertilizers for Bambara groundnut (Vigna subterranean). The study was carried out in a complete randomized block experimental design with three replications. All the isolates were able to produce ammonia and 1-aminocyclopropane-1-carboxylate, while 4.65, 12.28, and 27.91% produced hydrogen cyanide, indole acetic acid, and solubilized phosphate, respectively, making them important targets as biocontrol and biofertilizer agents. The field results revealed that treatment with rhizobacteria had significant results compared with the control. Characterization of selected isolates reveals their identity as B. amyloliquefaciens, B. thuringiensis, and Bacillus sp. These Bacillus isolates have proved to be plant growth-promoting agents that can be used as biofertilizers to enhance the growth of crops and consequent improved yield. This is the first time the rhizobacteria from the Bambara groundnut rhizosphere are applied as biofertilizer.

Exploration of Mycotoxin Accumulation and Transcriptomes of Different Wheat Cultivars during Fusarium graminearum Infection

Fusarium graminearum is one of the most devastating diseases of wheat worldwide, and can cause Fusarium head blight (FHB). F. graminearum infection and mycotoxin production mainly present in wheat and can be influenced by environmental factors and wheat cultivars. The objectives of this study were to examine the effect of wheat cultivars and interacting conditions of temperature and water activity (aw) on mycotoxin production by two strains of F. graminearum and investigate the response mechanisms of different wheat cultivars to F. graminearum infection. In this regard, six cultivars of wheat spikes under field conditions and three cultivars of post-harvest wheat grains under three different temperature conditions combined with five water activity (aw) conditions were used for F. graminearum infection in our studies. Liquid chromatography tandem mass spectrometry (LC–MS/MS) analysis showed significant differences in the concentration of Fusarium mycotoxins deoxynivalenol (DON) and its derivative deoxynivalenol-3-glucoside (D3G) resulting from wheat cultivars and environmental factors. Transcriptome profiles of wheat infected with F. graminearum revealed the lower expression of disease defense-factor-related genes, such as mitogen-activated protein kinases (MAPK)-encoding genes and hypersensitivity response (HR)-related genes of infected Annong 0711 grains compared with infected Sumai 3 grains. These findings demonstrated the optimal temperature and air humidity resulting in mycotoxin accumulation, which will be beneficial in determining the conditions of the relative level of risk of contamination with FHB and mycotoxins. More importantly, our transcriptome profiling illustrated differences at the molecular level between wheat cultivars with different FHB resistances, which will lay the foundation for further research on mycotoxin biosynthesis of F. graminearum and regulatory mechanisms of wheat to F. graminearum.

Fusarium culmorum Produces NX-2 Toxin Simultaneously with Deoxynivalenol and 3-Acetyl-Deoxynivalenol or Nivalenol

Fusarium culmorum is a major pathogen of grain crops. Infected plants accumulate deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ADON), or nivalenol (NIV), which are mycotoxins of the trichothecene B group. These toxins are also produced by F. graminearum species complex. New trichothecenes structurally similar to trichothecenes B but lacking the carbonyl group on C-8, designated NX toxins, were recently discovered in atypical isolates of F. graminearum from North America. Only these isolates and a few strains of a yet to be characterized Fusarium species from South Africa are known to produce NX-2 and other NX toxins. Here, we report that among 20 F. culmorum strains isolated from maize, wheat, and oat in Europe and Asia over a period of 70 years, 18 strains produced NX-2 simultaneously with 3-ADON and DON or NIV. Rice cultures of strains producing 3-ADON accumulated NX-2 in amounts corresponding to 2−8% of 3-ADON (1.2−36 mg/kg). A strain producing NIV accumulated NX-2 and NIV at comparable amounts (13.6 and 10.3 mg/kg, respectively). In F. graminearum, producers of NX-2 possess a special variant of cytochrome P450 monooxygenase encoded by TRI1 that is unable to oxidize C-8. In F. culmorum, producers and nonproducers of NX-2 possess identical TRI1; the reason for the production of NX-2 is unknown. Our results indicate that the production of NX-2 simultaneously with trichothecenes B is a common feature of F. culmorum.

Identification and Functional Characterisation of Two Oat UDP-Glucosyltransferases Involved in Deoxynivalenol Detoxification

Oat is susceptible to several Fusarium species that cause contamination with different trichothecene mycotoxins. The molecular mechanisms behind Fusarium resistance in oat have yet to be elucidated. In the present work, we identified and characterised two oat UDP-glucosyltransferases orthologous to barley HvUGT13248. Overexpression of the latter in wheat had been shown previously to increase resistance to deoxynivalenol (DON) and nivalenol (NIV) and to decrease disease the severity of both Fusarium head blight and Fusarium crown rot. Both oat genes are highly inducible by the application of DON and during infection with Fusarium graminearum. Heterologous expression of these genes in a toxin-sensitive strain of Saccharomyces cerevisiae conferred high levels of resistance to DON, NIV and HT-2 toxins, but not C4-acetylated trichothecenes (T-2, diacetoxyscirpenol). Recombinant enzymes AsUGT1 and AsUGT2 expressed in Escherichia coli rapidly lost activity upon purification, but the treatment of whole cells with the toxin clearly demonstrated the ability to convert DON into DON-3-O-glucoside. The two UGTs could therefore play an important role in counteracting the Fusarium virulence factor DON in oat.

