Comparison of rye,triticale, durum wheat and bread wheat genotypes for Fusarium head blight resistance and deoxynivalenol contamination

Small-grain winter cereal crops can be infected with Fusarium head blight (FHB) leading to mycotoxin contamination and reduction in grain weight and quality. Although a number of studies have investigated the genetic variation of genotypes within each small-grain cereal, a systematic comparison of the winter crops rye, triticale, durum and bread wheat for their FHB resistance, Fusarium-damaged kernels (FDK) and deoxynivalenol (DON) contamination across species is still missing. We have therefore evaluated twelve genotypes each of four crops widely varying in their FHB resistance under artificial infection with one DON-producing F. culmorum isolate at constant spore concentrations and additionally at crop-specific concentrations in two environments. Rye and triticale were the most resistant crops to FHB followed by bread and durum wheat at constant and crop-specific spore concentrations. On average, rye accumulated the lowest amount of DON (10.08 mg/kg) in the grains, followed by triticale (15.18 mg/kg) and bread wheat (16.59 mg/kg), while durum wheat had the highest amount (30.68 mg/kg). Genotypic variances within crops were significant (p ≤ .001) in most instances. These results underline the differing importance of breeding for FHB resistance in the different crops.     

Estimation of deoxynivalenol (DON) content by symptom rating and exoantigen content for resistance selection in wheat and triticale

Fusarium head blight (FHB) in wheat and triticale leads to contamination of the grain with the mycotoxin deoxynivalenol (DON) that is harmful to animal and man. A fast, low-cost, and reliable method for quantification of the DON content in the grain is essential for selection. We analysed 113 wheat and 55 triticale genotypes for their symptom development on spikes, Fusarium exoantigen (ExAg) and DON content in the grain after artificial inoculation with a highly aggressive isolate of F. culmorum in three (wheat) and six (triticale) location-by-year combinations. Additionally, in triticale the amount of Fusarium damaged kernels (FDK) was assessed. ExAg content was analysed by a newly developed Fusarium-specific plate-trapped antigen enzyme-linked immunosorbent assay (PTA-ELISA) and DON content by an immunoassay. A moderate disease severity resulted in an ExAg content of 0.87 optical density (OD) units in wheat and 1.02 OD in triticale. DON content ranged from 12.0 to 105.2 mg kg^–1 in wheat and from 24.2 to 74.0 mg kg^–1 in triticale. Genotypic and genotype-by-environment interaction variances were significant (P < 0.01). Coefficient of phenotypic correlation between DON content analysed by the immunoassay and ExAg content was r = 0.86 for wheat and r = 0.60 for triticale. The highest correlation between DON content and symptom rating was found by FHB rating in wheat (r = 0.77) and by FDK rating in triticale (r = 0.71). In conclusion, selection for reduced FHB symptoms should lead to a correlated selection response in low fungal biomass and low DON content in the grain.     

Correlation between Fusarium head blight severity and DON content in triticale as revealed by phenotypic and molecular data

Fusarium head blight (FHB) in triticale (× Triticosecale Wittmack) results in yield losses and mycotoxin contamination, for example, by deoxynivalenol (DON). This study aimed to analyse the correlation between FHB severity and DON content in a DH population of 146 entries across environments. Additionally, Fusarium damaged kernel (FDK) rating, heading stage and plant height were recorded. Highly significant (P < 0.001) genotypic variances were found throughout, but also significant (P < 0.001) genotype–environment interaction variances occurred. Correlation between FHB severity and heading stage or plant height was low (r = 0.144 and r = ?0.153, P < 0.10). A prediction of DON content from FHB severity or FDK rating is not possible caused by low correlations (r = 0.315 and 0.572, respectively, P < 0.001). A common quantitative trait locus (QTL) for all FHB‐related traits was found on wheat chromosome 2A being of minor importance for FHB severity, but of high importance for DON content and FDK rating. Another QTL on rye chromosome 5R was more important for FHB severity. In conclusion, DON content has to be measured in triticale after selection for FHB severity to gain for healthy and mycotoxin‐reduced feed.     

