Browsing by Subject "Photoperiode"

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Breeding winter durum wheat for Central Europe : assessment of frost tolerance and quality on a phenotypic and genotypic level
(2015) Sieber, Alisa-Naomi; Würschum, Tobias
Durum wheat (Triticum durum) is a tetraploid wheat that is used for pasta and other semolina products. Quality standards for semolina requested by the pasta industry are very high. Different characteristics should come with the cereal as raw material for an optimal end product. Vitreosity, the glassy and amber quality feature of durum wheat kernels, is an indicator for high semolina yield. The complex protein-starch matrix of glassy kernels breaks the grain into the typical semolina granulate instead of flour during milling. Humid conditions, like late summer rains in Central Europe, have a huge effect on this characteristic, changing this matrix irreversibly. Such processes in the kernel are less understood and challenge plant breeders to find genotypes with improved vitreosity. A set of F5 winter durum wheat lines (Chapter 2) was used to investigate the relationship between protein content and vitreosity as well as the impact of humidity on the stability of the trait. A method to evaluate the mealy part in kernels was improved and enabled to test for the influence of humidity on vitreosity. Furthermore, it was revealed that the vitreosity of a durum wheat kernel depends on the protein content up to a specific threshold as well as on the genotypic potential to form the complex endosperm matrix. The ability to maintain this kernel quality under humid conditions also highly depends on the genetics of a variety. In the Mediterranean region, durum wheat is grown as autumn-sown spring type. The mild winters as well as rain during spring allow the plants to develop well, and the dry summers enable an early harvest in June. Durum wheat production in Central Europe, on the other hand, is confronted with harsh winters and recurring severe frosts. The lack of a sufficient frost tolerance in combination with high quality, forces farmers to use the spring type with a spring sowing. Growing winter durum instead of spring durum wheat, would allow an autumn sowing. Using the winter type in this growing area, could have several advantages like an increased yield and stability due to a prolonged growing time. Further, the constant soil coverage would prevent soil erosion and the growth vigor of winter durum has advantages against weeds. The success of winter durum breeding depends on frost tolerance as a key factor for varieties with excellent winter survival. Discontinuous occurrence of frosts across years and protective snow coverage, however, limit the phenotypic selection for this trait under field conditions. Greenhouses or climate chambers could be used as alternative to test under the necessary conditions, but those fully-controlled tests are time consuming and labor-intensive. The ‘Weihenstephaner Auswinterungsanlage’ are wooden boxes with movable glass lids used as a semi-controlled test. Plants are exposed to all seasonal conditions, including frost stresses, in this test, but they can be protected from snow coverage. While this method is already successfully used to test for frost tolerance in bread wheat, the application in durum wheat has not been evaluated yet. The frost tolerance scorings of winter durum elite lines (F5 and F6) based on the ‘Weihenstephaner Auswinterungsanlage’ were compared to the field evaluation (Chapter 3). It was demonstrated that this semi-controlled test produces reliable and highly heritable (h2 = 0.83-0.86) frost tolerance data. The correlation of those results compared with the field data (r = 0.71) suggests this semi-controlled test as an indirect selection platform. Since it is now possible to test cost-efficient at early stages for frost tolerance, the next challenge was to determine whether the kernel quality or the grain yield suffers from an increased frost tolerance. In a survey with F5 winter durum elite lines, no negative association between frost tolerance and quality or other important agronomic traits could be found in European breeding material (Chapter 4). In order to support classical plant breeding, which relies predominantly on phenotypic data and parental information, molecular markers can be taken into account. Molecular markers can provide an in-depth look into the genetic architecture of traits, enable the determination of the relatedness of genotypes, identify the genetic variation in a population, or can assess the effect of geographic selection preferences. Furthermore, it is possible to assist knowledge-based selection. This improves plant breeding programs on a genetic level. The population structure in spring durum has already been examined with molecular methods in several studies. Winter durum, on the other hand, was only analyzed as a small group as part of spring durum studies or in groups of landraces. A highly diverse and unique panel of 170 winter durum and 14 spring durum lines was analyzed using a genotyping-by-sequencing (GBS) approach. A total of 30,611 