Browsing by Subject "Triticum aestivum"

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Analyse von Wachstum und Qualität von Weizen unter ansteigender CO2 Konzentration als Folge des Klimawandels
(2019) Dier, Markus; Zörb, Christian
The atmospheric CO2 concentration is expected to increase to 500–620 ppm in the future. Such an elevated atmospheric CO2 concentration (e[CO2]) increases grain yield, but can decrease tissue N concentrations by about 9% in wheat. This could endanger global food security. Moreover, in previous studies, a decrease of grain N concentration by e[CO2] has closely been associated with that of gluten proteins, indicating a decreased baking quality under e[CO2]. The mechanisms by which e[CO2] decreases N concentration are still unclear and FACE studies investigating CO2 x N interactions on the formation of grain yield and the quality of winter wheat are scarce. The first main objective was the analysis of a decreased N concentration in the grain by e[CO2] in winter wheat based on a two-year FACE experiment with widely differing N levels (35 to 320 kg N ha-1) and different N forms (NO3- and NH4+). The focus was on key processes of grain N acquisition that are leaf NO3- assimilation, N remobilization and post-anthesis N uptake. The hypotheses were: e[CO2] inhibits leaf NO3- assimilation, e[CO2] decreases N remobilization (Nrem) by decreased N concentrations at anthesis and e[CO2] decreases post-anthesis N uptake (Nabs) by inhibition of leaf NO3- assimilation or acceleration of senescence. The second main objective was the simultaneous analysis of the e[CO2] effect on the grain proteome and baking quality with the hypothesis that e[CO2] reduces gluten proteins and thereby baking quality. e[CO2] increased grain yield in all N levels by 10% to 17% mainly through enhanced grain number per m2 ground area. This was due to increased radiation use efficiency (chapter 2). These increases were smaller under N deficiency compared with high N supply. The reasons were a reduction of photosynthesis capacity by e[CO2] and a sink limitation concerning grain yield due to N deficiency during ear growth. The indication for the reduction of photosynthesis capacity was a decrease of leaf N concentration under e[CO2] regardless of green leaf area index under N deficiency. An indication for sink limitation of grain yield was the decrease of harvest index by e[CO2] because of a strong and small stimulation of stem and ear growth, respectively by e[CO2]. Grain N yield was increased by e[CO2] under all N levels (chapter 3). There was a strong linear relation between grain N yield and grain number that was unaffected by e[CO2]. In contrast with the hypotheses of an decreased Nrem and Nabs under e[CO2], e[CO2] resulted in an increase of Nrem, Nrem efficiency and Nabs, causing the increase of grain N yield. Nevertheless, e[CO2] slightly decreased grain N concentration (by 1 to 6%), whereby the smallest effect of 1% was found under N deficiency. This decrease was primarily related to a growth dilution effect due to an increased individual grain weight under e[CO2]. A further reason was a stronger increase of grain number than an increase of vegetative N yield at anthesis by e[CO2] and thereby a decrease of the ratio between the N source and the N sink. Indication for an e[CO2] induced inhibition of leaf NO3- assimilation was not found as e[CO2] did not result in a decreased activity of leaf nitrate reductase under all N levels at both cool (17 °C) and warm (28 °C) temperatures (chapter 4). Furthermore, the e[CO2] induced stimulation of growth and N acquisition was not stronger under NH4+ compared with NO3- based N-fertilization. Reduction of grain protein concentration by e[CO2] was associated with reduced albumin/globulin and gluten concentrations under all N levels (chapter 5). Under optimal N supply, the grain protein composition was changed by e[CO2] with altogether 19 decreased and 17 increased protein spots. 15 out of the 16 identified decreased proteins were globulins, whereas specific gluten proteins were not found to be affected by e[CO2]. Correspondingly, baking quality remained unaffected under e[CO2] under all N conditions. In conclusion, grain N yields were increased by e[CO2] due to an increase of Nrem and Nabs with grain number being the driving force. Grain N concentrations were slightly reduced under e[CO2] with a growth dilution effect and a changed source to sink ratio as the underlying mechanisms. The reduction of the grain N concentration by e[CO2] was not specifically associated with a reduction of gluten proteins.
