Assessment of infection in wheat by <Emphasis Type="Italic">Fusarium</Emphasis> protein equivalent levels

Determination of the Fusarium protein equivalent (FPE) levels in kernels for better characterisation of genotypes showing Fusarium head blight (FHB) resistance, and better detection of susceptibility to kernel infection among genotypes with slight symptom expression was carried out. Twelve wheat cultivars and eight hexaploid winter wheat lines derived from a cross of Triticum aestivum with related species T. macha, T. polonicum, and T. dicoccoides were evaluated for levels of spike and kernel infection, the content of the mycotoxin deoxynivalenol (DON) and FPE in kernels after artificial inoculation with the fungus Fusarium culmorum in the field in 2006–2007. The ELISA immunochemical method was employed for the quantitative analyses of DON and FPE. Three wheat lines had a significantly low infection of spikes and kernels compared to cvs Sumai 3 and Nobeoka Bozu, indicating the presence of specific resistance mechanisms to FHB. The significantly low AUDPC (area under the disease progress curve) and the high level of FPE and DON content in kernels indicated a lack of resistance in one wheat line (crossed with T. polonicum). The results showed highly significant correlations (P < 0.01) between FPE and DON content and between FPE and AUDPC. In addition, correlations between FPE and reductions in yield components were also highly significant. Quantification of Fusarium spp. in wheat kernels can be helpful for evaluating wheat genotypes for their levels of resistance to FHB.     

<Emphasis Type="Italic">Fusarium langsethiae</Emphasis> pathogenicity and aggressiveness towards oats and wheat in wounded and unwounded <Emphasis Type="Italic">in vitro</Emphasis> detached leaf assays

In vitro detached leaf assays involving artificial inoculation of wounded and unwounded oat and wheat leaves were used to investigate the potential pathogenicity and aggressiveness of F. langsethiae, which was linked recently to the production of type A trichothecenes, HT-2 and T-2 in cereals in Europe. In the first two experiments, two assays compared disease development by F. langsethiae with known fusarium head blight pathogen species each used as a composited inoculum (mixture of isolates) at 10°C and 20°C and found all fungal species to be pathogenic to oat and wheat leaves in the wounded leaf assay. In the unwounded leaf assay, F. langsethiae was not pathogenic to wheat leaves. Furthermore, there were highly significant differences in the aggressiveness of pathogens as measured by lesion length (P < 0.001). In the second two experiments, pathogenicity of individual F. langsethiae isolates previously used in the composite inoculum was investigated on three oat and three wheat varieties. The wounded leaf assay showed that all isolates were pathogenic to all oat and wheat varieties but only pathogenic towards oat varieties in the unwounded assay. Highly significant differences (P < 0.001) in lesion length were found between cereal varieties as well as between isolates in the wounded assay. Significant differences in lesion lengths (P = 0.014) were also observed between isolates in the unwounded assay. Results from the detached leaf assays suggest that F. langsethiae is a pathogen of wheat and oats and may have developed some host preference towards oats.     

Infection conditions of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> in barley are variety specific and different from those in wheat

Fusarium head blight is one of the most noxious cereal diseases. Worldwide, F. graminearum (FG) and the mycotoxin deoxynivalenol (DON) is the most dominant species/mycotoxin in barley and wheat. Barley is often produced as on farm feed and thus routine mycotoxin analyses similar to those of cereals for human consumption are not performed. Hence, an early prediction of mycotoxin levels is important for farmers to minimise the risk of contaminated feed but also of contaminated cereals entering the cereal supply chain. Therefore, climate chamber experiments with artificial FG infection of barley investigating the influence of different temperatures (10 °C, 15 °C, 20 °C) and durations (4 h, 8 h, 12 h) at 99% relative humidity were conducted to accumulate data to develop a forecasting system. An up to three times higher DON contamination in the 15 °C treatments for the feed barley variety Ascona was detected compared with the 10 °C and 20 °C treatments. For the malting barley variety Concerto, the prolonged humidity durations had a stronger effect under all tested temperatures and resulted in up to two times higher DON contaminations. In addition, field experiments where spore deposition during anthesis as well as disease incidence, fungal amount and mycotoxins were observed, showed that the overwintered straw treatment resulted, depending on the year, in a three times higher FG incidence and DON content compared with the control and freshly inoculated straw treatment.     

