The occurrence of culmorin and hydroxy-culmorins in cereals

Forty-five samples from 1988–1995 of naturally contaminated grain, barley, wheat and oats, three samples of mixed feed, and 16 samples of grain artificially inoculated with Fusarium culmorum during the flowering stage were analysed for deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-acetyl-DON), culmorin and hydroxy-culmorins. These compounds are secondary metabolites produced by the fungal species F. culmorum and F. graminearum. Acetonitrile-water extract of the samples was purified on a Mycosep^TM#225 column, derivetized using pentafluoropropionic anhydride (PFPA) and analysed by gas chromatography-mass spectrometry (GC-MS). The amount of each of culmorin, 5-, 12-, 14 and 15-hydroxy-culmorin and one unknown hydroxy-culmorin were determined relative to the amount of DON plus 3-acetyl DON for each sample. The ratio between the total amount of culmorin compounds and the DON compounds ranged from 0.14 to 1.07 in the samples. This study shows that there is a strong correlation between the amount of DON present in the grain and the amount of culmorin and hydroxy-culmorins present. The ratio of each of the culmorin compounds relative to the amount of DON compounds were in the same range in the grain artificially inoculated by F. culmorum as found in an earlier study for F. culmorum strains cultivated on rice, while the hydroxy-culmorin profile in the naturally contaminated grain was more similar to what was found for the F. graminearum cultures in the same study [1]. These results indicate that F. graminearum may be a relatively important source for DON in grain also in relatively cold areas. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mycoflora of Argentinian corn harvested in the main production area in 1990

Corn (Zea mays) is the main cereal produced in and exported from Argentina. The risk of contamination by mycotoxins is related to the mycoflora associated with the corn kernels. This paper reports on the identification of internal and external mycoflora of corn kernels harvested in the main production area in Argentina in 1990. A mycological survey was carried out on 178 corn samples, from five locations in that area and the isolation frequency and relative density of the prevalent fungal genera compared. GenusFusarium was the most prevalent component of the internal seedborne mycoflora in the five locations.Penicillium was prevalent in all locations, taking into account the frequency. However, this genus was predominant only in two locations, when the relative density was considered. The predominantFusarium wasF. moniliforme and the most frequently isolated species ofAlternaria, Aspergillus andPenicillium wereA. alternata, A. flavus andP. decumbens, respectively.Diplodia species were not isolated from any of the samples.     

Occurrence and distribution of <Emphasis Type="Italic">Microdochium nivale</Emphasis> and <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from barley,durum and soft wheat grains in France from 2000 to 2002

Fusarium Head Blight of small grain cereal is a disease of growing concern in Europe. Along with Microdochium nivale, several species of Fusarium may be associated with the disease, including species that are potentially toxigenic. This paper describes the results of a large scale survey of the variety and frequency of different Fusarium species and M. nivale in France. A total of 749 soft wheat, durum wheat and barley samples were collected and analyzed from 2000 to 2002. The most frequent species isolated were F.graminearum, F. avenaceum and F. poae. The frequency of F. poae seems to have increased while M.nivale and F. culmorum appear less frequent than previously described in France. Other Fusarium species detected in decreasing prevalence were F. tricinctum, F. equiseti, F. acuminatum, F. sambucinum, F.sporotrichioides, F. moniliforme, F. heterosporum, F. subglutinans and F. oxysporum. All the most frequent pathogenic species and also the less pathogenic ones were frequently associated with individual fields. The implications of these associations for the protection of cereals crops and for contamination by mycotoxins are discussed.     

