Browsing by Subject "Fusarium graminearum"

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CRISPR/SpCas9‐mediated double knockout of barley Microrchidia MORC1 and MORC6a reveals their strong involvement in plant immunity, transcriptional gene silencing and plant growth
(2021) Galli, Matteo; Martiny, Engie; Imani, Jafargholi; Kumar, Neelendra; Koch, Aline; Steinbrenner, Jens; Kogel, Karl‐Heinz
The Microrchidia (MORC) family proteins are important nuclear regulators in both animals and plants with critical roles in epigenetic gene silencing and genome stabilization. In the crop plant barley (Hordeum vulgare), seven MORC gene family members have been described. While barley HvMORC1 has been functionally characterized, very little information is available about other HvMORC paralogs. In this study, we elucidate the role of HvMORC6a and its potential interactors in regulating plant immunity via analysis of CRISPR/SpCas9‐mediated single and double knockout (dKO) mutants, hvmorc1 (previously generated and characterized by our group), hvmorc6a, and hvmorc1/6a. For generation of hvmorc1/6a, we utilized two different strategies: (i) successive Agrobacterium‐mediated transformation of homozygous single mutants, hvmorc1 and hvmorc6a, with the respective second construct, and (ii) simultaneous transformation with both hvmorc1 and hvmorc6a CRISPR/SpCas9 constructs. Total mutation efficiency in transformed homozygous single mutants ranged from 80 to 90%, while upon simultaneous transformation, SpCas9‐induced mutation in both HvMORC1 and HvMORC6a genes was observed in 58% of T0 plants. Subsequent infection assays showed that HvMORC6a covers a key role in resistance to biotrophic (Blumeria graminis) and necrotrophic (Fusarium graminearum) plant pathogenic fungi, where the dKO hvmorc1/6a showed the strongest resistant phenotype. Consistent with this, the dKO showed highest levels of basal PR gene expression and derepression of TEs. Finally, we demonstrate that HvMORC1 and HvMORC6a form distinct nucleocytoplasmic homo‐/heteromers with other HvMORCs and interact with components of the RNA‐directed DNA methylation (RdDM) pathway, further substantiating that MORC proteins are involved in the regulation of TEs in barley.
Electronic nose for the rapid detection of deoxynivalenol in wheat using classification and regression trees
(2022) Camardo Leggieri, Marco; Mazzoni, Marco; Bertuzzi, Terenzio; Moschini, Maurizio; Prandini, Aldo; Battilani, Paola
Mycotoxin represents a significant concern for the safety of food and feed products, and wheat represents one of the most susceptible crops. To manage this issue, fast, reliable, and low-cost test methods are needed for regulated mycotoxins. This study aimed to assess the potential use of the electronic nose for the early identification of wheat samples contaminated with deoxynivalenol (DON) above a fixed threshold. A total of 214 wheat samples were collected from commercial fields in northern Italy during the periods 2014–2015 and 2017–2018 and analyzed for DON contamination with a conventional method (GC-MS) and using a portable e-nose “AIR PEN 3” (Airsense Analytics GmbH, Schwerin, Germany), equipped with 10 metal oxide sensors for different categories of volatile substances. The Machine Learning approach “Classification and regression trees” (CART) was used to categorize samples according to four DON contamination thresholds (1750, 1250, 750, and 500 μg/kg). Overall, this process yielded an accuracy of >83% (correct prediction of DON levels in wheat samples). These findings suggest that the e-nose combined with CART can be an effective quick method to distinguish between compliant and DON-contaminated wheat lots. Further validation including more samples above the legal limits is desirable before concluding the validity of the method.
Genetic analysis of resistance to ear rot and mycotoxin contamination caused by Fusarium graminearum in European maize
(2012) Martin, Matthias; Melchinger, Albrecht E.
