Effect of different storage conditions on the mycotoxin contamination of Fusarium culmorum-infected and non-infected wheat straw

Accumulation of HT-2 toxin from contaminated mushroom compost by edible Agaricus bisporus

Wheat straw is commonly used as a cellulose source in mushroom compost and could be a secondary source of mycotoxin contamination in the food chain. We cultivated edible Agaricus bisporus and Pleurotus ostreatus on T-2/HT-2 artificially-contaminated mushroom compost and developed and in-house validated an UHPLC-MS/MS method for determination of T-2, HT-2, T2-triol and T2-tetraol in mushroom compost and mushroom basidiocarp. A rapid phase I metabolization of T-2 and HT-2 in mushroom compost was observed. In Agaricus bisporus, basidiocarps 8-15 µg kg^-1 accumulation of HT-2 calculated on wet weight was measured. No detectable mycotoxins were found in Pleurotus ostreatus basidiocarp.

Evaluation of Inner Exposure of Horses to Zearalenone (ZEN), Deoxynivalenol (DON) and Their Metabolites in Relation to Colic and Health-Related Clinical-Chemical Traits

Mycotoxin contaminated feed has been associated with colic of horses caused by intestinal disorders. Whether such disease conditions alter the intestinal toxin metabolism and transfer across a compromised mucosal barrier is unknown. A screening approach was used to relate blood residue levels of DON, ZEN and their metabolites to the status of the horses (sick vs. healthy). A total of 55 clinically healthy horses from 6 different farms with varying feeding background served as control for sick horses (N = 102) hospitalized due to colic. ZEN, alpha-zearalenol (ZEL), beta-ZEL and DON were detectable in peripheral blood as indicators for the inner exposure with significant farm effects for alpha- and beta-ZEL. However, the levels in sick horses were similar to all farms. Moreover, the proportion of beta-ZEL of all detected ZEN metabolites as an indicator for the degree of metabolism of ZEN was not different for sick horses but differed amongst the control farms. Although the incidence of DON in blood was generally low and not significantly different amongst healthy and sick horses, the positive samples were nearly exclusively found in sick horses suggesting either a higher toxin transfer, an association of DON with the development of colic or a different feeding background.

Occurrence of type A, B and D trichothecenes, zearalenone and stachybotrylactam in straw

Straw is the main by-product of grain production, used as bedding material and animal feed. If produced or stored under adverse hygienic conditions, straw is prone to the growth of filamentous fungi. Some of them, e.g. Aspergillus, Fusarium and Stachybotrys spp. are well-known mycotoxin producers. Since studies on mycotoxins in straw are scarce, 192 straw samples (wheat n = 80; barley n = 79; triticale n = 12; oat n = 11; rye n = 12) were collected across Germany within the German official feed surveillance and screened for the presence of 21 mycotoxins. The following mycotoxins (positive samples for at least one mycotoxin n = 184) were detected: zearalenone (n = 86, 6.0-785 μg/kg), nivalenol (n = 51, 30-2,600 μg/kg), deoxynivalenol (n = 156, 20-24,000 μg/kg), 15-acetyl-deoxynivalenol (n = 34, 20-2,400 μg/kg), 3-acetyl-deoxynivalenol (n = 16, 40-340 μg/kg), scirpentriol (n = 14, 40-680 μg/kg), T-2 toxin (n = 67, 10-250 μg/kg), HT-2 toxin (n = 92, 20-800 μg/kg), T-2 tetraol (n = 13, 70-480 μg/kg). 15-monoacetoxyscirpenol (30 μg/kg) and T-2 triol (60 μg/kg) were only detected in one barley sample. Macrocyclic trichothecenes (satratoxin G, F, roridin E, and verrucarin J) were also found in only one barley sample (quantified as roridin A equivalent: total 183 μg/kg). The occurrence of stachybotrylactam was monitored for the first time in four samples (n = 4, 0.96-7.4 μg/kg). Fusarenon-X, 4,15-diacetoxyscirpenol, neosolaniol, satratoxin H and roridin-L2 were not detectable in the samples. The results indicate a non-negligible contribution of straw to oral and possibly inhalation exposure to mycotoxins of animals or humans handling contaminated straw.

Antagonistic Activity of Chilean Strains of Pseudomonas protegens Against Fungi Causing Crown and Root Rot of Wheat (Triticum aestivum L.)

