Molecular mapping of resistance to Fusarium head blight in the spring wheat cultivar Frontana

Identification of Two Novel QTL for Fusarium Head Blight Resistance in German Wheat Cultivar Centrum

Fusarium head blight (FHB) is a devastating disease that occurs in warm and humid environments. The German wheat 'Centrum' has displayed moderate to high levels of FHB resistance in the field for many years. In this study, an F6:8 recombinant inbred line (RIL) population derived from cross 'Centrum' × 'Xinong 979' was evaluated for FHB response following point inoculation in five environments. The population and parents were genotyped using the GenoBaits Wheat 16 K Panel. Stable quantitative trait loci (QTL) associated with FHB resistance in 'Centrum' were mapped on chromosome arms 2DS and 5BS. The most effective QTL, located in 2DS, was identified as a new chromosome region represented by a 1.4 Mb interval containing 17 candidate genes. Another novel QTL was mapped in chromosome arm 5BS of a 5BS to 7BS translocation chromosome. In addition, two environmentally sensitive QTL were mapped on chromosome arms 2BL from 'Centrum' and 5AS from 'Xinong 979'. Polymorphisms of flanking phenotypic variance explained (PVE) markers (allele-specific quantitative PCR [AQP]) AQP-6 for QFhb.nwafu-2DS and 16K-13073 for QFhb.nwafu-5BS were validated in a panel of 217 cultivars and breeding lines. These markers could be useful for marker-assisted selection (MAS) of FHB resistance and provide a starting point for fine mapping and marker-based cloning of the resistance genes.

Effects of wheat varieties, fungicides and application time on Fusarium head blight and deoxynivalenol contamination control in wheat

BACKGROUND

Yield loss and toxin contamination caused by wheat Fusarium head blight (FHB) have always been a worldwide concern. Cultivating disease-resistant varieties and fungicide application are effective measures to control FHB. The comprehensive control technology system for FHB and toxin contamination of wheat in Anhui Province needs further improvement. This study compared the control efficacy of different wheat varieties, fungicides and application times on wheat FHB and deoxynivalenol (DON) contamination, and the dynamic change of DON accumulation after application.

RESULTS

Among the 93 main wheat varieties in Anhui Province, the disease-resistant and low-toxic wheat variety "Ningmai 26" was more suitable for planting in the central part of Anhui Province. At the same time, "Yangmai 22" was used for subsequent experiments. The field efficacy trials of different fungicides showed that 30% prothioconazole oil dispersion (OD) had the highest control efficacy on FHB and DON contamination, reaching 94.33 and 77.49%, respectively. The study on the optimum application time of prothioconazole showed that the 0-20% flowering stage was the key point of DON control. The survey of the dynamic changes of DON accumulation showed that prothioconazole could significantly reduce the level of DON accumulation while inhibiting the accumulation rate of DON. At the same time, the control fungicide carbendazim increased the level of DON contamination.

CONCLUSION

This study will provide excellent germplasm resources for cultivating disease-resistant and low-toxic wheat varieties, and provide a theoretical reference for establishing a collaborative prevention and control system of disease control and toxin reduction. © 2023 Society of Chemical Industry.

Multi-locus genome-wide association study of fusarium head blight in relation to days to anthesis and plant height in a spring wheat association panel

Fusarium head blight (FHB) is a highly destructive fungal disease of wheat to which host resistance is quantitatively inherited and largely influenced by the environment. Resistance to FHB has been associated with taller height and later maturity; however, a further understanding of these relationships is needed. An association mapping panel (AMP) of 192 predominantly Canadian spring wheat was genotyped with the wheat 90K single-nucleotide polymorphism (SNP) array. The AMP was assessed for FHB incidence (INC), severity (SEV) and index (IND), days to anthesis (DTA), and plant height (PLHT) between 2015 and 2017 at three Canadian FHB-inoculated nurseries. Seven multi-environment trial (MET) datasets were deployed in a genome-wide association study (GWAS) using a single-locus mixed linear model (MLM) and a multi-locus random SNP-effect mixed linear model (mrMLM). MLM detected four quantitative trait nucleotides (QTNs) for INC on chromosomes 2D and 3D and for SEV and IND on chromosome 3B. Further, mrMLM identified 291 QTNs: 50 (INC), 72 (SEV), 90 (IND), 41 (DTA), and 38 (PLHT). At two or more environments, 17 QTNs for FHB, DTA, and PLHT were detected. Of these 17, 12 QTNs were pleiotropic for FHB traits, DTA, and PLHT on chromosomes 1A, 1D, 2D, 3B, 5A, 6B, 7A, and 7B; two QTNs for DTA were detected on chromosomes 1B and 7A; and three PLHT QTNs were located on chromosomes 4B and 6B. The 1B DTA QTN and the three pleiotropic QTNs on chromosomes 1A, 3B, and 6B are potentially identical to corresponding quantitative trait loci (QTLs) in durum wheat. Further, the 3B pleiotropic QTN for FHB INC, SEV, and IND co-locates with TraesCS3B02G024900 within the Fhb1 region on chromosome 3B and is ~3 Mb from a cloned Fhb1 candidate gene TaHRC. While the PLHT QTN on chromosome 6B is putatively novel, the 1B DTA QTN co-locates with a disease resistance protein located ~10 Mb from a Flowering Locus T1-like gene TaFT3-B1, and the 7A DTA QTN is ~5 Mb away from a maturity QTL QMat.dms-7A.3 of another study. GWAS and QTN candidate genes enabled the characterization of FHB resistance in relation to DTA and PLHT. This approach should eventually generate additional and reliable trait-specific markers for breeding selection, in addition to providing useful information for FHB trait discovery.

High-density genetic mapping of Fusarium head blight resistance and agronomic traits in spring wheat

Fusarium head blight (FHB) has rapidly become a major challenge to successful wheat production and competitive end-use quality in western Canada. Continuous effort is required to develop germplasm with improved FHB resistance and understand how to incorporate the material into crossing schemes for marker-assisted selection and genomic selection. The aim of this study was to map quantitative trait loci (QTL) responsible for the expression of FHB resistance in two adapted cultivars and to evaluate their co-localization with plant height, days to maturity, days to heading, and awnedness. A large doubled haploid population of 775 lines developed from cultivars Carberry and AC Cadillac was assessed for FHB incidence and severity in nurseries near Portage la Prairie, Brandon, and Morden in different years, and for plant height, awnedness, days to heading, and days to maturity near Swift Current. An initial linkage map using a subset of 261 lines was constructed using 634 polymorphic DArT and SSR markers. QTL analysis revealed five resistance QTL on chromosomes 2A, 3B (two loci), 4B, and 5A. A second genetic map with increased marker density was constructed using the Infinium iSelect 90k SNP wheat array in addition to the previous DArT and SSR markers, which revealed two additional QTL on 6A and 6D. The complete population was genotyped, and a total of 6,806 Infinium iSelect 90k SNP polymorphic markers were used to identify 17 putative resistance QTL on 14 different chromosomes. As with the smaller population size and fewer markers, large-effect QTL were detected on 3B, 4B, and 5A that were consistently expressed across environments. FHB resistance QTL were co-localized with plant height QTL on chromosomes 4B, 6D, and 7D; days to heading on 2B, 3A, 4A, 4B, and 5A; and maturity on 3A, 4B, and 7D. A major QTL for awnedness was identified as being associated with FHB resistance on chromosome 5A. Nine small-effect QTL were not associated with any of the agronomic traits, whereas 13 QTL that were associated with agronomic traits did not co-localize with any of the FHB traits. There is an opportunity to select for improved FHB resistance within adapted cultivars by using markers associated with complementary QTL.

Characterization of Brazilian spring wheat germplasm and its potential for increasing wheat genetic diversity in Canada

In the present era of climate instability, Canadian wheat production has been frequently affected by abiotic stresses and by dynamic populations of pathogens and pests that are more virulent and aggressive over time. Genetic diversity is fundamental to guarantee sustainable and improved wheat production. In the past, the genetics of Brazilian cultivars, such as Frontana, have been studied by Canadian researchers and consequently, Brazilian germplasm has been used to breed Canadian wheat cultivars. The objective of this study was to characterize a collection of Brazilian germplasm under Canadian growing conditions, including the reaction of the Brazilian germplasm to Canadian isolates/pathogens and to predict the presence of certain genes in an effort to increase genetic diversity, improve genetic gain and resilience of Canadian wheat. Over 100 Brazilian hard red spring wheat cultivars released from 1986 to 2016 were evaluated for their agronomic performance in eastern Canada. Some cultivars showed good adaptability, with several cultivars being superior or statistically equal to the highest yielding Canadian checks. Several Brazilian cultivars had excellent resistance to leaf rust, even though only a few of these tested positive for the presence of either Lr34 or Lr16, two of the most common resistance genes in Canadian wheat. Resistance for stem rust, stripe rust and powdery mildew was variable among the Brazilian cultivars. However, many Brazilian cultivars had high levels of resistance to Canadian and African - Ug99 strains of stem rust. Many Brazilian cultivars had good Fusarium head blight (FHB) resistance, which appears to be derived from Frontana. In contrast FHB resistance in Canadian wheat is largely based on the Chinese variety, Sumai-3. The Brazilian germplasm is a valuable source of semi-dwarf (Rht) genes, and 75% of the Brazilian collection possessed Rht-B1b. Many cultivars in the Brazilian collection were found to be genetically distinct from Canadian wheat, making them a valuable resource to increase the disease resistance and genetic variability in Canada and elsewhere.