Fungi associated with food and feed commodities from Ecuador

Freshly harvested soybean, rice and corn from farms and corn-based pelleted feeds were collected from ranches from the coastal and mountain regions in Ecuador during 1998, and assessed for fungal contamination. The most prevalent fungi on pelleted feed were Aspergillus flavus and Fusarium graminearum. The prevalent fungi recovered from soybean were F. verticillioides, F. semitectum, Aspergillus flavus and A. ochraceus. In rice, F. oxysporum was the most prevalent toxigenic fungal species recorded, followed by F. verticillioides and A. flavus. In corn, F. verticillioides was the most prevalent fungus isolated in both the coastal and mountain regions, with high isolation frequencies of A. flavus and A. parasiticus at the coast. Based on the toxigenic species recovered, ochratoxin A may pose a contamination risk for soybean. A higher probability of aflatoxin contamination of corn was found in the coastal samples compared to those of the mountain region, while a risk of fumonisin contamination of corn exists in both regions.This revised version was published online in October 2005 with corrections to the Cover Date.     

Trichothecene production by Fusarium species isolated from grain and pasture throughout New Zealand

Liquid cultures of 200 Fusarium isolates selected to represent the most common species found in autumn pasture (70 isolates) and in grain (130 isolates) grown in New Zealand were analysed for trichothecenes and related compounds. Production of butenolide, cyclonerodiol derivatives and culmorins was also measured. The principal trichothecenes produced were derivatives of either nivalenol (NIV), deoxynivalenol (DON) or scirpentriol (Sctol), in order of frequency. The principal trichothecene producing species were F. crookwellense, F. culmorum and F. graminearum. Isolates of the first two species were predominantly NIV-chemotypes with one or two isolates respectively as Sctol-chemotypes. F. graminearum showed equal quantities of NIV- and DON-chemotypes, with the DON-chemotypes producing primarily 15-acetyldeoxynivalenol (15-ADON).     

Occurrence and distribution of Fusarium species in maize fields in New Zealand

Fusarium populations were investigated in maize grains and their husks about six weeks before harvest in three maize fields in the Manawatu region of New Zealand. The role of litter and soil as reservoirs for these fungi was also examined. Two techniques were used to examine populations, dilution plating and direct plating. Using the dilution plating technique the highest overall populations were found in husks (mean 2.2 × 10⁵/g) and litter (mean 1.4 × 10⁵/g), while similar lower numbers of viable propagules were obtained from grain (mean 2.1 × 10³/g) and soil (2.8 × 10³/g). With this technique five Fusarium spp. were commonly isolated; F. graminearum (Gibberella zeae), F. culmorum, F. subglutinans, F. oxysporum and F. acuminatum, of which F. graminearum was the most abundant. With the direct plating technique 87% of grains were infected with Fusarium spp., with some grains being infected with more than one species. Segments from husks and litter, 70% and 43% respectively, were colonised by Fusarium spp. F. graminearum was the most frequent species isolated from maize grain and husk segments(48.3 and 37.7% colonisation respectively). Other species, particularly F. culmorum and F. acuminatum, were also found to be common contaminants. A total of 15 Fusarium spp. was recovered from all material examined by both techniques. Cultures with characteristics resembling those of F. moniliforme were rarely observed.This revised version was published online in October 2005 with corrections to the Cover Date.     

Cytotoxicity of Fusarium species mycotoxins and culture filtrates of Fusarium species isolated from the medicinal plant Tribulus terrestris to mammalian cells

Ayurvedic medicine, which uses decoctions made of medicinal plants, is used to cure diseases in many Asian countries including Sri Lanka. Although proper storage facilities for medicinal plants are unavailable in Sri Lanka, neither the potential for growth of toxigenic fungi nor their ability to produce mycotoxins in stored medicinal plants has been investigated. We isolated three Fusarium species, F. culmorum, F. acuminatum and F. graminearum from the medicinal plant Tribulus terrestris. Culture extracts of the 3 Fusarium spp. were cytotoxic to mammalian cell lines BHK-21 and HEP-2. Three toxic metabolites produced by Fusarium spp; T-2 toxin, zearalenone, and diacetoxyscirpenol were also cytotoxic to the same mammalian cell lines. The 3 Fusarium spp. grown on rice media produced zearalenone. Plant material destined for medicinal use should be stored under suitable conditions to prevent growth of naturally occurring toxigenic fungi prior to its use.     