Trichothecene genotype and genetic variability of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> and <Emphasis Type="Italic">F. cerealis</Emphasis> isolated from durum wheat in Argentina

Fusarium head blight (FHB) is one of the most important fungal diseases affecting wheat worldwide and it is caused mainly by species within the Fusarium graminearum species complex (FGSC). This study evaluated the presence of FGSC in durum wheat from the main growing area in Argentina and analyzed the trichothecene genotype and chemotype of the strains isolated. Also, the genetic variability of the strains was assayed using ISSR markers. Molecular analysis revealed that among the strains isolated and identified morphologically as F. graminearum, there were 14 strains identified as F. cerealis. Also, it revealed that durum wheat grains were mostly contaminated by F. graminearum, being this the only species reported so far, within the FGSC, affecting durum wheat in Argentina. Analysis of molecular variance (AMOVA) indicated a high genetic variability within rather than between F. graminearum populations. All F. graminearum strains presented 15ADON genotype and were able to produce DON while all F. cerealis strains presented the NIV genotype and most of them were able to produce this toxin. The finding of F. cerealis in durum wheat grains indicates the need for investigating if this fungus is the responsible for the NIV contamination found in wheat in Argentina.     

Validation of a modified Petri-dish test to quantify aggressiveness of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> in durum wheat

Fusarium graminearum is a common agent causing Fusarium head blight (FHB) on wheat throughout the world. Aggressiveness is crucial for understanding the interaction between host-pathogen in the FHB-wheat system. In this paper, we modified and validated the Petri-dish test originally described by Mesterhazy (Phytopathologische Zeitschrift 93:12–25, 1978) to quantify the aggressiveness of 25 F. graminearum strains using four durum wheat cultivars with different resistance levels for FHB. The results were highly significant and correlated with those obtained using adult plants in the growth chamber and in the field (r = 0.94, P < 0.001 and r = 0.65, P < 0.001, respectively). The Petri-dish test was further investigated for its repeatability and stability in different durum wheat cultivars and highly significant correlation coefficients were obtained (r = 0.90–0.91 (P < 0.001), 0.89–0.95 (P < 0.001), respectively). In this study, we also demonstrated that germination rate reduction and coleoptile length reduction are parameters involved with aggressiveness of F. graminearum. The mean of three disease parameters from the modified Petri-dish method is introduced in this paper as a new parameter for aggressiveness and named “Petri-dish aggressiveness index”. The results obtained reveal that this modified Petri-dish test is rapid, reliable and stable with different durum wheat cultivars, and yields highly significant correlation coefficients with floret and ear inoculations, thus it is suitable to be used for quantification of aggressiveness of F. graminearum.     

Common resistance to different <Emphasis Type="Italic">Fusarium</Emphasis> spp. causing <Emphasis Type="Italic">Fusarium</Emphasis> head blight in wheat

Different sets of wheat genotypes were tested under field conditions by spraying inocula of isolates of seven Fusarium spp. and Microdochium nivale (formerly F. nivale) in the period 1998–2002. The severity of Fusarium head blight (FHB), Fusarium-damaged kernels (FDK), the yield reduction and the deoxynivalenol (DON) contamination were also measured to describe the nature of the resistance. The degrees of FHB severity of genotypes to F. graminearum, F. culmorum, F. avenaceum, F. sporotrichioides, F. poae, F.␣verticillioides, F. sambucinum and M. nivale were very similar, indicating that the resistance to F.␣graminearum was similar to that for other Fusarium spp. listed. This is an important message to breeders as the resistance relates not only to any particular isolate of F. graminearum, but similarly to isolates of other Fusarium spp. This holds true for all the parameters measured. The DON contamination refers only to DON-producers F. graminearum and F. culmorum. Highly significant correlations were found between FHB, FDK, yield loss and DON contamination. Resistance components such as resistance to kernel infection, resistance to DON and tolerance were identified in the more susceptible genotypes. As compared with western European genotypes which produced up to 700 mg kg⁻¹ DON, the Hungarian genotypes produced only 100 mg kg⁻¹ at a similar FDK level. This research demonstrates the importance of measuring both FDK and DON in the breeding and selection of resistant germplasm and cultivars.     