Evaluation of Fusarium Head Blight Resistance in 410 Chinese Wheat Cultivars Selected for Their Climate Conditions and Ecological Niche Using Natural Infection Across Three Distinct Experimental Sites

Exploiting wheat cultivars with stable resistance to Fusarium Head blight (FHB) and toxin accumulation is a cost-effective and environmentally friendly strategy to reduce the risk of yield losses and contamination with mycotoxins. To facilitate the deployment of stable cultivar resistance, we evaluated FHB resistance and resistance to mycotoxin accumulation in 410 wheat lines bred by local breeders from four major wheat growing regions in China after natural infection at three distinct locations (Hefei, Yangzhou and Nanping). Significant differences in disease index were observed among the three locations. The disease indexes (DI's) in Nanping were the highest, followed by Yangzhou and Hefei. The distribution of DI's in Yangzhou showed the best discrimination of FHB resistance in cultivars. Growing region and cultivar had significant effect on DI and mycotoxins. Among the climate factors, relative humidity and rainfall were the key factors resulting in the severe disease. Even though most cultivars were still susceptible to FHB under the strongly conducive conditions applied, the ratio of resistant lines increased in the Upper region of the Yangtze River (UYR) and the Middle and Lower Region of the Yangtze River (MLYR) between 2015 and 2019. Deoxynivalenol (DON) was the dominant mycotoxin found in Hefei and Yangzhou, while NIV was predominant in Nanping. Disease indexes were significantly correlated with DON content in wheat grain.

Fusarium graminearum Species Complex: A Bibliographic Analysis and Web-Accessible Database for Global Mapping of Species and Trichothecene Toxin Chemotypes

Fusarium graminearum is ranked among the five most destructive fungal pathogens that affect agroecosystems. It causes floral diseases in small grain cereals including wheat, barley, and oats, as well as maize and rice. We conducted a systematic review of peer-reviewed studies reporting species within the F. graminearum species complex (FGSC) and created two main data tables. The first contained summarized data from the articles including bibliographic, geographic, methodological (ID methods), host of origin and species, while the second data table contains information about the described strains such as publication, isolate code(s), host/substrate, year of isolation, geographical coordinates, species and trichothecene genotype. Analyses of the bibliographic data obtained from 123 publications from 2000 to 2021 by 498 unique authors and published in 40 journals are summarized. We describe the frequency of species and chemotypes for 16,274 strains for which geographical information was available, either provided as raw data or extracted from the publications, and sampled across six continents and 32 countries. The database and interactive interface are publicly available, allowing for searches, summarization, and mapping of strains according to several criteria including article, country, host, species and trichothecene genotype. The database will be updated as new articles are published and should be useful for guiding future surveys and exploring factors associated with species distribution such as climate and land use. Authors are encouraged to submit data at the strain level to the database, which is accessible at https://fgsc.netlify.app.

Host Genotype and Weather Effects on Fusarium Head Blight Severity and Mycotoxin Load in Spring Barley

Epidemiology of Fusarium Head Blight (FHB) of spring barley is relatively little understood. In a five-year study, we assessed quantitative resistance to FHB in an assortment of 17 spring barley genotypes in the field in southern Germany. To this end, we used soil and spray inoculation of plants with F. culmorum and F. avenaceum. This increased disease pressure and provoked genotypic differentiation. To normalize effects of variable weather conditions across consecutive seasons, we used a disease ranking of the genotypes based on quantification of fungal DNA contents and multiple Fusarium toxins in harvested grain. Together, this allowed for assessment of stable quantitative FHB resistance of barley in several genotypes. Fungal DNA contents were positively associated with species-specific Fusarium toxins in single years and over several years in plots with soil inoculation. In those plots, plant height limited FHB; however, this was not observed after spray inoculation. A multiple linear regression model of recorded weather parameter and fungal DNA contents over five years identified time periods during the reproductive phase of barley, in which weather strongly influenced fungal colonization measured in mature barley grain. Environmental conditions before heading and late after anthesis showed strongest associations with F. culmorum DNA in all genotypes, whereas for F. avenaceum, this was less consistent where we observed weather-dependent associations, depending on the genotype. Based on this study, we discuss aspects of practical resistance breeding in barley relevant to improve quantitative resistance to FHB and associated mycotoxin contaminations.