Nachweis von Fusarien und deren Mykotoxinen in Futterkonservaten aus Grünlandbeständen mit differenzierter Bewirtschaftungsintensität

Conservation forage (17 hay and 18 grass silage samples) from 15 farms with different intensities of grassland management in the Federal State of Brandenburg were examined for contamination with fusaria and their mycotoxins. The numbers of culturable filamentous fungi in hay were determined by plate counting andFusarium isolates were classified taxonomically. The mycotoxins Zearalenone (ZEA) and Deoxynivalenol (DON) were extracted from hay as well as silage by different procedures and detected chromatographically (HPLC). The numbers of filamentous fungi in the hay samples were 10² and 10⁶ CFU/g FM independently of intensive or extensive management. Only fourFusarium species were identified.Fusarium culmorum, a potential toxin producing species, was most frequently detected (52% of all isolates). ZEA was found in two hay and four silage samples (6-66 μg/kg), DON in three hay and seven silage samples (63–1290 μg/kg). There were no differences between forage samples of extensive and intensive cultivated grassland of the year 2003 regarding numbers of fusaria and the content of their mycotoxins.

Presented at the 26^th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004.     

Prevalence of Fusarium species of the Liseola section on selected Colombian animal feedstuffs and their ability to produce fumonisins

A total of 57 samples of feedstuffs commonly used for animal nutrition in Colombia (corn, soybean, sorghum, cottonseed meal, sunflower seed meal, wheat middlings and rice) were analyzed for Fusarium contamination. Fusarium fungi were identified at species level by means of conventional methods and the ability to produce fumonisins of the most prevailing species was determined. A total of 41 of the feedstuffs analyzed (71.9%) were found to contain Fusarium spp. Most contaminated substrates were corn (100%), cottonseed meal (100%), sorghum (80%), and soybean (80%). Wheat middlings and rice showed lower levels of contamination (40% and 20%, respectively), while no Fusarium spp. could be isolated from sunflower seed meal. The most prevalent species of Fusarium isolated were F. verticilliodes (70.8%), F.␣proliferatum (25.0%), and F. subglutinans (4.2%). All of them correspond to section Liseola.Production of fumonisins on corn by the isolated Fusarium was screened through liquid chromatography. Almost all strains of F. verticilliodes (97.1%) produced FB1 (5.6–25,846.4 mg/kg) and FB2 (3.4–7507.5 mg/kg). Similarly, almost all strains of F.␣proliferatum (91.7%) produced fumonisins but at lower levels than F.␣verticilliodes (FB1 from 6.9 to 3885.0 mg/kg, and FB2 from 34.3 to 373.8 mg/kg), while F. subglutinans did not produce these toxins. This is the first study in Colombia describing toxigenic Fusarium isolates from␣animal feedstuffs.     

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

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

Management of soil microbial communities to enhance populations of Fusarium graminearum-antagonists in soil

Fusarium head blight (FHB), incited by Fusarium graminearum Schwabe is one of the most devastating diseases of wheat. Primary inoculum generated on crop residue is the driving force of FHB epidemics. Fusarium survival on crop residues is affected by soil microbial antagonists. The incorporation of green manures has been shown to increase the density and diversity of microbes in soils, particularly the density and the pathogen-inhibitory activity of specific bacteria and fungi. Evidence of increased streptomycete populations in soil as a response to green manure incorporation, and their negative effect on the survival of Fusarium oxysporum Schlechtendahl in soil, suggests their potential use to reduce the survival of related pathogens. There is, however, no precedent for the use of green manures to promote indigenous streptomycete populations to control FHB. This study investigated the use of green manures (sorghum–sudangrass hybrid [Sorghum bicolor (L.) Moench–S. bicolor (L.) Moench var. sudanense (Piper)] and common buckwheat [Fagopyrum esculentum (Moench)]) for reducing F. graminearum survival in association with wheat residues. Soil bacterial density, streptomycete density and the density and inhibitory activity of F. graminearum-antagonists were monitored from planting until 3 and 6 months following the incorporation of green manures in greenhouse and field experiments, respectively. The decomposition of wheat residues and survival of Fusarium in residues was also assessed. The use of green manures did not statistically impact the survival of F. graminearum in wheat residue. However, green manures promoted the development of higher densities and antagonistic abilities of F. graminearum-antagonists in soils. Additionally, streptomycete densities and F. graminearum-antagonist densities were significantly and positively correlated with reduced survival of Fusarium. The results of our study suggest that the use of green manures can enhance populations of indigenous soil microorganisms antagonistic to the survival of F. graminearum in wheat residue.     

