Effects of Fusarium culmorum head blight on mycotoxin accumulation and yield traits in barley doubled haploids

The susceptibility of barley doubled haploids (DH) to Fusarium head blight (FHB) was investigated. Heads of 24 DH lines (11 two-rowed and 13 six-rowed) derived from F₁ Maresi (two-rowed) × Pomo (six-rowed) hybrids were inoculated with a conidial suspension of the single isolate IPO348-01 of Fusarium culmorum. The experiment was carried out in three consecutive years (1996–98) in one location. The number of kernels per ear, 1000-kernel weight and kernel weight per ear were recorded in inoculated and control plots. In the infected kernels nivalenol (NIV) content and deoxynivalenol (DON) content were determined. The effects of genotype, year and genotype-year interaction on reduction of yield traits were significant. For mycotoxin content only genotype and year effects were found to be important. The average NIV concentration in kernels of inoculated lines ranged from 0.15 mg/kg in the two-rowed line MP7 to 6.36 mg/kg in the six-rowed line MP113. A low accumulation of DON was observed in the studied population (from 0.01 to 0.20 mg/kg). Generally, no significant differences in mycotoxin content were found between two-rowed and six-rowed genotypes. The line MP7 was found to be superior — with the lowest mycotoxin accumulation, and reduction in yield traits. Environmental conditions (years) affected DON and NIV level in kernels; however, the tendency to a lower or higher accumulation of mycotoxin in individual lines was stable over the years.     

Characterisation of<Emphasis Type="Italic">fusarium graminearum</Emphasis> and<Emphasis Type="Italic">F. culmorum</Emphasis> isolates by mycotoxin production and aggressiveness to wheat

A total of 27Fusarium culmorum isolates from Germany and 41F. graminearum isolates from Kenya were investigated for aggressiveness and mycotoxin production on wheat ears. In addition, ergosterol content of the kernels from ears inoculated withF. graminearum was determined and theF. culmorum isolates were tested for mycotoxin productionin vitro. For both pathogens, isolates markedly differed in aggressiveness. 59% and 37% of theF. culmorum isolates produced NIV and DON, respectively,in vivo andin vitro. The DON-producing isolates also produced 3-acDONin vitro. The more aggressive isolates produced mainly DON while the less aggressive isolates produced mainly NIV. 12% and 85% of theF. graminearum isolates produced NIV and DON, respectively. The highly aggressive isolates produced higher amounts of DON, aggressiveness being highly correlated to DON content in the kernels. NIV-producing isolates were less aggressive. Ergosterol content of kernels was moderately correlated to aggressiveness but highly correlated to DON content. Disease severity was associated with kernel weight reduction.     

Deoxynivalenol accumulation and other scab symptoms in six romanian wheat genotypes inoculated withFusarium graminearum

At anthesis, under field conditions at Fundulea, each of 6 Romanian winter wheat genotypes was inoculated with 3Fusarium graminearum isolates used individually.Fusarium head blight (FHB) was assessed according to the following traits: relative weight of spikes (RWS), percentage of Fusarium damaged kernels (FDK), relative weight of kernels per head (RWKH), area under the disease progress curve (AUDPC) and deoxynivalenol (DON) content in total sample of kernels. Correlations between these traits and parameters revealed important differences between examined wheat genotypes in: DON accumulation, progress of FHB development, yield reduction, and models of host — pathogen interactions in theTriticum - Fusarium pathosystem. Significant correlations between different attributes of FHB were found forFusarium isolate 1 which is a moderate producer of DON (0.89 μg g^-1). Weight of spike was significantly correlated with weight of kernels per spike (r = 0.93**) and with percentage of damaged kernels (r = - 0.87**), while FDK was highly correlated with RWKH (r = - 0.85*) and with DON content (r = 0.82*). Area under the disease progress curve was also found to be significantly correlated with DON content (r = 0.86*).     

