Graminearum Chemotypes Research Articles

Identification and Differentiation of the Fusarium graminearum NX-2 Chemotype Using High-Resolution Melting (HRM).

Fusarium head blight causes significant yield losses in wheat and other cereals and contaminates grain products with trichothecene mycotoxins. F. graminearum isolates are classified into different chemotypes depending on the type of mycotoxin produced, including the type B trichothecenes 3-acetyl deoxynivalenol (3-ADON), 15-acetyl deoxynivalenol (15-ADON), nivalenol (NIV), and the recently identified type A trichothecene NX-2. Molecular tools to differentiate NX-2 producers from other chemotypes have remained relatively laborious and time consuming. In this study, we developed and validated a high-resolution melting (HRM) assay that can identify NX-2 producers quickly and cost-effectively. By analyzing TRI1 coding sequences from 183 geographically diverse isolates representing all four F. graminearum chemotypes, we selected a 75-base pair region containing four non-synonymous single nucleotide polymorphisms (SNPs) that are specific to the NX-2 genotypes. The amplicon generated two HRM profiles, one of which was specific for only NX-2. We confirmed that the assay is robust across qPCR platforms and unambiguously differentiates NX-2 from other chemotypes using a panel of 72 diverse isolates previously collected from North America. The HRM assay was also successful in identifying NX-2 producers directly from DNA extracted from infected wheat spikes with varying levels of disease severity and fungal DNA. The assay can detect as little as 0.01 ng of fungal DNA in a background of 50 ng of plant DNA. This new diagnostic assay can be used for high-throughput molecular detection of the NX-2 chemotype of F. graminearum from infected plant samples and culture collections, thus making it a valuable tool for surveys of contemporary and historical FHB pathogen populations.

Differential reaction of hexaploid and tetraploid wheat to Fusarium graminearum chemotypes in a controlled environment

Fusarium head blight (FHB) has a negative impact on cereal food safety, quality and yield. The majority of FHB resistance genes in wheat (Triticum spp.) have been identified based on reaction to Fusarium graminearum, which, in Canada, has two prevalent trichothecene chemotypes, 3-acetyl-deoxyinvalenol (ADON) and 15-ADON. Three hexaploid (Triticum aestivum L.) and four tetraploid (Triticum turgidum L. ssp. durum and Triticum turgidum L. spp. dicoccoides (Korn. ex Asch. & Graebn.) Thell.) wheat genotypes with different genes for resistance and with different reactions to F. graminearum were evaluated in replicated greenhouse trials to determine if the resistance genes currently deployed in Canadian wheat are effective against both the 3-ADON and 15-ADON chemotypes. The development of FHB was rated as disease severity. The genotypes showed differential responses, with a higher level of disease development in the hexaploid wheat genotypes inoculated with the 3-ADON than with the 15-ADON chemotype. The opposite was observed in the tetraploid wheat genotypes. Tetraploid genotype BGRC3487 and a hexaploid genotype ND2710 showed similar resistance to both 3-ADON and 15-ADON chemotypes. These would be effective sources to breed lines resistant to both 3-ADON and 15-ADON chemotypes and reduce FHB risk.

Prevalence of Mycoflora and Fusarium graminearum Chemotype DON in Wheat in Bechar Province of South-Western Algeria

Wheat and its derivatives are a main staple food for the Algerian populations. The objective of this study aims to analyze local and imported wheat grains for fungi particularly Fusarium graminearum chemotype DON and evaluate deoxynivalenol (DON) contaminated wheat collected from Bechar region, in south-western Algeria. A total of 64 of wheat samples were examined for fungal contamination and fungal load was determined by means of standard microbiological method. DON was detected using the ELISA technique. The results revealed that 98.44% of analyzed samples showed positive results regarding fungal contamination. More precisely, local wheat was dominated by Aspergillus and Penicillium and imported wheat was dominated by Fusarium, Penicillium and Aspergillus species. Results showed that 62.5% of F. graminearum strains produced DON. Contamination levels of wheat with DON ranging from <0.04 ppm to >5ppm for soft wheat and from <0.12ppm to >15ppm for durum wheat. So, 62.96% of soft wheat grains and 55.56% of durum wheat imported from France, and also 18.18% of local durum wheat exceed the permissible limit by far. This study provides basic grounds in assessing the degree of fungal and potential DON contamination in Algerian wheat.