Maize is affected by a number of diseases. Among the various ear rots of maize, Gibberella ear rot (GER) caused by Fusarium graminearum is prevalent in Central Europe. This fungal pathogen produces secondary metabolites (mycotoxins), which adversely affect the health of humans and animals. Two important mycotoxins are the immunosuppressant deoxynivalenol (DON) and the mycoestrogen zearalenone (ZEA). The most efficient method to reduce mycotoxin contamination in maize is cultivation of resistant varieties. However, resistance breeding using classical phenotypic selection is laborious and time-consuming. Therefore, marker-assisted selection (MAS) may be a promising alternative to classical selection. Furthermore, for setting up a breeding program, knowledge about the relevance of the different modes of gene action and genotypic correlations among resistance and agronomic traits is required. The objectives of this study were to (1) estimate quantitative genetic parameters for GER severity and mycotoxin concentration in connected populations of doubled haploid (DH) lines, (2) map quantitative trait loci (QTL) for GER resistance and reduced mycotoxin contamination in these populations, (3) examine the congruency of QTL in these populations, (4) evaluate the prospects of using MAS to breed for GER resistance and reduced mycotoxin contamination, (5) estimate the genotypic correlation between the resistance of DH lines per se and the resistance of their testcrosses, (6) evaluate the influence of selection for increased resistance on agronomic performance of hybrids and (7) examine the relevance of different modes of gene action involved in the expression of the resistance in flint maize. Three field experiments were conducted, each of which comprised a different set of plant material. Experiment I comprised five DH line populations derived from the following F1 crosses among elite flint inbred lines: D152×UH006, D152×UH007, UH007×UH006, UH009×UH006 and UH009×UH007. Experiment II comprised testcross progenies of 94 DH lines and a dent single cross tester. Experiment III comprised the five F1 crosses, from which the DH populations had been derived, the F2 and the first backcross generations to the parents (BC1-P1, BC1-P2) as well as the two parent lines of each cross. Plants were artificially infected with spores of F. graminearum shortly after mid-silking using the silk channel inoculation technique. The DH lines were genotyped with simple sequence repeat (SSR) DNA markers, genetic linkage maps were constructed and QTL analyses were performed for resistance to GER, DON and ZEA contamination. Estimates of genotypic and genotype-by-environment interaction variances in Experiment I for GER severity and mycotoxin concentration were significant and heritabilities were moderately high to high in all populations. Thus, differences among DH lines for the resistance traits were mainly caused genetically and the resistance response varied depending on the environment. Owing to the effectiveness of artificial inoculation, the prospects are good to improve line resistance using a small number of test environments. QTL were detected in the four largest populations. Depending on the population, the mapped QTL together explained 21-51% of the genotypic variance for GER severity and 19-45% for DON concentration and 52% for ZEA concentration. Additive gene action was more important than digenic interactions of QTL, as indicated by the number of QTL having significant additive effects, their relative contributions to the total genotypic variance explained and the magnitude of their effects. Colocalized QTL for resistance to GER and mycotoxin contamination were identified in each mapping population. This was in agreement with strong genotypic correlations among these traits. QTL located at similar positions were detected across three populations in two chromosomal regions and across two populations in additional two regions. The results of this study indicated that a combination of classical phenotypic selection and MAS is a promising strategy for resistance breeding. In Experiment II, significant genotypic variation for resistance in lines and testcrosses showed that selection will be successful in both groups. Owing to low genotypic correlations between lines and testcrosses, however, resources should be mainly allocated to the evaluation of GER in testcrosses. Correlations of resistance with agronomic traits were weak or not significant. Therefore, selection for resistance and better agronomic performance can be carried out simultaneously. In Experiment III, generation means analysis indicated a prevalence of additive gene action for resistance. Significant dominance effects were found in only one cross for resistance to GER, but in four crosses for resistance to DON contamination. Owing to prevalence of additive gene action, the prospects are good to improve the resistance of the flint germplasm and to accumulate more favorable gene combinations in future breeding lines. Comparing the hybrid performance of flint×flint crosses of Experiment II and flint×dent crosses of Experiment III with their corresponding mid-parent performances indicated mid-parent heterosis for resistance. Therefore, prediction of hybrid performance based on performance of their parents will be possible only to a very limited extent. Future research should focus on fine mapping and validating of the detected QTL. For an efficient use of the QTL in a marker-assisted breeding program, knowledge about their effects in different genetic backgrounds is needed. Of particular importance are thereby the QTL effects in flint×dent crosses, which represent the preferred type of hybrid in Central European maize breeding programs.