Trichothecene Content of Rye and Wheat Genotypes Inoculated with a Deoxynivalenol- and a Nivalenol-producing Isolate of Fusarium culmorum

Head blight caused by Fusarium culmorum may lead to yield reduction and the contamination of cereal grain with the mycotoxins deoxynivalenol (DON), 3-acetyl deoxynivalenol (3-ADON), nivalenol (NIV), fusarenone-X (FUS), and others. In this study, the covariation between DON and NIV accumulation of 12 rye and eight wheat genotypes that differed in resistance were analysed by inoculating them with a DON-and a NIV-producing isolate, respectively, in three locations. The resistance traits head blight rating and plot yield relative to the uninoculated plots of the same genotype were assessed and the contents of DON, 3-ADON, NIV, and FUS in the grain were analysed by gas chromatography with mass spectrometry. The NIV-producing isolate was significantly (P=0.05) less aggressive and led to a considerably lower mean NIV content in the grain compared with the aggressiveness and mean DON content of the DON-producing isolate (19.5 mg NIV/kg grain versus 48.4 mg DON/kg). Wheat and rye genotypes significantly differed in their DON and NIV accumulation. All genotypes reacted in a similar manner to both chemotypes of F. culmorum for the resistance traits and the respective mycotoxin contents with the exception of one wheat variety, that caused a change in rank order for mycotoxin content. In conclusion, resistance to head blight and tolerance to mycotoxin accumulation seems to be most likely the same for DON- and NIV-producing isolates of F. culmorum .     

Interaction of gene effects with environments for malting quality of barley doubled haploids

Barley doubled haploids covering a wide range of malting quality, along with their parental cultivars and F2, F3 hybrids, were investigated in six environments (three locations, two years) to study the genotype-environment (G x E) interaction structure and the influence of environments on additive, dominance and epistatic gene effects. Grain and malt characters, such as 1000-grain weight, percentage of plump kernels, malt extract yield, protein content, Kolbach index and malt fine-coarse difference (FCD), were measured. Main effects for genetic parameters were estimated and regression analysis was used to explain the interaction of gene effects with environments. The results show that additive effects had the greatest interaction with environments for all the analysed traits, but only for malt characters this interaction was linear. Interaction of dominance effects was much lower and only in the case of 1000-grain weight, protein content and Kolbach index it proved to be significant. The results suggest that effects of heterozygous loci are more stable in contrasting environments than effects of homozygous loci.     

Influence of Growth Stage on Fusarium Head Blight and Deoxynivalenol Production in Wheat

Fusarium head blight is a major concern for wheat production worldwide. The fungi that cause the disease may infect head tissues from flowering to late stages of kernel development, but a better understanding of the influence of the time of infection on grain weight reduction and mycotoxin accumulation resulting from the infection process is needed. We investigated the influence of wheat reproductive stage at the time of inoculation on disease and grain quality parameters, especially production of deoxynivalenol (DON) in mature grains. Heads of Norm wheat were spray inoculated with a macroconidial suspension of a DON‐producing isolate of Fusarium graminearum at each of six reproductive stages from flowering to hard dough. Plants were incubated in a mist chamber for 48 h and then moved to the greenhouse until maturity. Norm wheat was susceptible at all stages inoculated but the highest grain weight reduction and DON accumulation occurred in plants inoculated past flowering to late milk stages. However, high incidences of kernel infection and significant levels of DON accumulation resulted from inoculations as late as the hard dough stage, even though there was no corresponding reduction in grain weight compared to non‐inoculated plants. The occurrence of commercially significant levels of DON in plump, high‐yielding wheat may result from infections that occur during favourable environments well after the flowering stages. Late infection and DON production should therefore be a future research focus for wheat breeding and integrated management of FHB and an important consideration for grading systems that employ the presence of visibly damaged kernels as a means of estimating DON content of wheat.     

Differences in susceptibility of winter wheat varieties for Fusarium species under Belgian growing conditions

Fusarium head blight is an important disease of cereal crops caused by Fusarium species. It causes not only a reduction in yield, but most Fusarium species (F. graminearum. F. culmorum, F. avenaceum. F. poae) produce also a range of toxic metabolites such as deoxynivalenol (DON) and zearalenone (ZEA). The evaluation of Fusarium species was followed up under natural infection conditions during the growing seasons 2001--2002 and 2002--2003 in two varietal winter wheat experiments on the experimental farm of the Hogeschool Gent at Bottelare. Disease pressure, DON and ZEA content, different Fusarium species as well as growth and yield parameters were determined. In both years there were significant differences between the varieties concerning the susceptibility to Fusarium and the DON content. ZEA was not found in the kernels. The mean deoxynivalenol (DON) content was in 2002 (1,126 mg/kg) higher than in 2003 (0.879 mg/kg) although the mean disease severity was bigger in 2003 than in 2002 what means that the DON content was not always correlated with the disease severity. The Fusarium species most frequently identified in our two field trials (Bottelare) were F. graminearum and F. culmorum Varietal differences in susceptibility to Fusarium species and DON contamination could be detected.     

