Browsing by Subject "Getreide"

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Agronomic strategies to reduce potential precursors of acrylamide formation in cereals
(2020) Stockmann, Falko; Graeff-Hönninger, Simone
Food safety is of great importance as harmful substances formed during food processing can negatively affect human health. When the carcinogenic food ingredient acrylamide (AA) accidentally appeared in 2002, it was not expected that AA would take this much attention during the next years. Yet, after around 15 years of research, AA has finally been recognized as being harmful. In a first step, research focussed on food processing implications on AA formation. The impact of heat treatment, time of heating, baking agents, fermentation time, additives and enzymes were reported in several studies. Nevertheless, since 2011 food AA levels seem to stagnate or even increase in some years. Thus, the food industry did not show sufficient progress in reducing AA. Reducing sugars and amino acid free asparagine (Asn) are the main AA precursors. They can fluctuate in their content for instance in grain flour or potatoes shifting the focus of AA origin to the raw material. Thus, the production of raw material low in AA precursors seems important. However, lowering precursors of AA in the raw material necessitates suitable agronomic strategies to grow cereal species and cultivars low, especially in free Asn. Hence, the major goal of this thesis was to investigate the following questions concerning their impact on free Asn formation in cereals: 1. Which role does the management system plays, as organic vs. conventional farming systems highly differ in their cropping strategies? 2. What is the best nitrogen fertilization strategy when comparing organic vs. conventionally cropping systems? 3. Is there an impact of sulphur fertilization concerning sulphur amount and sulphur type? 4. Can expanding row distance and lowering seed density in low-input farming systems positively influence baking quality while keeping free Asn amounts low? 5. For organically grown cereals no level of free Asn was available. Thus, the question came up to which extent organically grown cereal species and cultivars including ancient grains like einkorn and emmer differ in free Asn. 6. Should free Asn be implemented in breeding programs if heritability is high? 7. Is there an impact of harvest timing on free Asn formation? Out of several field trials the following results were obtained: • The cropping system had a significant impact on grain yield, the level of free Asn and quality traits. Across all species, free Asn contents in flour were 26% lower under organic conditions compared to conventional farming. For wheat a maximum reduction of 50% in free Asn content was possible if organically produced. Spelt and rye were affected to a minor extend as only in single years organically grown cultivars showed up to 33% lower Asn contents. • Nitrogen (N) fertilization significantly influenced grain yield and baking quality in both cropping systems. In contrast, up to a certain amount of N free Asn was only affected to a minor extend. In particular, within the organic farming samples no significantly higher free Asn amounts were determined even if N fertilizer was raised or the N form was changed. A late N fertilization within the conventional cropping system increased crude protein content, while no clear effect was found on free Asn. Also, cultivars affected free Asn level significantly. Wheat cultivar Capo exhibited the lowest AA formation potential at a N supply of 180 kg N ha−1 while simultaneously reaching a crude protein content > 15% (conventional) and > 12% (organic). Thus, lowering free Asn by adjusting N treatments should not necessarily affect baking quality. In general, free Asn amounts in wheat varied widely both within cultivars and between cropping systems. Besides N, neither type nor amount of sulphur fertilization influenced free Asn significantly. • Extending row distance can increase quality traits protein and sedimentation value. Seed density was highly related to grain yield and test weight. Most importantly, free Asn was only minor affected by both treatments. Thus, larger row distances can be recommended to raise baking quality in organic farming systems without simultaneously affecting free Asn. Number of grains spike-1 seems to be related to free Asn (R2=0.72). This provides new insights on Asn synthesis during grain development and offers the opportunity to predict free Asn formation without expensive chemical analyzes. In contrast Asn and protein content did not show any relation while high protein contents in grain seem to lower AA amount in heated flour samples. • The impact of organically grown cereal species and cultivars in combination with marginal N supply on free Asn was clearly shown. A reduction potential of 85% was reached if rye was replaced by spelt. Surprisingly, the ancient species einkorn and emmer reached a very high free Asn content similar to rye. Heritability was high for wheat and spelt concerning locations, while regarding years, heritability was low for wheat but high for spelt and rye. For organically grown cereals, the relation between free Asn and AA formation was proven. Across species and years free Asn can serve as an indicator for AA formation (R2 of 0.69). • Harvest timing affects free Asn levels. In this context a delayed harvest can increase Asn significantly while shifting harvest 1-2 weeks earlier decreased Asn by up to 60% depending on cereal species and cropping system. After summarizing and stating the most promising steps in the frame of agronomic strategies to lower free Asn, a prediction tool for free Asn should be implemented that classifies the impact of agronomic strategies and leads to recommendations to farmers. Finally, the main riddle, that should be solved during the next studies is the question, why cereal species and cultivars differ in their Asn formation. This thesis gives some preliminary ideas but a much deeper insight is essential to establish long-term strategies to lower free Asn content.