Diversity of trichothecene genotypes of Fusarium graminearum sensu stricto from winter wheat in Serbia

Data related to genetic diversity of F. graminearum chemotypes in Serbia are limited, thus the main objective of this study was to analyze the divergence of genes associated with the trichothecene cluster. F. graminearum was shown to be the dominant Fusarium species in Serbia occurring with frequency of 65.6% in 2016/2017 growing season. Isolates of F. graminearum dominantly belonged to SCAR type 1 (104/105) producing PCR product of 420 bp, but one isolate was proven to be SCAR type 6 producing PCR product of 400 bp. This is the first report of the presence of SCAR type 6 in Southeastern Europe. Results from this study reveal that F. graminearum populations were shown to be DON-DON chemotype with respect to Tri7 and Tri13 genes. All but one of these isolates were 15-AcDON chemotypes based on Tri3 gene. One isolate carried a deletion of Tri7 and was found to be 3-AcDON by using Tri303F/R primer pair. This is the first record on the presence of a 3-AcDON isolate with the Tri7 deletion in Serbia. The Tri7F/Tri7DON primer pair was not effective if isolates carried more than four 11-bp repeats in the Tri7 gene. Primer pair GzTri7f1/r1 was proven to be more effective in comparison with Tri7F/Tri7DON. Genetic variation ranged from 57 to 80% with no significant association of Tri7 alleles with localities. Results of this study have brought new insights into the distribution and population structure of F. graminearum in Serbia.

Fusarium graminearum Chemotype-Spring Wheat Genotype Interaction Effects in Type I and II Resistance Response Assays.

Fusarium head blight (FHB), caused by several Fusarium spp., is a worldwide problem that severely impacts cereal grain yield and poses major risks to human and animal health due to production of the mycotoxin deoxynivalenol (DON) and its acetylated forms, 3-acetyl-DON (3-ADON) and 15-acetyl-DON (15-ADON). Recent studies suggest an inconsistent effect of F. graminearum chemotypes and resistance of wheat (Triticum aestivum) genotypes. To gain insight into the interaction effects of F. graminearum chemotypes and spring wheat genotypes on FHB resistance response, 10 spring wheat genotypes with varying levels of FHB resistance were inoculated with 10 F. graminearum isolates, consisting of 5 3-ADON- and 5 15-ADON-producing isolates and evaluated in type I (spray inoculation) and type II (point inoculation) resistance assays. Wheat genotypes carrying the resistance allele of the Fhb1 quantitative trait locus on chromosome 3BS had lower disease in type II evaluations, regardless of F. graminearum isolate or chemotype. Isolates of F. graminearum were also significantly different for disease aggressiveness. In addition, the 3-ADON-producing isolates were 18% more aggressive than the 15-ADON isolates in type I resistance assays. No difference in aggressiveness of the two chemotypes was observed, when tested in type II resistance assays. There was no interaction effect between F. graminearum chemotypes and spring wheat genotypes, suggesting that screening of germplasm for resistance can be performed with limited number of aggressive isolates.