Recent advances on genome-wide association studies (GWAS) and genomic selection (GS); prospects for Fusarium head blight research in Durum wheat

PURPOSE

Wheat is an important cereal crop that is cultivated in different parts of the world. The biotic stresses are the major concerns in wheat-growing nations and are responsible for production loss globally. The change in climate dynamics makes the pathogen more virulent in foothills and tropical regions. There is growing concern about FHB in major wheat-growing nations, and until now, there has been no known potential source of resistance identified in wheat germplasm. The plant pathogen interaction activates the cascade of pathways, genes, TFs, and resistance genes. Pathogenesis-related genes' role in disease resistance is functionally validated in different plant systems. Similarly, Genomewide association Studies (GWAS) and Genomic selection (GS) are promising tools and have led to the discovery of resistance genes, genomic regions, and novel markers. Fusarium graminearum produces deoxynivalenol (DON) mycotoxins in wheat kernels, affecting wheat productivity globally. Modern technology now allows for detecting and managing DON toxin to reduce the risk to humans and animals. This review offers a comprehensive overview of the roles played by GWAS and Genomic selection (GS) in the identification of new genes, genetic variants, molecular markers and DON toxin management strategies.

METHODS

The review offers a comprehensive and in-depth analysis of the function of Fusarium graminearum virulence factors in Durum wheat. The role of GWAS and GS for Fusarium Head Blight (FHB) resistance has been well described. This paper provides a comprehensive description of the various statistical models that are used in GWAS and GS. In this review, we look at how different detection methods have been used to analyze and manage DON toxin exposure.

RESULTS

This review highlights the role of virulent genes in Fusarium disease establishment. The role of genome-based selection offers the identification of novel QTLs in resistant wheat germplasm. The role of GWAS and GS selection has minimized the use of population development through breeding technology. Here, we also emphasized the function of recent technological developments in minimizing the impact of DON toxins and their implications for food safety.

Fhb1 disease resistance QTL does not exacerbate wheat grain protein loss at elevated CO2

Fusarium head blight, a devastating cereal crop disease, can cause significant yield losses and contaminate grain with hazardous fungal toxins. Concerningly, recent evidence indicates that substantial grain protein content loss is likely to occur in wheat that is moderately resistant to head blight when it is grown at elevated CO₂. Although wheat breeders in North America utilize a number of resistance sources and genes to reduce pathogen damage, the Fhb1 gene is widely deployed. To determine whether Fhb1 is associated with the protein content loss at elevated CO₂, twelve near-isogenic spring wheat lines from either a susceptible or moderately susceptible genetic background, and with, or without the Fhb1 QTL, were grown at ambient and elevated CO₂ conditions. The near-isogenic lines were evaluated for differences in physiology, productivity, and grain protein content. Our results showed that the Fhb1 QTL did not have any significant effect on plant growth, development, yield, or grain protein content at ambient or elevated CO_2. Therefore, other factors in the moderately susceptible wheat genetic background are likely responsible for the more severe grain protein loss at elevated CO₂.

QTL mapping and genomic prediction of resistance to wheat head blight caused by Fusarium verticillioides

Fusarium head blight (FHB), is one of the destructive fugue diseases of wheat worldwide caused by the Fusarium verticillioides (F.v). In this study, a population consisting of 262 recombinant inbred lines (RILs) derived from Zhongmai 578 and Jimai 22 was used to map Quantitative Trait Locus (QTL) for FHB resistance, with the genotype data using the wheat 50 K single nucleotide polymorphism (SNP) array. The percentage of symptomatic spikelet (PSS) and the weighted average of PSS (PSSW) were collected for each RIL to represent their resistance to wheat head blight caused by F.v. In total, 22 QTL associated with FHB resistance were identified on chromosomes 1D, 2B, 3B, 4A, 5D, 7A, 7B, and 7D, respectively, from which 10 and 12 QTL were detected from PSS and PSSW respectively, explaining 3.82%-10.57% of the phenotypic variances using the inclusive composite interval mapping method. One novel QTL, Qfhb. haust-4A.1, was identified, explaining 10.56% of the phenotypic variation. One stable QTL, Qfhb. haust-1D.1 was detected on chromosome 1D across multiple environments explaining 4.39%-5.70% of the phenotypic variation. Forty-seven candidate genes related to disease resistance were found in the interval of Qfhb. haust-1D.1 and Qfhb. haust-4A.1. Genomic prediction accuracies were estimated from the five-fold cross-validation scheme ranging from 0.34 to 0.40 for PSS, and from 0.34 to 0.39 for PSSW in in-vivo inoculation treatment. This study provided new insight into the genetic analysis of resistance to wheat head blight caused by F.v, and genomic selection (GS) as a potential approach for improving the resistance of wheat head blight.

The effect of the Rht1 haplotype on Fusarium head blight resistance in relation to type and level of background resistance and in combination with Fhb1 and Qfhs.ifa-5A

The effect of the Rht1-genes on FHB resistance depends on anther extrusion and level of background resistance. Qfhs.ifa-5A increases resistance and anther extrusion as efficiently as semi-dwarfing alleles decrease it. The semi-dwarfing reduced height alleles Rht-D1b and Rht-B1b have been deployed in modern wheat cultivars throughout the world, but they increase susceptibility to Fusarium head blight (FHB). Here, we investigated the impact of the Rht1 genes on anther retention (AR) in relation to FHB resistance using four different sets of near-isogenic lines (NILs) with contrasting levels and types of background FHB resistance. NILs were evaluated for FHB severity, plant height and AR in three greenhouse and three field trials using artificial spray inoculation. Rht-B1b and Rht-D1b alleles increased AR and FHB susceptibility in all genetic backgrounds. The magnitude of the effects differed between NIL groups. Increased FHB susceptibility largely followed increased AR. Differences in FHB susceptibility between tall and dwarf haplotypes were largest in the NIL group with the highest changes in AR. In the most resistant NIL group, dwarfed lines had only slightly higher AR than tall lines and maintained good resistance, while both tall and dwarf lines had high levels of retained anthers in the most susceptible NIL group. We further investigated the effect of the major Fusarium resistance QTL Fhb1 and Qfhs.ifa-5A in combination with the Rht1 genes. Qfhs.ifa-5A enhanced anther extrusion in tall as well as semi-dwarf haplotypes, whereas Fhb1 did not affect AR. Qfhs.ifa-5A supported FHB resistance more efficiently than Fhb1 in lines that were more responsive to AR, while both Fhb1 and Qfhs.ifa-5A were equally efficient in NILs that had high background resistance and low response to AR.

Molecular Mapping of Quantitative Trait Loci for Fusarium Head Blight Resistance in the Brazilian Spring Wheat Cultivar "Surpresa"

Fusarium head blight (FHB) is a devastating disease in wheat. The use of resistant germplasm from diverse sources can significantly improve resistance to the disease. "Surpresa" is a Brazilian spring wheat cultivar with moderate FHB resistance, different from currently used sources. In this study, we aimed to identify and map the genetic loci for FHB resistance in Surpresa. A mapping population consisting of 187 recombinant inbred lines (RILs) was developed from a cross between Surpresa and a susceptible spring wheat cultivar, "Wheaton." The population was evaluated for FHB by the point-inoculation method in three greenhouse experiments and four field trials between 2016 and 2018. Mean disease severity for Surpresa and Wheaton was 41.2 and 84.9% across the 3 years of experiments, ranging from 30.3 to 59.1% and 74.3 to 91.4%, respectively. The mean FHB severity of the NILs was 57%, with an overall range from 7 to 100%, suggesting transgressive segregation in the population. The population was genotyped using a two-enzyme genotyping-by-sequencing approach, and a genetic map was constructed with 5,431 single nucleotide polymorphism (SNP) markers. Four QTL for type II resistance were detected on chromosomes 3A, 5A, 6A, and 7A, explaining 10.4-14.4% of the total phenotypic variation. The largest effect QTL was mapped on chromosome 7A and explained 14.4% of the phenotypic variation; however, it co-localized with a QTL governing the days to anthesis trait. A QTL for mycotoxin accumulation was also detected on chromosome 1B, explaining 18.8% of the total phenotypic variation. The QTL for FHB resistance identified in the study may diversify the FHB resistance gene pool and increase overall resistance to the disease in wheat.

Fusarium head blight resistance exacerbates nutritional loss of wheat grain at elevated CO2

The nutritional integrity of wheat is jeopardized by rapidly rising atmospheric carbon dioxide (CO₂) and the associated emergence and enhanced virulence of plant pathogens. To evaluate how disease resistance traits may impact wheat climate resilience, 15 wheat cultivars with varying levels of resistance to Fusarium Head Blight (FHB) were grown at ambient and elevated CO₂. Although all wheat cultivars had increased yield when grown at elevated CO₂, the nutritional contents of FHB moderately resistant (MR) cultivars were impacted more than susceptible cultivars_. At elevated CO₂, the MR cultivars had more significant differences in plant growth, grain protein, starch, fructan, and macro and micro-nutrient content compared with susceptible wheat. Furthermore, changes in protein, starch, phosphorus, and magnesium content were correlated with the cultivar FHB resistance rating, with more FHB resistant cultivars having greater changes in nutrient content. This is the first report of a correlation between the degree of plant pathogen resistance and grain nutritional content loss in response to elevated CO₂. Our results demonstrate the importance of identifying wheat cultivars that can maintain nutritional integrity and FHB resistance in future atmospheric CO₂ conditions.