Analyzing resistance to ergot caused by Claviceps purpurea [Fr.] Tul. and alkaloid contamination in winter rye (Secale cereale L.)
(2022) Kodisch, Anna; Miedaner, Thomas
Ergot caused by Claviceps purpurea [Fr.] Tul. is one of the oldest well-known plant diseases leading already in medieval times to severe epidemic outbreaks. After the occurrence of honeydew, the characteristic ergot bodies called sclerotia are formed on the ear. These are containing toxic ergot alkaloids (EAs). Strict limits are set within the European Union. Rye (Secale cereale L.) as cross-pollinating crop is particularly vulnerable to ergot since the competitive situation of fungal spores and pollen during flowering. Nevertheless, even today the threat is real as agricultural practice is changing and screening studies revealed EAs in samples of the whole cereal value chain frequently. The aims were to establish a harmonized method to test ergot resistance and EA contamination in winter rye, to clarify major significant factors and their relevance and to reveal the suitability of one commercial ELISA test. Further, effort was paid to examine the covariation of ergot amount and EA content considering different factors because of prospective legislative changes. Genotypes showed significant variation for ergot severity and pollen-fertility restoration after natural infection as well as artificial inoculation whereas a high positive correlation could be found between both treatments. Additionally, variances of environment, general combining ability (GCA), specific combining ability (SCA), and interactions were significant. Although male pollen-fertility restoration was of utmost importance, the female component was also significant. This illustrates that apart from promising selection of high restoration ability the maternal restorability could be exploited in future breeding programs especially when a high pollen amount is already reached. A large-scale calibration study was performed to clarify the covariation of ergot severity, EA content (HPLC, ELISA) considering genotypes, locations, countries, years, and isolates. EA profile was rather stable across country-specific isolates although large differences regarding the EA content were detected. The moderate covariation between ergot severity and EA content (HPLC) indicates that a reliable prediction of the EA content based on ergot severity is not possible what can also not be explained by grouping effects of the factors. Further, EAs seem not to act as virulence factor in the infection process since EA content showed no relationship to disease severity. Additionally, the missing correlation of ELISA and HPLC leads to the conclusion that the ELISA is not an appropriate tool what can be used safely to screen samples regarding ergot in the daily life. The genetic variation of male-sterile CMS-single crosses was analysed in a special design without pollen in field and greenhouse to identify resistance mechanisms and to clarify whether ergot can be reduced in the female flower. At this, comparison of needle and spray inoculation revealed medium to high correlations illustrating that both methods were suitable for this research. Significant environment and genotype by environment interaction variances were detected. So, testing across several environments is necessary also without pollen. Further, small but significant genotypic variation and identification of one more ergot-resilient candidate revealed that selection of female lines could be promising to further reduce ergot. The EA content was lower for less susceptible genotypes. Thus, EA content can be considerably reduced by breeding. A strong positive correlation could be found for ergot severity and EA content when analysing 15 factorial single crosses. The male pollen-fertility restoration was also here the most relevant component but the female component contributed an obviously higher proportion for the EA content than for ergot severity. In conclusion, this thesis demonstrate that implementing of a high and environmental stable male fertility restoration ability via exotic Rf genes can effectively reduce ergot although also the female restorability enables great opportunities. The unpredictable covariation between ergot amount and EA content illustrates that both traits have to be assessed, in particular the EA content by a valid HPLC approach to guarantee food and feed safety.