Seed treatments with antagonistic bacteria could reduce the severity of crown and root rot diseases in wheat crops. The objective of this study was to evaluate the potential antagonistic activity of a bacterial consortium of three Chilean strains of Pseudomonas protegens against the wheat crown and root rot pathogens Gaeumannomyces graminis var. tritici, Rhizoctonia cerealis, and Fusarium culmorum. Two field experiments were carried out on artificially infested soil during two consecutive seasons (2016-2017 and 2017-2018) in an Andisol soil of southern Chile. Control treatments (not inoculated with fungi) were also included. Each treatment included a seed treatment of spring wheat cv. Pantera-INIA with and without the bacterial consortium. Both phytosanitary damage (incidence and severity) and agronomic components were evaluated. Bacterial populations with the phlD+ gene in the wheat plant rhizosphere during anthesis state (Z6) were also quantified. In both seasons, infection severity decreased by an average of 16.8% in seeds treated with P. protegens consortium, while yield components such as spikes m^-1 and number of grains per spike increased. The use of antagonistic bacteria resulted in a total yield increase only during the first experimental season (P < 0.05). In general, accumulated rainfall influenced the antagonistic effect of the consortium of P. protegens strains, accounting for the differences observed between the two seasons. The results suggest that this P. protegens consortium applied on seeds can promote plant growth and protect wheat crops against crown and root rot pathogens in Southern Chile under field conditions.

Zearalenone (ZEN) in Livestock and Poultry: Dose, Toxicokinetics, Toxicity and Estrogenicity

One of the concerns when using grain ingredients in feed formulation for livestock and poultry diets is mycotoxin contamination. Aflatoxin, fumonisin, ochratoxin, trichothecene (deoxynivalenol, T-2 and HT-2) and zearalenone (ZEN) are mycotoxins that have been frequently reported in animal feed. ZEN, which has raised additional concern due to its estrogenic response in animals, is mainly produced by Fusarium graminearum (F. graminearum), F. culmorum, F. cerealis, F. equiseti, F. crookwellense and F. semitectums, and often co-occurs with deoxynivalenol in grains. The commonly elaborated derivatives of ZEN are α-zearalenol, β-zearalenol, zearalanone, α-zearalanol, and β-zearalanol. Other modified and masked forms of ZEN (including the extractable conjugated and non-extractable bound derivatives of ZEN) have also been quantified. In this review, common dose of ZEN in animal feed was summarized. The absorption rate, distribution (“carry-over”), major metabolites, toxicity and estrogenicity of ZEN related to poultry, swine and ruminants are discussed.

Interactions among Fungal Community, Fusarium Mycotoxins, and Components of Harvested Wheat under Simulated Storage Conditions

Economic loss of postharvest wheat under poor storage conditions due to fungal spoilage and mycotoxin contamination is severe. In order to study the influencing factors of the aggravation of mildew in natural wheat during storage, we assessed changes in Fusarium mycotoxins by high performance liquid chromatography, changes in fungal communities by high-throughput sequencing, and changes in biochemical components in wheat stored under artificial simulation conditions. Deoxynivalenol was the dominant Fusarium mycotoxin, reaching 1103 μg/kg at 25 °C with 75% relative humidity after 30 weeks. Under these conditions, Fusarium dominated the fungal communities, and Fusarium graminearum was significantly negatively correlated with glutenin (p < 0.05). Low storage temperatures and low humidity result in lower levels of Fusarium mycotoxins. Different fungi tended to consume different wheat components, and the interaction between environmental and biological factors eventually leads to the deterioration of wheat quality. These findings might provide valuable information for control strategies of mildew occurrence during grain storage.

The influence of the conditions of acquisition and storage of table eggs on changes in their quality and the presence of mycobiota and Fusarium mycotoxins

The study showed that the hen housing system and egg storage conditions had significant influence on differences in the qualitative traits of eggs. The most rapid qualitative traits changes were observed in the eggs laid by the hens kept in the free-range and litter systems. After the first week of storage fungi were found on the eggshell surface but significant growth of fungi on the eggshell surface was noted after 3 wk, regardless of the storage conditions. Higher humidity during egg storage causes the dynamic development of fungi in the albumen. The principal component analysis proved the dependency between ergosterol and the trichothecene concentration in the albumen. Mycotoxins in the albumen indicate the presence of pathogenic species of microscopic fungi. The albumen of the eggs laid by the hens kept in cages had the lowest concentration of mycotoxins. The results of the study showed that the conditions of the henhouse environment significantly influenced the initial contamination of eggshells. Egg storage conditions, i.e., high air humidity, favor the development of fungi on the eggshell surface, affect the dynamics of fungal growth into the albumen and the production of mycotoxins.