markers, well distributed across the chromosomes, were obtained after filtering for marker quality. A principal coordinate analysis and a cluster analysis were applied. Together they revealed the absence of a major population structure (Chapter 5). The lines, however, grouped in a certain way, depending on their origin, associated with decreasing quality and increasing frost tolerance moving from South to Continental Europe. These groups allow breeders to conduct targeted crosses to further improve the frost tolerance in the Central European material. Another possibility is to build heterotic groups for hybrid breeding. The linkage disequilibrium (LD) decay was within 2-5 cM, indicating a high diversity in winter durum. The high marker density together with the extent of LD observed in this analysis allows to perform high-resolution association mapping in the present winter durum panel. The 30,611 markers and additional markers for candidate genes in frost tolerance were used to assess the genetic architecture of frost tolerance in durum wheat (Chapter 6). A major QTL was identified on chromosome 5A, likely being Frost Resistance-A2 (Fr-A2). Additional analysis of copy number variation (CNV) of CBF-A14 at Fr-A2 support this conclusion. CBF-A14 CNV explains about 90% of the proportion of genotypic variance. Two markers found in the QTL region were combined into a haploblock and enabled to capture the genetic variance of this QTL. Furthermore, the frequency of the QTL allele for frost tolerance shows a latitudinal gradient which is likely associated with winter conditions. In summary, the selection tools for vitreosity and frost tolerance provided in this study create a platform for winter durum breeding to select for high quality genotypes with excellent winter survival utilizing phenotypic as well as genotypic information.
Diurnal and photoperiodic effects on the immune system and glucocorticoid signaling in domestic pigs
(2019) Engert, Larissa; Stefanski, Volker
Physiology and behavior of humans and animals display pronounced diurnal and seasonal rhythmic variations. Diurnal rhythms are controlled by daylight and seasonal rhythms are adjusted by the photoperiod, i.e., the relative span of light per day. Modern human life and housing conditions of livestock are often directed against natural daylight conditions and thus, may entail circadian disruption causing misalignment between the central circadian pacemaker and peripheral tissues. Thereby, glucocorticoids are regarded as a main link between these compartments. Circadian disruption might be detrimental for health, in particular affecting immune function, which was mainly investigated in humans and nocturnal rodents but underlying mechanisms are not clearly defined yet. Therefore, the main objective of the present thesis was to investigate diurnal and photoperiodic effects on the immune system and glucocorticoid signaling as well as potential underlying endocrine, behavioral, and molecular mechanisms of these effects in domestic pigs. Adult male castrated pigs, held under specific lighting schedules, were surgically catheterized to enable blood collection without disturbance of the animals. Initially, domestic pigs were held under standard 12L:12D-lighting conditions and blood samples were taken every 2 hours over periods of up to 50 hours. Cosinor analyses revealed pronounced diurnal rhythmicity in peripheral leukocyte numbers of various immune cell populations. These rhythms were mainly comparable to results in humans and nocturnal rodents in relation to their respective rest-activity cycles, with the exception of porcine neutrophils differing from both species. Moreover, the investigated diurnal rhythms in activity behavior and plasma cortisol concentration confirmed that domestic pigs under the applied experimental conditions are diurnally active like humans. Linear mixed model analyses revealed associations of immune cell counts with plasma cortisol concentration, which also resembles results from humans and rodents. Subsequently, photoperiodic effects on diurnal rhythms in peripheral immune cell numbers were investigated for the first time in any species. Domestic pigs were held either under long day conditions (LD) or under short day conditions (SD) and were sampled every 2 hours over periods of 50 hours. Distinct photoperiodic differences in relative amplitudes and peak times of cell counts in various porcine leukocyte types were found, whereas mesor values did not differ. Moreover, photoperiodic effects on diurnal rhythms in plasma cortisol concentrations and activity behavior were found, which is in agreement with human and primate studies. Generalized linear mixed model analyses again revealed associations of leukocyte counts with plasma cortisol concentration and with activity behavior as well. In summary, the results imply stronger rhythmicity of peripheral immune cell numbers in general under SD than under LD. Common intrinsic mechanisms seem to regulate diurnal rhythms in peripheral leukocyte numbers in most immune cell types in domestic pigs, except for neutrophils again. Finally, to investigate potential