Selection for Fusarium head blight resistance in early generations reduces the deoxynivalenol (DON) content in grain of winter and spring wheat

Fusarium head blight (FHB) results in yield losses and contamination of kernels by mycotoxins, particularly deoxynivalenol (DON). For minimizing DON content in grain, indirect selection methods would increase gains from selection compared to the costly and time‐consuming DON analysis. The aim of this study was to examine whether an early selection for fewer FHB symptoms would lead to a reduced DON content in grain after inoculation with Fusarium culmorum. Starting with a double‐cross derived population of about 1,100 genotypes, 30 F_1:3 genotypes were selected for FHB rating in a two‐step selection in spring wheat with the non‐adapted resistance sources CM82036 and ‘Frontana’. In winter wheat, 30 F_1:2 genotypes were selected out of a double‐cross derived population of about 600 F₁ plants from crosses with German resistance sources (‘Dream’, G16‐92). Selected genotypes were grouped in three categories according to their FHB rating (low, moderate and high) and analysed afterwards for grain DON content. The three groups differed in their DON content illustrating that indirect selection should already be feasible in the earliest generations. Because of the wide genotypic ranges for DON contents within one grouping, a final DON analysis for selected materials is advisable to achieve full selection gain.     

Different quantitative trait loci for <Emphasis Type="Italic">Fusarium</Emphasis> resistance in wheat seedlings and adult stage in the Wuhan/Nyubai wheat population

Fusarium head blight (FHB), caused primarily by Fusarium graminearum (Schwabe), is an important wheat disease. In addition to head blight, F. graminearum also causes Fusarium seedling blight (FSB) and produces the mycotoxin deoxynivalenol (DON) in the grain. The objectives of this study were: (1) to compare the relationship between resistance of wheat lines to F. graminearum in the seedlings and spikes and (2) to determine whether the quantitative trait loci (QTL) for FSB were the same as QTLs for FHB resistance and DON level reported for the same population previously (Somers et al. 2003). There was no relationship between FSB infection and FHB index or DON content across the population. A single QTL on chromosome 5B that controlled FSB resistance was identified in the population; the marker WMC75 explained 13.8% of the phenotypic variation for FSB. This value implies that there may be other QTL with minor effects present, but they were not detected in the analysis. Such a QTL on chromosome 5B was not reported previously among the QTLs associated with FHB resistance and DON level in this population. However, because of recombination, some lines in the present study have Fusarium resistance for both seedling and head blight simultaneously. For example, DH line HC 450 had the highest level of resistance to FSB and FHB and was among the ten lines with lowest DON content. This line is a good candidate to be used as a parent for future crosses in breeding for Fusarium seedling resistance, together with breeding for head blight resistance. This approach may be effective in increasing overall plant resistance to Fusarium.     

Effect of 3B, 5A and 3A QTL for Fusarium head blight resistance on agronomic and quality performance of Canadian winter wheat

The objectives of this study were to investigate (i) the correlations between Fusarium head blight (FHB) index, deoxynivalenol (DON) accumulation and percentage of Fusarium‐damaged kernels (FDK) with agronomic and quality traits and (ii) the effect associated with the presence of single QTLs for FHB resistance on agronomic and quality traits in winter wheat. The population was derived from the cross between ‘RCATL33' (FHB resistance derived from ‘Sumai 3’ and ‘Frontana’) and ‘RC Strategy’. Parental lines and recombinant inbred lines (RILs) were genotyped with SSR markers associated with the 3B, 5A and 3A QTLs. The population was planted in FHB‐inoculated nurseries and in agronomy trials. Lines in the 3B QTL class had the lowest FHB index, DON content and FDK level and did not have a significantly lower yield, thousand kernel weight or protein content compared with the lines grouped in other QTL classes (including no QTL class). Marker‐assisted selection of the 3B QTL for FHB resistance into high‐yielding FHB‐susceptible winter wheat is the recommended approach for the development of lines with increased FHB resistance without significant yield and quality penalties.     