Mapping Resistance to Argentinean Fusarium (Graminearum) Head Blight Isolates in Wheat

Fusarium head blight (FHB) of wheat, caused by Fusarium graminearum (Schwabe), is a destructive disease worldwide, reducing wheat yield and quality. To accelerate the improvement of scab tolerance in wheat, we assessed the International Triticeae Mapping Initiative mapping population (ITMI/MP) for Type I and II resistance against a wide population of Argentinean isolates of F. graminearum. We discovered a total of 27 additive QTLs on ten different (2A, 2D, 3B, 3D, 4B, 4D, 5A, 5B, 5D and 6D) wheat chromosomes for Type I and Type II resistances explaining a maximum of 15.99% variation. Another four and two QTLs for thousand kernel weight in control and for Type II resistance, respectively, involved five different chromosomes (1B, 2D, 6A, 6D and 7D). Furthermore, three, three and five QTLs for kernel weight per spike in control, for Type I resistance and for Type II resistance, correspondingly, involved ten chromosomes (2A, 2D, 3B, 4A, 5A, 5B, 6B, 7A, 7B, 7D). We were also able to detect five and two epistasis pairs of QTLs for Type I and Type II resistance, respectively, in addition to additive QTLs that evidenced that FHB resistance in wheat is controlled by a complex network of additive and epistasis QTLs.

Mitochondrial phosphate transporter and methyltransferase genes contribute to Fusarium head blight Type II disease resistance and grain development in wheat

Fusarium head blight (FHB) is an economically important disease of wheat that results in yield loss and grain contaminated with fungal mycotoxins that are harmful to human and animal health. Herein we characterised two wheat genes involved in the FHB response in wheat: a wheat mitochondrial phosphate transporter (TaMPT) and a methyltransferase (TaSAM). Wheat has three sub-genomes (A, B, and D) and gene expression studies demonstrated that TaMPT and TaSAM homoeologs were differentially expressed in response to FHB infection and the mycotoxigenic Fusarium virulence factor deoxynivalenol (DON) in FHB resistant wheat cv. CM82036 and susceptible cv. Remus. Virus-induced gene silencing (VIGS) of either TaMPT or TaSAM enhanced the susceptibility of cv. CM82036 to FHB disease, reducing disease spread (Type II disease resistance). VIGS of TaMPT and TaSAM significantly reduced grain number and grain weight. This indicates TaSAM and TaMPT genes also contribute to grain development in wheat and adds to the increasing body of evidence linking FHB resistance genes to grain development. Hence, Fusarium responsive genes TaSAM and TaMPT warrant further study to determine their potential to enhance both disease resistance and grain development in wheat.

Evaluation of Genomic Prediction for Fusarium Head Blight Resistance with a Multi-Parental Population

Simple Summary

Genomic selection is a promising approach to select superior wheat lines with better resistance to Fusarium head blight. The accuracy of genomic selection is determined by many factors. In this study, we found a training population with large size, genomic selection models incorporating biological information, and multi-environment modelling led to considerably better predictabilities. A training population designed by the coefficient of determination (CDmean) could increase accuracy of prediction. Relatedness between training population (TP) and testing population is the key for accuracies of genomic selection across populations.

Abstract

Fusarium head blight (FHB) resistance is quantitatively inherited, controlled by multiple minor effect genes, and highly affected by the interaction of genotype and environment. This makes genomic selection (GS) that uses genome-wide molecular marker data to predict the genetic breeding value as a promising approach to select superior lines with better resistance. However, various factors can affect accuracies of GS and better understanding how these factors affect GS accuracies could ensure the success of applying GS to improve FHB resistance in wheat. In this study, we performed a comprehensive evaluation of factors that affect GS accuracies with a multi-parental population designed for FHB resistance. We found larger sample sizes could get better accuracies. Training population designed by CDmean based optimization algorithms significantly increased accuracies than random sampling approach, while mean of predictor error variance (PEVmean) had the poorest performance. Different genomic selection models performed similarly for accuracies. Including prior known large effect quantitative trait loci (QTL) as fixed effect into the GS model considerably improved the predictability. Multi-traits models had almost no effects, while the multi-environment model outperformed the single environment model for prediction across different environments. By comparing within and across family prediction, better accuracies were obtained with the training population more closely related to the testing population. However, achieving good accuracies for GS prediction across populations is still a challenging issue for GS application.

Identification of Fusarium head blight resistance loci in two Brazilian wheat mapping populations

Fusarium head blight (FHB) is a disease of wheat (Triticum aestivum L.) that causes major yield losses in South America, as well as many other wheat growing regions around the world. FHB results in low quality, contaminated grain due to the production of mycotoxins such as deoxynivalenol (DON). In Brazil, FHB outbreaks are increasing in frequency and are currently controlled by fungicides which are costly and potentially harmful to the wider environment. To identify the genetic basis of resistance to FHB in Brazilian wheat, two mapping populations (Anahuac 75 × BR 18-Terena and BR 18-Terena × BRS 179) segregating for FHB resistance were phenotyped and quantitative trait loci (QTL) analysis was undertaken to identify genomic regions associated with FHB-related traits. A total of 14 QTL associated with FHB visual symptoms were identified, each of which explained 3.7–17.3% of the phenotypic variance. Two of these QTL were stable across environments. This suggests FHB resistance in Anahuac 75, BR 18-Terena and BRS 179 is controlled by multiple genetic loci that confer relatively minor differences in resistance. A major, novel QTL associated with DON accumulation was also identified on chromosome 4B (17.8% of the phenotypic variance), as well as a major QTL associated with thousand-grain weight on chromosome 6B (16.8% phenotypic variance). These QTL could be useful breeding targets, when pyramided with major sources of resistance such as Fhb1, to improve grain quality and reduce the reliance on fungicides in Brazil and other countries affected by FHB.

Updating the Breeding Philosophy of Wheat to Fusarium Head Blight (FHB): Resistance Components, QTL Identification, and Phenotyping-A Review

Fusarium head blight has posed continuous risks to wheat production worldwide due to its effects on yield, and the fungus provides additional risks with production of toxins. Plant resistance is thought to be the most powerful method. The host plant resistance is complex, Types I–V were reported. From the time of spraying inoculation (Type I), all resistance types can be identified and used to determine the total resistance. Type II resistance (at point inoculation) describes the spread of head blight from the ovary to the other parts of the head. Therefore, it cannot solve the resistance problem alone. Type II QTL (quantitative trait locus) Fhb1 on 3BS from Sumai 3 descendant CM82036 secures about the same resistance level as Type I QTL does on 5AS and 5ASc in terms of visual symptoms, FDK (Fusarium damaged kernel), and deoxynivalenol response. Recently, increasing evidence supports the association of deoxynivalenol (DON) content and low kernel infection with FHB (Fusarium head blight) resistance (Types III and IV), as QTL for individual resistance types has been identified. In plant breeding practice, the role of visual selection remains vital, but the higher correlations for FDK/DON make it possible to select low-DON genotypes via FDK value. For phenotyping, the use of more independent inocula (isolates or mixtures) makes resistance evaluation more reliable. The large heterogeneity of the mapping populations is a serious source of underestimating genetic effects. Therefore, the increasing of homogeneity is a necessity. As no wheat varieties exist with full resistance to FHB, crops must be supported by proper agronomy and fungicide use.

Genetic Characterization of Multiple Components Contributing to Fusarium Head Blight Resistance of FL62R1, a Canadian Bread Wheat Developed Using Systemic Breeding

Fusarium head blight (FHB) is a devastating fungal disease of small-grain cereals that results in severe yield and quality losses. FHB resistance is controlled by resistance components including incidence, field severity, visual rating index, Fusarium damaged kernels (FDKs), and the accumulation of the mycotoxin deoxynivalenol (DON). Resistance conferred by each of these components is partial and must be combined to achieve resistance sufficient to protect wheat from yield losses. In this study, two biparental mapping populations were analyzed in Canadian FHB nurseries and quantitative trait loci (QTL) mapped for the traits listed above. Nine genomic loci, on 2AS, 2BS, 3BS, 4AS, 4AL, 4BS, 5AS, 5AL, and 5BL, were enriched for the majority of the QTL controlling FHB resistance. The previously validated FHB resistance QTL on 3BS and 5AS affected resistance to severity, FDK, and DON in these populations. The remaining seven genomic loci colocalize with flowering time and/or plant height QTL. The QTL on 4B was a major contributor to all field resistance traits and plant height in the field. QTL on 4AL showed contrasting effects for FHB resistance between Eastern and Western Canada, indicating a local adapted resistance to FHB. In addition, we also found that the 2AS QTL contributed a major effect for DON, and the 2BS for FDK, while the 5AL conferred mainly effect for both FDK/DON. Results presented here provide insight into the genetic architecture underlying these resistant components and insight into how FHB resistance in wheat is controlled by a complex network of interactions between genes controlling flowering time, plant height, local adaption, and FHB resistance components.

