Fusarium Head Blight Resistance Genes Research Articles

Assessment of Fusarium Head Blight Resistance Genes in Domestic Wheat Varieties

Assessment of Fusarium Head Blight Resistance Genes in Domestic Wheat Varieties

Identification and transferring of a new Fusarium head blight resistance gene FhbRc2 from Roegneria ciliaris 3ScL chromosome arm into common wheat

Fusarium head blight (FHB) threatens wheat production worldwide. Utilization of FHB resistant varieties is the most effective solution for disease control. Owing to the limited sources of FHB resistance, mining of novel resistance genes is crucial. Here, we report an FHB resistance gene from a wild wheat relative species, Roegneria ciliaris and developed FHB resistant germplasm containing this gene. Wheat-R. ciliaris disomic addition line DA3Sc showed enhanced type II FHB resistance compared to its sister line 3Sc-Null without chromosome 3Sc, indicating that the resistance was contributed by the addition of 3Sc. The resistance gene on 3Sc was validated using F2 and F2:3 populations derived from the cross between DA3Sc and susceptible Aikang 58 (a susceptible cultivar), demonstrating that the lines with 3Sc had significantly enhanced FHB resistance compared to the individuals without 3Sc. This was the second resistance gene identified in R. ciliaris, designated FhbRc2. To transfer FhbRc2 to common wheat, we produced a double-monosomic chromosome population by crossing DA3Sc with the Chinese Spring nulli-tetrasomic line N3DT3B. Eight alien chromosome lines containing 3Sc were identified using genomic/fluorescence in situ hybridization and 3Sc-specific marker analysis. Only the lines carrying the long arm of 3Sc conferred FHB resistance, further locating FhbRc2 on 3ScL. A compensating wheat-R. ciliaris Robertsonian translocation line T3DS·3ScL harboring FhbRc2 is developed and provides a potential genetic resource in wheat breeding for enhanced FHB resistance.

Cytogenetic identification and molecular mapping for the wheat-Thinopyrum ponticum introgression line with resistance to Fusarium head blight.

Xinong 511, a new wheat-Thinopyrum ponticum variety with excellent fusarium head blight resistance, the QTLs were mapped to the wheat chromosomes 5B and 7A with named QFhb.nwafu-5B and QFhb.nwafu-7A, respectively. Novel Fusarium head blight (FHB) resistance germplasms and genes are valuable for wheat improvement and breeding efforts. Thinopyrum ponticum, a wild relative of common wheat, is a valuable germplasm of disease resistance for wheat improvement and breeding. Xinong 511 (XN511) is a high-quality wheat variety widely cultivated in the Yellow and Huai Rivers Valley of China with stable FHB-resistance. Through analysis of pedigree materials of the wheat cultivar XN511, we found that the genetic material and FHB resistance from Th. ponticum were transmitted to the introgression line, indicating that the FHB resistance in XN511 likely originates from Th. ponticum. To further explore the genetic basis of FHB resistance in XN511, QTL mapping was conducted using the RILs population of XN511 and the susceptible line Aikang 58 (AK58). Survey with makers closely-linked to Fhb1, Fhb2, Fhb4, Fhb5, and Fhb7, indicated that both XN511 and the susceptible lines do not contain these QTL. Using bulked segregant analysis RNA-seq (BSR-Seq) and newly developed allele-specific PCR (AS-PCR) markers, QTLs in XN511 were successfully located on wheat chromosomes 5B and 7A. These findings are significant for further understanding and utilizing FHB resistance genes in wheat improvement.

Enzymatic Degradation of Deoxynivalenol with the Engineered Detoxification Enzyme Fhb7.