Breeding wheat and rye for resistance to Fusarium diseases

Fusarium culmorum and F. graminearum Groups 1 and 2 cause seedling blight, crown rot, foot rot and head blight in wheat and rye that may affect grain yield and quality for baking and feeding. This review starts with an analysis of Fusarium populations with regard to their genetic variation for aggressiveness, mycotoxin production, and isolate-by-host genotype interaction. To assess resistance in the different host growth stages, quantitative inoculation and disease assessment techniques are necessary. Based on estimated population parameters, breeding strategies are reviewed to improve Fusarium resistance in wheat and rye. Epidemiological and toxicological aspects of Fusarium resistance that are important for resistance breeding are discussed. F. culmorum and F. graminearum display large genetic variation for aggressiveness in isolate collections and in naturally occurring populations. The production of mycotoxins, especially deoxynivalenol and its derivatives, is a common trait in these populations. Significant isolate-by-host genotype interactions were not found across environments in wheat and rye. Artificial infections in the field are indispensable for improving Fusarium crown rot, foot rot and head blight resistance in wheat and rye. For a reliable disease assessment of large populations, disease severity ratings were found to be the most convenient. The differentiation of host resistance is greatly influenced by an array of nongenetic factors (macro-environment, microclimate, host growth stage, host organ) that show significant interactions with host genotype. Selection for environmentally stable resistance has to be performed in several environments under a maximum array of different infection levels. Selection in early growth stages or on one plant organ does not in most cases allow prediction of resistance in adult-plant stages or another plant organ. Significant genetic variation for resistance exists for all Fusarium-incited diseases in breeding populations of wheat and rye. The patho-systems studied displayed a prevalence of additive gene action with no consistent specific combining ability effects and thus rapid progress can be expected from recurrent selection. In wheat, intensive testing of parental genotypes allows good prediction of the mean head blight resistance after crossing. Subsequent selection during selfing generations enables the use of transgression towards resistance. In hybrid breeding of winter rye, the close correlation between foot rot resistance of inbred lines and their GCA effects implies that selection based on the lines per se should be highly effective. This is not valid for F. culmorum head blight of winter rye caused by a greater susceptibility of the inbred lines compared to their crosses. For both foot rot and head blight resistance, a high correlation between the resistance to F. graminearum and F. culmorum was found in wheat and rye. Mycotoxin accumulation occurs to a great extent in naturally and artificially infected plant stands. The correlation between resistance traits and mycotoxin contents are medium and highly dependent on the environment. Further experiments are needed to clarify whether greater resistance will lead to a correlated reduction of the mycotoxin content of the grains under natural infection.     

Whitened kernel surface: A fast and reliable method for assessing Fusarium severity on cereal grains by digital picture analysis

Fusarium head blight (FHB) is a cereal disease of major importance responsible for yield losses and mycotoxin contaminations in grains. Here, we introduce a new measurement approach to quantify FHB severity on grains based on the evaluation of the whitened kernel surface (WKS) using digital image analysis. The applicability of WKS was assessed on two bread wheat and one triticale grain sample sets (265 samples). Pearson correlation coefficients between Fusarium‐damaged kernels (FDK) and WKS range from r = 0.77 to r = 0.81 and from r = 0.61 to r = 0.86 for the correlation between deoxynivalenol (DON) content and WKS. This new scoring method facilitates fast and reliable assessment of the resistance to kernel infection and shows significant correlation with mycotoxin content. WKS can be automated and does not suffer from the “human factor” inherent to visual scorings. As a low‐cost and fast approach, this method appears particularly attractive for breeding and genetic analysis of FHB resistance where typically large numbers of experimental lines need to be evaluated, and for which WKS is suggested as an alternative to visual FDK scorings.     