molecular differences in diurnal regulation between different immune cell types, glucocorticoid receptor (GR) number and affinity were examined in peripheral blood mononuclear cells (PBMC) and granulocytes of domestic pigs. Thereby, a greater number of GR sites per cell and a higher GR binding affinity in PBMC compared to granulocytes were found, pointing to differences in the molecular mechanisms of glucocorticoid signaling between leukocyte populations. The results of the present thesis project are subsequently discussed in regard to specific implications for immune function and health as well as animal husbandry and welfare. Moreover, a methodological assessment of the approaches used within the thesis project was carried out and finally, suggestions for future research directions were given. In conclusion, the present thesis revealed for the first time diurnal and photoperiodic effects on the immune system as well as glucocorticoid signaling in domestic pigs and uncovered potential underlying mechanisms of these effects. Hence, an additional diurnally active model species in chronoimmunology research was established. Moreover, conducting chronoimmunology research in the porcine species represents an innovative approach in agricultural science and provides entirely new opportunities to improve animal health and welfare. Thereby, future studies might investigate diurnal differences in immune function, clarify the role of different zeitgebers on immune rhythms, and assess potential consequences of stressor exposure at different times of the day.
Overwintering and reproduction biology of Drosophila suzukii Matsumura (Diptera: Drosophilidae)
(2018) Zerulla, Florian Niklas; Zebitz, Claus P. W.
Drosophila suzukii (Matsumura) was introduced to southern Europe and the United States of America in 2008 through fruit imports from Southeast Asia and spread in the following years all over Europe, as well as South and North America. D. suzukii is a polyphagous pest which infests fruits of soft-skinned wild and cultivated plants. In contrast to the well-known D. melanogaster, healthy and ripe fruits are preferred. The infestation is caused by female D. suzukii who damage the fruit skin to deposit eggs underneath with the help of their serrated ovipositor. The feeding of hatching larvae and secondary infections, which can easily penetrate through the damaged fruit, can lead to complete yield losses. A short reproductive period, a large range of host plants and infestation of the fruits, shortly before harvesting makes it extremely difficult to control the pest. Due to comparatively late infestation, the possible period of application during ripening and harvesting is limited. The same applies to the frequency of application of insecticides at this time. Possible residues on the harvested products also carry the risk of rejection of the fruit on the market. Furthermore, an incomplete knowledge of the biology, especially overwintering biology under European environmental conditions makes an effective control of this invasive pest extremely difficult. Therefore, the main research topics are the induction and refraction of the postulated diapause, the detection of any possible hibernation sites and the influence of temperature on the oviposition behaviour of D. suzukii. Based on field experiments it could be shown that successful wintering could probably only take place in forest areas. After freezing, the forest was the only place where D. suzukii could resume its flight activity at warmer temperatures. It has also been confirmed that female flies are more resistant to temperatures below freezing than male flies. Accordingly, after a frost period, hardly any male D. suzukii were caught in bait traps. Similar results have also been obtained in laboratory tests, showing that D. suzukii adapted to low temperatures and shortday conditions had lower temperature preferences and a decreased mortality after changing environmental conditions. It can therefore be assumed that overwintering D. suzukii can spread better in spring due to a lower temperature preference and a higher physical activity under cold environmental conditions than flies without adaptation to winter conditions. Bait traps were also used to determine the developmental status of the ovaries by dissecting the abdomens of weekly captured D. suzukii. This enabled a correlation between microclimatic conditions of individual habitats and the reproductive status of females to be established. In winter, the majority of female D. suzukii had “immature ovaries”, whereas in the summer most females had “mature eggs” in their abdomen. For this reason, it can be assumed that D. suzukii entered a reproductive diapause, which is apparently influenced by winter climatic conditions, nutritional status and the availability of food. In addition, it was found that the developmental status of ovaries correlates positively with oviposition. Laboratory tests were carried out to determine the highest number of egg depositions at 20 °C. Most females with “mature eggs” were also documented under these simulated conditions. We detected that the preferred