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Landessaatzuchtanstalt

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/32

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Browsing Landessaatzuchtanstalt by Subject "Ährenfusariosen"

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    Molecular mapping of resistance and aggressiveness in the cereal/Fusarium head blight pathosystem
    (2016) Kalih, Rasha; Miedaner, Thomas
    Fusarium head blight (FHB) is one of the most destructive fungal diseases in small-grain cereals worldwide causing significant yield losses and contamination of grain with mycotoxins e.g., deoxynivalenol (DON). This renders the grain unsuitable for human consumption and animal feeding. Exploring the genetic mechanism of FHB resistance is considered the key tool for modern cereal breeding activities. Triticale, the intergeneric hybrid between wheat and rye, is an important cereal crop in Poland and Germany. Resistance breeding using genetic mapping to identify quantitative-trait loci (QTL) associated with FHB resistance represents the best strategy for controlling the disease. In parallel, understanding the mechanism of aggressiveness and DON production of F. graminearum will be a significant contribution to improve FHB management. The objectives of the present work were (1) identification of QTL related to FHB resistance in triticale, together with the analysis of the correlation of FHB severity with other related traits such as plant height and heading stage, (2) correlation between DON production and FHB severity, (3) mapping of dwarfing gene Ddw1 in triticale and studying its effect on FHB resistance, plant height and heading stage, (4) detection of SNPs in candidate genes associated with aggressiveness and DON production of a large Fusarium graminearum population in bread wheat. To study the genetic architecture of FHB resistance in triticale, five doubled-haploid (DH) triticale populations with 120 to 200 progenies were successfully tested under field conditions by inoculation with Fusarium culmorum (FC46) in multiple environments. All genotypes were evaluated for FHB resistance, plant height and heading stage. DArT markers were used to genotype triticale populations. Significant genotypic variances (P<0.001) were observed for FHB severity in all populations combined with high heritability. Twenty-two QTLs for FHB resistance in triticale were reported with two to five QTL per population, thus confirming the quantitative inheritance of FHB resistance in triticale. The most prominent (R2 ≥ 35%) QTLs were located on chromosomes 6A, 3B, 4R, and 5R. QTLs for plant height and heading stage were also detected in our work, some of them were overlapping with QTLs for FHB resistance. Correlation between FHB severity, DON content and Fusarium damaged kernels (FDK) in triticale was studied in the population Lasko x Alamo. Significant genotypic variance was detected for all traits. However, low correlation between FHB severity and DON content (r=0.31) was found. Interestingly, correlation between FHB severity and FDK rating was considerably higher (r=0.57). For FHB severity, two QTLs were detected in this population. A QTL located on chromosome 2A with minor effect for FHB severity was also a common QTL for DON content and FDK rating and explained ≥34% of genotypic variance for these two traits. A second QTL on chromosome 5R was a major QTL but it has no effect on DON content or FDK rating. For analyzing the rye dwarfing gene Ddw1 derived from the father Pigmej, 199 (DH) progenies were genotyped with DArT markers and in addition with conserved ortholog set (COS) markers linked to the Ddw1 locus in rye. QTL analyses detected three, four, and six QTLs for FHB severity, plant height and heading stage, respectively. Two specific markers tightly linked with Ddw1 on rye chromosome 5R explained 48, 77, and 71 % of genotypic variation for FHB severity, plant height, and heading stage, respectively. This is strong evidence, that we indeed detected the rye gene Ddw1 in this triticale population. Another objective was to highlight the association between quantitative variation of aggressiveness and DON production of 152 F. graminearum isolates with single nucleotide polymorphism (SNP) markers in seven candidate genes. One to three significant SNPs (P < 0.01 using cross-validation) were associated to FHB severity in four genes (i.e., Gmpk1, Mgv1, TRI6, and Erf2). For DON content, just one significant SNP was detected in the gene Mgv1 explaining 6.5% of the total genotypic variance. In conclusion, wide genetic variation in FHB resistance in triticale has been observed in five populations. QTL mapping analyses revealed twenty-two QTLs for FHB resistance derived from wheat and rye genomes. QTLs located on the rye genome were reported here for the first time and they are a new source for FHB resistance in triticale. In parallel, analysis of the diversity of four pathogenicity genes in F. graminearum is an important first step in inferring the genetic network of pathogenicity in this fungal pathogen.