Trichothecene chemotype diversity of Fusarium graminearum isolated from wheat, maize and barley in Serbia

Diversity of trichothecene chemotypes of Fusarium graminearum isolated from kernels of wheat, barley and maize grown under various agro-ecological conditions on 13 locations was analysed. Sixteen strains were tested for the effective capability to produce 15-ADON, 3-ADON and NIV, by using the liquid chromatography-tandem mass spectrometry (LC-MS/MS) system. Fourteen out of sixteen analyzed strains produced 15-ADON, while remaining two were of the 3-ADON chemotype. Multiplex PCR reaction with two sets of specific primers for TRI3 and TRI12 genes was applied to identify trichothecene chemotypes (3-ADON, 15-ADON and NIV). The expected sizes of amplified fragments for TRI3 gene primer set are 840 bp (NIV), 610 bp (15-ADON) and 243 bp (3-ADON). The amplified fragments for TRI12 gene primer set should be 840 bp (NIV), 670 bp (15-ADON) and 410 bp (3-ADON). All F. graminearum isolates were of the 15-ADON chemotype, i.e. their bands were 610 bp and 670 bp size for TRI3 and TRI12 genes, respectively. The results indicate that genotypic characterisation does not correspond to determined chemotypes and this is a reason why the analyses for the risk of mycotoxins contamination should not be based only on trichotecene genotype determination. Due to high temperature differences in cereal growing regions in Serbia, the presence of other chemotypes could be expected. In order to determine whether besides 15-ADON there are other F. graminearum chemotypes on wheat, barley and maize kernels, further studies should include a large number of isolates from different agro-ecological conditions.

Data independent acquisition-digital archiving mass spectrometry: application to single kernel mycotoxin analysis of Fusarium graminearum infected maize.

New and conjugated mycotoxins of concern to regulators are frequently being identified, necessitating the costly need for new method development and sample reanalysis. In response, we developed an LC-data independent acquisition (LC-DIA) method on a Q-Exactive Orbitrap mass spectrometer tailored for mycotoxins analysis. This method combines absolute quantification of targeted fungal metabolites with non-targeted digital archiving (DA) of data on all ionizable compounds for retrospective analysis. The quantitative power of this approach was assessed by spiking 23 mycotoxins at a range of concentrations into clean maize extracts. The linearity and limits of detection achieved were comparable to conventional LC-MS/MS and significantly better than 'all-ion-fragmentation' scanning mode. This method was applied to single kernel analysis of Fusarium infected maize, where we quantified nine Fusarium metabolites and three metabolites from unexpected contaminations by Alternaria and Penicillium species. Retrospective analysis of this data set allowed us to detect the recently reported 15-acetyldeoxynivalenol-3-O-β-D-glucoside without requiring re-analysis of the samples. To our knowledge, this is the first reported occurrence of this conjugated mycotoxin in naturally contaminated maize, and led us to further study maize artificially inoculated with the 3-acetyldeoxynivalenol and 15-acetyldeoxynivalenol chemotypes of Fusarium graminearum. Analysis of these samples showed that the maize genotype tested glycosylates 15-acetyldeoxynivalenol but not 3-acetyldeoxynivalenol likely because the glycosylation site was blocked. In addition to confirming that these two F. graminearum chemotypes behave differently when infecting the host plant, it demonstrates the utility of using a single screening method to quantify known mycotoxins and archive a completely non-targeted dataset for future analysis.

Mycotoxin accumulation and Fusarium graminearum chemotype diversity in winter wheat grown in southwestern Ontario