Genetics of resistance to ear diseases and mycotoxin accumulation in the pathosystems maize/Fusarium and wheat/Fusarium
(2010) Messerschmidt, Martin; Miedaner, Thomas
Infection of ears of maize with Fusarium graminearum (FG) reduces yield and, more important, contaminate the harvest with mycotoxins. F. verticillioides (FV) is an economically important cause of ear rot. Among other mycotoxins, FV produces the fumonisins (FUM) and FG produces deoxynivalenol (DON) and zearalenone (ZEA). All three mycotoxins are harmful to humans and animals. Therefore, the European Union released legally enforceable limits. One alternative to reduce ear rot severity and mycotoxin concentrations is breeding and growing varieties resistant to Fusarium infections. However, few is known about breeding parameters for resistance to Fusarium infections and mycotoxin accumulation in European maize breeding material. The main objective of this thesis was to draw conclusions for breeding of resistance to ear rot and mycotoxin accumulation with special attention on three European maize maturity groups. We investigated methodical aspects like (1) the comparison of natural and artificial inoculation to evaluate ear rot resistance and (2) the necessity of separate testing of FV and FG. Furthermore, quantitative-genetic parameters like heritabilities and correlations were estimated to draw conclusions about (3a) genetic variation in line and testcross performance and the relationships (3b) between ear rot severity and mycotoxin concentrations in lines and testcrosses and (3c) between line and testcross performance. Three maturity groups (early, mid-late, late) each comprising about 150 maize inbred lines were evaluated for ear rot resistance to FV. The same genotypes of the early maturity group were additionally evaluated for resistance to FG in separate, but adjacent trials. Field evaluation was conducted in two to six environments with silk channel inoculation and natural infection, respectively. In the late maturity group kernel inoculation was conducted additionally. Out of the 150 lines, 50 to 60 lines per maturity group were crossed with two unrelated testers of the opposite heterotic group. The concentrations of toxins FUM, DON and ZEA of the chosen lines and their testcrosses were analyzed by immunotests. Despite significant genotypic differences among the inbred lines after inoculation or natural infections, inoculation was found to be superior due to easier visual differentiation and increased accuracy. Therefore, inoculation should be conducted. In the late maturity group silk channel inoculation (simulating infection over the silks) and kernel inoculation (simulating secondary infection after wounding) were appropriate since both caused similar ear rot severity. However, both inoculation methods should be tested separately due to only moderate correlations between them. In the early maturity group resistance to FG or FV should be tested separately due to moderate correlations. Significant genotypic variances in large sets and subsets of lines and also in testcrosses revealed that there is genetic variation in all maturity groups and also within heterotic groups. In the flint group less lines were resistant to FV and FG than in dents indicating that resistance needs improvement, i.e. by introgression of resistance alleles followed by recurrent selection. Significant genotype x environment interactions may complicate selection and, therefore, multi-environmental trials are required for an accurate selection. High genotypic correlations between ear rot rating and mycotoxin concentrations were found among lines and testcrosses. The cost efficient indirect selection for mycotoxin concentrations based on ear rot rating could increase response to selection by testing more genotypes and/or in more test environments assuming a fixed budget. This should increase selection intensity and/or heritability. Moderate genotypic correlations between line and testcross performance were. One moderately to highly susceptible tester is sufficient due to high genotypic correlations between testcrosses of different testers. Both indicates a mainly additive gene action, but also non-additive gene action may play a role in some crosses. Selection for testcross performance based on line performance was less effective when calculating relative efficiencies. Different scenarios have been identified: (1) In Central Europe mainly resistance to ear rot in lines needs to be tested to ensure high seed quality, whereas resistance in testcrosses is not important due to low natural infection. (2) In Southern Europe, where high natural infections occur regularly, parallel selection for resistance to ear rot in lines and testcrosses is important. One susceptible tester should be used for creation of testcrosses. For selection in lines all parental lines should be inoculated but only lines selected out of testcrosses for agronomic traits would be rated afterwards saving resources. This is feasible due to later harvest date of lines than of testcrosses.
Gibberella ear rot resistance in European maize : genetic analysis by complementary mapping approaches and improvement with genomic selection
(2022) Han, Sen; Melchinger, Albrecht E.