surface temperature for egg depositing was very similar to the preferred ambient temperature of D. suzukii. Most of the eggs were deposited on fruits with a surface temperature of 22 °C. At this temperature, the highest net reproductive rate and intrinsic rate of population increase was found, too. Temperatures below 15 °C and above 35 °C were not preferred, which represented the thresholds for a successful development of D. suzukii. Temperatures between 10 and 15 °C and shortday conditions were the most important key stimuli for entering the reproductive diapause. Therefore, temperature had a stronger influence on oviposition behaviour than daylength. A complete disruption of diapause occurred at higher temperatures (20 °C) and longday conditions after 72 hours. The data presented in this work on the possibility of adapting D. suzukii to environmental conditions and key temperatures, which influence the development of ovaries and egg deposition, can provide an important contribution to the development of prediction and population dynamics models and can be used for long-term control strategies against D. suzukii. According to current knowledge and observations, overwintering is obviously a critical period for the survival of the populations. Therefore, the characterisation and identification of additional hibernation sites is of great importance. There, a targeted and environmentally friendly control of D. suzukii populations could be particularly efficient.
Studies on flowering time and photoperiod sensitivity in domesticated and wild amaranth species (Amaranthus spp.)
(2023) Baturaygil, Ali; Schmid, Karl J.
Flowering time plays fundamental roles in the local adaptation and agricultural productivity of the crops. Photoperiodic response regulates the time of flowering by adjusting the response of plant circadian rhythm to environmental signals. Amaranth (Amaranthus spp.) is a short-day crop native to Central and South America, and mainly used as grain and vegetable. Hence, photoperiod sensitivity is a pivotal trait for grain amaranths in Central Europe climatic and long-day conditions, as it determines the local adaptability and the cultivation purpose of the crop i.e., grain or biomass production. However, the knowledge on the different aspects such as breeding, domestication history and adaptation genetics is very limited in grain amaranths. In this project, we studied such different aspects of grain amaranths by addressing the elucidative photoperiod sensitivity trait. In the first study, the phenotypic evaluation of biomass yield components revealed two distinct growth types. Of those, our ten biomass genotypes showed mild to high photoperiod sensitivity, flowered late or completely rejected flowering, reached long final plant heights and low dry matter content. In contrast, the only grain type variety showed photoperiod insensitivity, flowered early, and reached a short final plant height and a relatively higher dry matter content. Our results suggested that selection for both high dry matter yield and content requires a trade-off between photoperiod sensitivity and early flowering, due to the negative correlation between these traits. In the second study, characterization of genebank accessions from the three major grain species (A. caudatus, A. cruentus, A. hypochondriacus) and their wild relative species (A. hybridus and A. quitensis) for adaptive traits such as flowering time and seed setting under long-day conditions discovered a larger photoperiodic variation in the Central American accessions ranging from insensitivity to high sensitivity, whereas South American accessions showed a more narrow variation, limited by mild sensitivity. This result suggests the Central American origin of the wild relative A. hybridus, which might have migrated from Central to South America, and potentially has been selected against high photoperiod sensitivity. Moreover, we studied the environmental variables that may influence seed setting. Photoperiod insensitive accessions set seed regardless of their origin. However, mild photoperiod-sensitive accessions set seed, only if they were from warm center of origin. In the third study, we investigated the genetic architecture of photoperiod sensitivity. The bimodal-like flowering time distributions, and the linkage and association mapping studies using three different populations revealed that photoperiod sensitivity trait is controlled in an oligogenic manner. In particular, all three populations consistently found the same ‘consensus region’ that includes a very promising candidate gene called ‘response regulator of two-component system’. The homologs of this candidate gene are responsible for photoperiodic response in a variety of different crops and the model species Arabidopsis thaliana. In addition, the phenotypic analyses, and the marker data (i) showed photoperiod sensitivity guided pleiotropic relationships between the traits, (ii) revealed a potential epistatic behavior of the genomic region controlling photoperiod sensitivity, and (iii) showed the dominance of photoperiod sensitivity over insensitivity in that region.
