Browsing by Subject "Barley"

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Characterization of genetic variation among Ethiopian barley (Hoerdeum vulgare L.) genotypes
(2019) Abtew, Wosene Gebreselassie; Knierim, Andrea
Barley (Hordeum vulgare L.) is a major cereal crop in Ethiopia and accounts for 8% of the total cereal production based on cultivation area. Farmers may face unpredictable rainfall and drought stress patterns such as terminal drought where rainfall ends before crops have completed their physiological maturity, which then poses a challenge to crop production. The absence of efficient weather forecasts and a lack of efficient communication channels for resource-poor farmers ask for the development of varieties that are robust to such irregularities. A goal of plant breeding for areas with variable climate and limited resources for agricultural inputs is to produce stable varieties with higher average yield across diverse environments and growing conditions. Genotype by environment (G x E) interactions, however, frequently interfere with the selection of widely adapted genotypes. Knowledge about the yield stability of existing Ethiopian barley varieties and landraces under changing environmental variables is important for the future development of barley varieties with high and stable yields. In addition, yield components are quantitative with substantial influence of environment. Yield components also compensate each other in trait correlation dynamics. Since grain yield is a more complex trait than its components, environmental effects and genotype-by-environment (G x E) interactions for grain yield are stronger than for its components. Therefore, indirect selection of yield components may be more efficient than selection on grain yield per se to obtain higher yielding and stable cultivars. A study, therefore, was initiated to 1) characterize the response of a diverse set of barley genotypes to different locations and variable planting dates and identify genotypes with wide adaptation and stable performance and/or genotypes with specific altitude and planting date 2) determine traits that contribute to high and stable yields across a range of different environments and planting dates 3) determine the pattern of population structure and genetic parameters among genotypes conserved in Ethiopian and German gene banks in for different period of time as well as currently growing in farmers’ field. In order to meet the objectives 18 genotypes were tested at four different sowing dates with 15 days interval in different locations (Ambo and Jimma) and years (2012 and 2013). The tested genotypes revealed a wide variation for both static and dynamic yield stability measures. Compared to improved cultivars, farmers landraces displayed higher average static stability and similar superiority indices (dynamic stability). These landraces are therefore a source of germplasm for breeding resilient barley cultivars. Staggered planting proved to be a useful method for evaluating genotype stability across environmental factors beyond location and season. In addition, we also noticed that compensatory relationship between kernels per spike and thousand kernel weight in landraces. Kernels per spike and number of fertile tillers can be proposed as robust traits in barley breeding for a wider adaptation as they had significant and consistent positive total effects on grain yield. In order to determine the pattern of population structure and genetic parameters among genotypes of different origin and gene banks, DNA samples were subject to double-digest by ApeK1 and Hind III enzymes. After sequencing, raw read was checked for major quality parameters. Sequence reads were then filtered for sequencing artifacts and low quality reads (preprocessing). The pre-processed reads were aligned to genome of barley cultivar Morex to call SNPs. Values of observed heterozygosity (Ho) ranged from 0.250 to 0.337 and were higher than the expected heterozygosity (He) that varied from 0.180 to 0.242 in genotypes of all origins. The inbreeding coefficient (FIS) values that ranged between -0.240 and -0.639 across the regions were also higher and negative suggesting existence of excess outcrossing than expected. Based on the inferred clusters by the ADMIXTURE, high Fst values were observed between clusters suggesting high genetic differentiation among the genotypes tested though differentiation was not based on location. In addition, genetic differentiation computed based on the predetermined location, altitude and source of genotypes suggested weak differentiation among the groups. These results indicate that, in Ethiopia, barley genetic variation between regions and altitudes were less pronounced than within region and altitude variations. This calls for the germplasm collection strategies to be cautious in considering location and altitude as a main factor of variation thus strategies should focus on exploiting the within region variation also for better germplasm conservation and utilization. The static yield stability of landrace has to be utilized by breeders for their wider recommendations for those farmers who cannot afford use of farm inputs and specific cultivars. In addition, the relative robustness as well as plasticity of traits sorted by the current study can be incorporated in the breeding strategy of barley in Ethiopia.