Mapping of quantitative-trait loci (QTL) for adult-plant resistance to Septoria tritici in five wheat populations (Triticum aestivum L.)
(2010) Risser, Peter; Miedaner, Thomas
Septoria tritici blotch (STB), caused by Septoria tritici (teleomorph Mycosphaerella graminicola), is one of the most important diseases in wheat varieties worldwide, responsible for severe damage of the leaves causing yield losses between 30 and 40 %. Control of STB includes crop rotation, soil tillage, fungicide application, and cultivation of resistant varieties. Profit-making wheat growers are forced to apply narrow crop rotations under reduced tillage. Some fungicides including widely-used strobilurins are no longer effective due to mutations in the highly variable pathogen population of S. tritici. Therefore, resistance breeding using genetic mapping to identify quantitative-trait loci (QTL) associated with STB resistance provides a promising strategy for controlling the disease. The main goal of this study was to detect chromosomal regions for quantitative adult-plant resistance of winter wheat to STB. Besides this, we analyzed the genetic diversity of 24 European varieties after inoculation with four different isolates of S. tritici. Multienvironmental field trials inoculated with S. tritici were applied to test isolates and varieties and to phenotype mapping populations. In detail, the objectives were to (1) compare natural infection and inoculation, (2) evaluate genotypic variation of adult-plant resistance to STB in European varieties, (3) analyze genotype x environment (G x E) interaction, (4) evaluate and analyze phenotypic data including STB severity, heading date (HED), and plant height (PLH) of five mapping populations, (5) construct genetic linkage maps of these populations using AFLP, DArT, and SSR markers, (6) determine number, positions, and genetic effects of QTL for evaluated traits, and (7) reveal QTL regions for multiple-disease resistance within mapping populations using QTL meta-analysis. In all trials, inoculation with one to four preselected isolates was performed and STB severity was visually scored plotwise as percentage coverage of flag leaves with lesions bearing pycnidia. 24 winter wheat varieties were chosen with maximal differentiation in resistance to STB and evaluated across three years including nine environments. Five mapping populations, Florett/Biscay, Tuareg/Biscay, History/Rubens, Arina/Forno, and Solitär/Bussard, each comprising a cross of a resistant and a susceptible variety, with population sizes ranging from 81 to 316, were phenotyped across four to six environments. In parallel, 221 to 491 polymorphic genetic markers were assigned to linkage groups covering 1,314 to 3,305 cM of the genome. Based on these linkage maps, the number, positions, and genetic effects of QTL could be determined by composite interval mapping. Furthermore, raw data of different experiments evaluated for resistance to two other pathogens, Fusarium head blight and Stagnospora glume blotch, were used to reveal multiple-disease resistance QTL within Arina/Forno and History/Rubens populations by the software package PLABMQTL. Results of inoculated field trials coincided with not inoculated trials showing natural infection (r = 0.84 to 0.99, P < 0.01), thus inoculation method was accurate to evaluate STB severity in the field. Genotypic variation between 24 varieties ranged from 8 % (Solitär) to 63 % (Rubens) flag leaf area infected. In the analysis of variance, genotypic variance had highest impact followed by G x E interaction (P < 0.01). Therefore, environmental stability of varieties should be a major breeding goal. The varieties Solitär, History, and Florett were most stable, as revealed by a regression approach. In contrast, disease symptoms of Biscay ranged from 19 to 72 % within the three experimental years. Phenotypic data revealed significant (P < 0.01) genotypic differentiation for STB, HED, and PLH within all five mapping populations and between the parents. Entry-mean heritabilities (h²) ranged from 0.69 to 0.87 for STB, the only exception was Tuareg/Biscay (h² = 0.38). For HED (h² = 0.78 to 0.93) and PLH (h² = 0.92 to 0.98) heritabilities were high. All correlations between STB and HED (r = -0.18 to -0.33) as well as between STB and PLH (r = -0.13 to -0.45) were negative and moderate. The exception was History/Rubens which is segregating at the Rht-D1 locus showing considerably higher correlation between STB and PLH (r = -0.55, P < 0.01). The five mapping populations showed a wide and continuous distribution of mean STB severity averaged across three to six environments in field trials at adult-plant stage. In QTL analysis, one to nine, zero to nine, and four to eleven QTL were detected for STB, HED, and PLH, respectively, across five wheat populations using composite interval mapping. One to two major QTL for resistance to STB were detected consistently across environments in each population (QStb.lsa_fb-3B, QStb.lsa_fb-6D, QStb.lsa_tb-4B, QStb.lsa_tb-6B, QStb.lsa_hr-4D, QStb.lsa_hr-5B.1, QStb.lsa_af-3B, QStb.lsa_bs-7A) explaining more than 10 % of normalized adjusted phenotypic variance. Altogether, resistance QTL explained 14 to 55 % of adjusted phenotypic variance. Both parents contributed resistant alleles. Major QTL, however, were all from the resistant parent. QTL meta-analysis revealed each of four loci for multiple-disease resistance located on chromosomes 3B, 4B, 5B, and 6D in Arina/Forno, and on chromosomes 2B, 4D, 5B, and 7B in History/Rubens. The most effective meta QTL was on chromosome 4D in History/Rubens closely linked to Rht-D1. The resistance allele from History reduced disease severity by 9.8 % for STB and 6.3 % for FHB, thus explaining 47 % and 60 % of partial phenotypic variance. In general, European wheat varieties showed a wide range of genotypic variation for STB resistance useful for breeding. Although the influence of environment and G x E interaction was high, some resistant varieties which were stable across multiple environments were found (Solitär, History, Florett). Genomic regions associated with STB resistance were mapped across 13 out of 21 wheat chromosomes. Together with the continuous distribution of five segregating populations for flag leaf infection, it can be concluded that the adult-plant resistance to S. tritici was inherited quantitatively depending on several loci explaining part of phenotypic variance. QTL meta-analysis across three severe pathogens, including Fusarium head blight, Stagnospora glume blotch, and STB, within two populations revealed eight loci for multiple-disease resistance with closely linked markers applicable in resistance breeding. Combining detected major QTL as well as meta QTL in present breeding material by applying marker-assisted selection seems a promising approach to the breeding of varieties with improved resistance to Septoria tritici blotch, Fusarium head blight, and Stagnospora glume blotch.
Prospects of genomic selection for disease resistances in winter wheat (Triticum aestivum L.)
(2019) Grote, Cathérine Pauline; Miedaner, Thomas
Die Ziele dieser Arbeit waren (i) die erstmalige Evaluierung des Effekts des Zwerggens Rht24 auf FHB- und STB-Resistenzen, Wuchshöhe und Ährenschieben im Vergleich zum weit genutzten Locus Rht-D1, (ii) die Untersuchung des Potenzials der nichtadaptierten QTL Fhb1 und Fhb5 für die Entwicklung von Kurzstrohweizen, (iii) die Analyse der Vorhersagegenauigkeit von GS innerhalb und zwischen Familien durch die Anwendung der beiden Modelle RR-BLUP (ridge-regression best linear unbiased prediction) und wRR-BLUP (weighted RR-BLUP) und (iv) die Berechnung des Selektionsgewinns bzw. die Bestimmung der korrekt selektierten Top-10 %-Genotypen für FHB- und STB-Resistenzen durch GS. Die Ergebnisse dieser Studie zeigten, dass das gibberellinsäuresensitive Zwerggen Rht24 auf Chromosom 6 die Wuchshöhe um durchschnittlich 8,96 cm senkte, ohne dabei die FHB- und STB-Resistenzen oder den Zeitpunkt des Ährenschiebens ungünstig zu beeinflussen. Demgegenüber senkte das weitläufig verwendete Allel Rht-D1b die FHB-Resistenz um durchschnittlich 10,05 Prozentpunkte in einer Winterweizenpopulation bestehend aus acht biparentalen Familien, die für diese Resistenzloci