In the era of global climate change, the increasingly severe Fusarium head blight (FHB) and deoxynivalenol (DON) contamination have caused economic losses and brought food and feed safety concerns. Recently, an FHB resistance gene Fhb7 coding a glutathione-S transferase (GST) to degrade DON by opening the critical toxic epoxide moiety was identified and opened a new window for wheat breeding and DON detoxification. However, the poor stability of Fhb7 and the elusiveness of the catalytic mechanism hinder its practical application. Herein, we report the first structure of Fhb7 at 2.41 Å and reveal a unique catalytic mechanism of epoxide opening transformation in GST family proteins. Furthermore, variants V29P and M10 showed that 5.5-fold and 266.7-fold longer half-life time than wild-type, respectively, were identified. These variants offer broad substrate scope, and the engineered biosafe Bacillus subtilis overexpressing the variants shows excellent DON degradation performance, exhibiting potential at bacterium engineering to achieve DON detoxification in the feed and biomedicine industry. This work provides a profound mechanistic insight into the enzymatic activities of Fhb7 and paves the way for further utilizing Fhb7-related enzymes in crop breeding and DON detoxification by synthetic biology.

Registration of WGC002 spring wheat containing wild grass‐derived Fusarium head blight resistance gene Fhb7The2

AbstractThe USDA‐ARS and North Dakota State University Agricultural Experiment Station jointly released the Fusarium head blight (FHB)‐resistant spring wheat (Triticum aestivum L.) germplasm WGC002 (Reg. no. GP‐1089, PI 702949) in May 2023. WGC002 is a wheat‐Thinopyrum elongatum 7B‐7E translocation line, designated 7BS·7BL‐7EL, with the wheat chromosome 7BL terminal region replaced by the homoeologous counterpart of the Th. elongatum chromosome 7EL that contains the novel FHB resistance gene Fhb7The2. WGC002 was developed from the Chinese Spring (CS) wheat‐Th. elongatum disomic substitution line DS 7E(7B) using our genomics‐enabled chromosome engineering pipeline. The pedigree of WGC002 is DS 7E(7B)/2*CS ph1b mutant//DS 7E(7B). WGC002 has consistently exhibited resistance to FHB in inoculations of greenhouse grown plants. WGC002 does not contain the yellow flour pigment gene in the Fhb7The2 haplotype present on the terminal 7EL segment of the 7BS·7BL‐7EL translocation and has not exhibited any obvious linkage drag on the 7EL segment. Therefore, WGC002 is ready for immediate use in wheat breeding. One sequence‐tagged site (STS) and two polymerase chain reaction allelic competitive extension markers were developed specifically for Fhb7The2 and validated in different wheat genotypes. They are highly diagnostic for Fhb7The2 and extremely useful in marker‐assisted introgression of Fhb7The2 in wheat breeding. In summary, WGC002 is a new wild grass‐derived FHB‐resistant spring wheat germplasm with diagnostic DNA markers available to conduct marker‐assisted selection of Fhb7The2, that will enhance and diversify FHB resistance of wheat.

Systemic development of wheat-Thinopyrum elongatum translocation lines and their deployment in wheat breeding for Fusarium head blight resistance.

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is one of the most destructive diseases of wheat (Triticum aestivum) around the world. FHB causes significant yield losses and reduces grain quality. The lack of resistance resources is a major bottleneck for wheat FHB resistance breeding. As a wheat relative, Thinopyrum elongatum contains many genes that can be used for wheat improvement. Although the novel gene Fhb-7EL was mapped on chromosome 7EL of Th. elongatum, successful transfer of the FHB resistance gene into commercial wheat varieties has not been reported. In this study, we developed 836 wheat-Th. elongatum translocation lines of various types by irradiating the pollen of the wheat-Th.elongatum addition line CS-7EL at the flowering stage, among which 81 were identified as resistant to FHB. By backcrossing the FHB-resistant lines with the main cultivar Jimai 22, three wheat-Th. elongatum translocation lines, Zhongke 1878, Zhongke 166, and Zhongke 545, were successfully applied in wheat breeding without yield penalty. Combining karyotype and phenotype analyses, we mapped the Fhb-7EL gene to the distal end of chromosome 7EL. Five molecular markers linked with the FHB resistance interval were developed, which facilitates molecular marker-assisted breeding. Altogether, we successfully applied alien chromatin with FHB resistance from Th. elongatum in wheat breeding without yield penalty. These newly developed FHB-resistant wheat-Th. elongatum translocation lines, Zhongke 1878, Zhongke 166, and Zhongke 545, can be used as novel resistance resources for wheat breeding.

Functional analysis of the glutathione S-transferases from Thinopyrum and its derivatives on wheat Fusarium head blight resistance.