During the last decades, implementation of molecular markers such as single nucleotide polymorphisms (SNPs) has transformed plant breeding practices from conventional phenotypic selection to marker-assisted selection (MAS) and genomic selection (GS) that are more precise, faster and less resource-consuming. In this dissertation, we investigated these three selection approaches for improving the polygenic trait Gibberella ear rot (GER) resistance in maize (Zea mays L.), which is an important fungal disease in Europe and North America leading to reduced grain yield and grain contaminated with mycotoxins such as deoxynivalenol (DON) and zearalenone (ZON). Three different sets of materials were evaluated in multiple environments and analyzed for different objectives. In the first study, five flint doubled-haploid (DH) families (with size 43 to 204) inter-connected at various levels through common parents, were generated in an incomplete half-diallel design with four parental lines developed by the University of Hohenheim. Significant genotypic variances and generally high heritabilities were observed for all three traits (i.e., GER, DON and days to silking (DS)) in all families, implying good prospects for resistance breeding and phenotypic selection against GER across different environments in European maize germplasm. Genetic correlations were extremely tight between DON and GER and moderately negative for DS with DON or GER, suggesting that indirect selection against GER would be efficient to reduce DON, but maturity should be considered in GER resistance breeding. Using a high-density consensus map with 2,472 marker loci, we compared classical bi-parental mapping of QTL (quantitative trait locus/loci) with multi-parental QTL mapping conducted with joint families and using four different biometric models. Multi-parental QTL mapping models identified all and even further QTL than the bi-parental QTL mapping model conducted within each family. Interestingly, QTL for DON and GER were mostly family-specific, yet multiple families had several common QTL for DS. Many QTL displayed large additive effects and most favorable alleles originated from the highly resistant parent. Interactions between detected QTL and genetic background (family) were rare and had comparatively small effects. Multi-parental QTL mapping models generally did not yield higher prediction accuracy than the bi-parental QTL mapping model for all traits. In the second study, two diversity panels consisting of 130 elite European dent and 114 flint lines, respectively, from the University of Hohenheim were evaluated and subject to a genome-wide association study within each pool. Similar to the first study, highly significant genotypic and genotype × environment interaction variances were observed for GER, DON and DS. Heritabilities were moderately high for GER and DON and high for DS in both pools. Estimated genomic correlations between pools were close to zero for DON and DS, and slightly higher for GER. The detected QTL for DON were all specific to each heterotic pool and none of them was in common with previously detected QTL. Furthermore, no QTL was detected for GER and DS in both pools. Genomic prediction (GP) across pools yielded low or even negative prediction accuracy for all traits. When the training set (TS) size was increased by combining lines from both heterotic pools, the combined-pool GP approaches had no higher prediction accuracy than the within-pool GP approach. Different from expectation, method BayesB did not outperform genomic best linear unbiased prediction (GBLUP). In the third study, we analyzed two backcross (BC) families derived from a resistant and a susceptible recurrent parent. Both BC populations differed substantially in their means for all traits, suggesting that the two recurrent parents have different QTL alleles for GER resistance. Relatively high correlations were observed between DON and ZON concentrations measured by immunoassays and GER visual severity scoring and NIRS (near-infrared spectroscopy) within each BC population. Thus, the mycotoxin content in grain can reliably be reduced by directional selection for GER severity and NIRS measurements that are less expensive and less laborious. In conclusion, GER resistance in European maize germplasm can be effectively improved through breeding with resistant donor lines. GER visual severity scoring and NIRS measurements were found to be reliable predictors for DON and ZON concentrations in grain. We observed that QTL for GER and DON are mostly specific to a few families or a limited number of materials, whereas QTL for DS are more commonly shared between families. The multi-parental QTL mapping approach is complementary to the classical bi-parental QTL mapping in that the latter has generally higher power to identify rare but large-effect QTL for traits such as GER and DON, whereas the former is superior in detecting common but small-effect QTL for traits such as DS. Composing the TS with materials more closely related to the prediction set and increasing the TS size generally resulted in higher prediction accuracy for MAS and GS, irrespective of the trait and statistical model.