Effect of Wheat Cultivar on the Concentration of Fusarium Mycotoxins in Wheat Stems

Effective control of Fusarium-mycotoxin accumulation in grain affected by Fusarium head blight (FHB) (caused by Fusarium graminearum) begins with selecting moderately resistant wheat cultivars; however, little is known about how this resistance affects mycotoxin levels in the stem. A study was conducted from 2011 to 2014 in a mist-irrigated FHB nursery in Urbana, IL to determine whether the FHB resistance class of a cultivar (very susceptible, susceptible, moderately susceptible, and moderately resistant) affects the concentration of Fusarium mycotoxins in the stem. FHB incidence, FHB severity, and Fusarium-damaged kernel ratings were collected and used to calculate FHB index; incidence, severity, and kernel damage (ISK) index; and deoxynivalenol (DON), incidence, severity, and kernel damage (DISK) index. Grain was assayed for levels of DON, and the bottom 25 cm of plant stems was collected from each plot and assayed for DON, 3-acetyl-deoxynivalenol (3ADON), and 15-acetyl-deoxynivalenol (15ADON). Significant differences in DON concentration in the grain were detected among cultivars (P = 0.0001) and for the concentration of all DON (P = 0.003), 3ADON (P = 0.03), and 15ADON (P < 0.0001) in the stem. Significant differences among resistance classes were observed for FHB index value (P < 0.0001), ISK index (P = 0.006), and DISK index (P = 0.004). In all years of this study, the concentration of DON in the grain and the concentrations of all mycotoxins in the stem were consistently lower in the moderately resistant cultivars. All three indices were poor indicators of mycotoxin concentrations in the stem. Overall, the selection of a moderately resistant cultivar provides effective control of DON accumulation in the grain and mycotoxin accumulation in the stem.

Characterisation of the Mycobiota on the Shell Surface of Table Eggs Acquired from Different Egg-Laying Hen Breeding Systems

Microbial safety is an important factor contributing to the egg quality. During egg acquisition, there is significant risk of contamination of the eggshell surface with microscopic fungi. Mycelial hyphae may grow on the eggshell surface and penetrate into the egg content. However, there is no information on the populations of microscopic fungi on the eggshell surface and, consequently, on possible production of mycotoxins. Therefore, the aim of the study was to identify the species of microscopic fungi present on the eggshell surface acquired from different breeding systems and to measure the number of selected mycotoxins. The qualitative analysis resulted in the identification of 41 isolates on the surface of eggs. There were 7 isolates from the organic production system, 11 from the free-range production system, 14 from the deep litter indoor housing system and 9 from the cage farming production system. The research proved that the diversification in the population of mycobiota on the eggshells depended on the egg-laying hen breeding system. The microscopic fungi isolated from the eggshells included toxigenic and pathogenic species such as Fusarium culmorum and F. equiseti. As the egg storage time increased, fungi, including the pathogenic species, penetrated through the eggshells. In consequence, mycotoxins were identified in the egg whites. Type-A and type-B trichothecenes were found in the eggshell samples containing F. culmorum.

Effect of Fusarium Head Blight Management Practices on Mycotoxin Contamination of Wheat Straw

Management of Fusarium graminearum-associated mycotoxins in wheat grain has been extensively evaluated, but little is known about management of mycotoxins in straw. Two research trials were conducted at four locations from 2011 to 2014. The objective of the first trial was to determine the efficacy of fungicides, and the objective of the second trial was to evaluate the use of integrated disease management strategies, for the control of Fusarium head blight (FHB) and reducing the concentration of the Fusarium mycotoxins deoxynivalenol, 3-acetyl-deoxynivalenol, and 15-acetyl-deoxynivalenol in straw. In the first trial, it was determined that demethylation inhibitor (DMI) fungicides did not offer significant (P ≤ 0.05) reductions of mycotoxin concentrations in the straw compared with a no-fungicide control treatment, but significant (P ≤ 0.05) reductions in mycotoxin concentration were observed in the control when compared with treatments with the application of quinone outside inhibitor (QoI)-containing fungicides. In the second trial, mycotoxin concentrations in the straw were significantly (P ≤ 0.05) reduced in the moderately resistant cultivar compared with the susceptible cultivar, but were not affected by the use of a fungicide. The practices typically used to manage Fusarium mycotoxins in wheat grain, especially the selection of resistant cultivars and not using a QoI fungicide, may be an effective means to reduce mycotoxin concentrations in the straw.