Secondary Metabolite Gene Regulation in Mycotoxigenic Fusarium Species: A Focus on Chromatin

Fusarium is a species-rich group of mycotoxigenic plant pathogens that ranks as one of the most economically important fungal genera in the world. During growth and infection, they are able to produce a vast spectrum of low-molecular-weight compounds, so-called secondary metabolites (SMs). SMs often comprise toxic compounds (i.e., mycotoxins) that contaminate precious food and feed sources and cause adverse health effects in humans and livestock. In this context, understanding the regulation of their biosynthesis is crucial for the development of cropping strategies that aim at minimizing mycotoxin contamination in the field. Nevertheless, currently, only a fraction of SMs have been identified, and even fewer are considered for regular monitoring by regulatory authorities. Limitations to exploit their full chemical potential arise from the fact that the genes involved in their biosynthesis are often silent under standard laboratory conditions and only induced upon specific stimuli mimicking natural conditions in which biosynthesis of the respective SM becomes advantageous for the producer. This implies a complex regulatory network. Several components of these gene networks have been studied in the past, thereby greatly advancing the understanding of SM gene regulation and mycotoxin biosynthesis in general. This review aims at summarizing the latest advances in SM research in these notorious plant pathogens with a focus on chromatin structure.

Identification of Quantitative Trait Loci Associated With Partial Resistance to Fusarium Root Rot and Wilt Caused by Fusarium graminearum in Field Pea

Fusarium root rot, caused by a complex of Fusarium spp., is a major disease of field pea (Pisum sativum). The development of genetic resistance is the most promising approach to manage the disease, but no pea germplasm has been identified that is completely resistant to root rot. The aim of this study was to detect quantitative trait loci (QTL) conferring partial resistance to root rot and wilting, caused by five fungal isolates representing Fusarium solani, F. avenaceum, F. acuminatum, F. proliferatum, and F. graminearum. Evaluation of the root rot-tolerant cultivar "00-2067" and susceptible cultivar "Reward" was carried out with the five species. There was a significant difference (p < 0.001) between the mean root rot values of the two cultivars inoculated with the F. avenaceum (F4A) and F. graminearum (FG2) isolates. Therefore, in the QTL study, the F8 recombinant inbred line (RIL) population derived from "Reward" × "00-2067" was inoculated in the greenhouse (4 ×) with only F4A and FG2. The parents and F8 population were genotyped using 13.2K single nucleotide polymorphisms (SNPs) and 222 simple sequence repeat (SSR) markers. A significant genotypic effect (p < 0.05) and high heritability (79% to 92.1%) were observed for disease severity, vigor, and plant height following inoculation with F4A and FG2. Significant correlation coefficients were detected among and within all traits. This suggested that a high proportion of the genetic variance was transmitted from the parents to the progeny. However, no significant QTL (LOD > 3) were detected for the RILs inoculated with F4A. In the case of the RILs inoculated with FG2, 5 QTL for root rot severity and 3 QTL each for vigor and plant height were detected. The most stable QTL for plant height (Hgt-Ps3.1) was detected on Chrom5/LGIII. The two most stable QTL for partial resistance to FG2, Fg-Ps4.1, and Fg-Ps4.2 were located in a 15.1-cM and 11.2-cM genomic region, respectively, on Chrom4/LGIV. The most stable QTL for vigor (Vig-Ps4.1) was found in the same region. Twenty-five major and moderate effect digenic epistatic interactions were detected. The identified region on chrom4/LGIV could be important for resistance breeding and marker development.

Production of type-B trichothecenes by Fusarium meridionale, F. graminearum, and F. austroamericanum in wheat plants and rice medium

Food security goes beyond food being available; the food needs to be free of contaminants. Trichothecenes mycotoxins, produced by Fusarium fungus, are. among the most frequently found contaminants of wheat. In this study, we evaluated the production of trichothecenes Deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), 15-acetyldeoxynivalenol (15-AcDON), and nivalenol (NIV) by Fusarium meridionale, F. austroamericanum, and F. graminearum grown in wheat plants and rice medium. Fusarim meridionale was efficient only in the production of NIV (production range (pr) from 1340 to 2864 µg kg^-1 in wheat plant), and F. austroamericanum in the production of 3-AcDON (pr from 50 to 192 µg kg^-1 in wheat plant, and from 986 to 7045 µg kg^-1 in rice medium) and DON (pr from 4076 to 13,701 µg kg^-1 in wheat plant, and from 184 to 43,395 µg kg^-1 in rice medium). Already, F. graminearum was efficient in the production of 3-AcDON only in rice medium (pr from 81 to 2342 µg kg^-1), 15-AcDON in wheat plant (pr from 80 to 295 µg kg^-1) and in rice medium (pr from 436 to 8597 µg kg^-1), and DON also in wheat plant (pr from 7746 to 12,046 µg kg^-1) and in rice medium (pr from 695 to 49,624 µg kg^-1). The specificity of F. meridionale in the production of NIV but not the production of DON could generate a food security problem in regions where this species occurs and the amounts of NIV in grains and derivatives are not regulated in the food chain, as in Brazil.