Breeding for resistance to Fusarium ear diseases in maize and small-grain cereals using genomic tools
(2021) Gaikpa, David Sewordor; Miedaner, Thomas
The world’s human and livestock population is increasing and there is the need to increase quality food production to achieve the global sustainable development goal 3, zero hunger by year 2030 (United Nations, 2015). However, biotic stresses such as Fusarium ear infections pose serious threat to cereal crop production. Breeding for host plant resistance against toxigenic Fusarium spp. is a sustainable way to produce more and safer cereal crops such as maize and small-grain winter cereals. Many efforts have been made to improve maize and small-grain cereals for ear rot (ER) and Fusarium head blight (FHB) resistances, using conventional and genomic techniques. Among small-grain cereals, rye had the shortest maturity period followed by the descendant, hexaploid triticale while both wheat species had the longest maturity period. In addition, rye and triticale were more robust to Fusarium infection and deoxynivalenol accumulation, making them safer grain sources for human and animal consumption. However, a few resistant cultivars have been produced by prolonged conventional breeding efforts in durum wheat and bread wheat. High genetic variation was present within each crop species and can be exploited for resistance breeding. In this thesis, the genetic architecture of FHB resistance in rye was investigated for the first time, by means of genome-wide association study (GWAS) and genomic prediction (GP). GWAS detected 15 QTLs for Fusarium culmorum head blight severity, of which two had major effects. Both weighted and unweighted GP approaches yielded higher prediction abilities than marker-assisted selection (MAS) for FHB severity, heading stage and plant height. Genomics-assisted breeding can shorten the duration of breeding rye for FHB resistance. In the past decade, genetic mapping and omics were used to identify a multitude of QTLs and candidate genes for ear rot resistances and mycotoxin accumulation in maize. The polygenic nature of resistance traits, high genotype x environment interaction, and large-scale phenotyping remain major bottlenecks to increasing genetic gains for ear rots resistance in maize. Phenotypic and molecular analyses of DH lines originating from two European flint landraces (“Kemater Landmais Gelb”, KE, and “Petkuser Ferdinand Rot”, PE) revealed high variation for Gibberella ear rot (GER) severity and three agronomic traits viz. number of days to female flowering, plant height and proportion of kernels per cob. By employing multi-SNP GWAS method, we found four medium-effect QTLs and many small-effect (10) QTLs for GER severity in combined DH libraries (when PCs used as fixed effects), none co-localized with the QTLs detected for the three agronomic traits analyzed. However, one major QTL was detected within KE DH library for GER severity. Two prioritized SNPs detected for GER resistance were associated with 25 protein-coding genes placed in various functional categories, which further enhances scientific knowledge on the molecular mechanisms of GER resistance. Genome-based approaches seems promising for tapping GER resistance alleles from European maize landraces for applied breeding. After several cycles of backcrossing and sufficient selection for agronomic adaptation traits, the resistant lines identified in this thesis can be incorporated into existing maize breeding programs to improve immunity against F. graminearum ear infection. Breeding progress can be faster using KE landrace than PE. A successful validation of QTLs identified in this thesis can pave way for MAS in rye and marker-assisted backcrossing in maize. Effective implementation of genomic selection requires proper design of the training and validation sets, which should include part of the current breeding population.
Degradation of crude protein and starch of corn and wheat grains in the rumen
(2016) Seifried, Natascha; Rodehutscord, Markus
The major objectives of the present thesis were to characterize the ruminal crude protein (CP) and starch degradation of different genotypes of corn and wheat grains and to predict the effective degradation (ED) of CP and starch with easily measurable characteristics. The in situ method is the standard technique to study the ruminal degradation of feeds in many feed evaluation systems. This technique was originally applied to study forages and it was therefore necessary to clarify methodical details related to the measurements of in situ starch degradation from cereal grains. Two in vitro and one in situ approach were conducted to study the loss of secondary starch particles from bags with different pore sizes used for the in situ incubation of different cereal grains. In the first in vitro study ground wheat was incubated in bags (pore size: 50 µm) over different time spans in a modified rumen simulation technique. Bag residues and fermenter fluids were analyzed for their starch content. In the second in vitro study ground wheat, barley, and corn were incubated with bags of pore sizes of 50, 30 (except corn), 20, and 6 µm. In the in situ study ground wheat, barley, corn, and oats were rumen incubated over different time spans using bags with pore sizes of 50, 20, and 6 µm. The starch content of the grains and bag residues was analyzed enzymatically and the degradation characteristics of starch were calculated for each grain type and pore size. It was shown for the first time that incubating wheat and barley in bags with 50 and 30 µm pore size lead to a substantial amount of secondary starch particle losses during incubation process in vitro. These losses were not detectable when the grains were incubated with bags having pore sizes of 20 and 6 µm. Independent of the bags’ pore size no secondary starch particle losses were found by the incubation of corn. Thus corn can be studied in situ even with bags with 50 µm pore size. Oats showed very high washout losses with all pore sizes tested in the present thesis and therefore none of them is suitable to study the starch degradation measurements of oats. Because of methodical problems of gas accumulation in bags having pore sizes < 50 µm, no recommendations can be provided for the in situ evaluation of wheat and barley. Further research is necessary to solve these problems. In the second and third study of the present thesis ruminal in situ degradation of 20 corn grain genotypes and 20 wheat grain genotypes was measured in three lactating Jersey cows. In both experiments the same techniques were used to characterize the ruminal degradation of CP and starch. Ground grains (2 mm) were rumen incubated in bags (50 µm pore size) over different time spans. Grains and bag residues were analyzed for their CP and starch content. The degradation parameters and the ED were calculated for dry matter (DM), CP, and starch. Gas production (GP) of ground grains (1 mm) was recorded after incubation over different time spans in buffered ruminal fluid and fitted to an exponential equation to determine GP parameters. To predict ED of CP and starch correlations with physical and chemical characteristics and in vitro measurements were evaluated and stepwise multiple linear regression analyses were applied. The in situ parameters (soluble fraction, potential degradable fraction, and degradation rate) varied widely between genotypes of corn and wheat grains. The ED of DM, CP, and starch showed a high variation for corn grain genotypes. Due to the high degradation rates, the ED of wheat grains were similar between genotypes. The GP rate was in good agreement with the in situ values for corn grains, whereas no systematic relationship between both methods was observed for wheat grains. Evaluation of correlation analysis showed significant relationships between calculated ED of CP and several amino acids (AA) for both grain types. This indicates that the protein composition of the grains influences CP degradation in the rumen. Similar relationships were found between the same AA and ED of starch of corn grains which highlights the impact of the protein composition on ruminal starch degradation for this grain type. For both grain types, the ED of starch and CP could be predicted accurately from physical and chemical characteristics alone or in combination with GP measurements. Thus, the equations presented in the present thesis can be used to obtain rapid and cost effective information on ruminal degradation of CP and starch for corn and wheat grains. The results of the present thesis show that there is considerable variation of ruminal CP and starch degradation from different genotypes of corn and also – albeit to a lesser extent – for wheat grains. Differences in ED of starch should be taken into account when formulating rations containing significant amounts of corn and wheat grains. In the case of corn grains differences in ED of CP should also be accounted for.
Effects of weeds on yield and determination of economic thresholds for site-specific weed control using sensor technology
(2014) Keller, Martina; Gerhards, Roland
Weeds can cause high yield losses. Knowledge about the weeds occurring, their distribution within fields and their effects on the crop yield is important to achieve effective weed control. The critical period for weed control (CPWC) and the economic threshold (ET) are important key concepts and management tools in weed control. While the former helps to time weed control in crops of low competitiveness, the latter provides a decision aid to determine whether weed control is necessary. This decision is generally taken at the field level. Weeds have been found to be distributed heterogeneously within fields. Site-specific weed control (SSWC) addresses this sub-field variation by determining weed distribution as input, by taking control decisions in the decision component and by providing control measures as output at high spatial resolution. Sensor systems for automated weed recognition were identified as prerequisite for SSWC since costs for scouting are too high. While experiences with SSWC using sensor data as input are still scarce, studies showed that considerable herbicide savings could be achieved with SSWC. ETs can serve as thresholds for the decision component in SSWC systems. However, the commonly used ETs were suggested decades ago and have not been updated to changing conditions since. The same is the case for the CPWC in maize in Germany. In addition, the approaches to determine the CPWC are usually not based on economic considerations, which are highly relevant to farmers. Thus, the objectives of this thesis are: 1. To test different models and to provide a straightforward approach to integrate economical aspects in the concept of the CPWC for two weed control strategies: Herbicide based (Germany) and hoeing based (Benin); 2. To determine the effect of weeds on yield and to calculate ETs under current conditions which can be used for SSWC; 3. To evaluate the use of bi-spectral cameras and shape-based classification algorithms for weed detection in SSWC; and 4. To determine changes in weed frequencies, herbicide use and yield over the last 20 years in southwestern Germany. Datasets in maize from Germany and Benin served as input for the CPWC analyses. The log-logistic model was found to provide a similar fit as the commonly used models but its parameters are biologically meaningful. For Germany, analyses using a full cost model revealed that farmers should aim at applying herbicides early before the 4-leaf stage of maize. In Benin, where weed control is mainly done by hoeing, analyses showed that one well- timed weeding operation around the 10-leaf stage could already be cost-effective. A second weeding operation at a later stage would assure profit. The precision experimental design (PED) was employed to determine the effect of weeds, soil properties and herbicides on crop yield in three winter wheat trials. In this design, large field trials’ geodata of weed distribution, herbicide application, soil properties and yield are used to model the effects of the former three on yield. Galium aparine, other broadleaved weeds and Alopecurus myosuroides reduced yield by 17.5, 1.2 and 12.4 kg ha-1 plant-1 m2 determined by weed counts. The determined thresholds for SSWC with independently applied herbicides were 4, 48 and 12 plants m-2, respectively. Bi-spectral camera based weed–yield estimates were difficult to interpret showing that this technology still needs to be improved. However, large weed patches were correctly identified. ETs derived of field trials’ data carried out at several sites over 13 years in the framework of the ’Gemeinschaftsversuche Baden-Württemberg’ were 9.2-9.8 and 4.5-8.9 % absolute weed coverage for winter wheat and winter barley and 3.7% to 5.5% relative weed coverage for maize. Overall, the weed frequencies in winter cereals were found to be more stable than the weed frequencies in maize during the observation period. In maize, a frequency increase of thermophilic species was found. Trends of considerable yield increases of 0.16, 0.08 and 0.2 t ha-1 for winter wheat, winter barely and maize, respectively, were estimated if weeds were successfully controlled. In order to evaluate the use of bi-spectral cameras and shapebased classification algorithms for weed detection in SSWC, herbicides were applied site-specifically using weed densities determined by bi-spectral camera technology in a winter wheat and maize field. Threshold values were employed for decision taking. Using this approach herbicide savings between 58 and 83 % could be achieved. Such reductions in herbicide use would meet the demand of society to minimize the release of plant protection products in the environment. Misclassification occurred if weeds overlapped with crop plants and crop leaf tips were frequently misclassified as grass weeds. Improvements in equipment, especially between the interfaces of camera, classification algorithms, decision component and sprayer are advisable for further trials. In conclusion, the derived ETs can be easily implemented in a straightforward SSWC system or can serve as decision aid for farmers in winter wheat and winter barley. Further model testing and adjusting would be necessary. For maize, the use of ETs at the field level is not suggested by this study, however the need for early weed control is clearly demonstrated. Bi-spectral camera technology combined with classification algorithms to detect weeds is promising for research use and for SSWC, but still requires some technical improvements.