Tamburic-Ilincic, L., Wragg, A. and Schaafsma, A. 2015. Mycotoxin accumulation and Fusarium graminearum chemotype diversity in winter wheat grown in southwestern Ontario. Can. J. Plant Sci. 95: 931–938. Fusarium head blight caused by Fusarium graminearum is a serious disease of wheat (Triticum aestivum L.). Deoxynivalenol (DON) is the mycotoxin most commonly detected in contaminated wheat grain in Ontario. A chemotype shift from 15-acetyldeoxynivalenol (15-ADON) to 3-acetyldeoxynivalenol (3-ADON) has been reported in some parts of North America. The objectives of this study were to investigate the mycotoxins accumulation and Fusarium graminearum chemotype diversity in different winter wheat cultivars grown in southwestern (SW) Ontario. Twenty winter wheat grain samples from SW Ontario were tested for DON concentrations in 2008, 24 in each of 2009 and 2010, 42 in 2011 and 36 in 2013 growing seasons. DON levels in grain ranged from none detected to 33 parts per million (ppm). The highest averaged levels of DON were detected in the 2013 season (19.8 ppm at Centralia, 11.8 ppm at Inwood and 4.1 ppm at Ridgetown). In addition to total DON, H-T2, T-2 and nivalenol mycotoxins were detected in low concentrations in a small number of samples collected in 2009 and/or 2013. The 15-ADON analogs were detected at approximately 1.5% of the total DON in harvested wheat grain in 2013. Ninety-seven percent of F. graminearum isolates, tested in 2010 using the polymerase chain reaction (PCR) method, were 15-ADON chemotype, while just 3% of isolates were the 3-ADON chemotype. Overall, there was no evidence in this study to support a shift from 15-ADON to 3-ADON chemotypes of F. graminearum in SW Ontario in 2010. It is recommended to continue monitoring mycotoxin accumulation and F. graminearum chemotype diversity so any changes can be detected early and addressed.

Mycotoxin accumulation and Fusarium graminearum chemotype diversity in winter wheat grown in southwestern Ontario

Tamburic-Ilincic, L., Wragg, A. and Schaafsma, A. 2015. Mycotoxin accumulation and Fusarium graminearum chemotype diversity in winter wheat grown in southwestern Ontario. Can. J. Plant Sci. 95: 931-938. Fusarium head blight caused by Fusarium graminearum is a serious disease of wheat (Triticum aestivum L.). Deoxynivalenol (DON) is the mycotoxin most commonly detected in contaminated wheat grain in Ontario. A chemotype shift from 15-acetyldeoxynivalenol (15-ADON) to 3-acetyldeoxynivalenol (3-ADON) has been reported in some parts of North America. The objectives of this study were to investigate the mycotoxins accumulation and Fusarium graminearum chemotype diversity in different winter wheat cultivars grown in southwestern (SW) Ontario. Twenty winter wheat grain samples from SW Ontario were tested for DON concentrations in 2008, 24 in each of 2009 and 2010, 42 in 2011 and 36 in 2013 growing seasons. DON levels in grain ranged from none detected to 33 parts per million (ppm). The highest averaged levels of ...

Chemotype and aggressiveness of isolates of Fusarium graminearum causing head blight of wheat in Nebraska

Fusarium head blight (FHB) or scab of wheat (Triticum aestivum L.) and its associated mycotoxin deoxynivalenol (DON) can cause devastating economic losses. In North America, FHB of wheat is caused mainly by Fusarium graminearum Schwabe [sexual stage Gibberella zeae (Schwein.) Petch]. In this study, the chemotype of 73 single-spore isolates of F. graminearum obtained from wheat kernels collected from 2007 to 2010 from FHB-affected fields and grain elevators in Nebraska was determined to be 15-ADON. Eight selected isolates were evaluated for aggressiveness on spikes and DON production in grain using the FHB-susceptible spring wheat cultivar ‘Wheaton’. Aggressiveness was quantified as disease severity and area under the disease progress curve (AUDPC). Disease severity at 21 days after inoculation ranged from 40.9% to 99.5% and AUDPC ranged from 284%-days to 1279%-days. DON production in grain, measured by enzyme-linked immunosorbent assay (ELISA), ranged from 0.2 to 11.0 µg g−1. Aggressiveness as measured using AUDPC was positively and linearly related to DON production in grain (R2 = 0.98; P < 0.0001). Isolates that produced the most DON were also the most aggressive. These results confirmed previous findings that the predominant F. graminearum chemotype in North America is 15-ADON and suggest that in Nebraska, there are highly aggressive populations of F. graminearum with high DON production capacity that have potential to cause severe losses due to reduction in yield and grain quality. This information will enhance farmers’ preparedness and willingness to apply management measures in years with a high risk for FHB outbreaks and will help researchers better understand FHB.