Genetic analyses of native Fusarium head blight resistance in two spring wheat populations identifies QTL near the B1, Ppd-D1, Rht-1, Vrn-1, Fhb1, Fhb2, and Fhb5 loci

QTL analyses of two bi-parental mapping populations with AC Barrie as a parent revealed numerous FHB-resistance QTL unique to each population and uncovered novel variation near Fhb1. Fusarium head blight (FHB) is a destructive disease of wheat worldwide, leading to severe yield and quality losses. The genetic basis of native FHB resistance was examined in two populations: a recombinant inbred line population from the cross Cutler/AC Barrie and a doubled haploid (DH) population from the cross AC Barrie/Reeder. Numerous QTL were detected among the two mapping populations with many being cross-specific. Photoperiod insensitivity at Ppd-D1 and dwarfing at Rht-B1 and Rht-D1 was associated with increased FHB susceptibility. Anthesis date QTL at or near the Vrn-A1 and Vrn-B1 loci co-located with major FHB-resistance QTL in the AC Barrie/Reeder population. The loci were epistatic for both traits, such that DH lines with both late alleles were considerably later to anthesis and had reduced FHB symptoms (i.e., responsible for the epistatic interaction). Interestingly, AC Barrie contributed FHB resistance near the Fhb1 locus in the Cutler population and susceptibility in the Reeder population. Analyses of the Fhb1 candidate genes PFT and TaHRC confirmed that AC Barrie, Cutler, and Reeder do not carry the Sumai-3 Fhb1 gene. Resistance QTL were also detected at the expected locations of Fhb2 and Fhb5. The native FHB-resistance QTL detected near Fhb1, Fhb2, and Fhb5 do not appear to be as effective as Fhb1, Fhb2, and Fhb5 from Sumai-3. The presence of awns segregated at the B1 awn inhibitor locus in both populations, but was only associated with FHB resistance in the Cutler/AC Barrie population suggesting linkage caused the association rather than pleiotropy.

Molecular Mapping of QTLs Conferring Fusarium Head Blight Resistance in Chinese Wheat Cultivar Jingzhou 66

Fusarium head blight (FHB) is a destructive disease of wheat (Triticum aestivum L.), which not only significantly reduces grain yield, but also affects end-use quality. Breeding wheat cultivars with high FHB resistance is the most effective way to control the disease. The Chinese wheat cultivar Jingzhou 66 (JZ66) shows moderately high FHB resistance; however, the genetic basis of its resistance is unknown. A doubled haploid (DH) population consisting 209 lines was developed from a cross of JZ66 and Aikang 58 (AK58), a FHB susceptible wheat cultivar, to identify quantitative trait loci (QTL) that contribute to the FHB resistance. Five field experiments were established across two consecutive crop seasons (2018 and 2019) to evaluate the DH lines and parents for FHB response. The parents and DH population were genotyped with the wheat 55K single-nucleotide polymorphism (SNP) assay. Six QTLs associated with FHB resistance in JZ66 were mapped on chromosome 2DS, 3AS, 3AL, 3DL, 4DS, and 5DL, respectively. Four of the QTL (QFhb.hbaas-2DS, QFhb.hbaas-3AL, QFhb.hbaas-4DS, and QFhb.hbaas-5DL) were detected in at least two environments, and the QTL on 3AL and 5DL might be new. The QTL with major effects, QFhb.hbaas-2DS and QFhb.hbaas-4DS, explained up to 36.2% and 17.6% of the phenotypic variance, and were co-localized with the plant semi-dwarfing loci Rht8 and Rht-D1. The dwarfing Rht8 allele significantly increased spike compactness (SC) and FHB susceptibility causing a larger effect on FHB response than Rht-D1 observed in this study. PCR–based SNP markers for QFhb.hbaas-2DS, QFhb.hbaas-3AL, QFhb.hbaas-4DS, and QFhb.hbaas-5DL, were developed to facilitate their use in breeding for FHB resistance by marker-assisted selection.

Fusarium Head Blight and Rust Diseases in Soft Red Winter Wheat in the Southeast United States: State of the Art, Challenges and Future Perspective for Breeding

Among the biotic constraints to wheat (Triticum aestivum L.) production, fusarium head blight (FHB), caused by Fusarium graminearum, leaf rust (LR), caused by Puccinia triticina, and stripe rust (SR) caused by Puccinia striiformis are problematic fungal diseases worldwide. Each can significantly reduce grain yield while FHB causes additional food and feed safety concerns due to mycotoxin contamination of grain. Genetic resistance is the most effective and sustainable approach for managing wheat diseases. In the past 20 years, over 500 quantitative trait loci (QTLs) conferring small to moderate effects for the different FHB resistance types have been reported in wheat. Similarly, 79 Lr-genes and more than 200 QTLs and 82 Yr-genes and 140 QTLs have been reported for seedling and adult plant LR and SR resistance, respectively. Most QTLs conferring rust resistance are race-specific generally conforming to a classical gene-for-gene interaction while resistance to FHB exhibits complex polygenic inheritance with several genetic loci contributing to one resistance type. Identification and deployment of additional genes/QTLs associated with FHB and rust resistance can expedite wheat breeding through marker-assisted and/or genomic selection to combine small-effect QTL in the gene pool. LR disease has been present in the southeast United States for decades while SR and FHB have become increasingly problematic in the past 20 years, with FHB arguably due to increased corn acreage in the region. Currently, QTLs on chromosome 1B from Jamestown, 1A, 1B, 2A, 2B, 2D, 4A, 5A, and 6A from W14, Ning7840, Ernie, Bess, Massey, NC-Neuse, and Truman, and 3B (Fhb1) from Sumai 3 for FHB resistance, Lr9, Lr10, Lr18, Lr24, Lr37, LrA2K, and Lr2K38 genes for LR resistance, and Yr17 and YrR61 for SR resistance have been extensively deployed in southeast wheat breeding programs. This review aims to disclose the current status of FHB, LR, and SR diseases, summarize the genetics of resistance and breeding efforts for the deployment of FHB and rust resistance QTL on soft red winter wheat cultivars, and present breeding strategies to achieve sustainable management of these diseases in the southeast US.

Fusarium head blight in wheat: contemporary status and molecular approaches

Fusarium head blight (FHB) disease that occurs in wheat is caused by Fusarium graminearum and is a major risk to wheat yield. Although several research efforts focusing on FHB have been conducted in the past several decades, conditions have become more critical due to the increase in its virulent forms. In such a scenario, conferring complete resistance in plants seems to be difficult for handling this issue. The phenotyping for FHB and finding a solution for it at the genetic level comprises a long-term process as FHB infection is largely affected by environmental conditions. Modern molecular strategies have played a crucial role in revealing the host-pathogen interaction in FHB. The integration of molecular biology-based methods such as genome-wide association studies and marker-based genomic selection has provided potential cultivars for breeding programs. In this review, we aim at outlining the contemporary status of the studies conducted on FHB in wheat. The influence of FHB in wheat on animals and human health is also discussed. In addition, a summary of the advancement in the molecular technologies for identifying and developing the FHB-resistant wheat genetic resources is provided. It also suggests the future measures that are required to reduce the world's vulnerability to FHB which was one of the main goals of the US Wheat and Barley Scab Initiative.

QTL mapping and successful introgression of the spring wheat-derived QTL Fhb1 for Fusarium head blight resistance in three European triticale populations

KEY MESSAGE

The spring wheat-derived QTL Fhb1 was successfully introgressed into triticale and resulted in significantly improved FHB resistance in the three triticale mapping populations. Fusarium head blight (FHB) is a major problem in cereal production particularly because of mycotoxin contaminations. Here we characterized the resistance to FHB in triticale breeding material harboring resistance factors from bread wheat. A highly FHB-resistant experimental line which derives from a triticale × wheat cross was crossed to several modern triticale cultivars. Three populations of recombinant inbred lines were generated and evaluated in field experiments for FHB resistance using spray inoculations during four seasons and were genotyped with genotyping-by-sequencing and SSR markers. FHB severity was assessed in the field by visual scorings and on the harvested grain samples using digital picture analysis for quantifying the whitened kernel surface (WKS). Four QTLs with major effects on FHB resistance were identified, mapping to chromosomes 2B, 3B, 5R, and 7A. Those QTLs were detectable with both Fusarium severity traits. Measuring of WKS allows easy and fast grain symptom quantification and appears as an effective scoring tool for FHB resistance. The QTL on 3B collocated with Fhb1, and the QTL on 5R with the dwarfing gene Ddw1. This is the first report demonstrating the successful introgression of Fhb1 into triticale. It comprises a significant step forward for enhancing FHB resistance in this crop.

Genetic Mapping and Prediction Analysis of FHB Resistance in a Hard Red Spring Wheat Breeding Population

Fusarium head blight (FHB) is one of the most destructive diseases in wheat worldwide. Breeding for FHB resistance is hampered by its complex genetic architecture, large genotype by environment interaction, and high cost of phenotype screening. Genomic selection (GS) is a powerful tool to enhance improvement of complex traits such as FHB resistance. The objectives of this study were to (1) investigate the genetic architecture of FHB resistance in a North Dakota State University (NDSU) hard red spring wheat breeding population, (2) test if the major QTL Fhb1 and Fhb5 play an important role in this breeding population; and (3) assess the potential of GS to enhance breeding efficiency of FHB resistance. A total of 439 elite spring wheat breeding lines from six breeding cycles were genotyped using genotyping-by-sequencing (GBS) and 102,147 SNP markers were obtained. Evaluation of FHB severity was conducted in 10 unbalanced field trials across multiple years and locations. One QTL for FHB resistance was identified and located on chromosome arm 1AL, explaining 5.3% of total phenotypic variation. The major type II resistance QTL Fhb1 only explained 3.1% of total phenotypic variation and the QTL Fhb5 was not significantly associated with FHB resistance in this breeding population. Our results suggest that integration of many genes with medium/minor effects in this breeding population should provide stable FHB resistance. Genomic prediction accuracies of 0.22-0.44 were obtained when predicting over breeding cycles in this study, indicating the potential of GS to enhance the improvement of FHB resistance.