Toxicity,of extracts of barley kernels inoculated withFusarium spp. toArtemia salina

Toxicity toA. salina, of the Fusarium metabolites: deoxynivalenol (DON), its acetylated derivatives (3- and 15-AcDON), zearalenone (ZON), neosolaniol (NEO), nivalenol (NIV), T-2, HT-2 toxins, has been examined and compared with toxicity of extracts of barley kernels (8 cultivars and 4 lines) inoculated withFusarium culmorum, F. graminearum andF. sporotrichioides respectively. Estimated LC₅₀ values were expressed as relative toxicity (RT) in mg DON/kg for samples inoculated withF. culmorum, F. graminearum or in mg T-2/kg forF. sporotrichioides inoculations. Toxicity of extracts of the same genotype/line kernels was compared among different pathogens used for inoculation and differences in Fusarium head blight susceptibility of different genotypes/lines inoculated with the sameFusarium strain were found. Significant correlation between toxicity of extracts (LC₅₀, RT) and toxic metabolites concentration was found ( $\bar r = 0.82$ ; P = 0.01). Bioassays withA. Salina offer a fast, easy and inexpensive method to examine cereal genotypes susceptibility to Fusarium head blight and mycotoxins accumulation in kernels.     

Susceptibility of Kenyan Wheat Varieties to Head Blight, Fungal Invasion and Deoxynivalenol Accumulation Inoculated with Fusarium graminearum

Fifteen wheat varieties commercially grown in Kenya were tested for their susceptibility to head blight and mycotoxin accumulation after inoculation with Fusarium graminearum in pot experiments. The strains of the pathogen used had been isolated from wheat collected in different growing areas of Kenya. Head blight susceptibility was assessed as the percentage of spikelets bleached and area under disease progress curve; kernel colonization by fungal mycelium was determined as ergosterol content. All varieties were found to be moderately to highly susceptible. However, the varieties differed in head blight susceptibility (29–68% of spikelets bleached; mean 54%), fungal colonization (67–187  μ g/g ergosterol content; mean 111  μ g/g) and the resulting mycotoxin contamination [deoxynivalenol (DON) 5–31  μ g/g; mean 13.5  μ g/g]. Grain weight reductions due to head blight ranged from 23 to 57% (mean 44%). The varieties could be therefore divided into partially resistant and highly susceptible genotypes. The kernels of highly susceptible varieties had higher mycotoxin and ergosterol contents. However, the kernels of some varieties contained more fungal mycelium (ergosterol) without the corresponding high amounts of DON, suggesting that they possess some resistance to DON accumulation. Less susceptible varieties showed resistance to fungal spread, as indicated by a slow disease development and lower content of fungal biomass.     

Progression of mycotoxin and nutrient concentrations in wheat after inoculation with Fusarium culmorum

The objective of this study was to follow the mycotoxin formation and changes in nutrient composition of wheat (cv. Ritmo) artificially inoculated with Fusarium culmorum. From anthesis until harvest, samples were taken once a week from the inoculated and control plots. The investigations were focused on monitoring the progression of the contamination of the wheat kernels with deoxynivalenol (DON) and zearalenone (ZON). Both the uncontaminated control kernels and the contaminated kernels were examined also for the presence of zearalenone-4-beta-D-glucopyranoside and several trichothecenes at harvest. Furthermore, the impact of the Fusarium inoculation on some nutrients as starch, crude protein, amino acid composition, crude ash, non starch polysaccharides (NSP) as well as viscosity and thousand seed weight (TSW) was examined. Also proteolytic and amylolytic activity as well as the NSP-degrading enzyme activities of inoculated and control samples were analysed at the time of harvest. DON was detected in higher concentrations and in earlier stages, while ZON was found later and in smaller amounts. On average 7.79 mg/kg DM of DON and 100 microg/kg DM of ZON were found in the inoculated kernels at the time of harvest. Neither in the contaminated nor in the control samples glucose conjugates of ZON (Zearalenone-4-beta-D-glucopyranoside) were detected. Moreover, the infection with Fusarium culmorum had pronounced effects on some quality parameters. The crude protein content of the inoculated kernels showed significantly higher values over the whole period compared to the control kernels. The protein content of the inoculated kernels amounted 13.9% DM at harvest, while only a concentration of 12.5% DM was detected in the control samples. Similarly, in almost all stages of development the crude ash content of inoculated samples was higher than in control samples. These distinct differences in kernel composition resulted possibly from the changes of the thousand seed weight. In the present work the grain harvested from the control plots showed a significantly higher TSW (24.2 g) as compared to their inoculated counterparts (15.5 g). Despite lower extract viscosity of inoculated samples at time of harvest, the content of soluble NSP of inoculated plots was higher than in control samples at the same time. Moreover, inoculation resulted in markedly increased activities of protease, amylase and several NSP-degrading enzyme activities. This would suggest that the cell wall penetrating properties of the fungus itself and/or that the fungus induced alterations of the metabolic activity of the embryo or other constituents of the wheat kernel could be responsible.     

