Morphological and molecular identification of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with head blight on wheat in East Croatia

Fusarium head blight (FHB) is an important fungal disease of wheat. The aim of this research was to determine the diversity of Fusarium species infecting winter wheat ears in East Croatia. In 2008 wheat kernels were obtained from three locations in the eastern part of Croatia (Tovarnik, Osijek, Pozega), and in 2009 from two additional locations (Slavonski Brod, Nova Gradiska). In total, 498 visually diseased kernels were selected for morphological identification of Fusarium spp. The identity of 226 selected isolates was further investigated by molecular techniques. The predominant species on wheat kernels in East Croatia in 2008 were F. graminearum, isolated and confirmed from more than 80% of sampled wheat kernels, followed by F. avenaceum (8%) and F. culmorum (7%). Incidence of F. poae was less than 2%. The most common species identified in 2009 were F. graminearum (50%), F. culmorum (13%), F. avenaceum (12%) and F. poae (7%). This is the first report on the identification of Fusarium species isolated from naturally infected wheat ears in Croatia.     

Genetic analysis and PCR-based identification of major <Emphasis Type="Italic">Fusarium</Emphasis> species causing head blight on wheat in Japan

Identifying the Fusarium species cause Fusarium head blight (FHB) and produces mycotoxins in wheat and other cereal is difficult and time consuming because of confusing phenotypic classification systems. In Japan, the F. graminearum complex, F. culmorum, F. avenaceum, and Microdochium nivale predominantly cause FHB. The internal transcribed spacer (ITS) and 5.8S of rDNA, a partial sequence of β-tubulin and mitochondrial cytochrome b (cytb) genes of the four species were PCR-amplified and analyzed. On the basis of the ITS, β-tubulin and cytb sequences, F. avenaceum and M. nivale are distinct from the F. graminearum complex and F. culmorum, whereas the F. graminearum complex is closely related to F. culmorum. Moreover, thiophanate–methyl-resistant isolates of the F. graminearum complex and F. culmorum did not have an amino acid substitution at amino acid codon 198 or 200 of β-tubulin. In contrast, very highly or highly thiophanate–methyl-resistant isolates of M. nivale had Glu (GAG) substituted with Ala (GCG) or Lys (AAG) at codon 198, respectively. The allele-specific PCR assay was used to identify the F. graminearum complex and F. culmorum, and these Fusarium species could be distinguished rapidly.     

Toxigenic Fusarium species and Mycotoxins Associated with Head Blight in Small-Grain Cereals in Europe

The Fusarium species predominantly found associated with Fusarium head blight (FHB) in wheat and other small-grain cereals all over Europe are F. graminearum, F. avenaceum and F. culmorum. Among the less frequently encountered species are several others which are less pathogenic or opportunistic, but also toxigenic. These include F. poae, F. cerealis F. equiseti F. sporotrichioides F. tricinctum and, to a lesser extent, F. acuminatum F. subglutinans F. solani F. oxysporum F. verticillioides F. semitectum and F. proliferatum. The species profile of FHB is due to several factors, primarily climatic conditions, particularly rain and the temperature at flowering stage, but also agronomic factors, such as soil cultivation, nitrogen fertilization, fungicides, crop rotation, and host genotype. The most frequently encountered Fusarium mycotoxins in FHB in Europe has proved to be deoxynivalenol and zearalenone produced by F. graminearum and F. culmorum with the former more common in southern (warmer) and the latter in northern (colder) European areas. Nivalenol was usually found associated with deoxynivalenol and its derivatives (mono-acetyldeoxynivalenols), together with fusarenone-X, formed by F. graminearum F. cerealis F. culmorum and, in northern areas, by F. poae. Moreover, from central to northern European countries, moniliformin has been consistently reported, as a consequence of the widespread distribution of F. avenaceum whereas the occurrence of T-2 toxin derivatives, such as T-2 toxin and HT-2 toxin, and diacetoxyscirpenol have been recorded in conjunction with sporadic epidemics of F. sporotrichioides and F. poae. Finally, beauvericin and various enniatins have recently been found in Finnish wheat colonized by F.avenaceum and F. poae.     