Changes in Protein Composition in the Grain and Malt after Fusarium Infection Dependently of Wheat Resistance

The grain yield, as well as the quality and safety of the wheat grains and corresponding malt can be compromised by Fusarium spp. infection. The protein content of the grain affects the chemical composition and enzyme levels of the finished malt. The malting industry demands varieties with good malting and brewing performance, as well as good agronomic performance and disease resistance. The best method of disease control is breeding and selection for resistant varieties. Due to higher requirements for malting wheat worldwide, the goal of this investigation was to explore changes in protein distribution in wheat grains and corresponding malt, which are under higher pressure of Fusarium head blight (FHB) infestation in field conditions. The present study provides new knowledge on the impact of the FHB on the distribution of protein components of naturally Fusarium-infected (control) and Fusarium-inoculated wheat varieties in the grain and the corresponding malt in two consecutive years (2015/2016 and 2016/2017). The results showed that Fusarium infection of the susceptible variety Golubica, decreased total glutenins (5.9%), and both high and low molecular weight glutenin subunits (2.5% and 3.5%, respectively) in wheat grains, compared to control, in 2016. In contrast, gliadins and α-gliadins increased significantly (+7.6% and +5.1%, respectively) in the same variety. Wheat grains of the more resistant variety Vulkan showed an increase of the total glutenins content (+4.3%), and of high and of low molecular weight glutenin subunits (+1.2% and +3.2%, respectively) after Fusarium-inoculation, compared to naturally infected grains in 2016. Susceptible variety Golubica increased total glutenins (+9.1%), and both high and low molecular weight glutenin subunits (+3.5% and +5.6%, respectively) after Fusarium-inoculation in wheat malt, compared to naturally infected malt in 2016. In 2017, when disease pressure was higher than in 2016, there was a tendency in all varieties to increase gliadins and its sub fractions after malting, and to decrease glutenins and its sub fractions in Fusarium-inoculated treatment. In conclusion, FHB dramatically depressed grain yield (up to 37%) and quality (glutenins and high molecular weight subunits) in the susceptible Fusarium variety, which makes it inconvenient for malting.

Fine-mapping of the Fusarium head blight resistance QTL Qfhs.ifa-5A identifies two resistance QTL associated with anther extrusion

Fine-mapping separated Qfhs.ifa-5A into a major QTL mapping across the centromere and a minor effect QTL positioned at the distal half of 5AS. Both increase Fusarium resistance and anther extrusion. The Fusarium head blight (FHB) resistance QTL Qfhs.ifa-5A resides in the low-recombinogenic pericentromeric region of chromosome 5A making fine-mapping particularly arduous. Qfhs.ifa-5A primarily contributes resistance to fungal entry with the favorable allele descending from the highly Fusarium resistant cultivar Sumai-3. Fine-mapping a near-isogenic recombinant inbred line population partitioned the Qfhs.ifa-5A interval into 12 bins. Near-isogenic lines recombining at the interval were phenotyped for FHB severity, anther retention and plant height. Composite interval mapping separated the initially single QTL into two QTL. The major effect QTL Qfhs.ifa-5Ac mapped across the centromere and the smaller effect QTL Qfhs.ifa-5AS mapped to the distal half of 5AS. Although Qfhs.ifa-5Ac and Qfhs.ifa-5AS intervals were as small as 0.1 and 0.2 cM, their corresponding physical distances were large, comprising 44.1 Mbp and 49.2 Mbp, respectively. Sumai-3 alleles at either QTL improved FHB resistance and increased anther extrusion suggesting a pleiotropic effect of anthers on resistance. This hypothesis was supported by greenhouse experiments using the susceptible cultivar Remus and its resistant near-isogenic line NIL3 carrying the entire Qfhs.ifa-5A segment. By manually removing anthers prior to spray inoculation both, Remus and NIL3 became almost equally resistant in the early phase of the disease development and were significantly less diseased than variants without anther manipulation. At late time points the positive effect of the anther removal became smaller for Remus and disappeared completely for NIL3. Results affirm that absence of anthers enhanced resistance to initial infection but did not protect plants from fungal spreading within spikes.

The Pressure of Fusarium Disease and Its Relation with Mycotoxins in The Wheat Grain and Malt

Fusarium head blight (FHB) is one of the most destructive wheat fungal diseases, causing yield loss, quality reduction, and accumulation of mycotoxins. The aim of this research was to summarize the occurrence of major Fusarium mycotoxins: deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), nivalenol (NIV), and zearalenone (ZEN) in two consecutive years to search the relationship between disease incidence and severity with mycotoxins found in control and inoculated grains and corresponding malt. In addition, deoxynivalenol-3-glucoside (D3G) in one-year research was measured. Tested wheat varieties showed infection scores of 3% (‘U1’ and ‘Sirban Prolifik’) to 79% (‘Golubica’) for Type I resistance evaluation. There were few moderately resistant varieties in view of their areas under the disease progress curve, which can be considered Type III resistance (‘Sirban Prolifik’ and ‘U1’). According to the data quantified by LC–MS/MS, DON decreased in infected malt in comparison to corresponding grain, while ZEN occurred only in infected malt samples. Both 3-AcDON and NIV increased in inoculated malt in comparison to corresponding grain, due to a combination of plant metabolism and de novo synthesis by molds during malting. Based on the results, we can draw a few conclusions: the resistance to Fusarium decreased quantified concentrations of DON; ZEN gets synthetized during malting; unregulated 3-AcDON and NIV increase during malting; more resistant varieties have converted DON to D3G more successfully. Modified mycotoxins should be also included to legislation, since they could be transformed back to the corresponding mycotoxins under food processing conditions or during digestion.

Meta-Analysis of the QTLome of Fusarium Head Blight Resistance in Bread Wheat: Refining the Current Puzzle

Background: Fusarium Head Blight (FHB) is a worldwide devastating disease of bread wheat (Triticum aestivum L.). Genetic resistance is the most effective way to control FHB and many QTL related to this trait have been mapped on the wheat genetic map. This information, however, must be refined to be more efficiently used in breeding programs and for the advance of the basic research. The objective of the present study was to in-depth analyze the QTLome of FHB resistance in bread wheat, further integrating genetic, genomic, and transcriptomic data, aiming to find candidate genes. Methods: An exhaustive bibliographic review on 76 scientific papers was carried out collecting information about QTL related to FHB resistance mapped on bread wheat. A dense genetic consensus map with 572,862 loci was generated for QTL projection. Meta-analysis could be performed on 323 QTL. Candidate gene mining was carried out within the most refined loci, containing genes that were cross-validated with publicly available transcriptional expression data of wheat under Fusarium infection. Most highlighted genes were investigated for protein evidence. Results: A total of 556 QTL were found in the literature, distributed on all sub-genomes and chromosomes of wheat. Meta-analysis generated 65 meta-QTL, and this refinement allows one to find markers more tightly linked to these regions. Candidate gene mining within the most refined meta-QTL, meta-QTL 1/chr. 3B, harvested 324 genes and transcriptional data cross-validated 10 of these genes, as responsive to FHB. One is of these genes encodes a Glycosiltransferase and the other encodes for a Cytochrome P450, and these such proteins have already been verified as being responsible for FHB resistance, but the remaining eight genes still have to be further studied, as promising loci for breeding. Conclusions: The QTLome of FHB resistance in wheat was successfully assembled and a refinement in terms of number and length of loci was obtained. The integration of the QTLome with genomic and transcriptomic data has allowed for the discovery of promising candidate genes for use in breeding programs.

The role of adapted and non-adapted resistance sources in breeding resistance of winter wheat to Fusarium head blight and deoxynivalenol contamination

Since resistance is the most important agent in regulating deoxynivalenol (DON), breeding for higher resistance is the key to improve food safety. Fusarium damaged kernels (FDK) show a closer correlation with DON than visual symptoms. This implies a difference in genetic regulation. For this reason, the mapping should be extended not only for the visual symptoms, but also for FDK and DON. Quantitative trait loci influencing only Fusarium head blight (FHB) symptoms, may not be relevant for FDK and DON. Type I and II were pooled to overall resistance at spray inoculation. From 2010 to 2016 three selection platforms were compared by checking running variety breeding programs. The use of exotic sources in breeding significantly increased the number of more resistant genotypes in each selection phase from F3-F8 generations compared to the control program where crosses were not planned for FHB resistance and screening in early generations was also not performed. However, also in this breeding platform – at a lower rate – moderately or highly resistant genotypes could be selected. Of them, eight cultivars were/are in commercial production. The Fusarium breeding program using only adapted and more resistant parents generally gave closer results to exotic breeds, and several highly resistant genotypes were produced as a result. For winter wheat the phenotypic screening at high disease pressure is the key to select highly resistant materials. At low infection pressure the high and medium resistant genotypes come in the same group. The use of more isolates increases the chance to have strong selection pressure each year. FHB resistance was combined with leaf rust, yellow rust, powdery mildew, leaf spot resistance and high protein content (15-18%). The cultivar registration and post registration screening is the key in improving food safety in commercial production.

Study of QTLs linked to awn length and their relationships with chloroplasts under control and saline environments in bread wheat

INTRODUCTION

Some studies in wheat showed that awns may have a useful effect on yield, especially under drought stress. Up to this time few researches has identified the awn length QTLs with different effect in salinity stress.

OBJECTIVE

The primary objective of this study was to examine the additive (a) and the epistatic (aa) QTLs involve in wheat awns length in control and saline environments.

