Browsing by Subject "Fusarium Head Blight"

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    Agronomic characteristics, malt quality, and disease resistance of barley germplasm lines with partial Fusarium head blight resistance
    (Crop Science, 2005-07) Steffenson, Brian; Urrea, Carlos A.; Horsley, Richard D.; Schwarz, Paul B.
    Fusarium head blight (FHB), incited by Fusarium graminearum Schwabe, has caused devastating losses in both yield and quality of barley (Hordeum vulgare L.) produced in the northern Great Plains from 1993 to 2003. Thirty-five barley germplasm lines with partial resistance to FHB have been identified in exotic and unadapted germplasm lines. Little is known about their agronomic characteristics, malt quality, and reaction to other diseases as compared to adapted cultivars. This information is needed so barley breeders can make informed decisions when planning crosses involving the resistant germplasm lines. The objective of this study was to compare the agronomic performance, malt quality, and disease reaction of barley germplasm lines with partial FHB resistance to cultivars grown in the northern Great Plains. Agronomic and malting data were collected on the 35 germplasm lines and five check cultivars grown in five environments in North Dakota from 1998 to 2000. Data for FHB severity and deoxynivalenol (DON, a mycotoxin produced by F. graminearum) accumulation were obtained for the same 40 entries grown in FHB-epidemic nurseries in North Dakota from 1997 to 1999. Seedling responses to foliar pathogens common in the northern Great Plains were determined in the greenhouse during fall 1997. None of the FHB-resistant barley germplasm lines had acceptable malt quality for all traits. Kernel plumpness, grain protein concentration, and malt extract were the traits impacted most severely. The FHB-resistant barley germplasm lines headed significantly later than the adapted barley cultivars. Most FHB-resistant germplasm lines were susceptible to the common foliar diseases of the northern Great Plains. At least four cycles of breeding will probably be necessary to develop FHB-resistant germplasm lines acceptable to producers and the malting and brewing industry.
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    A barley UDP-glucosyltransferase provides high levels of resistance to trichothecenes and Fusarium Head Blight in cereals
    (2017-08) Li, Xin
    Fusarium Head Blight (FHB) is a devastating disease that leads to severe economic losses to worldwide wheat (Triticum aestivum) and barley (Hordeum vulgare L.) production. During FHB disease development, the main causal fungal pathogen, Fusarium graminearum can infect a single spikelet and cause disease symptoms throughout the spike in susceptible wheat. Moreover, F. graminearum produces trichothecene mycotoxins (eg., deoxynivalenol (DON), nivalenol (NIV) and their derivatives) that facilitate FHB disease development, and toxin contamination of the grain poses a significant threat to human and animal health. Two major types of resistance have been identified and deployed in breeding programs including: type I (resistance to initial infection) and type II (resistance to spread of the symptoms). Although worldwide efforts have focused on germplasm screening and QTL mapping of FHB resistance, unfortunately, resistance to FHB is quantitatively controlled and only partial. Thus, research efforts have expanded to identifying genes and deploying them in transgenic wheat. Previous gene expression analysis in the barley cultivar ‘Morex’ led to discovery of a UDP-glucosyltransferase gene, HvUGT13248, that was shown to provide DON resistance in transgenic yeast and Arabidopsis thaliana via conjugation of DON to DON-3-O-glucoside (D3G), a much less toxic derivative. To test this promising gene in wheat, we developed transgenic wheat expressing HvUGT13248 and showed that these transgenic plants exhibited significant reduction of disease spread (type II resistance) in the spike compared with nontransformed controls. Expression of HvUGT13248 in transgenic wheat rapidly and efficiently conjugated DON to D3G. Under field conditions, FHB severity was variable between different transgenic lines; however, in some years the transgenic wheat showed significantly less severe disease phenotypes compared with the nontransformed controls. Moreover, HvUGT13248 is also capable of converting NIV to the detoxified derivative, NIV-3-O-β-D-glucoside (NIV3G). An enzymatic assay using HvUGT13248 purified from Escherichia coli showed that HvUGT13248 efficiently catalyzed NIV to NIV3G. Overexpression in yeast, Arabidopsis thaliana and wheat showed enhanced NIV resistance when grown on media containing different levels of NIV. Increased ability to convert nivalenol to NIV3G was observed in transgenic wheat, which also exhibits type II resistance to a NIV-producing F. graminearum strain. Transgenic wheat expressing HvUGT13248 also provides type II resistance to F. graminearum strains producing 3-ADON and NX-2, and resistance to root growth inhibition in 3,15-diANIV-containing media. Moreover, the HvUGT13248 transgene was introgressed into the elite wheat cultivars ‘Rollag’ and ‘Linkert’, and greenhouse point inoculation results showed that HvUGT13248 improved FHB resistance in elite backgrounds. HvUGT13248 overexpression in transgenic barley also enhanced DON resistance observed in a root assay. In conclusion, HvUGT13248 is a highly effective FHB resistant gene that can detoxify a wide spectrum of trichothecene chemotypes. Thus, the mechanism of resistance is by rapidly detoxifying trichothecenes to their glucoside forms.