Fungicide Resistance in Fusarium graminearum Species Complex

Fusariosis affects cereal grain crops worldwide and is responsible for devastating crops, reducing grain quality and yield, and producing strong mycotoxins. Benzimidazoles and triazoles were recommended to combat fusariosis; however, there were reports of resistance, making it necessary to reflect on the reasons for this occurrence. The purpose of this review was to evaluate the fusariosis resistance to the main agricultural fungicides, to observe whether this resistance can cause changes in the production of mycotoxins, and to verify the influence of resistance on the cereal grain production chain. Scientific articles were selected from the ScienceDirect, Scopus, and Pubmed databases, published at maximum 10 years ago and covering the main fungicide classes that combat phytopathogenesis and mycotoxin production. A high occurrence of resistance to carbendazim was found, while few reports of resistance to triazoles are available. The effectiveness of strobilurins is doubtful, due to an increase of mycotoxins linked to it. It is possible to conclude that the large-scale use of fungicides can select resistant strains that will contribute to an increase in the production of mycotoxins and harm sectors of the world economy, not only the agriculture, but also sanitation and foreign trade.

Contamination of durum wheat lines kernels with Fusarium species and deoxynivalenol

Fusarium infection and deoxynivalenol (DON) contamination in seven durum wheat lines kernel (six domestic durum lines ZP 16, ZP 34, ZP 41, ZP 74, ZP 120, ZP DSP 66, and one international durum line Cimmyt 7817) during two harvest seasons (2015-2016) has been studied. The four Fusarium species, F. graminearum, F. proliferatum, F. sporotrichioides, and F. verticillioides, were identified in 2015. A different structure of the Fusarium population, which in addition to F. graminearum, F. sporotrichioides and F. verticillioides, also comprised F. poae, F. semitectum, and F. subglutinans, was identified in 2016. F. graminearum was the predominant species in the durum wheat lines kernels and the potential producer of DON. The other Fusarium spp. were isolated sporadically and with a low incidence in the kernels. The incidence of F. graminearum and DON levels were significantly affected by the wheat genotypes and studied years and these parameters were negatively correlated. The incidence of F. graminearum was significantly higher in 2015 (75.86%) than in 2016 (63.43%), while the level of DON was significantly higher in 2016 (3.636 mg kg-1) compared to 2015 (1.126 mg kg-1). Statistically, there was a significantly higher incidence of F. graminearum in ZP DSP 66 (73.00%) and ZP 120 (72.75%) durum wheat lines than in the other durum genotypes. DON level was the highest in durum wheat line ZP 120 (3.854 mg kg-1). Considering all treatments tested, the mean DON level was 2.381 mg kg-1, while the mean incidence of F. graminearum was 69.64%. ?ested durum wheat lines showed susceptibility to F. graminearum, resulting in high DON levels in kernels. The results obtained suggest the importance of using the lines with improved resistance to Fusarium head blight in the breeding programs for new durum wheat cultivars.

Overexpression of chitinase in the endophyte Phomopsis liquidambaris enhances wheat resistance to Fusarium graminearum

Fusarium head blight (FHB) is a disease that affects wheat crops worldwide and is caused by Fusarium graminearum. Effective and safe strategies for the prevention and treatment of the disease are very limited. Phomopsis liquidambaris, a universal endophyte, can colonize wheat. Two engineered strains, Phomopsis liquidambaris OE-Chi and IN-Chi, were constructed by transformation with a plasmid and integration of a chitinase into the genome, respectively. The OE-Chi and IN-Chi strains could inhibit the expansion of Fusarium sp. in plate confrontation assays in vitro. Colonization of the OE-Chi strain in wheat showed better effects than colonization of the IN-Chi strain and alleviated the inhibition of wheat growth caused by F. graminearum. The shoot length, root length and fresh weight of infected wheat increased by 164.9%, 115.4%, and 190.7%, respectively, when the plants were inoculated with the OE-Chi strain. The peroxidase (POD) activity in the wheat root increased by 38.0%, and it was maintained at a high level in the shoot, which suggested that the OE-Chi strain could enhance the resistance of wheat to F. graminearum. The root and shoot superoxide dismutase (SOD) activities were decreased by 11.8% and 19.0%, respectively, which may be helpful for colonization by the OE-Chi strain. These results suggested that the Phomopsis liquidambaris OE-Chi strain may be a potential endophyte in the biocontrol of FHB.