Functional analysis of the glutathione S-transferases from Thinopyrum and its derivatives on wheat Fusarium head blight resistance.

Mapping Quantitative Trait Loci for Type II Fusarium Head Blight Resistance in Two Wheat Recombinant Inbred Line Populations Derived from Yangmai 4 and Yangmai 5.

Fusarium head blight (FHB) is a destructive wheat disease worldwide and significantly affects grain yield and quality in wheat. To understand the genetic basis underlying type II FHB resistance in two elite wheat cultivars Yangmai 4 (YM4) and Yangmai 5 (YM5), quantitative trait loci (QTL) mapping was conducted in two recombinant inbred lines (RIL) populations derived from the crosses of YM4 and YM5 with susceptible cultivar Yanzhan 1 (YZ1), respectively. Survey with markers linked to Fhb1, Fhb2, Fhb4, and Fhb5 in landrace Wangshuibai indicated the non-existence of these known FHB resistance genes/QTL in YM4, YM5, and YZ1. One overlapped resistance QTL was identified in both RIL populations, namely QFhb.Y4.2D/QFhb.Y5.2D, with a large effect on FHB resistance. One novel resistance QTL QFhb.Y4.5A mapped on chromosome 5A was detected only in YM4/YZ1 population. The resistance alleles of both QFhb.Y4.2D/QFhb.Y5.2D and QFhb.Y4.5A did not increase the plant height and did not significantly affect the heading date and flowering date. Kompetitive Allele-Specific PCR markers for QFhb.Y4.2D/QFhb.Y5.2D and QFhb.Y4.5A had been developed to verify in an additional set of 244 geographically diverse cultivars/lines. Pyramiding of the two resistance alleles decreased the percentage of symptomatic spikelets by 51.77% relative to the cultivars/lines without these two resistance alleles. QFhb.Y4.2D/QFhb.Y5.2D and QFhb.Y4.5A were shown to be useful alternatives in FHB resistance breeding programs. The results will facilitate the marker-assisted selection for introgression of the favorable alleles for improving FHB resistance in breeding programs.

Effects of Fhb1, Fhb2 and Fhb5 on Fusarium Head Blight Resistance and the Development of Promising Lines in Winter Wheat.

The development of Fusarium head blight (FHB)-resistant winter wheat cultivars using the gene Fhb1 has been conducted in northern China. Sumai 3, a Chinese FHB-resistant spring wheat cultivar, carries three FHB resistance genes: Fhb1, Fhb2 and Fhb5. To better use these genes for increasing FHB resistance in northern China, it is necessary to elucidate the pyramiding effects of Fhb1, Fhb2 and Fhb5 in winter wheat backgrounds. Eight gene combinations involving Fhb1, Fhb2 and Fhb5 were identified in a double haploid (DH) population, and the effects on FHB resistance were evaluated in six tests. At the single gene level, Fhb1 was more efficient than the other two genes in single-floret inoculation tests, whereas Fhb5 showed better resistance than Fhb1 and Fhb2 under a natural infection test. Pyramiding Fhb1, Fhb2 and Fhb5 showed better FHB resistance than the other gene combinations. Forty-nine DH lines showing consistently better resistance than the moderately susceptible control Huaimai 20 in multiple tests were evaluated for main agronomic traits, and no difference in grain yield was found between the mean values of DH lines and the recipient parents Lunxuan 136 and Lunxuan 6, which are higher than those of recipient parent Zhoumai 16 and the donor parent Sumai 3 (p < 0.05). Based on the phenotypic and genomic composition analyses, five promising DH lines fully combined the FHB resistance of donor Sumai 3 and the elite agronomic traits from the recipient parents. This study elucidates the pyramiding effects of three FHB resistance genes and that the promising DH lines with resistance to FHB can be directly applied in wheat production or as parents in winter wheat breeding programs.

Cytogenetic and genomic characterization of a novel tall wheatgrass-derived Fhb7 allele integrated into wheat B genome.

