For Fusarium Head Blight Resistance Research Articles

Appreciable genetic correlation between inbred lines and testcrosses facilitates breeding for resistance to Fusarium head blight in hybrid rye (Secale cereale)

AbstractHybrid breeding is based on selection of inbred lines in early generations. A sufficient genetic correlation between inbred lines and testcrosses is, however, the prerequisite for a higher selection gain in the hybrids. Therefore, we investigated this crucial parameter for Fusarium head blight (FHB) resistance on 60 inbred lines each of the heterotic groups Petkus and Carsten and their corresponding crosses with two testers each at four (inbred lines) or six (testcrosses) environments (location × year combinations). FHB severity measured as percentage of infected spikelets per plot was used as resistance trait, and a correction was made by using flowering time as covariate. Variances for genotype and genotype–environment interaction were high, and the heritability was estimated .84 and .74 for the line per se performance (Petkus and Carsten) and .71 and .78 for the general combining ability (GCA). For both inbred lines and testcrosses, negative correlations with plant height were found ranging from −.20 to −.51. FHB severity was considerably higher for the inbred lines than for the testcrosses. Genetic variance was lower for testcrosses, and dominance effects of the testers and heterosis may be key factors reducing the general infection level of three‐way hybrids. The effect of the tester (i.e., difference between testers) was very small and only significant for the Carsten group. The variance for specific combining ability (SCA) was very small, too. This, and high genetic correlations between line per se and GCA (r = .82 for Petkus and r = .72 for Carsten), does allow or even favour the selection based on line per se performance. Still, in the last generation before the official trials, testcrosses should also be tested for FHB resistance and mycotoxin contents to reliably improve food and feed quality in rye.

Genome-Wide Association Studies for Fusarium Head Blight Resistance and Its Trade-Off With Grain Yield in Soft Red Winter Wheat

Identification of quantitative trait loci for Fusarium head blight (FHB) resistance from different sources and pyramiding them into cultivars could provide effective protection against FHB. The objective of this study was to characterize a soft red winter wheat (SRWW) breeding population that has been subjected to intense germplasm introduction and alien introgression for FHB resistance in the past. The population was evaluated under misted FHB nurseries inoculated with Fusarium graminearum infested corn spawn for two years. Phenotypic data included disease incidence (INC), disease severity (SEV), Fusarium damaged kernels (FDK), FHB index (FHBdx), and deoxynivalenol concentration (DON). Genome-wide association studies by using 13,784 SNP markers identified twenty-five genomic regions at -logP ≥ 4.0 that were associated with five FHB-related traits. Of these 25, the marker trait associations that explained more than 5% phenotypic variation were localized on chromosomes 1A, 2B, 3B, 5A, 7A, 7B, and 7D, and from diverse sources including adapted SRWW lines such as Truman and Bess, and unadapted common wheat lines such as Ning7840 and Fundulea 201R. Furthermore, individuals with favorable alleles at the four loci Fhb1, Qfhb.nc-2B.1 (Q2B.1), Q7D.1, and Q7D.2 showed better FDK and DON scores (but not INC, SEV, and FHBdx) compared to other allelic combinations. Our data also showed while pyramiding multiple loci provides protection against FHB disease, it has significant trade-off with grain yield.

Identification of SSR markers for Fusarium head blight resistance in durum and bread wheat