The mycorrhizal fungi of Cymbidium promote the growth of Dendrobiumofficinale by increasing environmental stress tolerance

Dendrobium officinale is a medicinal herbal plant with important health care value and high demand. Due to its slow growth and scarcity in nature, its yield depends on intensified cultivation while biotic and abiotic stresses were important factors that causes production loss. Orchidaceae can form association with rhizoctonias collectively, and studies have found that some orchids showed a high level of strain-species specificity to orchid mycorrhizal fungi (OMF), yet the specificity of OMF on D. officinale needs to explored. In this study, the effects on D. officinale of four OMF isolated from Cymbidium were tested. The obviously higher mass yield of the treated plants in medium and pots indicated the growth promotion effect of the fungi. Furthermore, an abiotic stress test indicated stronger drought tolerance among the treated plants. For the biotic stress test, two root rot pathogens, Fusarium solani and Fusarium graminearum , were isolated and identified from root rot of D. officinale. In an in vitro inhibition test, the four OMF could resist the growth of these pathogens. In vivo studies showed that these four OMF could improve the survival rate and fresh weight and decrease the root rot rate of pathogen-inoculated seedlings. The four OMF namely; Hyphomycete sp., Umbelopsis sp., Ceratorhiza sp. and Ceratorhiza sp. are compatible strains for improving the growth rate of D. officinale by increasing its environmental stress tolerance, providing an effective way to supply resources through artificial reproduction.

The FaFlbA mutant of Fusarium asiaticum is significantly increased in nivalenol production

AIMS

Cereals contaminated with type B trichothecene nivalenol (NIV) and its acetylated derivative 4-acetyl-nivalenol (4-AcNIV) are a global mycotoxicological problem threatening the health of humans and livestock. Toxicological studies, quantitative determinations and screening for biodegrading micro-organisms require massive amounts of pure toxins. However, the low yield from fungal cultures and high prices of NIV and 4-AcNIV limit research progress in these areas. This work aimed to select Fusarium asiaticum mutant strains with enhanced production of NIV and 4-AcNIV.

METHODS AND RESULTS

A total of 62 NIV-producing F. asiaticum strains were isolated and compared regarding their ability to produce NIV. Strain RR108 had the highest yield of NIV among 62 field isolates surveyed and was then genetically modified for higher production. Targeted deletion of the FaFlbA gene, encoding a regulator of G protein signalling protein, resulted in a significant increase in NIV and 4-AcNIV production in the FaFlbA deletion mutant ΔFaFlbA. The expression of three TRI genes involved in the trichothecene biosynthetic pathway was upregulated in ΔFaFlbA. ΔFaFlbA produced the highest amount of NIV and 4-AcNIV when cultured in brown long-grain rice for 21 days, and the yields were 2.07 and 2.84 g kg^-1 , respectively. The mutant showed reduced fitness, including reduced conidiation, loss of perithecial development and decreased virulence on wheat heads, which makes it biologically safe for large-scale preparation and purification of NIV and 4-AcNIV.

CONCLUSIONS

The F. asiaticum mutant strain ΔFaFlbA presented improved production of NIV and 4-AcNIV with reduced fitness and virulence in plants.

SIGNIFICANCE AND IMPACT OF THE STUDY

Targeted deletion of the FaFlbA gene resulted in increased NIV and 4-AcNIV production. Our results provide a practical approach using genetic modification for large-scale mycotoxin production.

Species Diversity and Chemotypes of Fusarium Species Associated With Maize Stalk Rot in Yunnan Province of Southwest China

Maize stalk rot caused by Fusarium species is one of the most important fungal diseases of maize throughout the world. The disease is responsible for considerable yield losses and has also been associated with mycotoxin contamination of the crop. In this study, a survey of maize stalk rot was performed in seven locations of Yunnan Province in China during the cropping season of 2015 and 2016. Based on morphological and molecular characteristics, 204 isolates belonging to 12 Fusarium spp. from symptomatic stalks of maize were identified. Among the isolated strains, 83 were identified as Fusarium meridionale (40.5%), 46 as Fusarium boothii (22.5%), 34 as Fusarium temperatum (16.5%), 12 as Fusarium equiseti (5.9%), 10 as Fusarium asiaticum (4.9%), six as Fusarium proliferatum (3.0%), four as Fusarium verticillioides (2.0%), four as Fusarium incarnatum (2.0%), two as Fusarium avenaceum (1.0%), one as Fusarium cerealis (0.5%), one as Fusarium graminearum (0.5%), and one as Fusarium cortaderiae (0.5%). Fusarium cortaderiae was the first report on the causal agent of maize stalk rot disease in China. These isolates were divided into five chemotypes: nivalenol (NIV), deoxynivalenol (DON), beauvericin (BEA), zearalenone (ZEN), and fumonisin (FUM). Phylogenetic analysis based on partial sequences of the translation elongation factor 1α (TEF1-α) showed a high degree of interspecific polymorphisms among the isolates. Pathogenicity analysis on maize stalks indicated that all the 12 species of Fusarium were able to cause the disease symptoms with different aggressiveness. This study on population, pathogenicity, and toxigenic chemotypes of Fusarium species associated with maize stalk rot in Yunnan Province of southwest China, will help design an effective integrated control strategy for this disease.