Correlations among Fusarium culmorum head blight resistance, fungal colonization and mycotoxin contents in winter rye

Fusarium culmorum head blight infections may lead to accumulation of toxic metabolites in winter rye grain. To estimate the correlation between resistance traits, fungal colonization and accumulation of deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON) and zea-ralenone (ZEA), 27 winter rye single-cross hybrids were artificially inoculated in 1992 and 1993. Resistance traits were head blight rating and grain weight of the inoculated relative to the non-inoculated plots. Fungal colonization was determined by the analysis of ergosterol (ERG) content in the grain. Head blight rating and relative grain yield showed a medium to high disease severity and ERG indicated a considerable fungal colonization of the kernels with a mean of 85 mg/kg in 1992 and 66 mg/kg in 1993. DON content among genotypes ranged from 0.7–28 mg/kg in 1992 and from 11 to 35 mg/kg in 1993. 3-AcDON and ZEA contents were low in both years with overall means of 1.1 and 0.09 mg/kg, respectively. Across both years, considerable genotypic variation was found for head blight rating, relative grain weight, and ERG content with medium to high heritabilities (0.6–0.7). For the mycotoxin contents, however, genotype-year interaction variance was the most important source of variation. The correlations between relative grain weight and DON, 3-AcDON, or ZEA were low in 1992 (r ～ 0.3), but considerably higher in 1993 (r ～ 0.7, P = 0.01). In contrast, correlation between relative grain weight and ERG was significant in both years (r ～ 0.5, P = 0.01). In F. culmorum head blight infections, DON, 3-AcDON and ZEA contents appear to be affected, at least partially, by different environmental factors than resistance traits and fungal colonization.     

Field evaluation of resistance to kernel infection and mycotoxin accumulation caused by Fusarium head blight in western Japanese wheat (Triticum aestivum L.) cultivars

Fusarium head blight (FHB) remains a serious problem that causes yield and grain quality losses, and mycotoxin accumulation in wheat production in western Japan. A 3-year field trial with artificial FHB inoculation was conducted to evaluate varietal characteristics of FHB resistance among 31 wheat cultivars/lines cultivated in western Japan, including one standard line. Severity of FHB, frequency of Fusarium-damaged kernels (FDK), deoxynivalenol concentration (DON), nivalenol concentration (NIV), and grain yield showed significant differences among years and among cultivars/lines. Interaction between years and cultivars/lines was also significant in these traits, but F values were larger for cultivars/lines than for the interaction. Correlation analysis showed that cultivars/lines with lower FHB severities tended to have lower FDK, DON and NIV, and a higher yield. Resistance to kernel infection (RKI), residuals calculated by regressing FDK against FHB severity, and resistance to mycotoxin accumulation (RTA), residuals calculated by regressing DON + NIV against FDK, also differed significantly among cultivars/lines. These results indicated that varietal differences in response to FHB symptom development, RKI and RTA exist among wheat cultivars/lines in western Japan. Such information is important to aid producers in controlling the disease and for breeders to improve FHB resistance and reduce mycotoxin accumulation in commercial wheat cultivars.     

Phenotypic and marker-assisted evaluation of spring and winter wheat germplasm for resistance to fusarium head blight

Fusarium head blight (FHB) caused by Fusarium species, is among the most devastating wheat diseases, causing losses in numerous sectors of the grain industry through yield and quality reduction, and the accumulation of poisonous mycotoxins. A germplasm collection of spring and winter wheat, including nine reference cultivars, was tested for Type II FHB resistance and deoxynivalenol (DON) content. Genetic diversity was evaluated on the basis of Simple Sequence Repeat (SSR) markers linked to FHB resistance quantitative trait loci (QTLs) and Diversity Arrays Technology (DArT) markers. The allele size of the SSR markers linked to FHB resistance QTLs from known resistance sources was compared to a germplasm collection to determine the presence of these QTLs and to identify potentially novel sources of resistance. Forty-two accessions were identified as resistant or moderately resistant to Fusarium spread, and two also had very low DON concentrations. Genetic relationships among wheat accessions were generally consistent with their geographic distribution and pedigree. SSR analysis revealed that several resistant accessions carried up to four of the tested QTLs. Resistant and moderately resistant lines without any known QTLs are considered to be novel sources of resistance that could be used for further genetic studies.     