Inheritance of five quantitative characters of bread wheat

Summary Heritability estimates of five characters of the wheat plant were studied in five crosses involving six cultivars of bread wheat. Parents, F₁, F₂ and backcrosses to both parents were used in the estimation of the genetic parameters.Heritability was low for number of fertile spikes/plant, moderate for number of spikelets/spike, number of kernels/spike, 1000-kernel weight and moderately high for number of kernels/spike. Evidence for mainly nonadditive gene effects were observed in the expression of number of fertile spikes and 1000-kernel weight. Although nonadditives contributed to a lesser degree to the gene action, additives seemed to be the most important genetic expression regulating number of spikelets/spike, number of kernels/spike, and number of kernels/spikelet. Except for number of fertile spikes/plant, selection in F₂-populations seems to be promising.     

Mycological survey of Korean cereals and production of mycotoxins by Fusarium isolates.

The fungal species isolated from Korean cereals (barley, polished barley, wheat, rye, and malt) were Alternaria spp., Aspergillus spp., Chaetomium spp., Drechslera spp., Epicoccum sp., Fusarium spp., and Penicillium spp., etc. The number of Fusarium strains isolated was 36, and their ability to produce Fusarium mycotoxins on rice was tested. Nivalenol (NIV) was produced by Fusarium graminearum (7 of 9 isolates), Fusarium oxysporum (3 of 10 isolates), and Fusarium spp. (7 of 15 isolates). Of 15 isolates of Fusarium spp., 6 formed deoxynivalenol (DON). Fusarenon-X and 3-acetyl-DON were produced by most NIV- and DON-forming isolates, respectively. Zearalenone was produced by 3 isolates of F. graminearum, 1 isolate of Fusarium equiseti, and 11 isolates of Fusarium spp. T-2 toxin was not produced by any Fusarium isolates. The highest concentrations of mycotoxins produced by Fusarium isolates were 77.4 (NIV), 5.3 (DON), 138.3 (fusarenon-X), 40.6 (3-acetyl-DON), and 23.2 (zearalenone) micrograms/g.     

Natural occurrence of Fusarium mycotoxins (trichothecenes and zearalenone) in barley and corn in Korea.

Barley is produced in four provinces, Chonbuk, Chonnam, Kyungbuk, and Kyungnam, and corn is mainly produced in the Kangwon province in Korea. The natural occurrence of Fusarium mycotoxins was surveyed in 39 barley and 46 corn samples from different areas. Five 8-ketotrichothecenes, namely deoxynivalenol (DON), nivalenol (NIV), 4-acetylnivalenol (4-ANIV), 3-acetyldeoxynivalenol (3-ADON), and 4,15-diacetylnivalenol (4,15-DANIV), and zearalenone (ZEA) were detected in barley. DON, NIV, and ZEA were the major contaminants in barley, with mean levels of 170, 1,011, and 287 ng/g, respectively. On the other hand, DON, 15-acetyldeoxynivalenol (15-ADON), NIV, 4-ANIV, 4,15-DANIV, and ZEA were detected in corn samples. DON and 15-ADON were the major contaminants in corn, with mean levels of 310 and 297 ng/g, respectively. The survey indicated that the natural occurrence of monoacetyl-DON and the ratios of NIV to DON in two cereals were different. In addition, this is the first report of the natural occurrence of 4,15-DANIV in cereals.     

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.     