In the present study, 25 durum and 25 bread wheat genotypes were evaluated during 2016 and 2017 for Fusarium head blight (FHB) resistance under greenhouse conditions. FHB severity ranged from 10.33% to 94.20%. Highly significant (p < 0.01) genotypes differences were observed, indicating abundant genetic variability. High broad-sense heritability (0.87) and high genetic advance (70.3%) were obtained for FHB severity, suggesting considerable genetic improvement by selection. Of 50 genotypes tested, 6 genotypes showed <20%, 20 genotypes had >50%, and 24 genotypes showed 20–50% disease severity. The most resistant genotypes were BeniSuef-5, Sohag-3, Ciccio, Svevo, WA-88 and Misr-1 with average FHB severity of 10.84, 11.42, 11.49, 14.09, 16.03 and 18.69%, respectively, suggesting the presence of FHB resistance genes. On average, durum wheat genotypes showed lower FHB severity (39.9%) compared to bread wheat (49.1%). Of 18 simple sequence repeat (SSR) markers tested, Xgwm292-5A and Xgwm533-3B could be considered as markers associated with FHB resistance in the tested genotypes. However, further molecular analysis would be performed to confirm their usefulness for marker-assisted selection in wheat breeding programs.

Optimizing Training Population Size and Content to Improve Prediction Accuracy of FHB-Related Traits in Wheat

Genomic selection combines phenotypic and molecular marker data from a training population to predict the genotypic values of untested lines. It can improve breeding efficiency as large pools of untested lines can be evaluated for selection. Training population (TP) composition is one of the most important factors affecting the accuracy of genomic prediction. The University of Minnesota wheat breeding program implements genomic selection at the F5 stage for Fusarium head blight (FHB) resistance. This study used field data for FHB resistance in wheat (Triticum aestivum L.) to investigate the use of small-size TPs designed with and without stratified sampling for three FHB traits in three different F5 populations (TP17, TP18, and TP19). We also compared the accuracies of these two TP design methods with the accuracy obtained from a large size TP. Lastly, we evaluated the impact on trait predictions when the parents of F5 lines were included in the TP. We found that the small size TP selected randomly, without stratification, had the lowest predictive ability across the three F5 populations and across the three traits. This trend was statistically significant (p = 0.05) for all three traits in TP17 and two traits in TP18. Designing a small-size TP by stratified sampling led to a higher accuracy than a large-size TP in most traits across TP18 and TP19; this is because stratified sampling allowed the selection of a small set of closely related lines. We also observed that the addition of parental lines to the TP and evaluating the TP in two replications led to an increase in predictive abilities in most cases.

Effectiveness of multigenerational transfer of Sumai 3 Fusarium head blight resistance in hard red spring wheat breeding populations

Several quantitative trait loci (QTL) have been identified for Fusarium head blight (FHB) resistance in the cultivar Sumai 3. Wheat breeders need to know which Sumai 3 loci are present in derived lines used as parents for effective marker-assisted selection for genetic improvement. This study was conducted to identify the loci in Sumai 3 derived parents that contribute FHB resistance in breeding populations. Three doubled haploid (DH) populations utilizing Sumai 3 derived parents, ND3085, ND744, and Alsen, were evaluated during 2007 and 2008 in FHB nurseries near Carman, MB, Ottawa, ON and Charlottetown, PE. The percentage of incidence, severity, Fusarium-damaged kernels (FDK), and deoxynivalenol (DON) accumulation were measured, and FHB index calculated. DNA markers at six FHB resistance loci detected in Sumai 3 were evaluated on the populations. For each trait, a t test was applied to means of observations pooled by parental type of each marker to determine which loci contributed to resistance. The alleles at 3BS and 5AS most frequently contributed to Type I and Type II FHB resistance, as well as to reduced FDK and DON in all three populations. Markers revealed resistance on 3BS and 5AS in Alsen, ND3085, and ND744, on 3BSc, 4D, and 6BS in ND744, on 4D in ND3085, and on 6BS in Alsen. In some environments, the susceptible parent Infinity contributed minor QTL on 2D, 3BSc, and 6BS. Likewise, Helios contributed minor QTL on 5AS and 6BS.

Association mapping of wheat Fusarium head blight resistance-related regions using a candidate-gene approach and their verification in a biparental population.