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    Publication
    Quantitativ-genetische Untersuchungen zur Vererbung der Resistenz gegen Ährenfusarium bei Triticale (x Triticosecale Wittmack)
    (2004) Heinrich, Nicole; Miedaner, Thomas
    Fusarium head blight (FHB), caused by Fusarium culmorum (W.G. Smith) Sacc. and F. graminearum Schwabe, is recognized as one of the most destructive diseases of small-grain cereals. Fusarium infection can cause substantial yield losses. Infected grain may also be contaminated by mycotoxins that are harmful to humans and livestock. Agronomical measures and fungicides are only partly effective in controlling FHB. The development of disease-resistant cultivars together with appropriate crop management practices are effective strategies to control FHB. In this study, seven triticale cultivars and three breeding strains, representing a range of FHB resistances, their 45 diallel F1 crosses, progenies of 15 F2s from a six-parent diallel and their 30 backcrosses (BC, 15 to each parent), and five F2:3 bulks were investigated. Parents and their progenies were grown in several environments (years, locations) and tested for FHB resistance after artificial inoculation with Fusarium culmorum. Within the scope of this study, three experiments were conducted to estimate various quantitative-genetic parameters of several traits. In Experiment 1, the influence of FHB on yield-related traits of the ten parents was assessed. Compared to a non-inoculated variant, Fusarium reduced 1000-grain weight by 10.0%, spike weight by 9.3%, the number of kernels per spike by 4.3%, and test weight by 7.4%. Inoculation also increased deoxynivalenol (DON, 26.4 mg kg-1) and exoantigen (1.34 OD). content of the kernels. Genotypic variation and genotype-environment interaction were significant for all traits. The correlation between symptom ratings (spikes, kernels) and yield traits and between spike weight and kernels per spike were negative and high. The aim of Experiment 2 was to estimate combining ability, hybrid performance and heterosis for FHB ratings, DON and exoantigen content. Heterosis of FHB for spike and kernel rating was small. Across environments, the DON content in F1 crosses, however, was 15.5% higher than their mid-parent value. A high and significant (P = 0.01) correlation of r = 0.8 was found for both spike and kernel FHB symptom ratings between mid-parent and F1 performance. Except for exoantigen content, the general combining ability (GCA) was the main source of variation, suggesting additive gene effects for FHB resistance. Significant specific combining ability variance implies non-additive types of allelic interaction also. Therefore, in some crosses dominant effects can play an important role. The relationship between the GCA effect of a parent and its per se performance was close. In Experiment 3, genetic variation and effects for FHB resistance were estimated in segregating generations. The resistance level of the parents and their F2 progenies were similar. In contrast, the resistance of the BC progenies to the resistant parent was considerably higher than that of the backcrosses to the susceptible parent. Significant differences between the means of the 15 crosses and a high genetic variation within crosses were observed. Transgression could not be detected. F2:3 bulks and their parents had a comparable resistance level. For F2 and BC progenies, the additive effect was more important than the dominant effect. In contrast, the F1 crosses had a higher dominant effect, but with a large error. The study revealed considerable genetic variation in all generations for FHB resistance that can be exploited in a breeding programme. The mainly additive genetic effect makes it possible to select crossing parents on the basis of their per se performance. Due to the importance of genotype-environment interaction, resistance tests in various environments are strongly recommended. Screening for FHB resistance can best be accomplished by assessing symptom ratings of spikes and/or the spike weight relative to a non-inoculated variant. The high cross-environment interaction variance in the F2 generation points to the problem of selecting in unreplicated segregating material. Selection should be postponed to the F3 or later generations. The large genetic variation of FHB resistance and the preponderance of additive gene effects are encouraging to further increase resistance in triticale by recurrent selection.