Comparison of pathogenicity of the Fusarium crown rot (FCR) complex (<Emphasis Type="Italic">F. culmorum</Emphasis>, <Emphasis Type="Italic">F. pseudograminearum</Emphasis> and <Emphasis Type="Italic">F. graminearum)</Emphasis> on hard red spring and durum wheat

Fusarium species involved in the Fusarium crown rot (FCR) complex affect wheat in every stage of development from seedling to grain fill. This study was designed to compare the aggressiveness of the FCR complex members including F. culmorum, F. pseudograminearum and F. graminearum in causing seedling blight, decreased plant vigour and crown rot. To assess their relative pathogenicity, two hard red spring wheat cultivars and two durum wheat cultivars were inoculated in the field with five isolates from each of the three species for two years. Significant differences in patterns of pathogenicity were identified. In particular, F. culmorum caused greater seedling blight while F. pseudograminearum and F. graminearum caused greater crown rot. Greatest yield reductions were caused by F. pseudograminearum. Cultivar differences were identified with respect to seedling disease and late season crown rot. No interactions were identified between cultivar performance and isolates or species with which they were challenged.     

In vitro competition between <Emphasis Type="Italic">Fusarium graminearum</Emphasis> and <Emphasis Type="Italic">Epicoccum nigrum</Emphasis> on media and wheat grains

Competitive effects between Fusarium graminearum, causing Fusarium head blight, and the endophyte Epicoccum nigrum, were performed in in vitro competition assays between the two species. Two E. nigrum isolates were isolated from wheat grains and tested as competitors against two F. graminearum isolates. A dual petri dish assay showed that E. nigrum reduced the mycelial growth of F. graminearum and vice versa. A glass slide assay revealed that E. nigrum crude cultural filtrate also had reducing effect on the growth of F. graminearum comparable to that of E. nigrum spore suspensions. Microscopy showed hyphae of F. graminearum and E. nigrum with many side branches when in close proximity, in contrast to pronounced apical hyphal growth when growing alone. Combinations of F. graminearum and E. nigrum on sterilised wheat grains were studied over time by qPCR. F. graminearum biomass was significantly reduced in inoculations applying E. nigrum three days prior to F. graminearum. In conclusion, these results showed competition and mycelial behaviour effects between F. graminearum and E. nigrum and support that E. nigrum may have potential to reduce F. graminearum infections in wheat. Competition experiments should be carried out in planta to study the interaction further.     

Interactions Between <Emphasis Type="Italic">Barley yellow dwarf virus</Emphasis> and <Emphasis Type="Italic">Fusarium</Emphasis> spp. Affecting Development of Fusarium Head Blight of Wheat

Interactions between Barley yellow dwarf virus (BYDV) and Fusarium species causing Fusarium head blight (FHB) in winter wheat cvs Agent (susceptible to FHB) and Petrus (moderately resistant to FHB) were studied over three years (2001–2003) in outdoor pot experiments. FHB developed more rapidly in cv. Agent than in cv. Petrus. The spread of FHB was greater in BYDV-infected plants than in BYDV-free plants. Thousand grain weight (TGW) was reduced more in Fusarium-infected heads of cv. Agent than in cv. Petrus. A highly significant negative correlation was found between disease index and TGW in cv. Agent (r = −0.916), while in cv. Petrus the correlation was less significant (r = −0.765). Virus infection reduced TGW in cv. Petrus more than in cv. Agent. In plants with both infections, TGW reductions in cv. Petrus corresponded to those of BYDV infection, and in cv. Agent TGW was more diminished than in BYDV infection. Effects of different treatments determined over three years on ergosterol contents in grain were generally similar to effects on disease indices. Grain weight per ear and ear weight of the different treatments of both cultivars largely corresponded with the TGW results. Deoxynivalenol (DON) content in grain of cv. Agent infected with Fusarium spp. was 11–25 times higher compared to the corresponding treatments in cv. Petrus. The DON content in grain of plants of the two cultivars infected with both pathogens was higher than that of plants infected only with Fusarium over the three years.     