Histone H3K27 methylation perturbs transcriptional robustness and underpins dispensability of highly conserved genes in fungi

Epigenetic modifications are key regulators of gene expression and underpin genome integrity. Yet, how epigenetic changes affect the evolution and transcriptional robustness of genes remains largely unknown. Here, we show how the repressive histone mark H3K27me3 underpins the trajectory of highly conserved genes in fungi. We first performed transcriptomic profiling on closely related species of the plant pathogen Fusarium graminearum species complex. We determined transcriptional responsiveness of genes across environmental conditions to determine expression robustness. To infer evolutionary conservation, we used a framework of 23 species across the Fusarium genus including three species covered with histone methylation data. Gene expression variation is negatively correlated with gene conservation confirming that highly conserved genes show higher expression robustness. In contrast, genes marked by H3K27me3 do not show such associations. Furthermore, highly conserved genes marked by H3K27me3 encode smaller proteins, exhibit weaker codon usage bias, higher levels of hydrophobicity, show lower intrinsically disordered regions, and are enriched for functions related to regulation and membrane transport. The evolutionary age of conserved genes with H3K27me3 histone marks falls typically within the origins of the Fusarium genus. We show that highly conserved genes marked by H3K27me3 are more likely to be dispensable for survival during host infection. Lastly, we show that conserved genes exposed to repressive H3K27me3 marks across distantly related Fusarium fungi are associated with transcriptional perturbation at the microevolutionary scale. In conclusion, we show how repressive histone marks are entangled in the evolutionary fate of highly conserved genes across evolutionary timescales.

Chemotype and Aggressiveness Evaluation of Fusarium graminearum and Fusarium culmorum Isolates from Wheat Fields in Wisconsin

Fusarium graminearum commonly causes Fusarium head blight on wheat, barley, rice, and oats. F. graminearum produces nivalenol (NIV) and deoxynivalenol (DON) and forms derivatives of DON based on its acetylation sites. The fungus is profiled into chemotypes based on DON derivative chemotypes (3 acetyldeoxynivalenol [3ADON] chemotype; 15 acetyldeoxynivalenol [15ADON] chemotype), and/or the NIV chemotype. This study assessed the Fusarium population found on wheat and the chemotype profile of the isolates collected from 2016 and 2017 in Wisconsin. F. graminearum was isolated from all locations sampled in both 2016 and 2017. Fusarium culmorum was isolated only from Door County in 2016. Over both growing seasons, 91% of isolates were identified as the 15ADON chemotype, while 9% of isolates were identified as the 3ADON chemotype. Aggressiveness was quantified by area under the disease progress curve (AUDPC). The isolates with the highest AUDPC values were from the highest wheat-producing cropping districts in the state. Deoxynivalenol production in grain and sporulation and growth rate in vitro were compared with aggressiveness in the greenhouse. Our results showed that 3ADON isolates in Wisconsin were among the highest in sporulation capacity, growth rate, and DON production in grain. However, there were no significant differences in aggressiveness between the 3ADON and 15ADON isolates. The results of this research detail the baseline frequency and distribution of 3ADON and 15ADON chemotypes observed in Wisconsin. Chemotype distributions within populations of F. graminearum in Wisconsin should continue to be monitored in the future.

Key Global Actions for Mycotoxin Management in Wheat and Other Small Grains

Mycotoxins in small grains are a significant and long-standing problem. These contaminants may be produced by members of several fungal genera, including Alternaria, Aspergillus, Fusarium, Claviceps, and Penicillium. Interventions that limit contamination can be made both pre-harvest and post-harvest. Many problems and strategies to control them and the toxins they produce are similar regardless of the location at which they are employed, while others are more common in some areas than in others. Increased knowledge of host-plant resistance, better agronomic methods, improved fungicide management, and better storage strategies all have application on a global basis. We summarize the major pre- and post-harvest control strategies currently in use. In the area of pre-harvest, these include resistant host lines, fungicides and their application guided by epidemiological models, and multiple cultural practices. In the area of post-harvest, drying, storage, cleaning and sorting, and some end-product processes were the most important at the global level. We also employed the Nominal Group discussion technique to identify and prioritize potential steps forward and to reduce problems associated with human and animal consumption of these grains. Identifying existing and potentially novel mechanisms to effectively manage mycotoxin problems in these grains is essential to ensure the safety of humans and domesticated animals that consume these grains.