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    Exploring Variation for Fusarium Head Blight Resistance and Deoxynivalenol Distribution in the Naked Barley Diversity Panel
    (2022-07) Hawkins, John
    Hull-less or naked barley (Hordeum vulgare L.) is a grain of growing importance in food, feed, and malting applications. Fusarium Head Blight (FHB), a disease caused by fungi in the genus Fusarium, causes significant damage to barley grain through accumulation of mycotoxins and undesirable fungal proteins and reduction of grain mass and malting quality. The most important Fusarium mycotoxin in North America is deoxynivalenol (DON). Naked barley accumulates significant amounts of DON in hull tissue, which is discarded at threshing, providing a mechanism for limiting FHB discounts due to mycotoxin contamination. For this research, genome wide association studies were performed using the Naked Barley Diversity Panel genotyped with an array of 50,000 single nucleotide polymorphisms (SNPs) and phenotyped for traits associated with DON distribution in the barley spike. Three notable quantitative trait loci (QTLs) for disease related traits were discovered. A QTL on the short arm of chromosome 3H, linked to a hydroxyproline rich glycoprotein gene was associated with reduced FHB severity. Another QTL on the long arm of 3H, linked to sdw1, was associated with shorter plants, greater FHB severity under grain spawn inoculation, and earlier heading. A third QTL on the short arm of 2H, linked to PPD-H1, was associated with taller plants, later heading, and a greater proportion of the total DON being localized in the hull. Overall, there appears to be potential for the improvement of FHB resistance and DON mitigation in naked barley.
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    Genetic characterization of multiple disease resistance and agronomical/nutritional traits in hordeum
    (2013-08) Mamo, Bullo Erena
    Barley is an economically important crop plant whose yield and quality is affected by multiple diseases. Landrace and wild barley gene pools can be utilized to enhance disease resistance and nutrition in cultivated barley. To identify and map resistance loci for three important diseases (stem rust, spot blotch and Fusarium head blight [FHB]), and enhanced accumulation of two vital micronutrients (zinc and iron), genetic mapping was employed. The genetics of resistance to stem rust race TTKSK in Swiss landrace and wild barley accessions at the seedling stage was conducted through bi-parental mapping. Genetic analysis of F2:3 families derived from these accessions revealed that a single gene that maps to chromosome 5HL — at or in close proximity to the complex stem rust resistance locus rpg4/Rpg5 confers resistance. An association mapping approach was utilized to identify Quantitative Trait Loci (QTL) associated with disease resistance and zinc and iron concentration in 298 Ethiopian and Eritrean barley landraces genotyped with 7,842 single nucleotide polymorphism (SNP) markers. For stem rust race TTKSK, five seedling resistance loci were identified: one each on chromosome 2HS, 2HL, 3HL, 4HL, and 5HS. The ones on chromosomes 2HL and 4HL are novel, whereas the other three mapped to regions coincident with previously reported stem rust resistance QTL. For stem rust race MCCFC at the adult plant stage, one locus coincident with a known race TTKSK resistance QTL was identified on chromosome 5HL. For spot blotch, SNP markers located in close proximity with known adult plant spot blotch resistance QTL were found on chromosomes 2HL and 4HS in six-rowed barley landraces. For FHB, one common resistance QTL on chromosome 2HL, also associated with deoxynivalenol (DON) concentration, was identified. A locus mapping to a region of chromosome 4HL, known to contain QTL associated with DON, also was detected. The loci identified on chromosomes 2HL and 4HL associated with FHB and/or DON were not associated with heading date or plant height. Two novel loci associated with grain zinc concentration were identified on chromosomes 4HS and 6HL. For kernel weight, a known QTL region on chromosome 2HL was detected.