Moniliformin Accumulation in Kernels of Triticale Accessions Inoculated with Fusarium avenaceum, in Poland

Twelve Polish winter triticale cultivars and 14 doubled haploid lines (DH) (derived from the cv. Lasko × line SZD 366 hybrids) were inoculated with Fusarium avenaceum isolate ATCC 64451, mycotoxin moniliformin (MON) producer to evaluate their susceptibility to Fusarium head blight (FHB). Chemical analysis revealed MON accumulation in kernels of all inoculated cultivars in three consecutive years with the following averages and ranges: 1.50 mg/kg (0.47–2.67 mg/kg) in 1996, 2.63 mg/kg (0.11–8.14 mg/kg) in 1997 and 0.25 mg/kg (0.07–0.47 mg/kg) in 1998. Cultivar Malno kernels accumulated a low level of MON in all 3 years of the experiment. In most of the genotypes examined the reaction to the pathogen and MON content changed significantly from season to season. DH lines accumulated on average 2.62 and 0.85 mg/kg of MON in 1997 and 1998, respectively. Yield parameter reductions (1000 kernel weight, kernel number per head and kernel weight per head) were higher in 1997 than in 1998. The correlation coefficient for MON content/ Fusarium damaged kernels percentage was 0.539 in cultivars and 0.548 in the DH lines. This is the first report of FHB of a segregating population in triticale.     

Fusarium response to oxidative stress by H2O2 is trichothecene chemotype-dependent

The present study aims at clarifying the impact of oxidative stress on type B trichothecene production. The responses to hydrogen peroxide (H₂O₂) of an array of Fusarium graminearum and Fusarium culmorum strains were compared, both species carrying either the chemotype deoxynivalenol (DON) or nivalenol (NIV). In both cases, levels of in vitro toxin production are greatly influenced by the oxidative parameters of the medium. A 0.5 mM H₂O₂ stress induces a two- to 50-fold enhancement of DON and acetyldeoxynivalenol production, whereas the same treatment results in a 2.4- to sevenfold decrease in NIV and fusarenone X accumulation. Different effects of oxidative stress on toxin production are the result of a variation in Fusarium 's antioxidant defence responses according to the chemotype of the isolate. Compared with DON strains, NIV isolates have a higher H₂O₂-destroying capacity, which partially results from a significant enhancement of catalase activity induced by peroxide stress. A 0.5 mM H₂O₂ treatment leads to a 1.3- to 1.7-fold increase in the catalase activity of NIV isolates. Our data, which show the higher adaptation to oxidative stress developed by NIV isolates, are consistent with the higher virulence of these Fusarium strains on maize compared with DON isolates.     

Tri13 and Tri7 determine deoxynivalenol- and nivalenol-producing chemotypes of Gibberella zeae

Gibberella zeae, a major cause of cereal scab, can be divided into two chemotypes based on production of the 8-ketotrichothecenes deoxynivalenol (DON) and nivalenol (NIV). We cloned and sequenced a Tri13 homolog from each chemotype. The Tri13 from a NIV chemotype strain (88-1) is located in the trichothecene gene cluster and carries an open reading frame similar to that of Fusarium sporotrichioides, whereas the Tri13 from a DON chemotype strain (H-11) carries several mutations. To confirm the roles of the Tri13 and Tri7 genes in trichothecene production by G. zeae, we genetically altered toxin production in 88-1 and H-11. In transgenic strains, the targeted deletion of Tri13 from the genome of 88-1 caused production of DON rather than NIV. Heterologous expression of the 88-1 Tri13 gene alone or in combination with the 88-1 Tri7 gene conferred on H-11 the ability to synthesize NIV; in the latter case, 4-acetylnivalenol (4-ANIV) also was produced. These results suggest that Tri13 and Tri7 are required for oxygenation and acetylation of the oxygen at C-4 during synthesis of NIV and 4-ANIV in G. zeae. These functional analyses of the Tri13 and Tri7 genes provide the first clear evidence for the genetic basis of the DON and NIV chemotypes in G. zeae.     