Markers, located in Dicer1 and Ara6 genes, which are likely involved in cross-kingdom RNA trafficking, are associated with FHB resistance in GABI wheat population and were validated in biparental population. Association studies are a common approach to detect marker-trait associations for Fusarium head blight (FHB) resistance in wheat (Triticum aestivum), although verification of detected associations is exceptional. In the present study, candidate-gene association mapping (CG) of genes from silencing and secretory pathways, which may be involved in wheat resistance against FHB and cross-kingdom RNA trafficking, was performed. Fourteen markers, located in nine genes, were tested for association with FHB resistance in 356 lines from the GABI (genome analysis of the biological system of plants) wheat population. Three markers located in the genes Dicer1 and Ara6 were shown to be significantly associated with the studied trait. Verification of this finding was performed using the recombinant inbred lines (RILs) population 'Apache×Biscay', segregating for four of our 14 selected markers. We could show association of the Ara6 marker with plant height as well as association with FHB resistance for three markers located in Rab5-like GTPase gene Ara6 and Dicer1. These results confirmed the trait-marker associations detected also in the CG approach. Gene products of the associated genes are involved in response of the plant to pathogens, plant metabolism and may be involved in cross-kingdom RNA trafficking efficiency. The markers detected in the GABI wheat population, which were also validated in the biparental population, can potentially be used in wheat breeding.

An experimental approach for estimating the genomic selection advantage for Fusarium head blight and Septoria tritici blotch in winter wheat.

The genomic selection advantage for Fusarium head blight is promising but failed for Septoria tritici blotch. Selection of new breeding parents based on predictions must be treated with caution. Genomic selection (GS) is an approach that uses whole-genome marker data to estimate breeding values of untested genotypes and holds the potential to improve the genetic gain in breeding programs by shortening the breeding cycle and increasing the selection intensity. However, reported realized gain from genomic selection is limited to few experiments. In this study, a training population of 1120 winter wheat lines derived from 14 bi-parental families was genotyped with genome-wide single nucleotide polymorphism markers and phenotyped for Fusarium head blight (FHB) and Septoria tritici blotch (STB) severity, plant height and heading date. We used weighted ridge regression best linear unbiased prediction to calculate genomic estimated breeding values (GEBVs) of 2500 genotypes. Based on GEBVs, we selected the most resistant individuals as well as a random sample and tested them in a multi-location field trial. We computed moderate coefficients of correlation between observed and predicted trait values for FHB severity, plant height and heading date and achieved a genomic selection advantage of 10.62 percentage points for FHB resistance compared to the randomly chosen subpopulation. Genomic selection failed for the improvement of STB resistance with a genomic selection advantage of only 2.14 percentage points. Our results also indicate that the selection of new breeding parents based on GEBVs must be treated with caution. Taken together, the implementation of GS for FHB resistance, plant height and heading date seems to be promising. For traits with very strong genotype × environment variance, like STB resistance, GS appears to be still challenging.

Map-based cloning of QFhb.mgb-2A identifies a WAK2 gene responsible for Fusarium Head Blight resistance in wheat

Fusarium graminearum is one of the most threating pathogen of wheat, responsible for Fusarium head blight (FHB) which annually leads to yield losses, grain quality decay and accumulation of harmful mycotoxins in kernels. Host resistance represents the most effective approach to limit disease damages; however, only a limited number of resistant loci have currently been detected in durum genotypes. In this work we report the map-based cloning of a FHB-QTL on 2A chromosome of durum wheat, introgressed from a resistant line derived from the Chinese wheat cv. Sumai-3. A marker enrichment of the QTL region was carried out leading to the inclusion of 27 new SNPs respect to the previous map. A wall-associated receptor-like kinase (WAK2) gene was identified in the region and sequenced, in the resistant parent (RP) one gene was predicted accounting for a genomic sequence of 5,613 structured into 6 exons, whereas two adjacent genes were predicted on the same DNA plus strand of the susceptible parent (SP).t The involvement of WAK2 gene in FHB resistance mechanism was assessed by gene expression comparison between resistant and susceptible wheat lines, and disease symptoms evaluation in 3 TILLING mutants for WAK protein function.