Use of modeling to characterize phenology and associated traits among wheat cultivars
(2008) Herndl, Markus; Claupein, Wilhelm
Predicting phenology of wheat is important for many aspects of wheat production as for example facilitating accurate timing of pesticides, fertilizers and irrigation, avoiding stress at critical growth stages, and adapting cultivar characteristics to specific environmental constraints or global changes in climate. The aim of the dissertation was to characterize and test the impact of wheat phenology on agronomic traits through integrated use of crop models and information on the genetic makeup of cultivars. In an initial study, cultivar differences in vernalization requirement, photoperiod response and earliness per se were distinguished by field-based indices and compared with corresponding model parameters in CSM-Cropsim-CERES-Wheat model Version 4.0.2.0. To determine whether field-based indices can provide accurate characterization of vernalization requirement, photoperiod response and earliness per se, 26 winter wheat cultivars were evaluated under field conditions at Ihinger Hof, Germany using two natural photoperiod regimes (from different transplanting dates) and vernalization pre-treatments. Results indicated that combining planting dates with vernalization pre-treatments can permit reliable, quantitative characterization of vernalization requirement, photoperiod response and earliness per se of wheat cultivars. Furthermore, genotypic model parameters appeared to be reliable estimates of cultivar differences in response to vernalization and photoperiod. In a second study, the model parameters for vernalization requirement (P1V) and photoperiod response (P1D) were estimated using gene information. To estimate these model parameters through integrating effects of Vrn and Ppd loci, flowering data obtained for 29 cultivars tested in the International Winter Wheat Performance Nursery (IWWPN) were used. Summarizing, results indicated that gene-based estimation of model coefficients was effective for prediction of phenology over a wide range of environments and appears feasible for studying wheat response to environment. To assist plant breeding with crop models, a possibility could be to assess model parameters for designing improved plant types (ideotypes). CMS-Cropsim-CERES-Wheat was used in a third study to test model parameters concerning plant development and grain yield. In ideotyping sequences, the parameters were varied and the model was run in four different scenarios in the North China Plain. The parameter G1 (corresponding trait: kernel number per spike) showed the highest influence on yield over all scenarios followed by G2 (corresponding trait: kernel weight). Results obtained in this study could help breeders to select the relevant traits and integrate them in their breeding program for a specific population of environments. To investigate the coherences between pre-anthesis phenology and grain protein content in a fourth study the statistical analysis of causal relationships with genotypic model parameters was used. It was tested whether model-based characterizations of vernalization requirement, photoperiod response and earliness per se can help explain genotype x environment interactions for grain protein content. Twenty four winter wheat and five spring wheat cultivars (IWWPN) and twelve winter wheat cultivars (of a two year field study at Ihinger Hof, Germany) were characterized using CSM-Cropsim-CERES-Wheat. Covariance analyses indicated that vernalization requirement, photoperiod response, and earliness per se all influenced grain protein content, but their effects varied with site and year within region. Path analyses using data from two seasons in Germany confirmed that grain protein content increased with a shorter pre-anthesis phase and indicated in accordance with the covariance analyses the environmental dependence of this trait. The results proposed that efforts to improve grain protein content should target levels of vernalization requirement, photoperiod sensitivity and earliness per se to specific populations of environments and seek to reduce the apparent large influence of environment on grain protein content. The improved understanding of traits affecting phenology and the linkage with genotypic model parameters can be applied e.g. in China to solve arising and existing agricultural challenges. Model-based analyses can help adapting cropping systems to global warming. In the North China plain a more accurate timing of N-fertilizers and irrigation, as a result of modeling, can ensure a sustainable resource use while maintaining high yields. Summarizing, the findings of this dissertation showed that traits affecting phenology in wheat can be successfully characterized by field-based indices, genotypic model parameters and gene-based estimates of genotypic model parameters. Furthermore, the research showed how genotypic model parameters can be used for breeding purposes, and to test causal relationships both at regional and local geographic scales.