Occurrence and Pathogenicity of Fusarium Species in Cereals in Finland1

Several Fusarium species occurred abundantly in spring cereal seed samples studied in 1966, 1968 and 1972 in Finland. A total of 17 species of Fusarium were isolated and identified. The most frequently isolated species were F. avenaceum (Fr.) Sacc., F. culmorum (W. G. Sm.) Sacc., F. poae (Peck) Wr. and F. tricinctum (Cda) Sacc. These species were found in more than 40% of the seed samples from 1972. The same 4 Fusarium species in addition to F. graminearum Schwabe were used in the pathogenicity test. Artificially inoculated spring wheat and barley seeds were grown in the field during the growing season of 1973. Of these 5 species F. culmorum was clearly the most pathogenic. This species significantly lowered the shooting percentage and the yield of both cereals. Foot rot assessment also revealed F. culmorum as the most damaging species. Natural soil-borne infection obviously increased the foot and root rot, and thus the soil-borne F. culmorum strongly affected all treatments. In the harvested seed F. poae dominated in all treatments, but F. culmorum still occurred most abundantly in the seed lot harvested from plots originally inoculated with this species.     

Biodiversity of Fusarium species in ears and stalks of maize plants in Belgium

In order to investigate the pre-harvest contamination of maize plants by Fusarium species in Belgium, a three-year survey has been performed in five fields in which three hybrids differing in susceptibility to maize stalk rot were sampled at four different physiological stages. An extensive collection of 5,659 Fusarium isolates characterized at the species level was established during the 2005, 2006, and 2007 growing seasons, with a total of 23 different Fusarium species identified to occur on ears and stalks. A high number of plants was already contaminated by Fusarium spp. at the anthesis stage, although no symptoms were visible on ears or on stalks. As the season progressed, the incidence of Fusarium-infected maize plants reached 100% in several fields. At the end of the growing season, the most frequently isolated species in maize ears were F. graminearum, sometimes associated with F. avenaceum, F. crookwellense, F. culmorum, F. poae, and F. temperatum, a new species recently described on maize. The predominant Fusarium species detected in stalks at the end of the growing season were F. graminearum and F. crookwellense, often associated with F. culmorum and F. temperatum. Year-to-year variability observed for the incidence of F. graminearum can most likely be associated with differences in climatic conditions among the three years.     

Studies on in vitro Growth and Pathogenicity of European Fusarium Fungi

The effect of temperature on the in vitro growth rates and pathogenicity of a European Fusarium collection consisting of isolates of Fusarium graminearum, F. culmorum, F. avenaceum, F. poae and Microdochium nivale was examined. Irrespective of geographic origin, the optimum temperature for the growth of F. graminearum, F. culmorum and F. poae was 25 °C, while that for F. avenaceum and M. nivale was 20 °C. In general, the growth rates of F. graminearum, F. culmorum and F. poae increased between 10 and 25 °C and those of F. avenaceum and M. nivale increased between 10 and 20 °C. Pathogenicity tests were carried out by examining the effect of the five species on the in vitro coleoptile growth rate of wheat seedlings (cv. Falstaff). Irrespective of geographic origin, the temperature at which F. avenaceum, F. culmorum and F. graminearum caused the greatest retardation in coleoptile growth ranges 20–25 °C (>89.3% reduction), whilst for F. poae and M. nivale it was 10–15 °C (>45.6% retardation), relative to uninoculated control seedlings. In general, F. culmorum and F. graminearum were the most pathogenic of the five species, causing at least a 69% reduction in coleoptile growth at 10, 15, 20 and 25 °C. General linear model analysis (GLIM) showed that species accounted for 51.3–63.4% of the variation in isolate growth and from 19.5% to 44.3% of the variation in in vitro pathogenicity. Country of origin contributed from 22.6% to 51.9% to growth rate variation and from 0.73% to 7.61% to pathogenicity variation. The only significant correlation between in vitro growth and pathogenicity was that observed for M. nivale at 15 °C (r = -0.803, P < 0.05).     