Evaluation and improvement of N fertilization strategies in the wheat/maize double-cropping system of the North China Plain
(2015) Hartmann, Tobias Edward; Müller, Torsten
The North China Plain (NCP) is the main production area of cereal crops in China. The intensification of agricultural systems and the increased use of chemical N fertilizers are contributing to environmental pollution. One of the objectives of this thesis was to apply an Nmin based approach for the calculation of N application rates to a previously over-fertilized farmers field of the NCP and to evaluate the potential of reducing N inputs while maintaining the grain yield of a summer-maize/winter-wheat double-cropping system; and to evaluate fertilizer strategies, aiming to reduce N inputs and loss. Using an Nmin based approach for the calculation of fertilizer application rates, a reduction of fertilizer input by up to 50% compared to farmers practice (550 kg N ha-1 a-1) is possible without negatively affecting the grain yield of a wheat / maize double cropping system. The extreme re-supply of N during the summer-vegetation periods of maize in the first two experimental seasons resulted in high yields of the control treatment (CK: 2009: 5.7 and 2010: 5.9 Mg ha-1), which did not significantly differ from the fertilized treatments. This resulted in a reduced recovery efficiency of N (REN: 0.09 kg kg-1 – 0.30 kg kg-1). According to the results of this field experiment there was no agronomic justification for the application of fertilizer N. The grain yield of maize of the control treatment finally decreased in the third vegetation period of summer-maize. While maintaining the yield level, the optimized application of N increased REN (0.37 – 0.58 kg kg-1) significantly compared to farmers practice (0.21 kg kg-1) in this final vegetation period of maize. Wheat, in contrast to maize, is dependent on the application of fertilizer N for yield formation. In both vegetation periods of wheat, REN of the reduced treatments (0.34 – 1.0 kg kg-1) was significantly higher compared to FP (0.26 and 0.27 kg kg-1). The highest cumulated (5 vegetation periods) agronomic efficiency of N, as well as cumulated grain yield of the wheat/maize double-cropping system was observed when ammoniumsulphate-nitrate was applied in combination with the nitrification inhibitor 3,4-dimethylpyrazolephosphate (ASNDMPP: AEN: 19 kg kg-1, yield: 35 Mg ha-1) and according to crop N demand and residual soil mineral N. The highest REN was observed when urea ammonium nitrate was applied in a shallow, banded depot (UANDEP: 40 kg kg-1). The results of this field experiment further show that the N surplus (fertilized N - grain N) as well as the N balance (N Input - N output) after harvest are significantly lower when an optimized approach to fertilizer application is followed. The over-application of N for an optimized application of urea or ASNDMPP (Surplus: -25kg to 98 kg N ha-1; Balance: -36 to 102 kg N ha-1) was significantly reduced compared to current farmers practice (Surplus: 156kg to 187 kg N ha-1; Balance: 56 to 262 kg N ha-1). This leads to lower residual N in the soil horizon from 0 - 90 cm in the reduced treatments (113 kg N ha-1 at end of experiment) compared to FP (293 kg N ha-1). The results of this experiment indicate that N contained in the residues of maize is available only to the subsequent summer-crop and may sufficiently supply N for the yield formation of maize. Should the over-application of N be effectively reduced in the cropping systems of the NCP it is therefore necessary to take the N mineralization potential of soils into account. Based on the results of this field experiment and others, a crop-soil interface model (HERMES) was calibrated and validated to the conditions of the NCP. Finally, this research observed the effect of wheat straw and the urease inhibitor (UI) N-(n-buthyl) thiophosphoric triamide (nBPT) on the turnover of urea, as well as the loss of ammonia and nitrous oxide from an alkaline soil of the NCP. UI inhibit or reduce the appearance of ammonia after the application of urea and almost completely prevent the loss of N as ammonia (urea: 12 – 14% loss). nBPT effectively reduces the rate of urea hydrolysis but does not down-regulate the process enough to completely inhibit nitrification, thereby maintaining the availability of N from urea for plants. Further, the addition of wheat straw prolongs the appearance of ammonium after the application of urea while the appearance of nitrate is reduced. Wheat straw may therefore either act as a stimulant of hydrolysis or as an inhibitor of nitrification. The addition of urea increases soil respiration and the emission of N2O drastically, possibly acting as a C and N source for microbial organisms and causing a priming effect on microbial activity in soils. This effect was increased further when wheat straw as well as urea were added to soil. nBPT, in contrast, prevents a significant increase in CO2-respiration and N2O-emission. The urease inhibitor may therefore generally restrict microbial activity or shift nitrification/denitrification processes towards the emission of N2.