Differences in yield performance and yield stability between hybrids and inbred lines of wheat, barley, and triticale
(2015) Mühleisen, Jonathan; Reif, Jochen Christoph
Hybrids of wheat, barley, and triticale are expected to possess higher yield performance and yield stability compared to inbred lines. Assessment of yield performance as well as yield stability requires the evaluation of genotypes in plot-based yield trials across multiple environments. Evaluation of genotypes under stress conditions can be associated with increased field heterogeneity, which may result in imprecise estimates of genotypic values. The assessment of yield stability requires intensive testing in many environments, and it would be interesting to know how many test environments are required to reliably estimate yield stability. The key objectives of the present thesis were to (1) investigate optimal strategies to analyze field trials with high error variance due to spatially varying drought stress, (2) identify the required number of test environments to precisely estimate yield stability of individual barley genotypes, and (3) examine yield performance and yield stability of wheat, barley, and triticale hybrids and lines. Drought stress at two locations of a winter triticale trial caused increased field heterogeneity, resulting in lower heritabilities compared to the four non-stress locations. It was found that heritability could be increased by modeling incomplete block and row effects, by using visual scorings of drought stress intensity as covariates in an analysis of covariance, and by modeling a spatial covariance between adjacent plots. The most suitable model can be identified using the Akaike Information Criterion. In addition, it has to be ensured that the covariate is independent from genotypic effects and that it is linearly related with the response variable. Dynamic yield stability of genotypes was frequently found to depend strongly on the specific set of test environments. When the genotypes were evaluated in different environments, e.g. in the following year, the ranking in yield stability could be different. This would result in a low heritability. Theoretical assumptions and empirical studies showed that heritability can be increased when the number of test environments is increased. Five series of barley registration trials with a reduced number of 16 to 27 genotypes evaluated in 39 to 45 environments were used to investigate the relationship between magnitude of heritability of yield stability and number of test environments. Based on a cross-validation approach, it was found, that at least 40 test environments should be used to obtain a heritability of 0.5. Magnitude of heritability, however, varied strongly within and between series. Therefore, depending on the respective set of environments and genotypes, more or less test environments can be needed. Yield performance of wheat hybrids produced using chemical hybridizing agents (CHA) or cytoplasmic male sterility (CMS) was well investigated in other studies reporting around 10% midparent heterosis for grain yield. In the present thesis, CMS-based barley hybrids were compared with parental inbred lines and unrelated commercial inbred lines in breeding and registration trials. Midparent heterosis was around 10%. The comparison with commercial inbred lines in the registration trials revealed that hybrids could compete with and partially surpass outstanding inbred lines. Triticale hybrids, produced using CMS, were evaluated for grain yield at up to 20 environments with their parents and commercial inbred lines. Midparent heterosis amounted to 3% and no hybrid outyielded the best inbred line. The low yield performance of triticale hybrids is probably associated with CMS-system, since CHA-based triticale hybrids showed a midparent heterosis around 10% in early studies, which is comparable to the midparent heterosis found in wheat and barley. Yield stability of CHA-based wheat as well as CMS-based hybrids of barley and triticale was compared with yield stability of parental and commercial inbred lines on group level. The wheat and barley hybrids showed on average significantly higher dynamic yield stability compared to inbred lines, but the triticale hybrids did not. In the barley registration trials, hybrids had the highest dynamic yield stability on average. The CMS-based triticale hybrids, however, showed on average significantly lower dynamic yield stability as their female parents and the commercial inbred lines across 20 environments. In conclusion, hybrids of wheat and barley possessed an increased yield potential as well as an enhanced dynamic yield stability. In contrast, the CMS-based triticale hybrids showed only marginal yield advantages coupled with low dynamic yield stability. Further research is required to increase economical competitiveness of hybrids in all three crops, to identify and eliminate the reasons for poor performance of CMS-based triticale hybrids and to investigate the suitability of dynamic yield stability measures to identify vigorous and stress tolerant genotypes.