Evaluation of pathogenicity and aggressiveness of <Emphasis Type="Italic">F. langsethiae</Emphasis> on oat and wheat seedlings relative to known seedling blight pathogens

Fusarium and Microdochium species are causal agents of seedling blight of small-grain cereal crops where they may contribute to a significant reduction in crop establishment and final yield. Two experiments were carried out to investigate the potential pathogenicity and aggressiveness of F. langsethiae, a recently identified fungus linked with the contamination of cereals with high levels of the trichothecene mycotoxins, HT-2 and T-2. An artificial seed inoculation method involving conidial suspensions was used and the experiments conducted in a growth cabinet set at either 5 or 15°C with a 12 h photoperiod. Known seedling blight pathogens of the genus Fusarium and Microdochium were used for comparison. At 15oC, F. culmorum, M. nivale and M. majus caused seedling blight of oats and wheat with F. culmorum, on average being the most aggressive than the latter two. At 5oC, only F. culmorum and M. nivale caused seedling blight of oats and wheat. Under the experimental conditions employed, F. langsethiae and F. poae failed to produce seedling blight disease indicating that these two species are not pathogenic to oat and wheat cultivars, Gerald and Claire respectively, at the seedling stage of development. They are therefore unlikely to affect crop establishment and other yield components such as tiller number, grain yield per head as well as grain weight if there is no subsequent foot-rot and/or head blight where infected seeds are sown.     

Fusarium rot of hyacinth caused by <Emphasis Type="Italic">Gibberella zeae</Emphasis> (anamorph: <Emphasis Type="Italic">Fusarium</Emphasis><Emphasis Type="Italic"> graminearum</Emphasis>)

Severe rot of leaves, peduncles and flowers caused by Gibberella zeae (anamorph: Fusarium graminearum) was found on potted plants of hyacinth (Hyacinthus orientalis), a liliaceous ornamental, in greenhouses in Kagawa Prefecture, Japan, in January 2001. This disease was named “Fusarium rot of hyacinth” as a new disease because only the anamorph, F. graminearum, was identified on the diseased host plant. The authors contributed equally to this work. The fungal isolate and its nucleotide sequence data obtained in this study were deposited in the Genebank, National Institute of Agrobiological Sciences and the DDBJ/EMBL/GenBank databases under the accession numbers MAFF239499 and AB366161, respectively.     

Investigation into components of partial disease resistance,determined <Emphasis Type="Italic">in vitro</Emphasis>, and the concept of types of resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight (FHB) in wheat

This work presents an analysis of the relationship between components of partial disease resistance (PDR) detected using in vitro detached leaf and seed germination assays, inoculated with Microdochium majus, and Fusarium head blight (FHB) resistance to Fusarium graminearum assessed using point inoculation, termed Type II resistance. Relationships between in vitro-determined PDR components and FHB resistance using techniques which inoculate the wheat spike uniformly, termed Type I resistance (incidence and severity), have been reported previously. In this study shorter incubation periods, longer latent periods and shorter lesion lengths in the detached leaf assay and higher germination rates in the seed germination assay were related to greater FHB resistance measured by single point inoculation (Type II), collectively explaining 54% of the variation. Overall the relationships observed for Type II FHB resistance were similar to previous findings for Type I resistances. However, the relative magnitude of effects of the individual PDR components determined in vitro varied between FHB disease resistance parameters. Resistance in seed germination and latent period in the detached leaf assay were more strongly related to resistance assessed by point inoculation (Type II) and severity-Type I as opposed to incubation period which was most strongly related to disease incidence-Type I. The results provide evidence that individual components of partial disease resistance differentially affect aspects of FHB disease progression in the wheat spike. This work supports the view that the current model of types of resistance is an oversimplification of the interacting mechanisms underlying expression of FHB resistance.     

Hyperspectral quantification of wheat resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight: comparison of two <Emphasis Type="Italic">Fusarium</Emphasis> species

Experiments were conducted to determine the extent of Fusarium langsethiae infection in wheat, barley and oats grown under identical experimental conditions. In total, four experiments were conducted with both winter and spring sown experiments at two locations. The amount of F. langsethiae infection was determined by quantifying F. langsethiae DNA and quantifying the combined concentration of the trichothecene mycotoxins HT-2 and T-2 (HT-2 + T-2) in cereal head fractions (grain and rest of the head) after threshing at harvest. Results of the study showed that under identical experimental conditions, oats had the highest F. langsethiae DNA and HT-2 + T-2 concentrations compared to wheat and barley. This indicates that the high levels detected on UK oats compared to wheat and barley from surveys of commercial crops is a consequence of genetic differences rather than differences in agronomy applied to the cereal species. The concentration of HT-2 and T-2 per unit of F. langsethiae DNA in oats compared to wheat and barley was also significantly higher indicating host differences in either the stimulation of HT-2 and T-2 production or in the metabolism of HT-2 and T-2. The study also showed that the proportion of F. langsethiae DNA in threshed grains was significantly lower than that in the rest of the cereal head.     