Inheritance of quantitative resistance and aggressiveness in the wheat/Fusarium pathosystem with emphasis on Rht dwarfing genes
(2010) Voß, Hans-Henning; Miedaner, Thomas
Fusarium head blight (FHB), or scab, is one of the most devastating fungal diseases affecting small-grain cereals and maize, causing severe yield losses and contamination of grain with mycotoxins such as deoxynivalenol (DON) worldwide. Fusarium graminearum (teleomorph Gibberella zeae) and Fusarium culmorum are the most prevalent Fusarium species in wheat production in Central and Northern Europe. Breeding for increased resistance to FHB in wheat is considered the most effective strategy for large scale disease management and mycotoxin reduction. Height reducing Rht genes are extensively used in wheat breeding programmes worldwide in order to improve lodging resistance and yield potential, with Rht-D1b being the most important Rht allele in Northern Europe. However, their individual effects on FHB resistance are yet unclear. Due to the incremental approach to increase host resistance the question arises whether the Fusarium pathogen has the capability to adapt by increased aggressiveness and/or increased mycotoxin production. Therefore, the objectives of the present study were to investigate the effects on FHB resistance of Rht-D1b and additional Rht alleles, the segregation variance for FHB resistance and identification of FHB resistance QTL in subsequent mapping analyses in three crossing populations segregating for the semi-dwarfing Rht-D1b allele and two sets of isogenic wheat lines. Regarding the pathogen, the study aims to determine the segregation variance in two F. graminearum crosses of highly aggressive parental isolates and to examine the stability of host FHB resistance, pathogen aggressiveness and the complex host-pathogen-environment interactions in a factorial field trial. All experiments were conducted on the basis of multienvironmental field trials including artificial inoculation of spores. The presence of Rht-D1b resulted in 7-18% reduction in plant height, but considerably increased FHB severity by 22-53% within progenies from three tested European elite winter wheat crosses. In the following QTL mapping analyses the QTL with the strongest additive effects was located at the Rht-D1 locus on chromosome arm 4DS and accordingly coincided with a major QTL for plant height in all three wheat populations. On total, a high number of 8 to 14 minor QTL for FHB reaction that were found in the three populations which emphasised the quantitative inheritance of FHB resistance in European winter wheat. The detected QTL mostly showed significant QTL-by-environment interactions and often coincided with QTL for plant height. By means of isogenic lines in the genetic background of the variety Mercia, Rht-D1b and Rht-B1d significantly increased mean FHB severity by 52 and 35%, respectively, compared to the wild-type (rht). Among the Maris Huntsman data set, the Rht alleles increased mean FHB severity by 22 up to 83%, but only the very short lines carrying Rht-B1c or Rht-B1b+Rht-D1b showed significance. The analyses of 120 progenies of the crosses from each of the highly aggressive parental F. graminearum isolates revealed significant genetic variation for aggressiveness, DON and fungal mycelium production following sexual recombination. This variation resulted in stable transgressive segregants towards increased aggressiveness in one of the two progeny. The factorial field trial, including eleven F. graminearum and F. culmorum isolates varying in aggressiveness and seven European elite winter wheat varieties, varying in their FHB resistance level, displayed no significant wheat variety × isolate interaction. Nevertheless, isolates possessing increased aggressiveness significantly increased FHB severity and DON production at a progressive rate on varieties with reduced FHB resistance. In conclusion, the analysed Rht alleles led to differently pronounced negative effects on FHB resistance that strongly depended on the genetic background. However, significant genetic variation for FHB resistance exists for selection and, thus, to largely counteract these effects by accumulating major and minor FHB resistance QTL. Significant genetic variation for aggressiveness among F. graminearum and the capability to increase its level of aggressiveness beyond yet known levels simply by sexual recombination may lead to long term erosion of FHB resistance. The rate at which increased aggressiveness develops will depend on the selection intensity and whether it is of constant, episodic or balanced nature. Consequently, the selection pressure imposed on the pathogen should be minimized by creating and maintaining a broad genetic base of FHB resistance that relies on more than one genetically unrelated resistance source by combining phenotypic and marker-assisted selection to achieve a sustainably improved FHB resistance in wheat breeding.