Evaluation of association mapping and genomic prediction in diverse barley and cauliflower breeding material
(2018) Thorwarth, Patrick; Schmid, Karl J.
Due to the advent of new sequencing technologies and high-throughput phenotyping an almost unlimited amount of data is available. In combination with statistical methods such as Genome-wide association mapping (GWAM) and Genomic prediction (GP), these information can provide valuable insight into the genetic potential of individuals and support selection and crossing decisions in a breeding program. In this thesis we focused on the evaluation of the aforementioned methods in diverse barley (Hordeum vulgare L.) and cauliflower (Brassica oleracea var. botrytis) populations consisting of elite material and genetic resources. We concentrated on the dissection of the influence of specific parameters such as marker type, statistical models, influence of population structure and kinship, on the performance of GWAM and GP. For parts of this thesis, we additionally used simulated data to support findings based on empirical data. First, we compared four different GWAM methods that either use single-marker or haplotypes for the detection of quantitative trait loci in a barley population. To find out the required population size and marker density to detect QTLs of varying effect size, we performed a simulation study based on parameter estimates of the empirical population. We could demonstrate that already in small populations of about 100 individuals, QTLs with a large effect can be detected and that at least 500 individuals are necessary to detect QTLs with an effect < 10%. Furthermore, we demonstrated an increased power of haplotpye based methods in the detection of very small QTLs. In a second study we used a barley population consisting of 750 individuals as training set to compare different GP models, that are currently used by scientists and plant breeders. From the training set 33 offspring families were derived with a total of 750 individuals. This enabled us to assess the prediction ability not only based on cross-validation but also in a large offspring population with varying degree of relatedness to the training population. We investigated the effects of linkage disequilibrium and linkage phase, population structure and relatedness of individuals, on the prediction ability. We could demonstrate a strong effect of the population structure on the prediction ability and show that about 11,203 evenly spaced SNP markers are necessary to predict even genetically distant populations. This implies that at the current marker density prediction ability is based on the relatedness of the individuals. In a third study we focused on the evaluation of GWAM and GP in cauliflower. We focused on the evaluation of genotyping-by-sequencing and compared the influence of imputation methods on the prediction ability and the number of significant associations. We obtained a total 120,693 SNPs in a random collection of 174 cauliflower genebank accessions. We demonstrated that imputation did not increase prediction ability and that the number of detected QTLs only slightly differed between the imputed and the unimputed data set. GP performed well even in such a diverse gene bank sample, but population structure again influenced the prediction ability. We could demonstrate the usefulness and limitations of Genome-wide association mapping and genomic prediction in two species. Even though a lot of research in the field of statistical genetics has provided valuable insight, the usage of Genomic prediction should still be applied with care and only as a supporting tool for classical breeding methods.
Impact of climate change on future barley (Hordeum vulgare L.) production in Ethiopia
(2022) Gardi, Mekides W.; Graeff-Hönninger, Simone
Summary Barley (Hordeum vulgare L.) is the fourth major cereal crop in the world, and it accounts for 8% of the total cereal production in Ethiopia based on cultivation location. Farmers may face unpredictable rainfall and drought stress patterns, such as terminal drought, in which rainfall ends before crops reach physiological maturity, posing a challenge to crop production. Furthermore, climate change is expected to reduce crop production/yield due to increases in carbon dioxide (CO2) and ozone (O3) concentrations, temperatures, and extreme climate events such as floods, storms, and heatwaves, highlighting the importance of taking action to develop climate-resilient cultivars and secure future crop production. Against this background, a meta-analysis study was conducted to synthesize and summarize to assess the overall effect of elevated CO2 (eCO2), and its interaction with nitrogen (N) and temperature on barley grain yield and yield components. A climate chamber experiment was carried out to identify the impacts of projected CO2 enrichment (eCO2) on a set of landraces and released cultivars of Ethiopian barley. The crop-climate modeling approach was used to simulate future climate change and to identify the impacts of climate change on