High density genetic mapping of Fusarium head blight resistance QTL in tetraploid wheat.

Breeding for Fusarium head blight (FHB) resistance in durum wheat is complicated by the quantitative trait expression and narrow genetic diversity of available resources. High-density mapping of the FHB resistance quantitative trait loci (QTL), evaluation of their co-localization with plant height and maturity QTL and the interaction among the identified QTL are the objectives of this study. Two doubled haploid (DH) populations, one developed from crosses between Triticum turgidum ssp. durum lines DT707 and DT696 and the other between T. turgidum ssp. durum cv. Strongfield and T. turgidum ssp. carthlicum cv. Blackbird were genotyped using the 90K Infinium iSelect chip and evaluated phenotypically at multiple field FHB nurseries over years. A moderate broad-sense heritability indicated a genotype-by-environment interaction for the expression of FHB resistance in both populations. Resistance QTL were identified for the DT707 × DT696 population on chromosomes 1B, 2B, 5A (two loci) and 7A and for the Strongfield × Blackbird population on chromosomes 1A, 2A, 2B, 3A, 6A, 6B and 7B with the QTL on chromosome 1A and those on chromosome 5A being more consistently expressed over environments. FHB resistance co-located with plant height and maturity QTL on chromosome 5A and with a maturity QTL on chromosome 7A for the DT707 × DT696 population. Resistance also co-located with plant height QTL on chromosomes 2A and 3A and with maturity QTL on chromosomes 1A and 7B for the Strongfield × Blackbird population. Additive × additive interactions were identified, for example between the two FHB resistance QTL on chromosome 5A for the DT707 × DT696 population and the FHB resistance QTL on chromosomes 1A and 7B for the Strongfield × Blackbird population. Application of the Single Nucleotide Polymorphic (SNP) markers associated with FHB resistance QTL identified in this study will accelerate combining genes from the two populations.

Cloning and characterization of a specific UDP-glycosyltransferase gene induced by DON and Fusarium graminearum.

TaUGT5: can reduce the proliferation and destruction of F. graminearum and enhance the ability of FHB resistance in wheat. Deoxynivalenol (DON) is one of the most important toxins produced by Fusarium species that enhances the spread of the pathogen in the host. As a defense, the UDP-glycosyltransferase (UGT) family has been deduced to transform DON into the less toxic form DON-3-O-glucoside (D3G), but the specific gene member in wheat that is responsible for Fusarium head blight (FHB) resistance has been little investigated and proved. In this study, a DON and Fusarium graminearum responsive gene TaUGT5, which is specific for resistant cultivars, was cloned with a 1431bp open reading frame (ORF) encoding 476 amino acids in Sumai3. TaUGT5 is located on chromosome 2B, which has been confirmed in nulli-tetrasomic lines of Chinese Spring (CS) and is solely expressed among three homologs on the A, B and D genomes. Over-expression of this gene in Arabidopsis conferred enhanced tolerance when grown on agar plates that contain DON. Similarly, the coleoptiles of wheat over-expressing TaUGT5 showed more resistance to F. graminearum, evidencing reduced proliferation and destruction of plant tissue by the pathogen. However, the disease resistance in spikes was not as significant as that on coleoptile compared with wild-type plants. A subcellular localization analysis revealed that TaUGT5 was localized on the plasma membrane of tobacco leaf epidermal cells. It is possible that TaUGT5 could enhance tolerance to DON, protect the plant cell from the pathogen infection and result in better maintenance of the cell structure, which slows down pathogen proliferation in plant tissue.