Mycotoxins and fungi in wheat harvested during 1990 in test plots in the state of São Paulo,Brazil

Wheat from two cultivars with contrasting characteristics were harvested in ten experimental plots located in wheat producing areas of the State of São Paulo, Brazil. The samples (10 of each cultivar) were analyzed by a gaschromatographic method for deoxynivalenol (DON), nivalenol (NIV), diacetoxyscirpenol (DAS), toxins T-2 (T-2) and HT-2, T-2 tetraol, T-2 triol, and by a thin-layer chromatographic method for zearalenone (ZEN), aflatoxins B₁, B₂, G₁, G₂, ochratoxin A and sterigmatocystin. No mycotoxins were detected in 13 samples. DON was found in four samples (0.47–0.59 µg/g), NIV in three samples (0.16–0.40 µg/g), T-2 in two samples (0.40, 0.80 µg/g), DAS in one sample (0.60 µg/g), and ZEN in three samples (0.04–0.21 µg/g). The wheat samples were also examined for the incidence of fungi.Alternaria, Drechslera, Epicoccum andCladosporium were the prevailing genera. Among theFusarium spp.,F. semitectum was present in 19 samples andF. moniliforme in 18 samples. NoF. graminearum was isolated in the samples.Abbreviations DAS diacetoxyscirpenol - DON deoxynivalenol - NIV nivalenol - T-2 T-2 toxin - ZEN zearalenone     

Patterns of mycotoxin production by Fusarium gmminearum isolated from Argentine wheat

Fusarium graminearum was isolated from several wheat samples of the 1985/86 Argentine crop, taken from lots that had suffered extensive invasion by this fungus. Previous chemical analysis of the cereal, had revealed contamination with deoxynivalenol (DON), but the presence of the other mycotoxins could not be excluded with certainty, due to the low sensitivity of the analytical methodology employed.Twenty four F. graminearum isolates were grown on white corn with 50% water, for 21 days at 28 °C, or in liquid medium (Sucrose 3%, Peptone 0,1% and Yeast Extract 0,1%) for 7 days at 28 °C without shaking, and tested for the production of mycotoxins. Eight isolates (33% of the total) were found to produce toxins in one or both media. Toxins detected were: DON (6 isolates), 15-AcetylDON (5), 3-AcetylDON (2) and Zearalenone (3). No traces of Nivalenol, Fusarenon-X or other trichothecenes were found.These results suggest that strains of F. graminearum, prevailing in Argentine wheat-growing regions, might belong to the DON/AcetylDON chemotype, since no organisms of the Nivalenol/Fusarenon-X chemotype were detected in this study.     

Mycoflora of freshly harvested flint corn from Northwestern Provinces in Argentina

A mycological survey was carried out for the first time, on red flint corn samples from the northwestern Andinian region of Argentina in the 1999 and 2000 harvest seasons. Species of the genus Fusarium were the most prevalent component of the flint corn mycoflora present in all provinces.F. verticillioides was the predominant Fusarium isolated in the 1999 harvest season in the the region, and was found at higher incidence level than those observed on commercial semident corn hybrids harvested in the main corn production area in Argentina (Pampean region). During the 2000 harvest season, Fusarium graminearum was most commonly isolated species in Salta province.This revised version was published online in October 2005 with corrections to the Cover Date.     