selected barley genotypes and study locations in Ethiopia. Furthermore, adaption options were simulated and identified. Publication I, aimed to answer how eCO2 and its interaction with N and temperature affects barley yield at a global level. Peer-reviewed primary literature (published between 1991-2020) focusing on barley yield responses to eCO2, temperature, and N were searched on different search engines. The response of five yield variables of barley was synthesized and summarized using a meta-analysis technique. Different experimental factors which might affect the estimation of the response of barley yield to eCO2 were calculated. The results revealed that eCO2 increased barley yield components such as vegetative biomass (23.8%), grain number (24.8%), and grain yield (27.4%) at a global level. Barley vegetative biomass and grain yield were increased under the combination of eCO2 with the higher N level (151-200 kg ha-1) compared to the lower levels. Grain number and grain yield were increased when eCO2 combined with temperature level (21-25°C) this response was not evident. The response of barley to eCO2 was different among genotypes and experimental conditions. Publication II, the genetic diversity of Ethiopian barley was screened under eCO2 enrichment in a controlled exposure experiment. The experiment was conducted at the Institute of Landscape and Plant Ecology, the University of Hohenheim in 2019. A total of 30 (15 landrace and 15 released cultivars) were grown under two levels of CO2 concentration (400 and 550 ppm) in climate chambers. Plant-development-related measurements and water consumption were recorded once a week and yield was measured at the final harvest. A significant increment in plant height by 9.5 and 6.7%, vegetative biomass by 7.6 and 9.4%, and grain yield by 34.1 and 40.6% in landraces and released cultivars, respectively were observed due to eCO2. The effect of eCO2 was genotype-dependent, for instance, the response of grain yield in landraces ranged from -25% to +122%, while it was between -42% to 140% in released cultivars. The water-use efficiency of vegetative biomass and grain yield significantly increased by 7.9 and 33.3% in landraces, with 9.5 and 42.9% improvement in released cultivars, respectively under eCO2. Comparing the average response of landraces versus released Ethiopian barley cultivars, the highest percentage yield change due to eCO2 was recorded for released cultivars. However, higher actual yields under both levels of CO2 were observed for landraces. Publication III, Current and future climate change, its impact on Ethiopian barley production, and adaptation options were simulated using the DSSAT-CERES-Barley model. Climate change scenarios were set up over 60 years using Representative Concentration Pathways (4.5 and 8.5), and five Global Climate Models. The changes in Ethiopian climate and barley production were calculated from the baseline period (1981-2010). Different sowing dates, sowing densities, and fertilizer levels were tested as climate change impact mitigation strategies in a sensitivity analysis. The analysis of a crop-climate model revealed an increasing trend of temperature (1.5 to 4.9 °C) and a mixed trend of rainfall (-61.4 to +86.1%) in the barley-producing locations of Ethiopia. The response of two Ethiopian barley cultivars was simulated under different climate change scenarios and a reduction of yield up to 98% was recorded for cv. Traveler while cv. EH-1493 exhibited a reduction of up to 63%. Even though a similar trend was observed for most of the studied locations, cv. EH-1493 showed a yield gain of up to 14.7% at Holeta. The sensitivity analysis on potential adaptation options indicated that the negative effects of climate change could be mitigated by earlier sowing dates, with a 25% higher sowing density and a 50% higher fertilizer rate than the current recommendation. The results of the present dissertation show the change in the Ethiopian climate and its impact on barley production. Barley production could benefit from eCO2; however, the response varied among genotypes, additional stress, and experimental condition. A reduction of barley grain yield under different climate change scenarios was observed mainly due to increasing temperature. However, the reduction could be minimized through different adaptation options. The information from the current dissertation could be used to identify agro-economic implications of CO2 enrichment and climate variability on yield regarding appropriate genotype selection and adaptation of regional cropping systems (e.g., management and breeding strategies). Further experimental studies assessing crop production, nutritional quality, and adaptation options under multifactor climate conditions should be carried out to increase basic understanding and identify genotypes for future breeding programs.
Impacts of carbon dioxide enrichment on landrace and released Ethiopian barley (Hordeum vulgare L.) cultivars
(2021) Gardi, Mekides Woldegiorgis; Malik, Waqas Ahmed; Haussmann, Bettina I. G.