Förderung und Entmischung auf dem Vorbereitungsboden des Mähdreschers
(2013) Timofeev, Andrey; Böttinger, Stefan
In the last years with the increasing performance of the combine harvester capacity, the performance of the cleaning system has been the limiting factor, because the capacity of the threshing drum and the separation elements by the use of additional separation drums and rotors is not a problem anymore. The performance of the cleaning system can be greatly increased, especially through intense pre- segregation, whereas grain losses remain at a relatively low level even at high particle rates of approximately of m˙ K = 5,5 kg/(s·m). Grain- and NKB (chaff and other plant residue) -throughput affect both the conveying speed and the segregation on the grain pan. The grain throughput has a particularly strong impact on the conveyor speed, when throw occurs in the conveying process (Frv > 1). Thereby the elastic properties of the crop layer (straw and chaff rack) damps very strong the introduced mechanical agitation. This decreases the conveying speed strongly. The segregation in turn affects positively the speed of transfer from the grain pan to the material. The separation takes place substantially in the last third of the grain pan.
Genomic and phenotypic improvement of triticale (×Triticosecale Wittmack) line and hybrid breeding programs
(2021) Trini, Johannes Philipp; Würschum, Tobias
Triticale (×Triticosecale Wittmack) breeding is a success story as it evolved to a serious alternative in farmer’s crop rotations since the 1970s and is grown globally on around 4 million hectares today. New developments, however, pointed out additional possibilities to improve triticale line and hybrid breeding programs increasing its future competitiveness and were evaluated in this study. In more detail, these were to (i) examine the genetic control and evaluate long term genetic trends of plant height in Central European winter triticale, (ii) evaluate the potential of triticale hybrid breeding and hybrid prediction approaches in triticale with a focus on biomass yield, (iii) introduce and examine a concept bypassing the time and resource consuming evaluation of female candidate lines in cytoplasmatic male sterility (CMS) based hybrid breeding, and (iv) to draw conclusions for the future improvement of triticale line and hybrid breeding programs. The genome wide association study detected markers significantly associated with plant height and developmental stage, respectively. These explained 42,16% and 29,31% of the total genotypic variance of plant height and development stage and are probably related to four and three quantitative trait loci (QTL), respectively. The two major QTL detected for plant height were located on chromosomes 5A and 5R which most likely could be assigned to the known height reducing genes Rht12 from wheat and Ddw1 from rye. The third major QTL detected located on chromosome 4B could not be assigned to a known height reducing gene and it cannot be precluded, that these significantly associated markers are identifying one and the same QTL as the markers located on chromosome 5R, as these showed a high linkage disequilibrium amongst each other. Evaluating the 129 registered cultivars showed that plant height decreased since the 1980’s. Evaluating their genetic constitution revealed that most cultivars carried at least one height reducing QTL and that plant height could be reduced even further in cultivars combining more than one height reducing QTL. It was further observed that the frequency of cultivars carrying one or a combination of height reducing QTL increased since the 1980’s. A considerable amount of heterosis has been observed for biomass related traits in triticale hybrids before. However, the use of hybrid prediction approaches for these traits has not been evaluated. Hybrid prediction based on mid parent values already showed very good results illustrating their potential to preselect the most promising parents as prediction accuracies based on parental general combining ability (GCA) effects were only slightly better. When incorporating molecular markers into GCA based prediction accuracies, prediction accuracies decreased slightly compared to prediction accuracies solely based on phenotypic GCA effects. Predicting hybrids incorporating one or two untested parental lines, imitating a scenario where novel female and/or male candidate lines are introduced into a hybrid breeding program, reduced genomic prediction accuracies even further due to the decreasing amount of information which could be exploited from the parents. Additionally including specific combining ability (SCA) effects in the genomic prediction models did not yield additional use. A high proportion of SCA variance compared to the total genetic variance decreased prediction accuracies for the traits fresh and dry biomass yield. In this study simulation studies were used to demonstrate what a prediction accuracy of a specific value actually means for a hybrid breeding programs. Further, an approach was introduced and evaluated showing great potential to evaluate novel female candidate lines for their use in a CMS based hybrid breeding program by bypassing their time and resource demanding introgression into a male sterile cytoplasm using three way hybrids. Prediction accuracies obtained by this novel approach showed highly promising results for most evaluated traits compared to prediction accuracies based on GCA effects or mid parent performance. Additionally incorporating SCA effects into the prediction models showed only a little increase of the prediction accuracies. Further, the results were supported by simulation studies adjusting different parameters, such as the number of parents or the proportion of SCA variance compared to the total genetic variance.