Reaction of triticale,wheat and rye accessions to graminaceous Fusarium spp. infection at the seedling and adult plant growth stages

Summary Pathogenicity of 20 isolates of 12 Fusarium species recovered from triticale seed against seedlings of 14 varieties of winter cereals (triticale, wheat, and rye) was tested. The most pathogenic inoculum was a mixture of isolates (a composite isolate) of all the species. The following species were individually the most pathogenic: F. avenaceum, F. culmorum, F. sambucinum var. coeruleum, and F. graminearum. Winter triticale was more resistant to seedling blight than rye but more susceptible than wheat.Also reactions of 31 winter and 12 spring varieties of cereals to head inoculation with a composite isolate of 4 Fusarium spp. (F. avenaceum, F. culmorum, F. graminearum, and F. sambucinum var. coeruleum) was studied. In comparison to other cereals of similar type winter and spring wheat appeared to be the most susceptible while winter rye reaction was comparable to winter triticale. Spring and winter triticale varieties responded to head infection intermediately.There was no significant correlation between seedling and head reactions to infection with Fusarium spp. for winter rye and triticale. For winter wheat a negative trend was found. The above findings imply that screening of cereals at the seedling stage can not be used to predict the resistance to head blight. Nevertheless, resistance at the stage is highly desirable to prevent excessive damage of the crops due to the seedling blight incited by Fusarium spp..     

Combining different resistance components enhances resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight in spring wheat

Fusarium head blight (FHB) is a devastating disease in wheat throughout the world. FHB resistance consists of two components: resistance to initial infection (type I) and resistance to spread within infected spikes (type II). Current wheat breeding programs for FHB focus on type II resistance, which limits pathogen spread but may not be sufficiently durable. To combine type I with existing type II resistance, 113 F₉-derived recombinant inbred lines (RILs) were developed from a cross between three wheat genotypes Frontana, W9207, and Alsen. The RILs were evaluated for resistance to initial infection, FHB spread within spike, kernel damage, and deoxynivalenol (DON) content in two independent greenhouse experiments in 2006 and 2007. Among the 113 RILs, 20% lines showed ≤10% initial disease severity (IDS) and ≤11 to 30% final disease severity (FDS), and 19% had DON content ≤5 μg/g. Approximately 11% of the RILs showed tendency of higher resistance (as exhibited by lower IDS, FDS, and DON content) than the resistant parents. The 42 of the FHB-resistant RILs were analyzed with seven simple sequence repeat (SSR) markers or microsatellites known to be linked to FHB resistance. Approximately half of the RILs had molecular markers linked to both types of FHB resistance indicated the presence of type I and II resistance alleles in the RILs. The resistant RILs identified in this study should be useful for the future improvement of FHB resistance in spring wheat.     

Nature of wheat resistance to Fusarium head blight and the role of deoxynivalenol for breeding

Twenty (1990-93) and 25 (1994-96) wheat genotypes with different degrees of resistance and origins were tested with seven and eight isolates, respectively, of Fusarium graminearum and four Fusarium culmorum isolates of diverse origin in Europe. Infection severity depended largely on the genotypes and the isolates used. Head blight values, yield response and kernel infection values revealed close but varying relationships with deoxynivalenol (DON) content. This variability is explained by the presence of tolerance mechanisms which affect the relationship between Fusarium head blight severity and yield response. Kernel infection resistance accounted for decreasing Fusarium head blight values. Genotypes were found with lower infection severity and higher DON contamination and vice versa. Evidently, the cultivar has a significant influence on DON production in the infected tissue, i.e. highly susceptible genotypes may have moderate or low accumulation of DON. However, in the most resistant genotypes showing no infection to any of the isolates or only sporadic symptom development, no or very low accumulation of DON was detected. Resistant genotypes gave a stable reaction with b-values close to zero for all traits tested. Susceptible genotypes were unstable under different epidemic conditions and their stability was different for the traits investigated. Therefore, the mean of b-values is suggested to better describe the stability of the wheat genotypes. Significant positive relationships were found between aggressiveness of the isolates and their production of DON in the infected grain. The correlation improved significantly for the nivalenol-producing isolate (F89.4 from France) when the sum of DON and nivalenol contents were considered. This indicates that the total trichothecene toxin-producing capacity of the isolates may be a decisive component of pathogenicity. Since the tests included isolates from different European countries the results provide further proof that no host specificity exists within these pathogens in Europe. This was also valid for kernel infection, yield response and DON accumulation. Therefore, the nature of resistance is horizontal. The results also support the view that there is no difference between the resistance of the host plant to F. graminearum and to F. culmorum.     