We identified and integrated the novel FHB-resistant Fhb7The2 allele into wheat B genome and made it usable in both common and durum wheat breeding programs without yellow flour linkage drag. A novel tall wheatgrass-derived (Thinopyrum elongatum, genome EE) Fhb7 allele, designated Fhb7The2, was identified and integrated into the wheat B genome through a small 7B-7E translocation (7BS·7BL-7EL) involving the terminal regions of the long arms. Fhb7The2 conditions significant Type II resistance to Fusarium head blight (FHB) in wheat. Integration of Fhb7The2 into the wheat B genome makes this wild species-derived FHB resistance gene usable for breeding in both common and durum wheat. By contrast, other Fhb7 introgression lines involving wheat chromosome 7D can be utilized only in common wheat breeding programs, not in durum wheat. Additionally, we found that Fhb7The2 does not have the linkage drag of the yellow flour pigment gene that is tightly linked to the decaploid Th. ponticum-derived Fhb7 allele Fhb7Thp. This will further improve the utility of Fhb7The2 in wheat breeding. DNA sequence analysis identified 12 single nucleotide polymorphisms (SNPs) in Fhb7The2, Fhb7Thp, and another Th. elongatum-derived Fhb7 allele Fhb7The1, which led to seven amino acid conversions in Fhb7The2, Fhb7Thp, and Fhb7The1, respectively. However, no significant variation was observed in their predicted protein configuration as a glutathione transferase. Diagnostic DNA markers were developed specifically for Fhb7The2. The 7EL segment containing Fhb7The2 in the translocation chromosome 7BS·7BL-7EL exhibited a monogenic inheritance pattern in the wheat genetic background. This will enhance the efficacy of marker-assisted selection for Fhb7The2 introgression, pyramiding, and deployment in wheat germplasm and varieties.

Development and validation of diagnostic markers for the wheat Fusarium head blight resistance gene Fhb7

AbstractFusarium head blight (FHB), mainly incited by Fusarium graminearum Schwabe, has caused great losses in grain yield and quality of wheat globally. Fhb7, a gene with a major effect on FHB resistance, was recently cloned and shown to be a GST encoding glutathione S‐transferase. Fhb7 originated from the 7E chromosome of Thinopyrum ponticum and confers broad resistance to Fusarium species. However, high‐throughput diagnostic markers are not available for wider deployment of Fhb7 in breeding programs. To develop such DNA markers for high‐throughput screening of Fhb7, we designed two kompetitive allele specific polymerase chain reaction (KASP) markers (Fhb7‐KASP1 and Fhb7‐KASP2) based on the promoter and coding sequences of GST homologs and tested their cosegregation with Fhb7 FHB resistance in a recombinant inbred population. As a validation of their usefulness in marker‐assisted selection in breeding programs, Fhb7‐KASP1 and Fhb7‐KASP2 were shown to be diagnostic for Fhb7 status in a set of RWG34‐near‐isogenic lines (NILs) and a natural winter wheat population (RGON2020). Haplotype analysis of Thinopyrum accessions using the two markers and GST homolog sequences identified only six accessions with the Fhb7 resistance marker alleles and the Hap I‐R haplotype, and five of them were cytologically confirmed to be Th. ponticum, the species in which Fhb7 was originally identified. The development of the diagnostic markers in this study will facilitate the deployment of Fhb7 in wheat breeding programs to improve FHB resistance.

Genomic compatibility and inheritance of hexaploid-derived Fusarium head blight resistance genes in durum wheat.

Hexaploid-derived resistance genes exhibit complex inheritance and expression patterns in tetraploid backgrounds. This study aimed to characterize the inheritance patterns and genomic compatibilities of hexaploid-derived Fusarium head blight (FHB) resistance genes in tetraploid durum wheat (Triticum durumDesf.). Evaluation of FHB resistance for F1 hybrids of hexaploid 'Sumai 3' crossed with tetraploid and hexaploid wheats indicated that Sumai 3-derived FHB resistance genes exhibit a dominant phenotypic effect seen only in hexaploid hybrids. Alternately, the hexaploid-derived FHB resistance genes from PI 277012 exhibited complete dominance in the crosses with both tetraploid and hexaploid wheat. FHB evaluation of the F1 hybrids of Sumai 3 and PI 277012 crossed with 'Langdon' (LDN)-'Chinese Spring' D-genome substitution lines suggested that chromosomes 2B, 3B, 4B, 5B, 6B, 3A, 4A, 6A, and 7A contain genes that suppress expression of the Sumai 3-derived FHB resistance, whereas chromosomes 4A, 6A, and 6B contain genes required for expression of PI 277012-derived FHB resistance. A wide range of segregation for FHB severity (10-90%) was observed in the F2 generation of Sumai 3 crossed with durum cultivars LDN and 'Divide', but the distribution of F3 families derived from the most resistant F2 segregants was skewed towards susceptibility. Similar segregation trends were observed in the crosses of PI 277012 with other durum wheats, whereby FHB resistance became slightly diluted over successive generations. These results suggest tetraploid durum wheat contains the unique alleles at multiple gene loci on different chromosomes that positively and/or negatively regulate the expression of hexaploid-derived FHB resistance genes, which complicate efforts to deploy these genes in durum breeding programs.