Genetic Variability of Central European Isolates of the <Emphasis Type="Italic">Fusarium graminearum</Emphasis> Species Complex

The main causative agents of Fusarium head blight in central Europe are Fusarium graminearum and F. culmorum. We examined the mycotoxin producing ability, aggressiveness and molecular variability of F. graminearum isolates. Altogether twenty-six Hungarian, three Austrian isolates and representatives of eight species identified in the F. graminearum species complex were involved in this study. Mycotoxin producing abilities of the isolates were tested by GC-MS and HPLC. The central European isolates were found to belong to chemotype I (producing deoxynivalenol). Most isolates produced more 15-acetyl-deoxynivalenol than 3-acetyl-deoxynivalenol suggesting that they belong to chemotype Ib. All F. graminearum isolates were found to be highly pathogenic in in vitro aggressiveness tests. Phylogenetic analysis of random amplified polymorphic DNA profiles, and restriction profiles of the intergenic spacer region of the ribosomal RNA gene cluster of the isolates allowed clustering of the central European isolates into 17 and 16 haplotypes, respectively. When RAPD and IGS-RFLP data were combined, almost every single central European F. graminearum isolate could be differentiated (27/29 haplotypes). Sequence analysis of a putative reductase gene of some isolates was also performed. Based on molecular data, the majority of the central European isolates belonged to F. graminearum sensu stricto characteristic to the northern hemisphere, with the exception of one Hungarian isolate, which was not related to any known species of the F. graminearum species complex based on sequence data. The taxonomic assignment of two other Hungarian isolates, previously suggested as belonging to F. boothii based on mitochondrial DNA restriction profiles, was supported by sequence analysis.     

Evaluation of the temporal distribution of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> airborne inoculum above the wheat canopy and its relationship with Fusarium head blight and DON concentration

With the aim of unravelling the role of airborne Fusarium graminearum inoculum in the epidemic of Fusarium head blight (FHB) caused by this species in wheat spikes, a network of Burkard air samplers was set up in five wheat fields distributed in Belgium from 2011 to 2013. Each year from April to July, the daily amounts of F. graminearum inoculum above the wheat canopy were quantified using a newly developed TaqMan qPCR assay. The pattern of spore trapping observed was drastically different per year and per location with a frequency of detection between 9 and 66% and a mean daily concentration between 0.8 and 10.2 conidia-equivalent/m³. In one location, air was sampled for a whole year. Inoculum was frequently detected from the wheat stem elongation stage until the end of the harvesting period, but high inoculum levels were also observed during the fall. Using a window-pane analysis, different periods of time around wheat flowering (varying in length and starting date) were investigated for their importance in the relation between airborne inoculum and FHB parameters (FHB severity, frequency of F. graminearum infection and DON). For almost all the combinations of variables, strong and significant correlations were found for multiple window lengths and starting times. Inoculum quantities trapped around flowering were highly correlated with F. graminearum infection (up to R?=?0.84) and DON (up to R?=?0.9). Frequencies of detection were also well correlated with both of these parameters. DON concentrations at harvest could even be significantly associated with the F. graminearum inoculum trapped during periods finishing before the beginning of the anthesis (R?=?0.77). Overall, these results highlight the key role of the airborne inoculum in F. graminearum epidemics and underline the importance of monitoring it for the development of disease forecasting tools.     