Quantitative trait loci associated to Fusarium head blight resistance in wheat populations containing Annong–1124 and Zhoumai–27

The selection for Fusarium head blight (FHB) resistance is a bit difficult in breeding programs due to the complex inheritance of the resistance genes and the climatic effect on disease vigorous and expression. The present study was performed to assess microsatellite markers related to the resistance against FHB and examine the efficiency of these microsatellite markers while choosing for the resistance genes in all populations derived from a resistant parent. Both recombinant inbred lines (RIL) of Annong1124 (02P67/Aizao87//Yangmai158) and segregating lines of Zhoumai–27 × Shengxuani–6 were evaluated for their resistance to FHB by inoculating with Fusarium graminearum in the greenhouse as well as in the field. A total of 19 and 15 microsatellite markers from the chromosomes 3BS and 5A, respectively, were applied to RIL and each population of Zhoumai–27 (F2, F3). On the other hand, seven microsatellite markers from chromosomes 4B were applied to F2 and F3 segregating populations but there was a general lack of marker polymorphism on 4B for the employed parents of RIL. The most significant SSR markers were detected on the chromosome 3B and 5A explaining 7.30% and 21.74% of phenotypic variation, respectively, for the resistance in the RIL. The best quantitative trait loci (QTL) were detected on 4B for F2 and F3 populations with marker interval of WMC238-GWM66 with the LOD score 40.49 and 41.52, respectively. The phenotypic variations for F2 and F3 on chromosome 5A were detected with the account of 0.49 and 2.33 (BARC197-GWM179), respectively. The additive effects on chromosomes 3BS, 4B, and 5A were clearly higher in F3 population as compared to the F2 population. SSR markers on the chromosome 3BS in addition to SSR markers on 4B and 5A have the potential for improving the wheat cultivars with improved FHB resistance through the use of marker-assisted selection.

Registration of ‘Pembroke 2014’ Soft Red Winter Wheat

The Kentucky wheat (Triticum aestivum L.) crop is always at risk for Fusarium head blight (FHB) because of the prevalent grain crop rotation used by farmers. Corn (Zea mays L.) is followed by wheat, which is followed by double‐crop soybean [Glycine max (L.) Merr.]. The wheat crop is planted directly into corn stubble that harbors the causal fungus for FHB, Fusarium graminearum Schwabe. Therefore, developing FHB‐resistant winter wheat cultivars is a major goal of the wheat breeding program in Kentucky. ‘Pembroke 2014’ (Reg. No. CV‐1113, PI 675564) is an early maturing, semidwarf soft red winter wheat cultivar developed and released in 2014 by the Kentucky Agricultural Experiment Station for the combination of resistance to FHB, high yield potential, excellent test weight, and resistance to lodging. Pembroke 2014 was developed from the cross ‘25R18’/KY92C‐0010‐17//KY96C‐0767‐1. 25R18 is a soft red winter wheat cultivar with FHB resistance that likely traces to ‘Sumai 3’ or one of its derivatives. KY92C‐0010‐17 is a breeding line derived from the cross T63/VA85‐54‐290. KY96C‐0767‐1 is derived from the cross ‘2552’/VA92‐51‐12. The cross was made in 2003, and Pembroke 2014 was initially selected from F4:5 headrows in 2008 using a modified bulk breeding method. Selected rows that gave rise to Pembroke 2014, tested as KY03C‐1237‐32, carried the resistance allele at a major FHB resistance quantitative trait locus, Fhb1. Pembroke 2014 was extensively tested in multilocation replicated yield trials, the Uniform Eastern Soft Red Winter Wheat Nursery, the Uniform Northern Scab Nursery, and the Kentucky Wheat Variety Trial.

Registration of Near-Isogenic Winter Wheat Germplasm Contrasting in Fhb1 for Fusarium Head Blight Resistance