Analysis of Fhb1 gene and resistance to Fusarium head blight in 3,177 diverse wheat accessions

Fusarium head blight (FHB), elicited mainly by the fungal pathogen Fusarium graminearum (Fg), causes serious damages to global wheat production. Development of resistant cultivars is the most efficient measure for controlling FHB, which requires efficient identification and utilization of the wheat germplasm carrying FHB resistance genes. Because the Fhb1 gene recently cloned from the wheat cultivars Sumai 3 and Wangshuibai, designated here as Fhb1-R, confers type II resistance to FHB, we investigated the presence of Fhb1-R in 3,177 wheat accessions from different countries of the world. By PCR screening with a functional molecular marker amplifying a part of Fhb1 genomic sequence, Fhb1-R was detected in 33 of the 3,177 accessions. Through two independent inoculation tests with Fg under greenhouse conditions, eight Fhb1-R carrying lines were found to exhibit relatively high levels of type II resistance to FHB, seven of which were newly identified in this work. Remarkably, a substantial proportion of Fhb1-R carrying accessions were actually susceptible to Fg infection, highlighting the fact that the presence of Fhb1-R is not always associated with type II FHB resistance. Further analysis of representative Fhb1-R carrying accessions led to the finding of one Fhb1-R carrying, but FHB susceptible, wheat accession showing moderate resistance to Fusarium crown rot (FCR), another serious disease caused mainly by Fusarium pseudograminearum (Fp). Our work provides insight into the presence of Fhb1-R in a large set of diverse wheat germplasm lines and new genetic resources likely useful for improving wheat resistance to FHB or FCR in the future.

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.

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.

Disease Resistance and Genes in 146 Wheat Cultivars (Lines) from the Huang-Huai-Hai Region of China

Wheat stripe rust, powdery mildew, and Fusarium head blight (FHB) are the three most important diseases in wheat worldwide. Growing resistant cultivars is the most economic and effective method to control these diseases. To assess the disease resistance of commercial wheat cultivars and regional trial wheat lines in the Huang-Huai-Hai region of China, 146 wheat entries were inoculated with the Chinese prevalent Puccinia striiformis f. sp. tritici (Pst) races CYR32, CYR33, CYR34, and Blumeria graminis f. sp. tritici (Bgt) isolate E09 under controlled greenhouse conditions, respectively; these entries were also tested with the mixed Pst races, Bgt and FHB isolates at adult-plant stage in the field, respectively. The results showed that 108 (73.97%), 83 (56.85%), 99 (67.81%), and 22 (15.07%) entries were resistant to CYR32, CYR33, CYR34, and E09 at the seedling stage, respectively; 102 (69.86%), 24 (16.44%), and 2 (1.37%) entries were resistant to stripe rust, powdery mildew, and Fusarium head blight at the adult-plant stage, respectively. Additionally, the possible resistance gene(s) in these entries were postulated by the closely linked markers of stripe rust resistance genes Yr5, Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, powdery mildew resistance gene Pm21, and Fusarium head blight resistance gene Fhb1. Combined with disease resistance and molecular markers tests, 62, nine, and three wheat entries were postulated to carry the Yr9, Yr17, Yr26 gene, respectively, and no entries contained Yr5, Yr10, Yr15, Yr18, Pm21, and Fhb1 gene. This study laid a theoretical foundation for rational utilization of these entries and gene in wheat breeding programs and disease control.