Invited review: Diagnosis of zearalenone (ZEN) exposure of farm animals and transfer of its residues into edible tissues (carry over)

The aim of the review was to evaluate the opportunities for diagnosing the zearalenone (ZEN) exposure and intoxication of farm animals by analyzing biological specimens for ZEN residue levels. Metabolism is discussed to be important when evaluating species-specific consequences for the overall toxicity of ZEN. Besides these toxicological facts, analytics of ZEN residues in various animal-derived matrices requires sensitive, matrix-adapted multi-methods with low limits of quantification, which is more challenging than the ZEN analysis in feed. Based on dose-response experiments with farm animals, the principle usability of various specimens as bio-indicators for ZEN exposure is discussed with regard to individual variation and practicability for the veterinary practitioner. ZEN residue analysis in biological samples does not only enable evaluation of ZEN exposure but also allows the risk for the consumer arising from contaminated foodstuffs of animal origin to be assessed. It was compiled from literature that the tolerable daily intake of 0.25 μg ZEN/kg body weight and day is exploited to approximately 8%, when a daily basket of animal foodstuffs and associated carry over factors are assumed at reported ZEN contamination levels of complete feed.

Deoxynivalenol, zearalenone, and Fusarium graminearum contamination of cereal straw; field distribution; and sampling of big bales

Sampling of straw bales from wheat, barley, and oats was carried out after harvest showing large variations in deoxynivalenol (DON) and zearalenone (ZEN) levels. In the wheat field, DON was detected in all straw samples with an average DON concentration of 976 μg/kg and a median of 525 μg/kg, while in four bales, the concentrations were above 3000 μg/kg. For ZEN, the concentrations were more uniform with an average concentration of 11 μg/kg. The barley straw bales were all positive for DON with an average concentration of 449 μg/kg and three bales above 800 μg/kg. In oat straw, the average DON concentration was 6719 μg/kg with the lowest concentration at 2614 μg/kg and eight samples above 8000 μg/kg. ZEN contamination was detected in all bales with an average concentration of 53 μg/kg with the highest concentration at 219 μg/kg. Oat bales from another field showed an average concentration of 16,382 μg/kg. ZEN concentrations in the oat bales were on average 153 μg/kg with a maximum at 284 μg/kg. Levels of Fusarium graminearum DNA were higher in oat straw (max 6444 pg DNA/mg straw) compared to straw from wheat or barley. The significance of mycotoxin exposure from straw should not be neglected particularly in years when high levels of DON and ZEN are also detected in the feed grain. With a limited number of samples preferably using a sampling probe, it is possible to distinguish lots of straw that should not be used as bedding material for pigs.

Fusarium culmorum: causal agent of foot and root rot and head blight on wheat

Fusarium culmorum is a ubiquitous soil-borne fungus able to cause foot and root rot and Fusarium head blight on different small-grain cereals, in particular wheat and barley. It causes significant yield and quality losses and results in contamination of the grain with mycotoxins. This review summarizes recent research activities related to F. culmorum, including studies into its population diversity, mycotoxin biosynthesis, mechanisms of pathogenesis and resistance, the development of diagnostic tools and preliminary genome sequence surveys. We also propose potential research areas that may expand our basic understanding of the wheat-F. culmorum interaction and assist in the management of the disease caused by this pathogen.

TAXONOMY

Fusarium culmorum (W.G. Smith) Sacc. Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordariomycetes; Subclass Hypocreomycetidae; Order Hypocreales; Family Nectriaceae; Genus Fusarium.