Enhanced mycotoxin production of a lipase-deficient <Emphasis Type="Italic">Fusarium graminearum</Emphasis> mutant correlates to toxin-related gene expression

Fusarium graminearum causes important diseases of small-grain cereals and maize and produces several mycotoxins. Among them, deoxynivalenol (DON) and zearalenone (ZEA) can accumulate in feedstuffs and foods to health-threatening levels. Although DON is important for fungal virulence in wheat, disease severity in the field does not correlate with mycotoxin concentrations. We compared gene expression and mycotoxin production of lipase-deficient mutants (Δfgl1), strongly reduced in virulence, and the respective wild-type isolate. Δfgl1 mutants exhibited up-regulated DON production during wheat head infection. On isolated wheat kernels, DON was only produced in low quantities, but higher in wild-type than in Δfgl1 mutants. In contrast, neither wild-type nor Δfgl1 mutants produced ZEA during wheat head infection. However, ZEA was clearly detectable on wheat kernels. Here, Δfgl1 mutants revealed a dramatically enhanced ZEA production. We could correlate the altered amounts of DON and ZEA directly with the expression of the toxin-related genes Tri5 for DON and PKS4 and PKS13 for ZEA. Based on Tri5 expression and the infection pattern of the wild-type and Δfgl1 mutants, we suggest that the transition zone of rachilla and rachis is important in the induction of DON synthesis. Gene expression studies indicate an involvement of the lipase FGL1 in regulation of 8 PKS genes and ZEA production.     

<Emphasis Type="Italic">Fusarium langsethiae</Emphasis> (Torp and Nirenberg), investigation of alternative infection routes in oats

Fusarium langsethiae is a recently characterized fungus within the genus Fusarium. It is found as a grain contaminant of small grain cereals such as oats and barley, and to a lesser extent wheat. Fusarium langsethiae is particularly widespread in the Nordic countries and the UK where it poses a serious problem as the main producer of T-2 and HT-2 mycotoxins. The biology of F. langsethiae and its interaction with the plant remains poorly understood, partly hampered by difficulties reproducing a natural level of infection under controlled conditions. The reported study was designed as a series of glasshouse experiments to advance our understanding of F. langsethiae biology by investigating alternative infection routes and its proliferation in oats, Avena sativa. Various methods of seed, soil, and seedling inoculation, boot injection and spray inoculation, were tested. The results clearly show a strong preference of F. langsethiae for the panicle, ruling out alternative infection routes. At relatively low temperatures spray infection, accompanied by prolonged humidity, ensured a thorough establishment of the fungus both at flowering and at early dough stage. Boot injection proved to be a reliable working tool for production of an even and predictable grain infection. Apart from in the panicle, considerable fungal proliferation was only detected in flag leaf nodes, and was a direct consequence of the boot injection method. Fungal presence in the node tissue also correlated with significant stunting of infected shoots. In light of the results the pathogenic and endophytic abilities of F. langsethiae are discussed.     

Aggressiveness and mycotoxin production of eight isolates each of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> and <Emphasis Type="Italic">Fusarium verticillioides</Emphasis> for ear rot on susceptible and resistant early maize inbred lines

Fusarium graminearum and F. verticillioides are among the most important pathogens causing ear rot of maize in Central Europe. Our objectives were to (1) compare eight isolates of each species on two susceptible inbred lines for their variation in ear rot rating and mycotoxin production across 3 years, and (2) analyse two susceptible and three resistant inbred lines for potential isolate x line interactions across 2 years by silk-channel inoculation. Ear rot rating, zearalenone (ZEA) and deoxynivalenol (DON) concentrations were evaluated for all F. graminearum isolates. In addition, nivalenol (NIV) concentrations were analysed for two NIV producers. Fumonisin (FUM) concentrations were measured for all F. verticillioides isolates. Mean ear rot severity was highest for DON producers of F. graminearum (62.9% of the ear covered by mycelium), followed by NIV producers of the same species (24.2%) and lowest for F. verticillioides isolates (9.8%). For the latter species, ear rot severities differed highly among years (2006: 24%, 2007: 3%, 2008: 7%). Mycotoxin concentrations among isolates showed a broad range (DON: 100–284 mg kg⁻¹, NIV: 15–38 mg kg⁻¹, ZEA: 1.1–49.5 mg kg⁻¹, FUM: 14.5–57.5 mg kg⁻¹). Genotypic variances were significant for isolates and inbred lines in all traits and for both species. Isolate x line interactions were significant only for ear rot rating (P < 0.01) and DON concentration (P < 0.05) of the F. graminearum isolates, but no rank reversals occurred. Most isolates were capable of differentiating the susceptible from the resistant lines for ear rot severity. For resistance screening, a sufficiently aggressive isolate should be used to warrant maximal differentiation among inbred lines. With respect to F. verticillioides infections, high FUM concentrations were found in grains from ears with minimal disease symptoms.