Epidemiology of Fusarium Infection and Deoxynivalenol Content in Winter Wheat in the Rhineland, Germany

Details of our long-term research programme concerning the epidemiology of Fusarium spp. and mycotoxin production are summarized. Evaluation of the occurrence of Fusarium spp., mainly on winter wheat (Triticum aestivum), was carried out by investigating Fusarium infection and mycotoxin contamination. Two to 15% of grains were infested during 1995–1998 at three climatologically differing localities of the Rhineland, Germany. Disease progress was accelerated by rainfall during the flowering season. The species most frequently isolated were Fusarium avenaceum, F. poae, F. culmorum and F. graminearum. The mean deoxynivalenol (DON) content varied from 19gkg^–1 (1995) to 310gkg^–1 (1998) and was not always correlated with disease severity. Organic farming systems showed lower rates of infection with ear blight and lower mycotoxin contamination than conventional farming systems.     

Molecular and Morphological Diversity of Fusarium Species in Finland and North-Western Russia

In 2001 the range of the total Fusarium contamination percentage of infected seeds was between 0% and 44%, while in 2002 the contamination level was 2–25% in naturally infected Finnish samples and 5–14.5% in six samples from northwestern Russia. The most common Fusarium species in barley were F. avenaceum, F. arthrosporioides, F. sporotrichioides and F. culmorum, while in spring wheat the most common Fusarium species were F. avenaceum, F. arthrosporioides, F. culmorum, F. sporotrichioides and F. graminearum. In most cases, molecular identification with species-specific primers corresponded to the morphological analyses and allowed the identification of degenerated and otherwise morphologically difficult cultures. It was even possible to separate most of the F. arthrosporioides isolates from Finland from the closely-related F. avenaceum isolates. In the phylogenetic analysis of combined β-tubulin, IGS and ITS sequences most European F. arthrosporioides formed a separate clade from most isolates of F. avenaceum and from all isolates of F. tricinctum. Most of the species-specific primers also amplified DNA extracted from grain samples. It was, for instance, possible to detect F. avenaceum in all barley samples with contamination levels higher than 1% and in all spring wheat samples with contamination levels higher than 3%. The detection level for F. graminearum was at a contamination level of 3–5% and that for F. culmorum at a contamination level of 1–5%. In addition, the first Finnish F. langsethiae isolate was found by means of species-specific primers.     

Differential Control of Head Blight Pathogens of Wheat by Fungicides and Consequences for Mycotoxin Contamination of Grain

Fusarium head blight of wheat is caused by a disease complex comprised of toxigenic pathogens, predominantly Fusarium spp., and a non-toxigenic pathogen Microdochium nivale, which causes symptoms visually indistinguishable from Fusarium and is often included as a causal agent of Fusarium head blight. Four field trials are reported here, including both naturally and artificially inoculated trials in which the effect of fungicide treatments were noted on colonisation by Fusarium and Microdochium, and on the production of deoxynivalenol (DON) mycotoxin. The pathogen populations were analysed with quantitative PCR and samples were tested for the presence of the mycotoxin DON. Application of fungicides to reduce Fusarium head blight gave a differential control of these fungi. Tebuconazole selectively controlled F. culmorum and F. avenaceum and reduced levels of DON, but showed little control of M. nivale. Application of azoxystrobin, however, selectively controlled M. nivale and allowed greater colonisation by toxigenic Fusarium species. This treatment also lead to increased levels of DON detected. nobreak Azoxystrobin application two days post-inoculation increased the production of DON mycotoxin per unit of pathogen in an artificially inoculated field trial. This result indicates the potential risk of increased DON contamination of grain following treatment with azoxystrobin to control head blight in susceptible wheat cultivars. This is the first study to show differential fungicidal control of mixed natural pathogen populations and artificial inoculations in field trials.     