Genomics-assisted breeding strategies for quantitative resistances to Northern corn leaf blight in maize (Zea mays L.) and Fusarium diseases in maize and in triticale (× Triticosecale Wittm.)
(2021) Galiano Carneiro, Ana Luísa; Miedaner, Thomas
Fusarium head blight (FHB) in triticale (× Triticosecale Wittm.), Gibberella ear rot (GER) and Northern corn leaf blight (NCLB) in maize (Zea mays L.) are devastating crop diseases causing yield losses and/or reducing grain quality worldwide. Resistance breeding is the most efficient and sustainable approach to reduce the damages caused by these diseases. For all three pathosystems, a quantitative inheritance based on many genes with small effects has been described in previous studies. Hence, this thesis aimed to assess the potential of genomics-assisted breeding strategies to reduce FHB, GER and NCLB in applied breeding programs. In particular, the objectives were to: (i) Dissect the genetic architecture underlying quantitative variation for FHB, GER and NCLB through different quantitative trait loci (QTL) and association mapping approaches; (ii) assess the potential of genomics-assisted selection to select superior triticale genotypes harboring FHB resistance; (iii) phenotype and characterize Brazilian resistance donors conferring resistance to GER and NCLB in multi-environment trials in Brazil and in Europe; and (iv) evaluate approaches for the introgression and integration of NCLB and GER resistances from tropical to adapted germplasm. The genome-wide association study (GWAS) conducted for FHB resistance in triticale revealed six QTL that reduced damages by 5 to 8%. The most prominent QTL identified in our study was mapped on chromosome 5B and explained 30% of the genotypic variance. To evaluate the potential of genomic selection (GS), we performed a five-fold cross-validation study. Here, weighted genomic selection increased the prediction accuracy from 0.55 to 0.78 compared to the non-weighted GS model, indicating the high potential of the weighted genomic selection approach. The successful application of GS requires large training sets to develop robust models. However, large training sets based on the target trait deoxynivalenol (DON) are usually not available. Due to the rather moderate correlation between FHB and DON, we recommend a negative selection based on genomic estimated breeding values (GEBVs) for FHB severity in early breeding stages. In the long-run, however, we encourage breeders to build and test GS calibrations for DON content in triticale. The genetic architecture of GER caused by Fusarium graminearum in maize was investigated in Brazilian tropical germplasm in multi-environment trials. We observed high genotype-by-environment interactions which requires trials in many environments for the identification of stable QTL. We identified four QTL that explained between 5 to 22% of the genotypic variance. Most of the resistance alleles identified in our study originated from the Brazilian tropical parents indicating the potential of this exotic germplasm as resistance source. The QTL located on chromosome bin 1.02 was identified both in Brazilian and in European trials, and across all six biparental populations. This QTL is likely stable, an important feature for its successful employment across different genetic backgrounds and environments. This stable QTL is a great candidate for validation and fine mapping, and subsequent introgression in European germplasm but possible negative linkage drag should be tackled. NCLB is another economically important disease in maize and the most devastating leaf disease in maize grown in Europe. Virulent races have already overcome the majority of known qualitative resistances. Therefore, a constant monitoring of S. turcica races is necessary to assist breeders on the choice of effective resistances in each target environment. We investigated the genetic architecture of NCLB in Brazilian tropical germplasm and identified 17 QTL distributed along the ten chromosomes of maize explaining 4 to 31% of the trait genotypic variance each. Most of the alleles reducing the infections originated from Brazilian germplasm and reduced NCLB between 0.3 to 2.5 scores in the 1-9 severity scale, showing the potential of Brazilian germplasm to reduce not only GER but also NCLB severity in maize. These QTL were identified across a wide range of environments comprising different S. turcica race compositions indicating race non-specific resistance and most likely stability. Indeed, QTL 7.03 and 9.03/9.04 were identified both in Brazil and in Europe being promising candidates for trait introgression. These major and stable QTL identified for GER and NCLB can be introgressed into elite germplasm by marker-assisted selection. Subsequently, an integration step is necessary to account for possible negative linkage drag. A rapid genomics-assisted breeding approach for the introgression and integration of exotic into adapted germplasm has been proposed in this thesis. Jointly, our results demonstrate the high potential of genomics-assisted breeding strategies to efficiently increase the quantitative resistance levels of NCLB in maize and Fusarium diseases in maize and in triticale. We identified favorable QTL to increase resistance levels in both crops. In addition, we successfully characterized Brazilian germplasm for GER and NCLB resistances. After validation and fine mapping, the introgression and integration of the QTL identified in this study might contribute to the release of resistant cultivars, an important pillar to cope with global food security.