The Chinese wheat germplasm Ning7840 (Triticum aestivum L.) contains Fhb1, a quantitative trait locus (QTL) for Fusarium head blight (FHB) resistance that explains as much as 53% of the phenotypic variation in segregating populations. Ning7840 has been widely used as a resistant parent in breeding programs worldwide, but because of its poor adaptation in the United States, its progenies usually exhibit reduced grain yield due to the transfer of undesirable genes from Ning7840. The development of five near-isogenic lines (NILs: ‘Clark’*7/Ning7840) (NIL75, Reg. No. GS-174, PI 668559; NIL78, Reg. No. GS-175, PI 668560; NIL80, Reg. No. GS-176, PI 668561; NIL90, Reg. No. GS-177, PI 668562; NIL98, Reg. No. GS-178, PI 668563) contrasting in Fhb1 alleles was intended to overcome this potential limitation. Marker-assisted backcrossing was used to develop the NILs. Approximately 2000 BC7F2 plants from the backcross of Ning7840 by Clark (recurrent parent) were screened with two Fhb1-flanking markers (Xgwm533 and Xgwm493), and selected BC7F3 families were evaluated for FHB resistance in greenhouses. Both genotypic and phenotypic data confirm the presence of Fhb1 in the four resistant NILs and absence in the one susceptible NIL. All resistant NILs had significantly higher FHB resistance and lower deoxynivalenol content than Clark and the susceptible NIL but yield similar to Clark (P = 0.295). Marker-assisted backcross efficiently transferred Fhb1 into U.S. hard winter wheat without transferring undesirable traits from Ning7840, and these Fhb1 NILs should be useful parents for effective use of Fhb1 in U.S. winter wheat.

Effects of introgression of two QTL for fusarium head blight resistance from Asian spring wheat by marker-assisted backcrossing into European winter wheat on fusarium head blight resistance, yield and quality traits

Breeding for fusarium head blight (FHB) resistance of wheat is a continuous challenge for plant breeders. Resistance to FHB is a quantitative trait, governed by several to many genes and modulated by environmental conditions. The presented study was undertaken to assess the effect on improving FHB resistance and on possible unwanted side effects (‘linkage drag’) of two resistance QTL, namely Fhb1 and Qfhs.ifa-5A, from the spring wheat line CM-82036 when transferred by marker-assisted backcrossing into several European winter wheat lines. To achieve these goals, we developed and evaluated fifteen backcross-two–derived families based on nine European winter wheat varieties as recipients and the FHB resistant variety CM-82036 as resistance donor. The QTL Qfhs.ifa-5A had a relatively small impact on increasing FHB resistance. On average lines with Fhb1 plus Qfhs.ifa-5A combined were only slightly more resistant compared to lines with Fhb1 alone. The obtained results suggest that the effect of the spring wheat–derived QTL on improving FHB resistance increases in the order Qfhs.ifa-5A < Fhb1 ≤ Qfhs.ifa-5A plus Fhb1 combined. The genetic background of the recipient line had a large impact on the resistance level of the obtained lines. No systematic negative effect of the spring wheat–derived QTL on grain yield, thousand grain weight, hectoliter weight and protein content was found. The use of spring wheat–derived FHB resistance QTL for breeding high yielding cultivars with improved FHB resistance appears therefore highly promising.

Indirect selection for lower deoxynivalenol (DON) content in grain in a winter wheat population

Selection for Fusarium head blight (FHB) resistance and lower deoxynivalenol (DON) content is an important goal in many wheat-breeding programs worldwide. Preliminary screening for less severe FHB symptoms in the early segregating generations can be an important tool to assist breeders in determining which lines to advance to homozygosity. The objectives of this study were: (1) to test influence of plant height, heading date, presence of awns and number of spikelets per spike on FHB index and DON content and (2) to estimate the reliability of indirect selection for lower DON content based on FHB index. A Ruby × Frontana winter wheat population was spray inoculated with a spore suspension of Fusarium graminearum in 2001 and 2002. Plant height was significantly associated with DON content in both years; taller lines accumulated less DON than shorter ones. The moderately resistant lines, based on FHB index after in oculation, had a statistically lower DON accumulation compared with the highly susceptible ones (17.7 ppm vs. 20.6 ppm and 0.6 ppm vs. 2.0 ppm in 2001 and 2002) respectively. The results from this study suggest that selection for FHB resistance can be an indirect selection method for lowering DON accumulation in wheat grain. A breeder can identify and discard those early generation lines that are highly susceptible to FHB as they likely would have higher DON levels. Key words: Fusarium graminearum (Schwabe), morphology, resistance, Triticum aestivum L.