Aggressiveness of different Fusarium graminearum chemotypes within a population from Northern-Central Italy

The aggressiveness of 32 Fusarium graminearum strains isolated from durum wheat cultivated in Northern-Central Italy was assessed. The chemotype (15-acetyldeoxynivalenol-, 3-acetyldeoxynivalenol- or nivalenol-producer) of each strain was characterized with multiplex PCR. Two aggressiveness assays (single floret inoculation and the Petri-dish test), which yielded three aggressiveness indices, were used. One strain from southern Italy (moderately aggressive) was added as the positive control to evaluate the accuracy of the aggressiveness quantification in both assays. The results showed that all 32 F. graminearum strains are pathogenic and a wide range of aggressiveness levels was observed. The positive control strain is pathogenic and showed moderately aggressive in both assays, thus indicated that our aggressiveness quantifications are valid. Six highly aggressive strains, representing all three chemotypes, were stable in the different aggressiveness assays. There was no significant difference in aggressiveness among the three different chemotypes (P = 0.909–0.972) determined by three aggressiveness indices. Highly significant correlations of AUDPCstandard to mean and terminal disease severity (r = 0.91, P < 0.001 in both cases) reveal the potential of using the Petri-dish test for selection of F. graminearum inocula with the proper and/or varying aggressiveness levels for breeding purposes.

Deoxynivalenol levels and chemotype frequency in barley cultivars inoculated with two chemotypes of Fusarium graminearum

Corn kernels colonized by Fusarium graminearum were spread between lines of barley (Hordeum vulgare) in an irrigated Fusarium head blight (FHB) nursery at a 2 : 1 ratio of isolates producing 15-acetyldeoxynivalenol (15 ADON) to isolates producing 3-acetyldeoxynivalenol (3 ADON) (in 2008) or 1 : 1 ratio (in 2009, 2010). In 2008, it was the first use in this field of a 3 ADON isolate after 9 years of artificial inoculation with exclusively 15 ADON isolates. Sets of three 2-row and three 6-row cultivars were used as checks throughout the nursery, representing a range of susceptibility to FHB. Composites of these cultivars were prepared and analysed for per cent F. graminearum infection, chemotype frequency and levels of deoxynivalenol (DON), 3 ADON and 15 ADON. Seed infection by F. graminearum ranged from 83.5% (2009) to 98.5% (2010), with little difference across the nursery. In 2008, the chemotype distribution of F. graminearum and DON levels on infected kernels showed a several-fold difference from the eastern side (67% 3 ADON isolates and 46 ppm DON) to the western end of the field (16% 3 ADON isolates and 13 ppm DON), but not in the subsequent 2 years. In both 2009 and 2010, the 3 ADON chemotype was recovered from only 18% and 13% of the seeds, and overall average DON levels were 18 ppm and 24 ppm, respectively. In 2008, the highest DON and 3 ADON levels were associated with the highest frequency of the 3 ADON chemotype. In all years, the recovery of isolates did not reflect the ratio of the initial inoculum, suggesting that other factors influenced the ultimate infection of the seed. However, the relative relationship among the barley cultivars was consistent throughout all 3 years: DON levels were much lower in the most resistant cultivars compared with the most susceptible cultivars in all years and composites. Genotypic response to DON accumulation did not show strong interaction with 3 ADON frequency, suggesting that the underlying genetic resistance of the barley cultivars is cross-applicable between chemotypes.

Greenhouse Studies Reveal Increased Aggressiveness of Emergent Canadian Fusarium graminearum Chemotypes in Wheat.