METHODS

A F7 RIL population consisting of 319 sister lines, derived from a cross between wheat cultivars Roshan and Falat (seri82), and the two parents were grown in two environments (control and Saline) based on an alpha lattice design with two replications in each environment. At flowering, awn length was measured for each line. For QTL analysis, the linkage map of the ''Roshan × Falat'' population was used, which included 748 markers including 719 DArT, 29 simple sequenced repeats (SSRs). Additive and pleiotropic QTLs were identified. In order to reveal the relationship between the identified QTL for awns length and the role of the gene or genes that it expresses, the awns length locus location and characteristics of its related CDS, gene, UTRs, ORF, exons and Introns were studied using ensemble plant ( http://plants.ensembl.org/Triticum_aestivum ). Furthermore, the promoter analysis has been done using NSITE-PL.

RESULTS

We identified 6 additive QTLs for awn length by QTL Cartographer program using single-environment phenotypical values. Also, we detected three additive and two epistatic QTLs for awn length by the QTLNetwork program using multi-environment phenotypical values. Our results showed that none of the additive and epistatic QTLs had interactions with environment. One of the additive QTLs located on chromosome 4A was co-located with QTLs for number of sterile spikelet per spike in both environment and number of seed per spike in control environment.

COCLUSION

Studies of the locus linked to the awns length QTL revealed the role of awn and its chloroplasts in grain filing during abiotic stress could be enhanced by over expression of some genes like GTP-Binding proteins which are enriched in chloroplasts encoded by genes included wPt-5730 locus.

Molecular Mapping of Fusarium Head Blight Resistance in the Spring Wheat Line ND2710

ND2710 is a hard red spring wheat line with a very high level of resistance to Fusarium head blight (FHB). It was selected from the progeny of a cross between ND2603 (an advanced breeding line derived from the Sumai 3/Wheaton cross) and Grandin (a spring wheat cultivar). The FHB resistance of ND2710 is presumably derived from Sumai 3 because the other parents (Grandin and Wheaton) are very susceptible to FHB. To identify and map the quantitative trait loci (QTL) for FHB resistance in ND2710, we developed a mapping population consisting of 233 recombinant inbred lines (RILs) from the cross between ND2710 and the spring wheat cultivar Bobwhite. These RILs along with their parents and checks were evaluated for reactions to FHB in three greenhouse experiments and one field experiment during 2013 to 2014. The population was also genotyped with the wheat 90K iSelect single-nucleotide polymorphism (SNP) assay, and a genetic linkage map was developed with 1,373 non-cosegregating SNP markers, which were distributed on all 21 wheat chromosomes spanning 914.98 centimorgans of genetic distance. Genetic analyses using both phenotypic and genotypic data identified one major QTL (Qfhb.ndwp-3B) on the short arm of chromosome 3B, and three minor QTL (Qfhb.ndwp-6B, Qfhb.ndwp-2A, and Qfhb.ndwp-6A) on 6B, 2A, and 6A, respectively. The major QTL on 3B was detected in all experiments and explained 5 to 20% of the phenotypic variation, while the three minor QTL on 6B, 2A, and 6A explained 5 to 12% phenotypic variation in at least two experiments, except for Qfhb.ndwp-2A, which was only detected in the field experiment. Qfhb.ndwp-3B and Qfhb.ndwp-6B were mapped to the genomic regions containing Fhb1 and Fhb2, respectively, confirming that they originated from Sumai 3. The additive effect of the major and minor QTL may contribute to the high level of FHB resistance in ND2710. The SNP markers closely linked to the FHB resistance QTL will be useful for marker-assisted selection of FHB resistance in wheat breeding programs.

Canopy and Ear Traits Associated With Avoidance of Fusarium Head Blight in Wheat

Doubled haploid and elite wheat genotypes were ground inoculated in three field experiments and head spray inoculated in two glasshouse experiments, using mixed Fusarium and Microdochium species, to identify crop canopy and ear traits associated with Fusarium head blight (FHB) disease. In all experiments, flag leaf length and tiller number were consistently identified as the most significant canopy traits contributing to progression of FHB caused by Fusarium graminearum, F. culmorum, and F. avenaceum. The influence of ear traits was greater for F. poae that may possess more diverse routes for transmission and spread. Consistently, spikelet density was associated with increased disease severity in the field. F. graminearum, F. culmorum, and F. langsethiae were the main mycotoxin producers and their respective toxins were significantly related to fungal biomass and number of spikelets per ear. Genotypes with lower tiller numbers, shorter flag leaves and less dense ears may be able to avoid FHB disease caused by F. graminearum, F. culmorum, F. avenaceum, or Microdochium species however selection for these canopy and ear architectural traits to enable disease avoidance in wheat is likely to result in a potential trade-off with grain yield and therefore only moderately advantageous in susceptible genotypes.

Evaluation of the Potential for Genomic Selection to Improve Spring Wheat Resistance to Fusarium Head Blight in the Pacific Northwest

Fusarium Head Blight (FHB) has emerged in spring wheat production in Pacific Northwest during the last decade due to factors including climate changes, crop rotations, and tillage practices. A breeding population with 170 spring wheat lines was established and screened over a 2-year period in multiple locations for FHB incidence (INC), severity (SEV), and deposition of the mycotoxin, deoxynivalenol (DON). A genome-wide association study suggested that the detectable number of genetic loci and effects are limited for marker-assisted selection. In conjunction with the success of breeding on FHB resistance in other programs, genomic selection (GS) was suggested as a better option. To evaluate the prediction accuracy of GS in the current breeding population, we conducted a variety of validations by varying proportions of testing populations and cohorts based on both FHB resistance and market class, including soft white spring (SWS), hard white spring (HWS), and hard red spring (HRS). We found that INC had higher heritability, higher correlation across years and locations, and higher prediction accuracy than SEV and DON. Prediction accuracy varied among the scenarios that restricted the testing population to a certain cohort. For a small set of newly developed or introduced lines (<17), prediction accuracy will be about 60% if the lines have similar genetic relationships as those among the current 170-line training population. However, we expect a lower prediction accuracy if new lines are selected for a specific characteristic, such as FHB resistance or market class. With the exception of DON in the SWS lines, the current training population is capable of making reasonably accurate predictions for FHB-resistant lines in most of the major market classes. For SWS, adding more lines or further phenotyping is required to improve prediction accuracy. These results demonstrate the potential and challenges of GS, especially for developing FHB-resistant varieties in the SWS market class.

Validation of Molecular Markers for Use With Adapted Sources of Fusarium Head Blight Resistance in Wheat

Genetic control of resistance to Fusarium head blight (FHB) is quantitative, making phenotypic selection difficult. Genetic markers to resistance are helpful to select favorable genotypes. This study was conducted to determine if Fhb1 and Fhb5 present in the Sumai 3 source of FHB resistance occur in Sumai 3-derived North American spring wheat cultivars and to understand the appropriateness of using markers to select for the favorable alleles at these loci in breeding. Sumai 3-derived parents Alsen, ND3085, ND744, Carberry, and Glenn were used in crosses to generate 14 doubled haploid breeding populations. The parents and progeny were genotyped with five Fhb1 and three Fhb5 microsatellite markers. Progeny were selected based on performance relative to parents and other control cultivars in FHB nurseries near Portage la Prairie and Carman, MB. χ² and t test analyses were performed on marker and FHB data. The χ² test frequently determined the proportion of lines carrying molecular variants associated with FHB resistance increased following nursery selection for FHB. Similarly, the t test regularly demonstrated that selection for FHB resistance lowered the mean level of disease associated with resistant marker haplotypes. The study affirmed FHB resistance sources Alsen, Carberry, ND3085, and ND744 have Fhb1 and Fhb5 loci like Sumai 3, but no evidence was found that Glenn carries Fhb1 and Fhb5 resistance alleles. The results justified use of Fhb1 and Fhb5 markers for marker assisted selection in populations derived from Alsen, Carberry, ND3085, and ND744, but not Glenn. Combined or individual application of Xgwm493 and Xgwm533 in selection of genotypes carrying Fhb1, and Xgwm150, Xgwm304, and Xgwm595 for Fhb5 will enhance FHB resistance in wheat.

Identification and characterization of a fusarium head blight resistance gene TaACT in wheat QTL-2DL

Fusarium head blight (FHB) resistance in wheat is considered to be polygenic in nature. Cell wall fortification is one of the best resistance mechanisms in wheat against Fusarium graminearum which causes FHB. Metabolomics approach in our study led to the identification of a wide array of resistance-related (RR) metabolites, among which hydroxycinnamic acid amides (HCAAs), such as coumaroylagmatine and coumaroylputrescine, were the highest fold change RR metabolites in the rachis of a resistant near-isogenic line (NIL-R) upon F. graminearum infection. Placement of these metabolites in the secondary metabolic pathway led to the identification of a gene encoding agmatine coumaroyl transferase, herein referred to as TaACT, as a candidate gene. Based on wheat survey sequence, TaACT was located within a FHB quantitative trait loci on chromosome 2DL (FHB QTL-2DL) between the flanking markers WMC245 and GWM608. Phylogenetic analysis suggested that TaACT shared closest phylogenetic relationship with an ACT ortholog in barley. Sequence analysis of TaACT in resistant and susceptible NILs, with contrasting levels of resistance to FHB, led to the identification of several single nucleotide polymorphisms (SNPs) and two inversions that may be important for gene function. Further, a role for TaACT in FHB resistance was functionally validated by virus-induced gene silencing (VIGS) in wheat NIL-R and based on complementation studies in Arabidopsis with act mutant background. The disease severity, fungal biomass and RR metabolite analysis confirmed TaACT as an important gene in wheat FHB QTL-2DL, conferring resistance to F. graminearum.