DISEASE SYMPTOMS

Foot and root rot (also known as Fusarium crown rot): seedling blight with death of the plant before or after emergence; brown discoloration on roots and coleoptiles of the infected seedlings; brown discoloration on subcrown internodes and on the first two/three internodes of the main stem; tiller abortion; formation of whiteheads with shrivelled white grains; Fusarium head blight: prematurely bleached spikelets or blighting of the entire head, which remains empty or contains shrunken dark kernels. IDENTIFICATION AND DETECTION: Morphological identification is based on the shape of the macroconidia formed on sporodochia on carnation leaf agar. The conidiophores are branched monophialides, short and wide. The macroconidia are relatively short and stout with an apical cell blunt or slightly papillate; the basal cell is foot-shaped or just notched. Macroconidia are thick-walled and curved, usually 3-5 septate, and mostly measuring 30-50 × 5.0-7.5 μm. Microconidia are absent. Oval to globose chlamydospores are formed, intercalary in the hyphae, solitary, in chains or in clumps; they are also formed from macroconidia. The colony grows very rapidly (1.6-2.2 cm/day) on potato dextrose agar (PDA) at the optimum temperature of 25 °C. The mycelium on PDA is floccose, whitish, light yellow or red. The pigment on the reverse plate on PDA varies from greyish-rose, carmine red or burgundy. A wide array of polymerase chain reaction (PCR) and real-time PCR tools, as well as complementary methods, which are summarised in the first two tables, have been developed for the detection and/or quantification of F. culmorum in culture and in naturally infected plant tissue.

HOST RANGE

Fusarium culmorum has a wide range of host plants, mainly cereals, such as wheat, barley, oats, rye, corn, sorghum and various grasses. In addition, it has been isolated from sugar beet, flax, carnation, bean, pea, asparagus, red clover, hop, leeks, Norway spruce, strawberry and potato tuber. Fusarium culmorum has also been associated with dermatitis on marram grass planters in the Netherlands, although its role as a causal agent of skin lesions appears questionable. It is also isolated as a symbiont able to confer resistance to abiotic stress, and has been proposed as a potential biocontrol agent to control the aquatic weed Hydrilla spp.

USEFUL WEBSITES

http://isolate.fusariumdb.org/; http://sppadbase.ipp.cnr.it/; http://www.broad.mit.edu/annotation/genome/fusarium_group/MultiHome.html; http://www.fgsc.net/Fusarium/fushome.htm; http://plantpath.psu.edu/facilities/fusarium-research-center; http://www.phi-base.org/; http://www.uniprot.org/; http://www.cabi.org/; http://www.indexfungorum.org/

Bioavailability of the Fusarium toxin deoxynivalenol (DON) from wheat straw and chaff in pigs

Fusarium infections do not only affect the grain, but also the rest of the plant, which result in contamination of plants with the mycotoxin deoxynivalenol (DON). The bioavailability of DON may be influenced by the matrix due to the differences in nutrient composition between grain and straw, particularly the high fibre component in straw. The experiment was carried out by exposing 18 male castrated pigs (30-40 kg live weight) with a single dose of DON from wheat grain, straw and chaff in the diet. The courses of DON serum concentrations were evaluated using toxicokinetic methods. The absorption of DON was not influenced by the source of DON. The invasion half-life of DON from grain, straw and chaff amounted to 0.76, 0.77 and 0.48 h, respectively, and were not significantly different. The elimination of DON was also not affected by the DON source. The bioavailability of DON, calculated by the dose corrected area under the curve of the serum-DON-concentrations, amounted to 81.9, 87.3 and 109.8% for straw, grain and chaff, respectively, without significant differences. Thus, the uptake of DON from straw may contribute comparably to the overall exposure of animals.

Mycotoxins in the environment: I. Production and emission from an agricultural test field

Mycotoxins are secondary metabolites that are naturally produced by fungi which infest and contaminate agricultural crops and commodities (e.g., small grain cereals, fruits, vegetables, and organic soil material). Although these compounds have extensively been studied in food and feed, only little is known about their environmental fate. Therefore, we investigated over nearly two years the occurrence of various mycotoxins in a field cropped with winter wheat of the variety Levis, which was artificially inoculated with Fusarium spp., as well as their emission via drainage water. Mycotoxins were regularly quantified in whole wheat plants (0.1-133 mg/kg(dry weight), for deoxynivalenol), and drainage water samples (0.8 ng/L to 1.14 μg/L, for deoxynivalenol). From the mycotoxins quantified in wheat (3-acetyl-deoxynivalenol, deoxynivalenol, fusarenone-X, nivalenol, HT-2 toxin, T-2 toxin, beauvericin, and zearalenone), only the more hydrophilic ones or those prevailing at high concentrations were detected in drainage water. Of the total amounts produced in wheat plants (min: 2.3; max: 292 g/ha/y), 0.5-354 mg/ha/y, i.e. 0.002-0.12%, were emitted via drainage water. Hence, these compounds add to the complex mixture of natural and anthropogenic micropollutants particularly in small rural water bodies, receiving mainly runoff from agricultural areas.