The Distribution of Fusarium graminearum and Fusarium asiaticum Causing Fusarium Head Blight of Wheat in Relation to Climate and Cropping System

In the main wheat production area of China (the Huang Huai Plain [HHP]), both Fusarium graminearum and Fusarium asiaticum, the causal agents of Fusarium head blight (FHB), are present. We investigated whether the relative prevalence of F. graminearum and F. asiaticum is related to cropping systems and/or climate factors. A total of 1,844 Fusarium isolates were obtained from 103 fields of two cropping systems: maize-wheat and rice-wheat rotations. To maximize the differences in climatic conditions, isolates were sampled from the north and south HHP regions. Based on the phylogenetic analysis of EF-1α and Tri101 sequences, 1,207 of the 1,844 isolates belonged to F. graminearum, and the remaining 637 isolates belonged to F. asiaticum. The former was predominant in the northern region: 1,022 of the 1,078 Fusarium isolates in the north were F. graminearum. The latter was predominant in the southern region: 581 of the 766 Fusarium isolates belonged to F. asiaticum. Using an analysis based on generalized linear modeling, the relative prevalence of the two species was associated more with climatic conditions than with the cropping system. F. graminearum was associated with drier conditions and cooler conditions during the winter but also with warmer conditions in the infection and grain-colonization period as well as with maize-wheat rotation. The opposite was true for F. asiaticum. Except for the 15-acetyldeoxynvalenol genotype, the trichothecene chemotype composition of F. asiaticum differed between the two cropping systems. The 3-acetyldeoxynivalenol genotype was more prevalent in the maize-wheat rotation, whereas the nivalenol genotype was more prevalent in the rice-wheat rotation. The results also suggested that environmental conditions in the overwintering period appeared to be more important than those in the infection, grain-colonization, and preanthesis sporulation periods in affecting the relative prevalence of F. graminearum and F. asiaticum. More research is needed to study the effect of overwintering conditions on subsequent epidemic in the following spring.

Analysis of the Fusarium graminearum Species Complex from Gramineous Weeds Near Wheat Fields in Jiangsu Province, China

Several weed species are known as alternative hosts of the Fusarium graminearum species complex (FGSC), and their epidemiological significance in Fusarium head blight (FHB) has been investigated; however, scant information is available regarding FGSC occurrence in weeds near Chinese wheat fields. To evaluate the potential role of gramineous weeds surrounding wheat fields in FHB, 306 FGSC isolates were obtained from 210 gramineous weed samples in 2018 in Jiangsu Province. Among them, 289 were Fusarium asiaticum, and the remainder were F. graminearum. Trichothecene genotype and mycotoxin analyses revealed that 74.3% of the F. asiaticum isolates were the 3-acetyldeoxynivalenol (3ADON) chemotype, and the remainder were the nivalenol (NIV) chemotype. Additionally, 82.4% of F. graminearum isolates were the 15-acetyldeoxynivalenol (15ADON) chemotype, and the remainder were the NIV chemotype. FHB severity and trichothecene analysis indicated that F. asiaticum isolates with the 3ADON chemotype were more aggressive than those with the NIV chemotype in wheat. 3ADON and NIV chemotypes of F. asiaticum isolated from weeds and wheat showed no significant differences in pathogenicity in wheat. All selected F. asiaticum isolates produced perithecia, with little difference between the 3ADON and NIV chemotypes. These results highlight the epidemiology of the FGSC isolated from weeds near wheat fields, with implications for reducing FHB inoculum in China.

Fusarium verticillioides and Aspergillus flavus Co-Occurrence Influences Plant and Fungal Transcriptional Profiles in Maize Kernels and In Vitro

Climate change will increase the co-occurrence of Fusarium verticillioides and Aspergillus flavus, along with their mycotoxins, in European maize. In this study, the expression profiles of two pathogenesis-related (PR) genes and four mycotoxin biosynthetic genes, FUM1 and FUM13, fumonisin pathway, and aflR and aflD, aflatoxin pathway, as well as mycotoxin production, were examined in kernels and in artificial medium after a single inoculation with F. verticillioides or A. flavus or with the two fungi in combination. Different temperature regimes (20, 25 and 30 °C) over a time-course of 21 days were also considered. In maize kernels, PR genes showed the strongest induction at 25 °C in the earlier days post inoculation (dpi)with both fungi inoculated singularly. A similar behaviour was maintained with fungi co-occurrence, but with enhanced defence response at 9 dpi under 20 °C. Regarding FUM genes, in the kernels inoculated with F. verticillioides the maximal transcript levels occurred at 6 dpi at 25 °C. At this temperature regime, expression values decreased with the co-occurrence of A. flavus, where the highest gene induction was detected at 20 °C. Similar results were observed in fungi grown in vitro, whilst A. flavus presence determined lower levels of expression along the entire time-course. As concerns afl genes, considering both A. flavus alone and in combination, the most elevated transcript accumulation occurred at 30 °C during all time-course both in infected kernels and in fungi grown in vitro. Regarding mycotoxin production, no significant differences were found among temperatures for kernel contamination, whereas in vitro the highest production was registered at 25 °C for aflatoxin B1 and at 20 °C for fumonisins in the case of single inoculation. In fungal co-occurrence, both mycotoxins resulted reduced at all the temperatures considered compared to the amount produced with single inoculation.