Genetic variation for head blight resistance in triticale caused by Fusarium graminearum isolates of different deoxynivalenol production

Summary Fusarium head blight infection causes severe yield losses and contamination of the grain with mycotoxins in triticale (× Triticosecale Wittmack) grown in temperate and semihumid areas. In a two-year experiment thirty-six genotypes were inoculated separately with two isolates of Fusarium graminearum differing fivefold in their in vitro deoxynivalenol (DON) production and the effect on various traits was studied. All traits were significantly affected by head blight. The two isolates differed considerably in their aggressiveness resulting in a mean reduction of grain weight per spike of almost 25% and 50%, respectively. Inter-annual correlation was high for average disease rating (r=0.63, P<-0.01) and low for the other traits. Therefore, disease rating, averaged from two to three records, was regarded a suitable criterion for screening purposes. The effect of isolates on genotypes was not stable over years. The mean DON content of five genotypes with diverse resistance levels was 68 mg kg^-1. In vitro DON production of the two isolates used for inoculation did not correspond to their aggressiveness and DON contamination of the grain.     

Resistance to Fusarium head blight and deoxynivalenol accumulation in wheat

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe (telomorph =Gibberella zeae (Schw.)), is an important wheat disease world‐wide. Production of deoxynivalenol (DON) by F. graminearum in infected wheat grain is detrimental to livestock and is also a safety concern in human foods. An international collection of 116 wheat lines was evaluated for FHB resistance and concentration of DON in grain. Plants were inoculated with mixed isolates of F. graminearum in the greenhouse by injecting conidia into a single spikelet of each spike and in the field by scattering F. graminearum‐infected wheat kernels on the soil surface. FHB symptoms were evaluated by visual inspection in both the greenhouse and field, and DON was analysed by HPLC. Significant differences in FHB ratings and DON levels were observed among cultivars. In the greenhouse test, visual symptoms varied from no spread of FHB from the inoculated spikelet to spread throughout the spike, and DON levels ranged from trace levels to 283 mg/kg. In the field test, DON ranged from 2.8 to 52 mg/kg. The greenhouse test identified 16 wheat lines from various origins that accumulated less than 2 mg/kg DON. These lines may be useful as sources for breeding wheat cultivars with lower DON levels. Correlation coefficients were significant between FHB symptom ratings, seed quality traits, and DON levels. Thus, the percentage of scabbed spikelets and kernels can be generally used to predict DON levels in harvested wheat grain. In breeding programmes, selection for plants having few scabbed spikelets and scabbed kernels is most likely to result in low DON levels.     

Genotypic and environmental variation of resistance to head blight in triticale inoculated with Fusarium culmorum

Fusarium head blight (FHB) is a widespread disease of small‐grain cereals and can cause substantial losses in grain yield. To assess quantitative genetic parameters as a basis for an efficient breeding programme for resistance, 100 triticale (×Triticosecale Wittm.) genotypes were tested in various environments and artificially inoculated at anthesis with an aggressive isolate of Fusarium culmorum. A visual rating (1–9 scale) was used to assess head blight infection. Five grain yield traits relative to an uninoculated control were also measured. The mean value of the average rating, calculated from four or five readings, was 4.4. It ranged from 3.0 to 5.9 and showed continuous variation. Infection caused a 48% reduction of mean kernel weight per spike, which was the result of 26% fewer kernels per spike and a 32% lower 1000‐kernel weight. The 50‐ml kernel weight was affected by only 20%. The range and genotypic variation was highest for relative kernel weight per spike. For all relative grain yield traits, the most important source of variation was the environment, followed by genotype‐environment interaction, with genotype generally coming last. In contrast, genotypic variation was the most important factor for the disease rating, which also had the highest heritability (h²= 0.89). Phenotypic correlations between the average head blight rating and relative grain yield traits were moderate (r = 0.42–0.57). In conclusion, an average disease rating provides a quantitative assessment of resistance and is suitable for screening large numbers of genotypes. Relative kernel weight per spike gives a ranking of the genotypes that is very similar to the visual score.     