Quantitative Trait Loci Controlling Fusarium Head Blight Resistance and Low Deoxynivalenol Content in Hexaploid Wheat Population from ‘Arina’ and NK93604

ABSTRACTBreeding for Fusarium head blight (FHB) resistant wheat adapted to the Norwegian climatic conditions is one of the top priorities in the country. This study was conducted to characterize QTLs for FHB resistance and low deoxynivalenol (DON) content in a population of 93 double haploid lines from a cross between ‘Arina’ and NK93604. Both parents have moderate levels of resistance to FHB. The population was assessed for FHB resistance under field conditions for 3 yr (2001 to 2003), and DON content was analyzed from seed samples in the 2002 experiment. The two traits showed significant genetic variation and were significantly correlated with each other. Composite interval mapping (CIM) identified four QTLs using the 3 yr mean for FHB resistance on chromosomes 1AL, 1BL, 6BS, and 7AL. The QTLs on 1AL, 1BL, and 7AL were consistently detected in all 3 yr, and explained 27.9, 19.6, and 14.8% of the phenotypic variation, respectively. The QTLs on chromosomes 1BL and 6BS originated from Arina, whereas those on 1AL and 7AL were from NK93604. None of the QTLs for FHB resistance detected in this study were coincident with those previously reported in the Arina/‘Forno’ population. Two major QTLs, both derived from NK93604, on chromosomes 1AL and 2AS were identified for DON content that explained 27.9 and 26.7% of the variation, respectively. A major QTL for FHB resistance on 1AL coincided with a QTL for DON content. As far as we are aware, the QTL on chromosome 1AL is novel and not reported elsewhere. Data from the present study provides breeders with additional information on chromosomal regions associated with FHB resistance and DON content in European wheats and will help guide the development of FHB‐resistant wheat.

Mapping of FHB resistance QTLs in tetraploid wheat

Triticum turgidum L var. durum is known to be particularly susceptible to infection by Fusarium graminearum, the causal agent for Fusarium head blight (FHB), which results in severe yield losses and grain contaminated with mycotoxins. This research was aimed at identifying FHB resistance in tetraploid wheat and mapping the location of FHB resistance genes. A tetraploid cross of durum wheat ('Strongfield') x Triticum carthlicum ('Blackbird') was used to generate a doubled-haploid (DH) population. This population was evaluated for type II resistance to F. graminearum in replicated greenhouse trials, in which heads were innoculated and the percent of infected spikelets was determined 21 days later. The population was also genotyped with microsatellite markers to construct a map of 424 loci, covering 2 052 cM. The FHB reaction and genotypic data were used to identify FHB resistance quantitative trait loci (QTLs). It was determined that 2 intervals on chromosomes 2BL and 6BS controlled FHB resistance in this tetraploid cross. The FHB resistance allele on chromosome 2BL (r2=0.26, logarithm of odds (LOD)=8.5) was derived from 'Strongfield', and the FHB resistance allele on chromosome 6BS (r2=0.23, LOD=6.6) was derived from 'Blackbird'. Two other loci, on chromosomes 5AS and 2AL, were shown to regulate FHB infection and to have an epistatic effect on the FHB resistance QTL on chromosome 6BS. Further, the FHB resistance QTL peak on chromosome 6BS was clearly coincident with the known FHB resistance gene Fhb2, derived from Sumai 3. The results show that FHB resistance can be expressed in durum wheat, and that T. carthlicum and Triticum aestivum likely share a common FHB resistance gene on chromosome 6BS.