Barley (Hordeum vulgare L.) is an important food security crop due to its high-stress tolerance. This study explored the effects of CO2 enrichment (eCO2) on the growth, yield, and water-use efficiency of Ethiopian barley cultivars (15 landraces, 15 released). Cultivars were grown under two levels of CO2 concentration (400 and 550 ppm) in climate chambers, and each level was replicated three times. A significant positive effect of eCO2 enrichment was observed on plant height by 9.5 and 6.7%, vegetative biomass by 7.6 and 9.4%, and grain yield by 34.1 and 40.6% in landraces and released cultivars, respectively. The observed increment of grain yield mainly resulted from the significant positive effect of eCO2 on grain number per plant. The water-use efficiency of vegetative biomass and grain yield significantly increased by 7.9 and 33.3% in landraces, with 9.5 and 42.9% improvement in released cultivars, respectively. Pearson’s correlation analysis revealed positive relationships between grain yield and grain number (r = 0.95), harvest index (r = 0.86), and ear biomass (r = 0.85). The response of barley to eCO2 was cultivar dependent, i.e., the highest grain yield response to eCO2 was observed for Lan_15 (122.3%) and Rel_10 (140.2%). However, Lan_13, Land_14, and Rel_3 showed reduced grain yield by 16, 25, and 42%, respectively, in response to eCO2 enrichment. While the released cultivars benefited more from higher levels of CO2 in relative terms, some landraces displayed better actual values. Under future climate conditions, i.e., future CO2 concentrations, grain yield production could benefit from the promotion of landrace and released cultivars with higher grain numbers and higher levels of water-use efficiency of the grain. The superior cultivars that were identified in the present study represent valuable genetic resources for future barley breeding.
Impacts of temperature increase and change in precipitation pattern on ecophysiology, biomass allocation and yield quality of selected crops
(2023) Drebenstedt, Ireen; Högy, Petra
Climate change poses a challenge for the production of crops in the twenty-first century due to alterations in environmental conditions. In Central Europe, temperature will be increased and precipitation pattern will be altered, thereby influencing soil moisture content, physiological plant processes and crop development in agricultural areas, with impacts on crop yield and the chemical composition of seeds. Warming and drought often occur simultaneously. The combination of multiple abiotic stresses can be synergistic, leading to additive negative effects on crop productivity. To date, little information is available from multi-factor experiments analyzing interactive effects of warming and reduced precipitation in an arable field. In addition, one major issue of studying climate change effects on crop development in the long-term is that weather conditions can vary strongly between years, e.g., with hot and dry summers in comparison to cool and wet ones, which directly affects soil moisture content and indirectly affects crop development. Thus, considering yearly weather conditions seems to be important for the analyses of climate change effects on aboveground biomass and harvestable yield of crops. The aim of the present work was to identify single and combined effects of soil warming (+2.5 °C), reduced summer precipitation amount (-25%), and precipitation frequency (-50%) on crop development, ecophysiology, aboveground biomass and yield as well as on yield quality of wheat, barley, and oilseed rape grown in the Hohenheim Climate Change (HoCC) field experiment. This thesis presents novel results from the HoCC experiment in the long-term perspective. Thus, aboveground biomass and yield data (2009-2018) of the three crops were analyzed with regard to their inter-annual variability, including annual fluctuations in weather conditions.This thesis consists of three publications. In the first and second publication a field experiment within the scope of the HoCC experiment was conducted with spring barley (Hordeum vulgare L. cv. RGT Planet) and winter oilseed rape (Brassica napus L. cv. Mercedes) in 2016 and 2017. The objective was to investigate the impacts of soil warming, altered precipitation pattern and their interactions on biomass production and crop yield. In addition, it was examined, whether the simulated climate changes affecting barley photosynthesis and the seed quality compounds of oilseed rape. In the third publication, long-term plant productivity data of wheat, barley, and oilseed rape were evaluated, including aboveground biomass and yield data from the field experiment in 2018 with winter wheat (Triticum aestivum L. cv. Rebell).