QTL mapping of Fusarium head blight resistance in three related durum wheat populations

KEY MESSAGE

The QTL Fhb1 was successfully introgressed and validated in three durum wheat populations. The novel germplasm and the QTL detected will support improvement of Fusarium resistance in durum wheat. Durum wheat (Triticum durum Desf.) is particularly susceptible to Fusarium head blight (FHB) and breeding for resistance is hampered by limited genetic variation within this species. To date, resistant sources are mainly available in a few wild relative tetraploid wheat accessions. In this study, the effect of the well-known hexaploid wheat (Triticum aestivum L.) quantitative trait locus (QTL) Fhb1 was assessed for the first time in durum wheat. Three F7-RIL mapping populations of about 100 lines were developed from crosses between the durum wheat experimental line DBC-480, which carries an Fhb1 introgression from Sumai-3, and the European T. durum cultivars Karur, Durobonus and SZD1029K. The RILs were evaluated in field experiments for FHB resistance in three seasons using spray inoculation and genotyped with SSR as well as genotyping-by-sequencing markers. QTL associated with FHB resistance were identified on chromosome arms 2BL, 3BS, 4AL, 4BS, 5AL and 6AS at which the resistant parent DBC-480 contributed the positive alleles. The QTL on 3BS was detected in all three populations centered at the Fhb1 interval. The Rht-B1 locus governing plant height was found to have a strong effect in modulating FHB severity in all populations. The negative effect of the semi-dwarf allele Rht-B1b on FHB resistance was compensated by combining with Fhb1 and additional resistance QTL. The successful deployment of Fhb1 in T. durum was further substantiated by assessing type 2 resistance in one population. The efficient introgression of Fhb1 represents a significant step forward for enhancing FHB resistance in durum wheat.

Mapping the A Genome for QTL Conditioning Resistance to Fusarium Head Blight in a Wheat Population with Triticum timopheevii Background

Development and use of resistant wheat cultivars is the most practical and economical approach for the control of Fusarium head blight (FHB). In the present study, a population of recombinant inbred lines derived from the cross between 'AC Brio' (a Canadian bread wheat cultivar moderately susceptible to FHB) and 'TC 67' (an FHB-resistant cultivar derived from Triticum timopheevii) was used to map quantitative trait loci (QTL) for FHB resistance using microsatellite molecular markers. Multiple interval mapping detected several QTL for FHB resistance on the chromosomes 5AL and 6A. The QTL detected in the marker interval of cfd6.1-barc48 on chromosome 5AL explained 10.9, 5.2, and 7.8% of phenotypic variation for disease incidence (type I resistance), disease severity (a combination of type I and type II resistance), and Fusarium-damaged kernels (FDK) (type IV resistance) under field conditions, respectively. The second QTL mapped to 5AL, in the marker interval of cfd39-cfa2185, explained 19.4 and 20.6% of phenotypic variation for FDK under field conditions and disease severity in the greenhouse (type II resistance), respectively. The QTL located on chromosome 6A conferred resistance to disease incidence and severity under field conditions and to disease severity in the greenhouse, explaining 6.8 to 11.8% of phenotypic variation for these traits. Several QTL for agronomic traits were also mapped in this study, including one and two QTL to the chromosomes 2A and 5AL, respectively, all for plant height, and two QTL to chromosome 6A for plant height and flowering date, respectively. The 5AL QTL for FHB resistance mapped in the marker interval of cfd39-cfa2185 in the present study is a novel QTL that originated from T. timopheevii and is reported here for the first time. Further validation of this QTL is required for wheat breeding programs to enhance resistance levels to FHB.

Reevaluation of Two Quantitative Trait Loci for Type II Resistance to Fusarium Head Blight in Wheat Germplasm PI 672538

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is a destructive disease in wheat. A population consisting of 229 F₂ and F_2:3 plants derived from the cross PI 672538 × L661 was used to evaluate the reactions to FHB. The FHB resistance data distribution in the F₂ population indicates that some quantitative trait loci (QTLs) were controlling the FHB resistance in PI 672538. We further detected two major QTLs (Qfhs-2B, Qfhs-3B) from analysis of the resistance data and the PCR-amplified results using WinQTLCart 2.5 software. Qfhs-2B, flanked by Xbarc55-2B and Xbarc1155-2B, explained more than 11.6% of the phenotypic variation of the percentage of diseased spikelets (PDS), and Qfhs-3B, flanked by Xwmc54-3B and Xgwm566-3B, explained more than 10% of the PDS phenotypic variation in the F_2:3 population. In addition, Qfhs-3B was different from Fhb1 in terms of the pedigree, inheritance, resistance response, chromosomal location, and marker diagnosis. We also detected QTLs for other disease resistance indices, including the percentage of damaged kernels and 1,000-grain weight, in similar chromosomal regions. Therefore, the FHB resistance of PI 672538 was mainly controlled by two major QTLs, mapped on 2B (FhbL693a) and 3B (FhbL693b). PI 672538 could be a useful germplasm for improving wheat FHB resistance.

The Semidwarfing Alleles Rht-D1b and Rht-B1b Show Marked Differences in Their Associations with Anther-Retention in Wheat Heads and with Fusarium Head Blight Susceptibility

The semidwarfing alleles reduced height (Rht)-D1b and Rht-B1b are widely deployed in wheat breeding. Both alleles have similar effects on plant height but differ in their effect on Fusarium head blight (FHB) severity. A double-haploid population and a backcross population, segregating for Rht-B1a/Rht-B1b and Rht-D1a/Rht-D1b, were evaluated for FHB severity, plant height, and anther retention in field trials in three consecutive years. The semidwarfing alleles reduced plant height and increased the proportion of retained anthers. Reduced plant height and a high proportion of retained anthers were associated with increased FHB severity. The Rht-D1b allele had a significantly greater impact on anther retention and FHB severity than the Rht-B1b allele. Fusarium graminearum establishes infection sites predominantly inside the floral cavity and retained anthers potentially support colonization and initial hyphal growth, leading to a higher disease level in genotypes with a higher proportion of retained anthers. This is the first report demonstrating that differences in disease severity associated with Rht-D1b and Rht-B1b can be partly explained by their different effect on the extent of anther retention.

Multiple Minor QTLs Are Responsible for Fusarium Head Blight Resistance in Chinese Wheat Landrace Haiyanzhong

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, is a devastating disease in wheat (Triticum aestivum L.). Use of host resistance is one of the most effective strategies to minimize the disease damage. Haiyanzhong (HYZ) is a Chinese wheat landrace that shows a high level of resistance to FHB spread within a spike (type II resistance). To map the quantitative trait loci (QTLs) in HYZ and identify markers tightly linked to the QTLs for FHB resistance, a population of 172 recombinant inbred lines (RILs) from a cross between HYZ and Wheaton (FHB susceptible) was genotyped using simple sequence repeats (SSRs) and single-nucleotide polymorphisms (SNPs) derived from genotyping-by-sequencing (GBS), and evaluated for percentage of symptomatic spikelets (PSSs) per spike in three greenhouse experiments. Six QTLs for type II resistance were identified in HYZ, indicating that multiple minor QTLs together can provide a high level of FHB resistance in wheat. The QTL with the largest effect on FHB resistance was mapped on the chromosome arm 5AS, and the other five from HYZ were mapped on the chromosomes 6B, 7D, 3B, 4B and 4D. In addition, two QTLs from Wheaton were mapped on 2B. Critical SNPs linked to the QTLs on chromosomes 5A, 6B, and 2B were converted into KBioscience competitive allele-specific PCR (KASP) assays, which can be used for marker-assisted selection (MAS) to pyramid these QTLs in wheat.

The Response of Selected Triticum spp. Genotypes with Different Ploidy Levels to Head Blight Caused by Fusarium culmorum (W.G.Smith) Sacc

Several cultivars and pure lines of Triticum monococcum, T. dicoccon, T. polonicum, T. spelta and T. aestivum were inoculated with Fusarium culmorum, the causal agent of Fusarium head blight in wheat. During the three-year study, the infection decreased the values of the analyzed yield components: spike weight (by 5.6% to 15.8%), number of kernels per spike (by 2.8% to 11.8%) and one kernel weight (by 8.4% to 10.7%). T. spelta was characterized by the weakest average response to infection. The grain from inoculated spikes contained significantly higher concentrations of deoxynivalenol (DON) and its 3-β-D-glucoside (D3G) than control grain. The D3G/DON ratio ranged from 11.4% to 21.4% in control grain and from 8.1% to 11.6% in inoculated grain. The lowest levels of mycotoxins were found in spelt, and the highest in T. polonicum lines and Kamut. PCA revealed that the grain of T. polonicum was characterized by an entirely different mycotoxin profile. The weakest response to F. culmorum infections was noted in T. spelta, and the strongest response in T. polonicum breeding lines and Kamut.

Mapping QTLs for Fusarium Head Blight Resistance in an Interspecific Wheat Population

Fusarium head blight (scab) is one of the most widespread and damaging diseases of wheat, causing grain yield and quality losses and production of harmful mycotoxins. Development of resistant varieties is hampered by lack of effective resistance sources in the tetraploid wheat primary gene pool. Here we dissected the genetic basis of resistance in a new durum wheat (Triticum turgidum ssp. durum) Recombinant inbred lines (RILs) population obtained by crossing an hexaploid resistant line and a durum susceptible cultivar. A total of 135 RILs were used for constituting a genetic linkage map and mapping loci for head blight incidence, severity, and disease-related plant morphological traits (plant height, spike compactness, and awn length). The new genetic map accounted for 4,366 single nucleotide polymorphism markers assembled in 52 linkage groups covering a total length of 4,227.37 cM. Major quantitative trait loci (QTL) for scab incidence and severity were mapped on chromosomes 2AS, 3AL, and 2AS, 2BS, 4BL, respectively. Plant height loci were identified on 3A, 3B, and 4B, while major QTL for ear compactness were found on 4A, 5A, 5B, 6A, and 7A. In this work, resistance to Fusarium was transferred from hexaploid to durum wheat, and correlations between the disease and morphological traits were assessed.