Differential reaction of hexaploid and tetraploid wheat to Fusarium graminearum chemotypes in a controlled environment

Fusarium head blight (FHB) has a negative impact on cereal food safety, quality and yield. The majority of FHB resistance genes in wheat (Triticum spp.) have been identified based on reaction to Fusarium graminearum, which, in Canada, has two prevalent trichothecene chemotypes, 3-acetyl-deoxyinvalenol (ADON) and 15-ADON. Three hexaploid (Triticum aestivum L.) and four tetraploid (Triticum turgidum L. ssp. durum and Triticum turgidum L. spp. dicoccoides (Korn. ex Asch. & Graebn.) Thell.) wheat genotypes with different genes for resistance and with different reactions to F. graminearum were evaluated in replicated greenhouse trials to determine if the resistance genes currently deployed in Canadian wheat are effective against both the 3-ADON and 15-ADON chemotypes. The development of FHB was rated as disease severity. The genotypes showed differential responses, with a higher level of disease development in the hexaploid wheat genotypes inoculated with the 3-ADON than with the 15-ADON chemotype. The opposite was observed in the tetraploid wheat genotypes. Tetraploid genotype BGRC3487 and a hexaploid genotype ND2710 showed similar resistance to both 3-ADON and 15-ADON chemotypes. These would be effective sources to breed lines resistant to both 3-ADON and 15-ADON chemotypes and reduce FHB risk.

Molecular breeding of wheat lines for multiple rust and Fusarium head blight resistance

Bread wheat is a widely cultivated crop with production that is often negatively influenced by disease outbreaks. Biological constraints in production include the wheat rusts (leaf rust, stem rust and stripe rust) and Fusarium head blight (FHB). Different strategies are available in the control of these important fungal diseases. However, resistance breeding remains the preferred option of control as it lowers the risk of disease outbreaks and is a more cost effective and environmentally friendly approach. Many effective rust and FHB resistance genes have been discovered and successfully deployed through resistance breeding worldwide. However, some of these genes, when deployed singly, are vulnerable to evolving pathogens. In this study we aimed to develop wheat lines with the prospect of durable resistance against the rusts and FHB through combining eight resistance genes/quantitative trait loci; Lr19, Lr34/Yr18/Sr57/Pm38/Ltn1, Sr2/Yr30, Sr26, Sr39, Fhb1, Qfhs.ifa-5A-1 and Qfhs.ifa-5A-2 into a single wheat plant using marker-assisted selection. Cross and self-pollinated populations were developed to increase the frequency and homozygosity levels of resistance genes in progeny. Molecular markers were furthermore applied to determine the identity of the high molecular weight-glutenin subunits (HMW-GS) and to screen for the presence of the 1BL.1RS translocation in the final populations. We were successful in developing wheat plants containing complex sources of rust and FHB resistance and confirmed the presence of HMW-GS markers linked to strong dough strength and good bread making qualities in these genotypes.

Integrated metabolo-transcriptomics and functional characterization reveals that the wheat auxin receptor TIR1 negatively regulates defense against Fusarium graminearum.

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe (teleomorph Gibberella zeae (Schw.) Perch) results in large yield losses in annual global wheat production. Although studies have identified a number of wheat FHB resistance genes, a deeper understanding of the mechanisms underlying host plant resistance to F. graminearum is required for the control of FHB. Here, an integrated metabolomics and transcriptomics analysis of infected wheat plants (Triticum aestivum L.) enabled identification of 789 differentially accumulated metabolites, including flavonoids, phenolamides, tryptamine derivatives, and phytohormones, and revealed altered expression of more than 100 genes that function in the biosynthesis or regulation of these pathways. Our data regarding the effects of F. graminearum infection on flavonoids and auxin signaling led to follow-up experiments that showed that exogenous kaempferide and apigenin application on spikes increased wheat resistance to FHB, while exogenous auxin treatment increased FHB susceptibility. RNAi-mediated knockdown of the gene encoding the auxin receptor, TaTIR1, increased FHB resistance. Our data supported the use of TaTIR1 knockdown in controlling FHB. Our study provides insights on the wheat response to F. graminearum infection and its FHB resistance mechanisms while illustrating the potential of TaTIR1 knockdown in increasing FHB resistance during crop improvement programs.

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.