Progression of mycotoxin and nutrient concentrations in wheat after inoculation with Fusarium culmorum

The objective of this study was to follow the mycotoxin formation and changes in nutrient composition of wheat (cv. Ritmo) artificially inoculated with Fusarium culmorum. From anthesis until harvest, samples were taken once a week from the inoculated and control plots. The investigations were focused on monitoring the progression of the contamination of the wheat kernels with deoxynivalenol (DON) and zearalenone (ZON). Both the uncontaminated control kernels and the contaminated kernels were examined also for the presence of zearalenone-4-beta-D-glucopyranoside and several trichothecenes at harvest. Furthermore, the impact of the Fusarium inoculation on some nutrients as starch, crude protein, amino acid composition, crude ash, non starch polysaccharides (NSP) as well as viscosity and thousand seed weight (TSW) was examined. Also proteolytic and amylolytic activity as well as the NSP-degrading enzyme activities of inoculated and control samples were analysed at the time of harvest. DON was detected in higher concentrations and in earlier stages, while ZON was found later and in smaller amounts. On average 7.79?mg/kg DM of DON and 100?μg/kg DM of ZON were found in the inoculated kernels at the time of harvest. Neither in the contaminated nor in the control samples glucose conjugates of ZON (Zearalenone-4-beta-D-glucopyranoside) were detected. Moreover, the infection with Fusarium culmorum had pronounced effects on some quality parameters. The crude protein content of the inoculated kernels showed significantly higher values over the whole period compared to the control kernels. The protein content of the inoculated kernels amounted 13.9% DM at harvest, while only a concentration of 12.5% DM was detected in the control samples. Similarly, in almost all stages of development the crude ash content of inoculated samples was higher than in control samples. These distinct differences in kernel composition resulted possibly from the changes of the thousand seed weight. In the present work the grain harvested from the control plots showed a significantly higher TSW (24.2?g) as compared to their inoculated counterparts (15.5?g). Despite lower extract viscosity of inoculated samples at time of harvest, the content of soluble NSP of inoculated plots was higher than in control samples at the same time. Moreover, inoculation resulted in markedly increased activities of protease, amylase and several NSP-degrading enzyme activities. This would suggest that the cell wall penetrating properties of the fungus itself and/or that the fungus induced alterations of the metabolic activity of the embryo or other constituents of the wheat kernel could be responsible.     

普通玉米籽粒性状的遗传效应分析

采用二倍体种子遗传模型及其分析方法,研究了５个玉米籽粒性状的直接效应、母体效应和细胞质效应．分析结果表明,各性状的遗传同时受种子直接效应和母体效应的影响,细胞质基因对百粒重和粒宽具有极显著影响．除粒长、粒厚的直接显性效应与母体显性效应间的协方差外,直接效应与母体效应间的协方差均不显著．因此,通过母体植株的表现可对这些性状进行有效的选择．Ｓ_２２和 ８７－１是改良粒重的优良亲本．选择粒较宽的自交系作母本有利于提高后代选系及Ｆ_１的百粒重．     

Variation in 8-ketotrichothecenes and zearalenone production by Fusarium graminearum isolates from corn and barley in Korea

A total of 214 Fusarium graminearum isolates were obtained from corn and barley which were collected from Kangwon province and the southern part of Korea, respectively, and were tested for 8-ketotrichothecenes and zearalenone (ZEA) production on rice grains. The incidences of trichothecene production by 105 isolates of F. graminearum from corn were 59.0% for deoxynivalenol (DON), 37.1% for 15-acetyldeoxynivalenol(15-ADON), 13.3% for 3-acetyldeoxynivalenol (3-ADON), 7.6% for 3,15-diacetyldeoxynivalenol (3,15-DADON), 20.0% for nivalenol (NIV), 6.7% for 4-acetylnivalenol (4-ANIV), and 1.0% for 4,15-diacetylnivalenol (4,15-DANIV). DON chemotypes frequently produced 15-ADON as the major isomer rather than 3-ADON and 9 of the 61 DON chemotypes produced low levels of NIV. On the other hand, the incidences of trichothecene production of 109 isolates by F. graminearum from barley were 24.8% for DON, 72.5% for NIV, 62.4% for 4-ANIV, and 10.1% for 4,15-DANIV. Of these isolates, 78 were NIV chemotypes and only one isolate produced DON and 3-ADON as major toxins. In addition, 26 of the 78 NIV chemotypes produced low levels of DON. ZEA was frequently produced by the trichothecene-producing isolates and the incidences of ZEA were 51.4% and 31.2% for the isolates from corn and barley, respectively. There was a great regional difference in trichothecene production by F. graminearum isolates between corn- and barley-producing areas in Korea.