Mapping QTLs for Fusarium Head Blight Resistance in an Interspecific Wheat Population

Fusarium head blight (scab) is one of the most widespread and damaging diseases of wheat, causing grain yield and quality losses and production of harmful mycotoxins. Development of resistant varieties is hampered by lack of effective resistance sources in the tetraploid wheat primary gene pool. Here we dissected the genetic basis of resistance in a new durum wheat (Triticum turgidum ssp. durum) Recombinant inbred lines (RILs) population obtained by crossing an hexaploid resistant line and a durum susceptible cultivar. A total of 135 RILs were used for constituting a genetic linkage map and mapping loci for head blight incidence, severity, and disease-related plant morphological traits (plant height, spike compactness, and awn length). The new genetic map accounted for 4,366 single nucleotide polymorphism markers assembled in 52 linkage groups covering a total length of 4,227.37 cM. Major quantitative trait loci (QTL) for scab incidence and severity were mapped on chromosomes 2AS, 3AL, and 2AS, 2BS, 4BL, respectively. Plant height loci were identified on 3A, 3B, and 4B, while major QTL for ear compactness were found on 4A, 5A, 5B, 6A, and 7A. In this work, resistance to Fusarium was transferred from hexaploid to durum wheat, and correlations between the disease and morphological traits were assessed.

Mapping a Type 1 FHB resistance on chromosome 4AS of Triticum macha and deployment in combination with two Type 2 resistances

Markers closely flanking a Type 1 FHB resistance have been produced and the potential of combining this with Type 2 resistances to improve control of FHB has been demonstrated. Two categories of resistance to Fusarium head blight (FHB) in wheat are generally recognised: resistance to initial infection (Type 1) and resistance to spread within the head (Type 2). While numerous sources of Type 2 resistance have been reported, relatively fewer Type 1 resistances have been characterised. Previous study identified a Type 1 FHB resistance (QFhs.jic-4AS) on chromosome 4A in Triticum macha. Little is known about the effect of combining Type 1 and Type 2 resistances on overall FHB symptoms or accumulation of the mycotoxin deoxynivalenol (DON). QFhs.jic-4AS was combined independently with two Type 2 FHB resistances (Fhb1 and one associated with the 1BL/1RS translocation). While combining Type 1 and Type 2 resistances generally reduced visual symptom development, the effect on DON accumulation was marginal. A lack of polymorphic markers and a limited number of recombinants had originally prevented accurate mapping of the QFhs.jic-4AS resistance. Using an array of recently produced markers in combination with new populations, the position of QFhs.jic-4AS has been determined to allow this resistance to be followed in breeding programmes.

Comparative mapping of quantitative trait loci for Fusarium head blight resistance and anther retention in the winter wheat population Capo × Arina

KEY MESSAGE

Fusarium resistance in Arina is highly quantitative and governed by multiple small effect QTL. Anther retention has a high correlation with FHB susceptibility and appears a practicable indirect selection target for enhancing FHB resistance. The Swiss winter wheat cultivar Arina possesses a high resistance level constituted by a number of small to medium effect QTL reported from three independent mapping populations. Yet these overlap only for one resistance QTL on the long arm of chromosome 1B. The present study characterized Fusarium head blight (FHB) resistance in a population of 171 recombinant inbred lines from a cross between Arina (resistant) and Capo (moderately resistant). The population was evaluated for FHB resistance under field conditions for 3 years. Additionally, we phenotyped anther retention, plant height and flowering date to analyze their association with resistance. Lines with a low proportion of retained anthers after flowering and tall plants were significantly less diseased, while flowering date had no association with FHB severity. QTL analysis identified eight small to medium effect QTL for FHB severity, of which QTL on 1BS, 3B, 4AL and 6BL likely correspond to resistance alleles already detected in previously studied Arina populations. QTL for anther retention mapped to 4AL, 6BL and 5AS. Notably, QTL on 4AL and 6BL overlapped with QTL for FHB severity. A single small effect QTL for plant height was detected on 5AS and no QTL was identified for flowering date. Genotypes having three or four resistance alleles in combination showed a good resistance level, indicating pyramiding resistance QTL as a powerful approach for breeding resistant cultivars. Selection for rapid and complete anther extrusion appears promising as an indirect selection criterion for enhancing FHB resistance.

Genetic architecture of fusarium head blight resistance in four winter triticale populations

Fusarium head blight (FHB) is a devastating disease that causes significant reductions in yield and quality in wheat, rye, and triticale. In triticale, knowledge of the genetic architecture of FHB resistance is missing but essential due to modern breeding requirements. In our study, four doubled-haploid triticale populations (N=120 to 200) were evaluated for resistance to FHB caused by artificial inoculation with Fusarium culmorum in four environments. DArT markers were used to genotype triticale populations. Seventeen quantitative trait loci (QTL) for FHB resistance were detected across all populations; six of them were derived from rye genome and located on chromosomes 4R, 5R, and 7R, which are here reported for the first time. The total cross-validated ratio of the explained phenotypic variance for all detected QTL in each population was 41 to 68%. In all, 17 QTL for plant height and 18 QTL for heading stage were also detected across all populations; 3 and 5 of them, respectively, were overlapping with QTL for FHB. In conclusion, FHB resistance in triticale is caused by a multitude of QTL, and pyramiding them contributes to higher resistance.

Variations for Fusarium head blight resistance associated with genomic diversity in different sources of the resistant wheat cultivar 'Sumai 3'

Fusarium head blight (FHB), caused by Fusarium graminearum, is a serious disease of wheat (Triticum aestivum L.) associated with contamination by the mycotoxin deoxynivalenol (DON). The FHB-resistant wheat cultivar 'Sumai 3' has been used extensively around the world. The existence of variation in FHB resistance among 'Sumai 3' accessions has been discussed. In this study, genetic variation among 'Sumai 3' accessions collected from six countries were identified using SSR markers; our results demonstrate unique chromosome regions in Sumai 3-AUT and Sumai 3-JPN ('Sumai 3' accessions from Austria and Japan, respectively). Field evaluation indicated strong resistance to FHB in Sumai 3-AUT. The polymorphic rate (number of polymorphic markers/number of available markers × 100) based on a DArT array was 12.5% between the two 'Sumai 3' accessions. Genotyping for DNA markers flanking FHB-resistant quantitative trait loci (QTLs) revealed genetic variations for the QTL regions on 5AS and 2DS; however, no variation was observed for the QTL regions on 3BS and 6B. Thus, the variation in FHB resistance among 'Sumai 3' accessions in the field is due to genetic diversity.

Genetic mapping of QTL for resistance to Fusarium head blight spread (type 2 resistance) in a Triticum dicoccoides × Triticum durum backcross-derived population

Improvement of resistance to Fusarium head blight (FHB) is a continuous challenge for durum wheat breeders, particularly due to the limited genetic variation within this crop species. We accordingly generated a backcross-derived mapping population using the type 2 FHB resistant Triticum dicoccoides line Mt. Gerizim #36 as donor and the modern Austrian T. durum cultivar Helidur as recipient; 103 BC1F6:7 lines were phenotyped for type 2 FHB resistance using single-spikelet inoculations and genotyped with 421 DNA markers (SSR and AFLP). QTL mapping revealed two highly significant QTL, mapping to chromosomes 3A and 6B, respectively. For both QTL the T. dicoccoides allele improved type 2 FHB resistance. Recombinant lines with both favorable alleles fixed conferred high resistance to FHB similar to that observed in the T. dicoccoides parent. The results appear directly applicable for durum wheat resistance breeding.

Whole genome association mapping of Fusarium head blight resistance in European winter wheat (Triticum aestivum L.)

A total of 358 recent European winter wheat varieties plus 14 spring wheat varieties were evaluated for resistance to Fusarium head blight (FHB) caused by Fusarium graminearum and Fusarium culmorum in four separate environments. The FHB scores based on FHB incidence (Type I resistance)×FHB severity (Type II resistance) indicated a wide phenotypic variation of the varieties with BLUE (best linear unbiased estimation) values ranging from 0.07 to 33.67. Genotyping with 732 microsatellite markers resulted in 782 loci of which 620 were placed on the ITMI map. The resulting average marker distance of 6.8 cM allowed genome wide association mapping employing a mixed model. Though no clear population structure was discovered, a kinship matrix was used for stratification. A total of 794 significant (-log10(p)-value≥3.0) associations between SSR-loci and environment-specific FHB scores or BLUE values were detected, which included 323 SSR alleles. For FHB incidence and FHB severity a total of 861 and 877 individual marker-trait associations (MTA) were detected, respectively. Associations for both traits co-located with FHB score in most cases. Consistent associations detected in three or more environments were found on all chromosomes except chromosome 6B, and with the highest number of MTA on chromosome 5B. The dependence of the number of favourable and unfavourable alleles within a variety to the respective FHB scores indicated an additive effect of favourable and unfavourable alleles, i.e. genotypes with more favourable or less unfavourable alleles tended to show greater resistance to FHB. Assessment of a marker specific for the dwarfing gene Rht-D1 resulted in strong effects. The results provide a prerequisite for designing genome wide breeding strategies for FHB resistance.