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    QTL Mapping for Discovery and Characterization of an Inhibitor of Fhb1 in Hexaploid Wheat (Triticum aestivum)
    (2017-05) Seda, Brian
    Fusarium head blight (FHB) is one of the most destructive diseases of wheat worldwide, resulting in decreased grain yield and seed quality, and infected grain that is unacceptable for end use due to the presence of mycotoxins, such as deoxynivalenol (DON). Asian sources of resistance have had the most impact worldwide, with the most prevalent resistance gene in many wheat breeding programs being Fhb1, originally mapped in the Chinese variety ‘Sumai 3.’ DON is the primary Fusarium graminearum virulence factor, and Fhb1 has been successful at preventing epidemics due to its dual role in fungal defense and DON detoxification, resulting in both reduction in DON concentration and prevention of disease spread within the grain head. However, during candidate gene investigation, segregating susceptibility occurred in the homozygous presence of Fhb1 in the moderately susceptible variety ‘Bobwhite.’ Other studies have also found resistance conferred by susceptible parents, which along with these candidate gene results, indicate there may be inhibitory genes present in some backgrounds that suppress the effect of FHB resistance genes. This study was conducted to first identify additional regions of the genome responsible for FHB resistance, and then determine if any of these regions could be inhibiting Fhb1. The 260-2 (Sumai 3/Stoa//MN97448 resistant NIL)/Bobwhite population used in the candidate gene study was recreated with separate sub-populations selected for the homozygous presence or absence of Fhb1, and genotyped with the 9K Infinium SNP chip. Quantitative trait loci for resistance and correlated traits (FHB spread, FHB severity, FHB incidence, DON accumulation, visually scabby kernels, 30 head weight, micro test weight, plant height, and heading date) were mapped in each sub-population, and phenotypic analysis indicated polygenic inheritance for all traits. Both populations identified genomic regions coincident with previously reported major genes (Fhb2 and Ppd-D1), as well as a potentially novel QTL on the long arm of chromosome 2A. The Fhb2 and 2A QTL regions were highly significant for FHB resistance and exhibited similar additive effects under both Fhb1 states. The combination of all trials conducted here indicates no interaction between any QTL and Fhb1. Although there is no evidence of resistance gene suppression, the results present a thorough investigation of additive gene action for Fusarium head blight resistance in the context of Fhb1-mediated resistance. Selection for QTL at multiple loci will enable wheat breeders to develop improved Fusarium head blight resistance, especially in the presence of Fhb1.
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    Registration of ‘Quest’ spring malting barley with improved resistance to Fusarium head blight
    (Journal of Plant Registrations, 2013-01-25) Steffenson, Brian; Smith, K.P.; Budde, A.; Dill-Macky, R.; Rasmusson, D.C.; Schiefelbein, E.; Wiersma, J.J.; Wiersma, J.V.; Zhang, B.
    ‘Quest’ (Reg No. CV-348, PI 663183) is a spring, six-rowed, malting barley (Hordeum vulgare L.) released by the Minnesota Agricultural Experiment Station in January 2010 on the basis of its improved resistance to Fusarium head blight [FHB; caused by Fusarium graminearum Schwabe; teleomorph Gibberella zeae (Schwein) Petch]. Quest was developed over three breeding cycles of selection for yield, malting quality, and FHB resistance. Disease resistance traces to the Midwest cultivar MNBrite and the two-rowed accession from China Zhedar1. Quest has about half the level of disease and about 40% less of the associated mycotoxin, deoxynivalenol, compared to the historically important cultivar in the region ‘Robust’. Quest is similar in yield to the current dominant varieties in the region and was approved as a malting variety by the American Malting Barley Association.
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    Trichothecene transport in the phytopathogen Fusarium graminearum and trichothecene production in the entomopathogen Beauveria bassiana.
    (2020-09) O'Mara, Sean
    This dissertation explores the transport mechanisms involved in the export of the trichothecene mycotoxin deoxynivalenol (DON) in the plant pathogenic fungus Fusarium graminearum, and the potential expression of a trichothecene biosynthetic gene homolog in the insect pathogen Beauveria bassiana. First, our current understanding of the biosynthesis and transport of fungal secondary metabolites is reviewed. The major classes of fungal secondary metabolites and the biosynthetic enzymes and gene clusters which produce them are covered, and notable examples of each secondary metabolite class are highlighted. This review emphasizes how our understanding of the biosynthesis of many secondary metabolites is far more complete than our understanding of the mechanisms which export or sequester the final bioactive molecule. Then, the role of the F. graminearum vesicular t-SNARE Sso2 in the export of DON is investigated. A knockout mutant of Sso2 is generated and shown to have an essential role in DON accumulation, virulence, and xenobiotic resistance. A double mutant, generated by crossing the Δsso2 mutant with the membrane-bound transporter mutant Δabc1, was shown to be further reduced in DON accumulation and virulence, indicating potentially interconnected, but independent, modes of DON export. Deletion of Sso2 is shown to down-regulate the expression of a number of F. graminearum secondary metabolite gene clusters and up-regulate many cellular repair gene categories. Subsequently, the role of Abc1 and other membrane-bound transporters in DON accumulation, virulence, and xenobiotic defense is investigated in further detail. Through in vitro, in planta, and heterologous expression studies it is shown that Abc1 plays the most substantial role in these processes, and other membrane-bound transporters may function primarily in defense and as accessory DON exporters. Afterwards, this dissertation examines the whether other Hypocreales fungi contain homologs for the trichothecene biosynthetic enzymes and identifies a putative trichothecene biosynthetic cluster in B. bassiana. Deletion attempts of the B. bassiana Tri5 homolog are undertaken but are unsuccessful, and further work suggests that a new antibiotic selection agent may be necessary. Expression studies indicate, however, that the BbTri5 homolog is not expressed in conditions known to induce trichothecene production in F. graminearum, bringing into question whether the B. bassiana trichothecene cluster is expressed in unknown conditions or not at all. This dissertation concludes by revisiting the major findings of each chapter and proposing future perspectives and experiments which have arisen throughout this body of research. Further examination of unused F. graminearum deletion mutants and heterologous expression of B. bassiana Tri homologs are emphasized for future consideration.