Isolates of Fusarium graminearum collected 40–320?meters above ground level cause Fusarium head blight in wheat and produce trichothecene mycotoxins

The aerobiology of fungi in the genus Fusarium is poorly understood. Many species of Fusarium are important pathogens of plants and animals and some produce dangerous secondary metabolites known as mycotoxins. In 2006 and 2007, autonomous unmanned aerial vehicles (UAVs) were used to collect Fusarium 40–320 m above the ground at the Kentland Farm in Blacksburg, Virginia. Eleven single-spored isolates of Fusarium graminearum (sexual stage Gibberella zeae) collected with autonomous UAVs during fall, winter, spring, and summer months caused Fusarium head blight on a susceptible cultivar of spring wheat. Trichothecene genotypes were determined for all 11 of the isolates; nine isolates were DON/15ADON, one isolate was DON/3ADON, and one isolate was NIV. All of the isolates produced trichothecene mycotoxins in planta consistent with their trichothecene genotypes. To our knowledge, this is the first report of a NIV isolate of F. graminearum in Virginia, and DON/3ADON genotypes are rare in populations of the fungus recovered from infected wheat plants in the eastern United States. Our data are considered in the context of a new aerobiological framework based on atmospheric transport barriers, which are Lagrangian coherent structures present in the mesoscale atmospheric flow. This framework aims to improve our understanding of population shifts of F. graminearum and develop new paradigms that may link field and atmospheric populations of toxigenic Fusarium spp. in the future.     

Occurrence and variability of mycotoxigenicFusarium species associated to wheat and maize in the South West of Spain

The contamination of cereals with mycotoxins produced by species ofFusarium is an important risk to human and animal health. The toxigenic profile is different depending on theFusarium species considered and, in some species, differences can also be observed at intraspecific level. Information about the distribution and variability of the mycotoxigenicFusarium species allow prediction of the toxins that may occur and to devise control strategies. In this work, the occurrence of mycotoxigenicFusarium species associated to cereals was analysed in a wide sample of durum wheat fields (Triticum durum Desf.) and maize from the South West of Spain (Andalucía).F. equiseti, F. graminearum andF. culmorum were the most frequentFusarium species detected in wheat fields followed byF. sambucinum andF. avenaceum, whereas in the case of maize,F. verticillioides andF. proliferatum were the onlyFusarium species present. The relationships of the Spanish isolates from theF. equiseti, F. avenaceum andF. sambucinum species were analysed by nucleotide sequence comparison of a partial region of the Elongation Factor 1 alpha (EF-1α) with other sequences available in data bases. The results indicated thatF. avenaceum andF. equiseti showed high variability and that the SpanishF. equiseti isolates seemed to belong toF. equiseti type II. Presented at the EU-USA Bilateral Workshop on Toxigenic Fungi & Mycotoxins, New Orleans, USA, July 5–7, 2005 Financial support: MCYT (AGL2004/07549/C05/5). M. Jurado was supported by pre-doctoral fellowship by the MCYT     

Biological detoxification of the mycotoxin deoxynivalenol and its use in genetically engineered crops and feed additives

Deoxynivalenol (DON) is the major mycotoxin produced by Fusarium fungi in grains. Food and feed contaminated with DON pose a health risk to humans and livestock. The risk can be reduced by enzymatic detoxification. Complete mineralization of DON by microbial cultures has rarely been observed and the activities turned out to be unstable. The detoxification of DON by reactions targeting its epoxide group or hydroxyl on carbon 3 is more feasible. Microbial strains that de-epoxidize DON under anaerobic conditions have been isolated from animal digestive system. Feed additives claimed to de-epoxidize trichothecenes enzymatically are on the market but their efficacy has been disputed. A new detoxification pathway leading to 3-oxo-DON and 3-epi-DON was discovered in taxonomically unrelated soil bacteria from three continents; the enzymes involved remain to be identified. Arabidopsis, tobacco, wheat, barley, and rice were engineered to acetylate DON on carbon 3. In wheat expressing DON acetylation activity, the increase in resistance against Fusarium head blight was only moderate. The Tri101 gene from Fusarium sporotrichioides was used; Fusarium graminearum enzyme which possesses higher activity towards DON would presumably be a better choice. Glycosylation of trichothecenes occurs in plants, contributing to the resistance of wheat to F. graminearum infection. Marker-assisted selection based on the trichothecene-3-O-glucosyltransferase gene can be used in breeding for resistance. Fungal acetyltransferases and plant glucosyltransferases targeting carbon 3 of trichothecenes remain promising candidates for engineering resistance against Fusarium head blight. Bacterial enzymes catalyzing oxidation, epimerization, and less likely de-epoxidation of DON may extend this list in future.     