Survey of zearalenone and type-B trichothecene mycotoxins in swine feed in the USA

New information is needed regarding the types and concentrations of mycotoxins in swine feed. We hypothesized that (1) the mycotoxins deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), 15-acetyldeoxynivalenol (15-AcDON), nivalenol (NIV), and zearalenone (ZEN) vary among swine ingredient and feed types, and (2) the inclusion of specific ingredients is associated with mycotoxin contamination in complete feed. A total of 707 samples were collected from cooperators in 14 states between June 2018 and January 2020 then analyzed for DON, 3-AcDON, 15-AcDON, NIV, and ZEN contamination using gas chromatography-mass spectrometry (GC-MS). Ninety-four percent (663/707) of samples contained DON, 33% (230/707) of samples contained 3-AcDON, 57% (404/707) of samples contained 15-AcDON, 1% (6/707) of samples contained NIV, and 47% (335/707) of samples contained ZEN. Seventy-three percent (514/707) of samples contained multiple mycotoxins. Resulting DON concentrations were below the national advisory limits for all sample types, and no advisory limits are imposed for the other mycotoxins studied. Increased incorporation of distiller's dried grains with solubles (DDGS) was associated with increased DON in complete feed (R² = 0.82).

Uncovering Diagnostic Value of Mitogenome for Identification of Cryptic Species Fusarium graminearum Sensu Stricto

Fungal complexes are often composed of morphologically nearly indistinguishable species with high genetic similarity. However, despite their close relationship, they can exhibit distinct phenotypic differences in pathogenicity and production of mycotoxins. Many plant pathogenic and toxigenic fungi have been shown to consist of such cryptic species. Identification of cryptic species in economically important pathogens has added value in epidemiologic studies and provides opportunities for better control. Analysis of mitochondrial genomes or mitogenomics opens up dimensions for improved diagnostics of fungi, especially when efficient recovery of DNA is problematic. In comparison to nuclear DNA, mitochondrial DNA (mtDNA) can be amplified with improved efficacy due to its multi-copy nature. However, to date, only a few studies have demonstrated the usefulness of mtDNA for identification of cryptic species within fungal complexes. In this study, we explored the value of mtDNA for identification of one of the most important cereal pathogens Fusarium graminearum sensu stricto (F.g.). We found that homing endonucleases (HEGs), which are widely distributed in mitogenomes of fungi, display small indel polymorphism, proven to be potentially species specific. The resulting small differences in their lengths may facilitate further differentiation of F.g. from the other cryptic species belonging to F. graminearum species complex. We also explored the value of SNP analysis of the mitogenome for typing F.g. The success in identifying F.g. strains was estimated at 96%, making this tool an attractive complement to other techniques for identification of F.g.

Biocontrol Agents Reduce Progression and Mycotoxin Production of Fusarium graminearum in Spikelets and Straws of Wheat

The aim of this study was to evaluate the interactions between wheat plant (spikelets and straws), a strain of mycotoxigenic pathogen Fusarium graminearum and commercial biocontrol agents (BCAs). The ability of BCAs to colonize plant tissue and inhibit the pathogen or its toxin production was observed throughout two phases of the life cycle of pathogens in natural conditions (colonization and survival). All evaluated BCAs showed effective reduction capacities of pathogenic traits. During establishment and the expansion stage, BCAs provoked an external growth reduction of F. graminearum (77–93% over the whole kinetic studied) and mycotoxin production (98–100% over the whole kinetic studied). Internal growth of pathogen was assessed with digital droplet polymerase chain reaction (ddPCR) and showed a very strong reduction in the colonization of the internal tissues of the spikelet due to the presence of BCAs (98% on average). During the survival stage, BCAs prevented the formation of conservation perithecia of the pathogen on wheat straw (between 88 and 98% of perithecia number reduction) and showed contrasting actions on the ascospores they contain, or perithecia production (−95% on average) during survival form. The mechanisms involved in these different interactions between F. graminearum and BCAs on plant matrices at different stages of the pathogen’s life cycle were based on a reduction of toxins, nutritional and/or spatial competition, or production of anti-microbial compounds.

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.