segregierten. Diese Arbeit hat zusätzlich aufgezeigt, dass die Resistenzallele von Fhb1 und Fhb5 die FHB-Anfälligkeit um 6,54 bzw. 11,33 Prozentpunkte reduzierten und somit bereits allein das nicht-adaptierte Allel Fhb5b in der Lage ist, den negativen Effekt von Rht-D1b auf die FHB-Resistenz im untersuchten Material auszugleichen. Das verdeutlicht, dass die Wahl der Zwerg- und Resistenzgene in Zuchtprogrammen, in denen FHB-Resistenz ein Selektionsmerkmal ist, von entscheidender Bedeutung ist. In dieser Studie wurde des Weiteren das Potenzial der GS innerhalb und zwischen Familien untersucht. Die Vorhersagegenauigkeiten innerhalb einer Familie waren für alle Zielmerkmale höher als die zwischen Familien und unterschieden sich zwischen den einzelnen Familien und Vorhersagekonstellationen. Die stärkere Gewichtung von signifikanten Markern durch das wRR-BLUP-Modell führte zu einer Verbesserung der Vorhersagegenauigkeit im Vergleich zum weit genutzten RR-BLUP-Modell, wenn einzelne Gene, wie Rht-D1, oder Major-QTL, wie Fhb5, vorhanden waren. In dieser Studie wurden die genomisch geschätzten Zuchtwerte (GEBVs) von 2.500 ungeprüften Genotypen bestimmt, basierend auf einer partiell verwandten Trainingspopulation von 1.120 Genotypen. Die 10 % FHB- und STB-resistentesten Linien und eine zufällige Stichprobe wurden unter Berücksichtigung der Wuchshöhe genomisch selektiert und phänotypisch in einem vierortigen Feldversuch evaluiert. Für die FHB-Resistenz wurde ein Selektionserfolg von 10,62 Prozentpunkten relativ zur zufällig selektierten Populationsstichprobe ermittelt. Die GS erhöhte die STB-Resistenz allerdings nur um 2,14 Prozentpunkte. Auch die Selektion von neuen Kreuzungseltern auf der Basis von GS erscheint nicht ausreichend zuverlässig, da nur 19 % der Top-10 %-Individuen korrekt selektiert wurden. Zusammenfassend stellt die GS ein wertvolles Werkzeug dar, um den Zuchtfortschritt für die komplex vererbte FHB-Resistenz über kürzere Zyklen und größere Populationen zu unterstützen. In Kombination mit der Nutzung geeigneter Zwerggene und des nicht adaptierten QTL Fhb5 kann dadurch eine Steigerung der FHB-Resistenz im Winterweizen erzielt werden.
Studies on water-soluble carbohydrates in wheat (Triticum aestivum L.): regulating traits, model analysis, early chilling effects, and future perspectives
(2009) Valluru, Ravi; Claupein, Wilhelm
Wheat is one of the major staple food crops of the world. Although a wealth of research has been made a significant progress in wheat productivity through genetic interventions in the last two decades, there remains an untapped potential for further yield gain. Water-soluble carbohydrates (WSCs) are excess carbohydrates stored in vegetative organs such as stem, sheaths, and tiller base during vegetative period. They are highly heritable agronomic trait that regulates plant growth and development as well as grain yields. In addition, WSCs also contribute to plant adaptation to abiotic stresses. Improving current understanding of the multi-faceted roles of WSCs is therefore essential for future crop improvement. The present thesis provides information on WSCs, its associated traits and future perspectives that derived from several experiments conducted under field and glasshouse conditions. Typically, the thesis has four objectives dealing with a specific set of questions. The first objective explains the traits regulating WSCs under three N levels (0, 100 and 200 kg ha-1). N concentration in the plant is negatively correlated with WSCs storage. The traits associated with total WSCs storage are also influenced by N levels. Three vegetative traits, viz., total biomass, flag-leaf width, root: shoot ratio and two physiological traits, viz., radiation use efficiency, and leaf N concentration were considered. Under high N level, lower biomass, flag-leaf width and root: shoot ratio is beneficial to increase total WSC storage. In contrast, increasing biomass and flag-leaf width is advantageous under lower N level. However, a specific set of traits, rather than a single trait, appeared to evolve under N-specific selection maximizing total WSC storage. The second objective