Field resistance of Martonvásár winter wheat cultivars against Fusarium head blight

Fifty Triticum aestivum genotypes, including winter wheat cultivars from Martonvásár, were tested for fusarium head blight (FHB) resistance under artificially inoculated conditions. Field resistance, kernel infection, and the relative yield components (test weight, thousand kernel weight and kernel weight/heads) were examined following infection with Fusarium graminearum and F. culmorum isolates. Using data from two years, a number of Martonvásár varieties with above-average resistance to FHB were identified. On the basis of field infection, AUDPC values close to those of resistance sources were calculated for the variety Mv Emese, while 67.5% of the varieties tested had values which did not differ significantly from those of the control variety Arina. The yield components examined were modified substantially by artificial FHB infection. The thousand kernel weight and test weight of the variety exhibiting the greatest degree of infection were only 21.14% and 25.58%, respectively, of the untreated control. In one case the decline in the kernel weight/head was more than 90%. The results of multivariable statistical analysis indicated that among the Hungarian wheat genotypes, Bánkúti 1201, B9086-95 (a line derived from Bánkúti 1201), Mv Emese, Martonvásári4 and Mv Táltos could be grouped with the best sources of resistance. The experimental data revealed wide genetic variability for FHB resistance in the Martonvásár breeding stock.

Fusarium head blight reactions and accumulation of deoxynivalenol, moniliformin and zearalenone in wheat grains

Deoxynivalenol (DON), moniliformin (MON) and zearalenone (ZON) are the most important mycotoxins detected in Fusarium infected wheat grains in Austria. Our goal was to identify an evaluation method for Fusarium head blight (FHB) symptoms, which is closely related to the toxin content in grains of artificially inoculated wheat genotypes. In total 108 wheat lines with varying FHB resistance were treated with F. culmorum (DON producer), F. avenaceum (MON producer) or F. graminearum (ZON producer). Several FHB evaluation methods were investigated and the data were correlated with the mycotoxin content of the grains. Data on the visual scores of the FHB development in the field, percentage of Fusarium damaged kernels and specific grain weight showed acceptable correlations with the DON content (r=0.75-0.81). MON contamination was closely related to the percentage of Fusarium damaged kernels (r=0.70). No suitable method was identified to predict ZON concentrations. Only in grain samples of highly resistant genotypes consistently a low ZON content was measured.

Marker Assisted Evaluation of Fusarium Head Blight Resistant Wheat Germplasm

A major QTL (quantitative trait locus) for Fusarium head blight (FHB) resistance, Qfhs.ndsu‐3BS, derived from ‘Sumai 3’, has been identified and verified by several research groups via molecular marker analysis. Further study of this QTL is worthwhile because it explains a large portion (25–60%) of the variation in FHB resistance in the reported studies. The objectives of this study were to (i) identify additional molecular markers for Qfhs.ndsu‐3BS, (ii) construct a cytologically based physical map of chromosome 3BS, and (iii) identify germplasm with novel FHB resistance genes with SSR markers near Qfhs.ndsu‐3BS Two new simple sequence repeat (SSR) markers (XBARC133 and XBARC102), two sequence tagged site (STS) markers (XSTS3B1 and Xsun2), and one restriction fragment length polymorphism (RFLP) marker (Xfbb185), were mapped to the Qfhs.ndsu‐3BS region. On the basis of deletion line analysis, this major QTL is likely located on the deletion bin 3BS 0.78‐0.87. Fifty‐four FHB resistant lines from throughout the world and 20 North American spring wheat (Triticum aestivum L.) lines of historical prominence were genotyped by five SSR markers (Xgwm389, Xgwm533, XBARC133, Xgwm493, and XBARC102) associated with Qfhs.ndsu‐3BS The Sumai 3 haplotype is rare. Only 25 out of 54 FHB resistant lines and one North American spring wheat line have Sumai 3‐type alleles for at least one of these five SSR markers. Twelve FHB resistant lines have the same SSR allele as Sumai 3 for at least four of the five SSR markers, and therefore most likely contain this major QTL. The other 42 FHB resistant lines may carry novel FHB resistance genes, and are worthy of further genetic study.