Relationship between European corn borer resistance and concentration of mycotoxins produced by Fusarium spp. in grains of transgenic Bt maize hybrids, their isogenic counterparts, and commercial varieties

The European corn borer (ECB), Ostrinia nubilalis Hb., is a major pest of maize in central Europe and promotes the infection of maize with Fusarium spp. In this study, transgenic Bt maize hybrids were compared with their isogenic counterparts, and with commercial hybrids from the recommended list with regard to their level of ECB resistance and their concentration of deoxynivalenol (DON), its 15‐acetyl (15‐A‐DON) and 3‐acetyl (3‐A‐DON) derivatives, nivalenol (NIV), fusarenon‐X (FUS‐X), fumonisins (FUM), and zearalenon (ZEN) in harvested grains. The field experiments were performed in Germany at four locations in 1999 and at five locations in 2000. Transgenic Bt hybrids showed significantly lower means than their corresponding isogenic counterparts and than commercial hybrids for all resistance traits: damage rating of stalks, number of larvae per plant, number of larvae per ear, and percentage of damaged plants or ears under infestation. Among all mycotoxins analysed, DON consistently showed the highest concentration across all year × location combinations. Mycotoxin concentrations varied significantly between locations, years and genotypes, whereas mycotoxin concentrations were not significantly different between infested and protected plots. Associations between ECB resistance traits and mycotoxin concentrations were not consistent across years. It is concluded that under central European conditions, the use of Bt maize hybrids will only slightly reduce the contamination of maize kernels with mycotoxins produced by Fusarium spp.     

Alleles on the two dwarfing loci on 4B and 4D are main drivers of FHB‐related traits in the Canadian winter wheat population “Vienna” × “25R47”

Fusarium head blight (FHB), leaf rust and stem rust are among the most destructive wheat diseases. High‐yielding, native disease resistance sources are available in North America. The objective of this study was to map loci associated with FHB traits, leaf rust, stem rust and plant height in a “Vienna”/”25R47” population. DArT markers were used to generate a genetic map, and quantitative trait loci (QTL) analysis was performed by evaluating 113 doubled haploid lines across three environments in Ontario, Canada. FHB resistance QTL were identified on chromosomes 4D, 4B, 2D and 7A, while a QTL for leaf and stem rust resistance was identified on chromosome 1B. The dwarfing alleles of both Rht‐B1 and Rht‐D1 were associated with increased FHB index and DON content.     

Means and variances for Fusarium head blight resistance of F2-derived bulks from winter triticale and winter wheat crosses

Fusarium head blight (FHB), caused by Fusarium graminearum and Fusarium culmorum, is a devastating disease in cereals. This study was undertaken to estimate progeny means and variances in each of five winter triticale and winter wheat crosses using unselected F₂−derived lines in F₄ or F₅ generation bulked at harvest of the previous generation. Fifty (triticale) and 95 (wheat) progeny per cross were inoculated in two (triticale) or three (wheat) field environments. FHB rating was assessed on a whole-plot basis. Mean disease severities of the parents ranged from 2.3 to 6.4 in triticale and from 3.1 to 6.5 in wheat on a 1-to-9 scale (1 = symptomless, 9 = 100% infected). The midparent values generally resembled the means of their derived progeny. Significant (P < 0.01) genotypic variance was detected within each cross, but genotype × environment interaction and error variances were also high for both crops. Medium to high entry-mean heritabilities (0.6–0.8) underline the feasibility of selecting F₂-derived bulks on a plot basis in several environments. Phenotypic correlation of FHB resistance between generation F_2:4 and F_2:5 was r = 0.87 (P < 0.01) tested across 150 wheat bulks at two locations. Our estimates of selection gain are encouraging for breeders to improve FHB resistance in triticale and wheat by recurrent selection within adapted materials.