Resistance Reaction of Conifer Species (European Larch, Norway Spruce, Scots Pine) to Infection by Selected Necrotrophic Damping-off Pathogens

Three conifer species (European larch, Norway spruce, Scots pine) were investigated for their resistance to five damping-off pathogens (Rhizoctonia solani, Fusarium solani, F. oxysporum, F. culmorum, F. avenaceum). Inoculation of the primary roots of seedlings with these pathogens caused host cell death which did not prevent the invasive growth of these fungi; seedlings that had formed secondary and tertiary roots could overcome the infection to a significant degree. Infections with R. solani caused significant mortality to all the conifer species. In contrast, the tree species expressed different levels of resistance when challenged with the Fusarium isolates, with Norway spruce being the most resistant compared to uninoculated controls. Some of the Fusarium isolates were more pathogenic to certain hosts than others; F. oxysporum for European larch, F. avenaceum for Scots pine, F. solani for European larch; only F. culmorum was significantly pathogenic to Norway spruce. No significant differences in disease severity were observed at different soil pH (4.3–7.5). Disease progression was delayed at lower (10–15°C) rather than higher temperatures (20–25°C).     

Genetic variation among <Emphasis Type="Italic">Fusarium</Emphasis> isolates from onion,and resistance to <Emphasis Type="Italic">Fusarium</Emphasis> basal rot in related <Emphasis Type="Italic">Allium</Emphasis> species

The aim of this research was to study levels of resistance to Fusarium basal rot in onion cultivars and related Allium species, by using genetically different Fusarium isolates. In order to select genetically different isolates for disease testing, a collection of 61 Fusarium isolates, 43 of them from onion (Allium cepa), was analysed using amplified fragment length polymorphism (AFLP) markers. Onion isolates were collected in The Netherlands (15 isolates) and Uruguay (9 isolates), and received from other countries and fungal collections (19 isolates). From these isolates, 29 were identified as F. oxysporum, 10 as F. proliferatum, whereas the remaining four isolates belonged to F. avenaceum and F. culmorum. The taxonomic status of the species was confirmed by morphological examination, by DNA sequencing of the elongation factor 1-α gene, and by the use of species-specific primers for Fusarium oxysporum, F. proliferatum, and F. culmorum. Within F. oxysporum, isolates clustered in two clades suggesting different origins of F. oxysporum forms pathogenic to onion. These clades were present in each sampled region. Onion and six related Allium species were screened for resistance to Fusarium basal rot using one F. oxysporum isolate from each clade, and one F. proliferatum isolate. High levels of resistance to each isolate were found in Allium fistulosum and A. schoenoprasum accessions, whereas A. pskemense, A. roylei and A. galanthum showed intermediate levels of resistance. Among five A. cepa cultivars, ‘Rossa Savonese’ was also intermediately resistant. Regarding the current feasibility for introgression, A. fistulosum, A. roylei and A. galanthum were identified as potential sources for the transfer of resistance to Fusarium into onion.     

Major Changes in Fusarium spp. in Wheat in the Netherlands

The re-emergence of fusarium head blight throughout the world and especially in Western Europe prompted a survey of the situation in the Netherlands. To allow for a high throughput screening of large numbers of samples, a diagnostic PCR method was developed to detect the most common species of Fusarium occurring on wheat. Seven primer pairs were tested for their ability to identify isolates of Fusarium avenaceum, F. culmorum, F. graminearum, F. poae, F. proliferatum and Microdochium nivale var. majus and M. nivale var. nivale. Each primer pair only generated a PCR product with the corresponding Fusarium species and all PCR fragments had different molecular sizes. This allowed the generation of these amplicons using a mixture of all seven primer pairs. The robustness of this multiplex PCR encouraged us to screen a large series of isolates collected in 2000 and 2001. In both years 40 fields were sampled leading to a collection of 209 isolates from 2000 and 145 isolates from 2001. The results of the multiplex PCR demonstrated that F. graminearum was the most abundant species in the Fusarium complex on wheat in both years. This is in sharp contrast to reports from the 1980s and early 1990s, which found F. culmorum as the predominant species. Primers derived from the tri7 and tri13 genes, which are implicated in the acetylation and oxygenation of the C-4 atom of the backbone of the trichothecene molecule, were used to discriminate between deoxynivalenol and nivalenol (NIV) producers. The populations of F. culmorum and F. graminearum both showed a slight increase in NIV-producers in 2001.     