The role of Fusarium graminearum trichothecene-chemotypes in disease outcomes was evaluated by point inoculation in a series of wheat lines with different levels of resistance to Fusarium head blight (FHB). Four inocula, each consisting of a composite of four strains with either 15-acetyldeoxynivalenol (ADON) chemotypes from "traditional" or emergent populations, a 3-ADON chemotype, or a nivalenol (NIV) chemotype, were compared. The evaluated wheat included Canadian lines with different levels of FHB resistance/susceptibility and double haploid lines developed from crosses of these lines. Highly resistant lines were resistant to infection by all of the F. graminearum chemotypes evaluated. In the moderately susceptible/resistant wheat lines, the 3-ADON producers and the emergent 15-ADON population were, in some instances, more aggressive and resulted in higher Fusarium damaged kernel scores and levels of trichothecene accumulation. The data presented in this study demonstrate the importance of growing highly resistant wheat cultivars in the current climate of an evolving F. graminearum population, and suggest that moderate levels of FHB resistance may not be sufficient to minimize trichothecene contamination of grain from F. graminearum-infected wheat.

Difference in TRI13 gene sequences between the 3-acetyldeoxynivalenol producing Fusarium graminearum chemotypes from Canada and China.

Positive-negative PCR assays based on the genes involved in the trichothecene biosynthesis pathway are useful in assessing the risk of trichothecene contamination in grain and are important in epidemiological studies. A single PCR detection method based on the structural gene sequence of TRI13 gene has been developed to predict the 3-ADON, 15-ADON and NIV chemotypes in China. The chemotypic differences are based on the deletions within the TRI13 gene. The objective of this study was to assess the reliability of using this single primer based on the TRI13 gene to differentiate the F. graminearum chemotypes in Canada. In this study, we found that, this single PCR detection method based on the deletions in the TRI13 gene cannot be used to differentiate the 3-ADON and 15-ADON chemotypes in the Canadian F. graminearum isolates; further sequence analysis of the PCR products confirmed that both Canadian 3-ADON and 15-ADON chemotypes have the 61 bp deletion in the TRI13 gene. This 61 bp deletion was absent in the Chinese 3-ADON isolates. Therefore these findings revealed that there are genetic differences between the examined 3-ADON F. graminearum isolates from Canada and China. The observed genetic differences between the 3-ADON chemotype populations in Canada and China may be resulted from a random mutation (insertion/deletion) that took place in one of the populations and accumulated due to genetic drift and/or selection.

Sphaerodes mycoparasitica biotrophic mycoparasite of 3-acetyldeoxynivalenol- and 15-acetyldeoxynivalenol-producing toxigenic Fusarium graminearum chemotypes

Fusarium spp. are economically important crop pathogens and causal agents of Fusarium head blight (FHB) of cereals worldwide. Of the FHB pathogens, Fusarium graminearum 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON) are the most aggressive mycotoxigenic chemotypes, threatening food and feed quality as well as animal and human health. The objective of the study was to evaluate host specificity and fungal-fungal interactions of Sphaerodes mycoparasitica- a recently described mycoparasite - with F. graminearum 3- and 15-ADON strains by employing in vitro, microscopic and PCR techniques. Results obtained in this study show that the germination of mycoparasite ascospore in the presence of F. graminearum 3- and 15-ADON filtrates was greatly improved compared with Fusarium proliferatum and Fusarium sporotrichioides filtrates, suggesting a compatible interaction. Using quantitative real-time PCR with Fusarium-specific (Fg16N) and trichothecene Tri5 (Tox5-1/2)-specific primer sets, S. mycoparasitica was found to reduce the amount of F. graminearum 3-ADON and 15-ADON DNAs under separate coinoculation assays. Sphaerodes mycoparasitica was not only able to germinate in the presence of F. graminearum filtrates, but also established biotrophic mycoparasitic relations with two F. graminearum chemotypes and suppressed Fusarium growth.