Production of trichothecene mycotoxins byFusarium graminearum andFusarium culmorum on barley and wheat

Wheat cultivars (Stoa, MN87150, SuMai-3, YMI-6, Wheaton) and barley cultivars (Robust, Excel, Chevron, M69) were inoculated in the field with isolates ofFusarium graminearum andF. culmorum. The diseased (Fusarium head blight) kernels were analyzed for deoxynivalenol (DON), 15-acetyldeoxynivalenol (15-ADON) and nivalenol (NIV).F. culmorum produced all three trichothecenes on all cultivars tested whereasF. graminearum only produced DON and 15-ADON. There was no well defined correlation between DON production in the host and resistance although the data tended to favor SuMai-3 as having definitive resistance to bothF. graminearum andF. culmorum.Minnesota Agricultural Experiment Station, Paper No. 20 279.     

香蕉植株根区土壤的真菌多样性分析

尖孢镰孢菌古巴专化型(Fusarium oxysporum f.sp.cubense)是香蕉枯萎病的病原菌,该菌是一种土壤习居菌,了解香蕉根区土壤中真菌多样性及镰孢菌属(Fusarium)真菌所占比例,对如何减少土壤中的病原菌、预防香蕉枯萎病的发生有重要的指导意义。该文通过采集不同宿根年限的香蕉健康植株和枯萎病植株的根区土壤,利用高通量测序技术测定土壤样品中的真菌种群。结果表明:(1)同一宿根年限的香蕉植株中,健康植株根区土壤中所获的reads及OTUs数量均高于枯萎病植株,说明健康植株根区土壤的真菌多样性丰富于枯萎病植株。(2)除了一年生香蕉枯萎病植株以担子菌门(Basidiomycota)为主外,其他土壤样品中均以子囊菌门(Ascomycota)为主,其中的丛赤壳科最高相对丰度来自三年生健康植株的根区土壤(26.02%),其次是五年生的枯萎病植株根区土壤(15.56%)。(3)在丛赤壳科中,镰孢菌属在三年生健康植株土壤中的相对丰度最高(2.54%),在其他样品中的相对丰度在0.1%～0.65%之间;在镰孢菌属中,腐皮镰孢菌(Fusarium solani)的相对丰度(0～1.59%...     

Occurrence of Aspergillus section Flavi and aflatoxin B1 in corn genotypes and corn meal in Argentina

A study has been carried out in Argentina on samples of corn genotypes from a breeding station as well as in commercially available corn meal. All samples were analyzed for fungal infection and aflatoxin B₁.Mycological analysis of corn genotypes showed the presence of three principal genera of filamentous fungi Fusarium (100%), Penicillium (67%) and Aspergillus (60%). In the genus Fusarium three species were identified, F. moniliforme (42%), F. nygamai (56%) andF. proliferatum (1.8%). Eight species ofPenicillium were identified, the predominant species isolated were P. minioluteum, P. funiculosum and P. variabile. In the genus ranked third in isolation frequency, two species were identified, A. flavus and A. parasiticus, the percentage of infection was 78% and 21%, respectively. Only one corn genotype was contaminated with aflatoxin B₁ at a level of 5 ppb. The cornmeal samples showed great differences in fungal contamination, the values ranging from 1 × 10¹ to 7 × 10⁵ cfu g^–1. Fusarium (68%), Aspergillus (35%) and Penicillium (21%) were the most frequent genera isolated. Among the genus, Aspergillus, A. parasiticus (38%) was the most frequent species isolated. All the samples of corn meal were negative to aflatoxin B₁. These results indicate a low degree of human exposure to aflatoxins in Argentina through the ingestion of maize or corn meal.This revised version was published online in October 2005 with corrections to the Cover Date.