Predominance and association of pathogenic fungi causing Fusarium ear blightin wheat in four European countries

Two years of field sampling aimed to establish the predominance and association among the fungal pathogens causing Fusarium ear blight (FEB) in four European countries (Hungary, Ireland, Italy and the UK). A PCR-based method was used to detect four Fusarium species and two varieties of Microdochium nivale present in the samples. The prevalence of FEB pathogens differed significantly between countries. Overall, all pathogens were commonly detected in Ireland and to a lesser extent in the UK. In contrast, only two species, F. graminearum and F. poae, were regularly detected in Italy and Hungary. Fusarium culmorum was rarely detected except in Ireland. Log-linear models were used to determine whether there is the independence of the six FEB pathogens at each sampling site. Significant two-pathogen interactions were frequently observed, particularly in harvest samples; all these significant two-pathogen interactions were of the synergistic type, except between F. poae and F. culmorum, and were generally consistent over the 2 years and four countries. Fusarium graminearum and F. poae were least frequently involved in two pathogen interactions but were involved in most of the nine significant three-pathogen interactions. However, only the interaction between F. graminearum, F. avenaceum and F. poae was significant in both years. Potential implications of the present results in FEB management are discussed.     

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.     

Early PCR-based detection of Fusarium culmorum,F. graminearum,F. sporotrichioides and F. poae on stem bases of winter wheat throughout Poland

Foot rot and crown rot are fungal diseases of wheat caused by a complex of Fusarium species. They have a huge economic impact mainly due to yield reduction. A survey was conducted to identify four Fusarium species, occurring on wheat stem bases, using species-specific PCR assays in samples collected during spring of 2012. The dominant species was F. graminearum, which was identified in above 64 % of samples. F. culmorum was detected in 15.71 %, F. poae in 15.71 % and F. sporotrichioides in 5.71 % wheat fields. Most of the wheat fields in the eastern Poland were infected with at least one or two of Fusarium species, while in central Poland no Fusarium species were identified in most of the fields. The presence of F. graminearum tends to favor the presence of F. culmorum and this effect was visible also for F. poae and F. sporotrichioides. The frequency of F. graminearum and F. culmorum detections were highest where wheat crops were preceded by maize and in the samples from late sown fields. The opposite observation was made for F. poae and F. sporotrichioides, where the number of detections of these species was higher in samples from early sown fields. The number of detected Fusarium species was significantly lower in samples collected from fields protected with autumn herbicide in comparison to unprotected fields. The rate of autumn N fertilization did not affect the number of Fusarium detections.     

Identity and pathogenicity of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with crown rot on wheat (<Emphasis Type="Italic">Triticum</Emphasis> spp.) in Turkey

An extensive survey was carried out to collect Fusarium species colonizing the lower stems (crowns) of bread wheat (Triticum aestivum L.) and durum wheat (T. durum Desf.) from different wheat growing regions of Turkey in summer 2013. Samples were collected from 200 fields representing the major wheat cultivation areas in Turkey, and fungi were isolated from symptomatic crowns. The isolates were identified to species level by sequencing the translation elongation factor 1-alpha (TEF1-α) gene region using primers ef1 and ef2. A total of 339 isolates representing 17 Fusarium species were isolated. The isolates were identified as F. culmorum, F. pseudograminearum, F. graminearum, F. equiseti, F. acuminatum, F. brachygibbosum, F. hostae, F. redolens, F. avenaceum, F. oxysporum, F. torulosum, F. proliferatum, F. flocciferum, F. solani, F. incarnatum, F. tricinctum and F. reticulatum. Fusarium equiseti was the most commonly isolated species, accounting for 36% of the total Fusarium species isolated. Among the damaging species, F. culmorum was the predominant species being isolated from 13.6% of sites surveyed while F. pseudograminearum and F. graminearum were isolated only from 1% and 0.5% of surveyed sites, respectively. Six out of the 17 Fusarium species tested for pathogenicity caused crown rot with different levels of severity. Fusarium culmorum, F. pseudograminearum and F. graminearum caused severe crown rot disease on durum wheat. Fusarium avenaceum and F. hostae were weakly to moderately virulent. Fusarium redolens was weakly virulent. However, F. oxysporum, F. equiseti, F. solani, F. incarnatum, F. reticulatum, F. flocciferum, F. tricinctum, F. brachygibbosum, F. torulosum, F. acuminatum and F. proliferatum were non-pathogenic. The result of this study reveal the existence of a wide range of Fusarium species associated with crown rot of wheat in Turkey.     