describes the simulation model for WSC accumulation under three N levels. A simple phenological model for carbon accumulation, in the form of WSCs, during vegetative period in four wheat genotypes was developed. This model was integrated and evaluated under crop management factors such as low (0 kg ha-1), medium (100 kg ha-1), and high (200 kg ha-1) nitrogen supply. The proposed model predicted higher rate of WSC accumulation in the early stages of crop growth and lower rates in the later stages. Overall, the model predicted the rate of WSC accumulation with a RMSE of 6.58, suggesting that the proposed model simulated well. Nevertheless, the predicted rate of WSC accumulation was close to the observed data only in low and high N level. The model predicted total WSCs well with the observed data; however, it overestimated total WSCs at early stages and underestimated total WSCs at later stages, largely due to the respective rate of WSC accumulation. Overall, evaluation of the model with the predicted dataset indicated that the prediction errors for the rate of WSC accumulation were more with RMSE between 20-30% in all N levels. For total WSC accumulation, the prediction errors were less, and the RMSE, in most cases, was less than 20% in all N levels. The third objective reveals the plasticity of the phenotypic expression of two primitive wheat species (Triticum monococcum L. and T. dicoccum S.) in response to early chilling stress (4 oC). Early chilling stress resulted in lower total WSCs, in addition to lower flag leaf size, total biomass, specific leaf area and early flowering. While lower specific leaf area may reduce the early chilling stress effects at an individual leaf level, a higher leaf mass ratio and utilization of reserve carbohydrates indicated that the compensatory growth of chilled plants during the recovery period relied on the concerted action of altered resource allocations and reserve carbohydrate consumption. However, the lack of direct selection on sucrose indicates that sucrose has indirect effects on total WSCs. Thus, the total effects of reserve sucrose on relative fitness seem to be buffered via rapid growth rate in chilled plants. Nevertheless, a significant cost of plasticity was evident only for fructans. Further, a regression of daily cumulative plant biomass derived from a crop growth simulation model (CERES-Wheat) on crop growing period revealed a divergent developmental pathway for early chilled plants. These results showed that not only are the characteristic architectures in two Triticum species plastic, but the regulating mechanism of intrinsic developmental (ontogenetic) pathway is also sensitive to early chilling stress. Fourth objective provides future perspectives for WSCs, in particular fructans. Fructans can be involved in freezing tolerance by protecting cellular membranes. This opinion postulates that fructans can be transported from vacuole (site of synthesis) to apoplast (site of action) through vesicles derived from the vacuole. These results can improve the current understanding of WSCs in plant growth and development as well as grain yields. Traits can be used as WSCs markers to prescreen a large number of wheat germplasm for high total WSCs contents. However, a further understanding of different dimensions of WSCs in grain yield improvement and plant growth and development deserves more attention.
The wheat AMT2 (AMmonium Transporter) family, possible functions in ammonium uptake and pathogenic/symbiotic interactions
(2023) Porras‐Murillo, Romano; Zhao, Yufen; Hu, Jinling; Ijato, Toyosi; Retamal, Joseline Palafox; Ludewig, Uwe; Neuhäuser, Benjamin
Ammonium uptake into wheat roots relies primarily on two AMmonium Transporters of subfamily one, while the wheat genome comprises 4 to 6 AMT2 type transporters. Plant AMT2s generally show functions in root‐to‐shoot translocation or pathogenic and symbiotic plant–microorganism interactions. We addressed the activity of TaAMT2s in ammonium transport. Nitrogen‐dependent expression implicated a physiological function in ammonium uptake for TaAMT2;1 and in ammonium distribution for TaAMT2;2‐6.