Molecular and phenotypic analyses of pathogenicity, aggressiveness, mycotoxin production, and colonization in the wheat-Gibberella zeae pathosystem
(2004) Cumagun, Christian Joseph R.; Miedaner, Thomas
Fusarium head blight (FHB), caused by Gibberella zeae (Schwein.) Petch (anamorph: Fusarium graminearum Schwabe), is one of the principal diseases responsible for extensive damage in wheat fields and contamination of grain with the mycotoxins deoxynivalenol (DON) and nivalenol (NIV), rendering the harvest unsafe for human and animal consumption. Control of FHB is difficult because of the complex nature of host-pathogen-environment interaction and the nonavailability of highly effective fungicides. Agronomic practices and resistance breeding, therefore, offer the best strategies for disease management. Mapping by molecular markers provides an accurate approach for genetic analyses of simple and complex traits particularly pathogenicity, aggressiveness, and mycotoxin production. Pathogenicity, as defined here, is the ability to cause disease whereas aggressiveness is the quantity of disease induced by a pathogenic isolate on a susceptible host in which isolates do not interact differentially with host cultivars. The project aims to (1) map pathogenicity and aggressiveness of G. zeae based on a published genetic map (2) estimate genetic diversity of four parent isolates by PCR-based markers (3) examine the inheritance of pathogenicity, aggressiveness, mycotoxin type (DON/NIV), and DON production on a phenotypic basis, (4) analyse genetic covariation among aggressiveness, DON, and fungal colonization, (5) and compare aggressiveness of 42 isolates in greenhouse and field environments. Two crosses of G. zeae using nit (nitrate nonutilizing) marker technique were performed: (1) pathogenic DON-producing Z-3639 (Kansas, USA) x nonpathogenic NIV-producing R-5470 (Japan) belonging to lineage 7 and 6, respectively, and (2) DON-producing FG24 (Hungary) x FG3211 (Germany), both aggressive lineage 7 isolates. For the first cross, 99 progeny segregated in a consistent 61:38 for pathogenicity: nonpathogenicity in a two-year greenhouse experiment. Among the 61 pathogenic progeny, disease severity, measured as percentage infected spikelets, varied significantly (P = 0.01). Heritability for aggressiveness was high. Pathogenicity locus was mapped on linkage group IV near loci PIG1 (red pigment production), TOX1 (trichothecene toxin amount), and PER1 (perithecial production) explaining 60%, 43%, and 51% of the phenotypic variation, respectively. Two large aggressiveness QTLs were mapped on linkage group I linked to the locus TRI5 (trichodiene synthase in the trichothecene gene cluster) and an amplified fragment length polymorphism (AFLP) marker (EAAMTG0655K), explaining 51% and 29% of the observed phenotypic variation, respectively. These unlinked loci suggest that genetic basis between pathogenicity and aggressiveness were different. TRI5 is located in the same gene cluster as a previously identified gene known as TRI13, which determines whether DON or NIV will be produced. DON-producing progeny were, on average, twice as aggressive as were those producing NIV. Loci were only detected in the two linkage groups mentioned from the nine linkage groups present in the map. For the second cross FG24 x FG3211 with 153 progeny, head blight rating and relative plot yield were used as aggressiveness traits. DON production was measured by a commercial kit enzyme immunoassay. These three traits were quantitatively inherited among 153 progeny across three environments. Repeatabilities within each environment were medium to high but heritabilities across environments were medium only due to high progeny-environment interaction. DON was a less environmentally stable trait than aggressiveness. Transgressive segregants were detected frequently. This implies that even a cross within a lineage could lead to an increase in aggressiveness. Mapping of this cross was not initiated because the parents were not polymorphic enough to construct a genetic map. Instead, the parents were analysed for polymorphism in comparison to the parents of the first cross using 31 AFLP primer combinations and 56 random amplified polymorphic DNA (RAPD) primers. Polymorphism between Z-3639 and R-5470 was about three to four times higher than between FG24 and FG3211. Cluster analysis revealed that R-5470 was genetically separated from the other three parents, thus confirming the lineage assignments. Among preselected 50 progeny from the same field experiments that showed normal distribution for aggressiveness - head blight rating, fungal colonization, and DON production were correlated (r = 0.7, P = 0.01). Fungal colonization measured as Fusarium exoantigen (ExAg) content using enzyme-linked immunosorbent assay (ELISA) varied also quantitatively, but heritability was lower due to high progeny-environment interaction and error. Strong correlations among all traits indicate control by similar genes or gene complexes. No significant variation was observed for DON/ExAg ratio. Aggressiveness traits and DON production were more environmentally stable compared to Fusarium ExAg content. Our findings imply that aggressiveness may have other components apart from mycotoxin production. Genotypic variation for aggressiveness among the 42 progeny in one greenhouse and three field environments was significant and their correlation was moderate (r = 0.7, P = 0.01). High heritability in both environments again indicates that aggressiveness was a relatively stable trait, although methods of inoculation differed, i.e., injection for greenhouse and spraying for field experiments. Greenhouse aggressiveness could predict aggressiveness in the field, and thereby should reduce costs for resistance and phytopathological studies. In conclusion, we consider G. zeae as medium-risk pathogen with the potential to evolve to a higher level of aggressiveness due to sexual recombination. Erosion of quantitative resistance in FHB cannot be ignored, especially if host resistances with oligogenic inheritance, e.g. Sumai 3 from China, are used on a large acreage. Consequently, the rather simple inheritance of pathogenicity and aggressiveness in G. zeae could lead to a gradual increase of aggressiveness. These results should enhance efforts of plant breeders to use several, genetic distinct sources of resistance in order to avoid possible FHB outbreaks in the future.