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.     

Spatial variability of fusarium head blight pathogens and associated mycotoxins in wheat crops

The spatial pattern of Fusarium‐infected kernels and their mycotoxin contamination was studied in four wheat fields in Germany using geo‐referenced sampling grids (12–15 × 20–30 m, 28–30 samples per field) at harvest. For each sample, frequency of Fusarium‐infected kernels and spectrum of species were assessed microbiologically; mycotoxin contents were determined by HPLC‐MS/MS analysis. Spatial variability of pathogens and mycotoxins was analysed using various parameters including Spatial Analysis by Distance IndicEs (sadie^® ). Microdochium majus, the most frequent head blight pathogen in 1998, was less frequent in 1999 and could not be detected in kernels from two fields in 2004. Fusarium avenaceum, F. graminearum and F. poae were the most frequent Fusarium species, with 7–8 species per field. The frequency of Fusarium‐infected kernels was 3–15% and the incidence of species showed considerable within‐field variability. Spatial patterns varied among Fusarium species as well as from field to field. Although pathogens and mycotoxin were often distributed randomly in the field, F. avenaceum, F. graminearum, F. poae, F. sporotrichioides, F. tricinctum and the mycotoxin moniliformin had an aggregated pattern in at least one field. Patterns are discussed in relation to spread of Fusarium species depending on inoculum sources, spore type, kind of dispersal, availability of susceptible host tissue and micro‐climate. Sampling of wheat fields for representative assessment of mycotoxins is complicated by random patterns of Fusarium‐infected kernels, especially where the frequency of infection is small.     

Deoxynivalenol, Nivalenol and Moniliformin in Wheat Samples with Head Blight (scab) Symptoms in Poland (1998–2000)

Fusarium head blight (scab) epidemics of wheat occurred in uawy (Northern Poland) during 1998 and in Wielkopolska (West) and in Southern regions of Poland in 1999. Four species were identified in wheat heads with scab symptoms: Fusarium culmorum, Fusarium graminearum, Fusarium avenaceum and Microdochium nivale. A significant increase in the frequency of F. graminearum (between 23% and 38%), was observed, compared to about 10% during the previous decade. The mycotoxins deoxynivalenol (DON), nivalenol (NIV) and moniliformin (MON) in amounts up to 24.3, 14.2 and 1.72mgkg^–1respectively, were identified in kernels samples.     

Genetic variation of aggressiveness in individual field populations ofFusarium graminearum andFusarium culmorum tested on young plants of winter rye

Fusarium graminearum andF. culmorum are capable of infecting winter cereals at all growth stages. From natural field epidemics of wheat head blight and rye foot rot, three fungal populations were collected with 21, 38 and 54 isolates, respectively; their aggressiveness was analyzed in comparison to collections ofF. graminearum (25 isolates) andF. culmorum (70 isolates) that represent a wide range of geographical locations and host species. All isolates were tested for aggressiveness on young plants of winter rye in the greenhouse and scored for disease severity on a 1–9 scale. Disease ratings of individual isolates ranged from 1.5 to 5.7 indicating quantitative variation of aggressiveness. Genotypic variance was highest in the twoFusarium collections. No substantial difference was found in the amount of genotypic variation betweenF. graminearum andF. culmorum. Individual field populations revealed 57–66% of the total genotypic variation of the collections. This implies a high degree of diversity of aggressiveness within single field populations ofF. graminearum andF. culmorum causing natural epidemics.