Trichothecene Mycotoxins Associated with Potato Dry Rot Caused by Fusarium graminearum

Fusarium graminearum, a known producer of trichothecene mycotoxins in cereal hosts, has been recently documented as a cause of dry rot of potato tubers in the United States. Due to the uncertainty of trichothecene production in these tubers, a study was conducted to determine the accumulation and diffusion of trichothecenes in potato tubers affected with dry rot caused by F. graminearum. Potato tubers of cv. Russet Burbank were inoculated with 14 F. graminearum isolates from potato, sugar beet, and wheat and incubated at 10 to 12 degrees C for 5 weeks to determine accumulation of trichothecenes in potato tubers during storage. Twelve of the isolates were classified as deoxynivalenol (DON) genotype and two isolates were as nivalenol (NIV) genotype. Trichothecenes were detected only in rotted tissue. DON was detected in all F. graminearum DON genotype isolates up to 39.68 microg/ml in rotted potato tissue. Similarly, both NIV genotype isolates accumulated NIV in rotted potato tissue up to 18.28 microg/ml. Interestingly, isolates classified as genotype DON accumulated both DON and NIV in the dry rot lesion. Potato tubers were then inoculated with two isolates of F. graminearum chemotype DON and incubated up to 7 weeks at 10 to 12 degrees C and assayed for DON diffusion. F. graminearum was recovered from >53% of the isolations from inoculated tubers at 3 cm distal to the rotted tissue after 7 weeks of incubation but DON was not detected in the surrounding tissue. Based in this data, the accumulation of trichothecenes in the asymptomatic tissue surrounding dry rot lesions caused by F. graminearum is minimal in cv. Russet Burbank potato tubers stored for 7 weeks at customary processing storage temperatures.

Chemotypes ofFusarium graminearumisolates and accumulation of deoxynivalenol (DON), 15-ADON and 3-ADON in naturally infected and inoculated winter wheat in Ontario, Canada

Fusarium graminearum (Schwabe) causes Fusarium head blight (FHB), an important wheat disease. A shift in the presence of two F. graminearum chemotypes, 15-acetyl DON (15-ADON) and 3-acetyl DON (3-ADON) was identified in some part of North America (Ward et al. 2008). F. graminearum isolates collected from winter wheat in Ontario are mainly of the 15-ADON chemotype (Tamburic-Ilincic et al. 2006). Deoxynivalenol (DON) is the most important mycotoxin produced by F. graminearum; 15-ADON and 3-ADON analogs may also be produced. In the first study the objectives were to identify Fusarium species and to measure level of DON from commercial wheat fields in Ontario from 2004 to 2007 and level of 15-ADON and 3-ADON from fields in 2007. In the second study, the objective was to compare level of DON and the analogs produced after wheat cultivars were spray-inoculated with 15-ADON and 3-ADON isolates of F. graminearum.

Production of mycotoxins by selectedFusarium graminearumandF. crookwellenseisolates

Corn cultures (five isolates each of Fusarium graminearum Group 1 from wheat crowns, Group 2 from scabby wheat grains and from ear rot of corn and five isolates of F. crookwellense) were screened for their ability to produce deoxynivalenol (DON), nivalenol (NIV), fusarenon-x (FUS-X) and zearalenone (ZEA). Nine of the ten F. graminearum isolates from wheat produced DON (5-165 micrograms g-1) but none produced either NIV or FUS-X. Conversely, 3/5 and 2/5 of the F. graminearum isolates from corn produced NIV (5-40 micrograms g-1) and FUS-X (5-7 micrograms g-1), respectively, while none produced DON. All but one of the F. graminearum isolates produced ZEA (2-1160 micrograms g-1). None of the F. crookwellense isolates produced DON, but 5/5 and 4/5 produced NIV (6-170 micrograms g-1) and FUS-X (3-90 micrograms g-1), respectively, and all produced ZEA (605-1030 micrograms g-1). The results confirmed previous findings on the presence of two distinct F. graminearum chemotypes.