Mapping stem rust and leaf rust resistances in winter rye (Secale cereale L.)
(2023) Gruner, Paul; Miedaner, Thomas
Rye (Seale cereale L.) is one of the few cross-pollinating small-grain cereals and is mainly used for bread baking, biogas production and as animal feed. In its largest cultivation area (Northern, Central and Eastern Europe, including the Russian Federation) two major rust diseases, stem rust (SR) caused by Puccinia graminis f. sp. secalis and leaf rust (LR) caused by Puccinia recondita, can cause severe yield losses. Whereas LR can be found in most rye growing areas every year, SR is occurring less regularly, but can become epidemic in some years. The general occurrence of stem rust in Germany is becoming more regular, especially when hot summers provide optimum conditions for the growth and the spread of this fungus. Resistant cultivars can be a successful way to control both diseases, but SR is not assessed in the (German) variety registration and still several cultivars can be found that are susceptible or medium resistant for LR. Before the studies of this thesis were conducted, no marker-associated SR resistance gene locus was known and only six LR resistance loci had been reported. Rust resistances can be classified into all-stage resistances (ASR), that are usually caused by single R-genes and adult-plant resistances (APR), that are characterized by smaller (quantitative) effects and can only be observed in the adult-plant stage and thus make field tests mandatory. This thesis aimed on identifying resistant genotypes and respective resistance loci for SR and LR resistances in the rye genome. Two different material groups were used: biparental populations composed of inbred lines and populations composed of self-incompatible single plants. In total ten biparental populations and two additional testcross populations were studied, each constituting 68-90 genotypes. Self-incompatible populations were genetic resources from the Russian Federation, Austria and the United States of America and had 68-74 single plants each. Inbred lines were assessed in multi-environmental field trials (4-6 environments per population) and to guarantee high disease pressure, SR was artificially inoculated in contrast to naturally occurring LR in all environments. In addition, two different kind of seedling tests, one based on inoculations of entire seedling plants and one based on inoculation of detached leaves, were used to assess SR resistance. Mixed linear models were used to analyze the phenotypic data from field experiments and (mixed) cumulative logit models were used to analyze ordinal data resulting from seedling tests. Due to small sample size of a single detached leaf per genotype and isolate in self-incompatible populations, the results based on cumulative modes were cross checked with a non-parametric test. Both, progenies from biparental populations and single plants from self-incompatible populations were genotyped with single nucleotide polymorphism (SNP) based markers (Illumina iSelect 10K SNP chip or DArTseqTM) and appropriate statistical tests for phenotype-marker association were applied. This was achieved by extending phenotypic models with additive and dominant marker effects and their respective interaction with the environment or the isolates. Two marker-associated SR ASR loci (Pgs1, Pgs3.1) could be identified in biparental populations that were responsible for (large) qualitative differences between resistant and susceptible plants in the field and/or seedling stage. Additionally, 14 quantitative trait loci (QTLs) were shown to be responsible for SR APR. For LR, except one QTL found at similar position compared to a previous study, two new genes (Pr7, Pr8) and three QTLs were identified. Self-incompatible rye populations were used for the first time for association mapping and three SR resistance loci (Pgs1 - Pgs3) could be identified. Two thereof were also found within biparental mapping populations by means of QTL mapping and this was considered as prove of this new method. Throughout all studies, the natural cross-pollinating character of rye had to be considered in choosing appropriate methods and for developing rust resistant rye hybrids. This thesis includes breeding material from the largest European rye breeding companies and experiments were conducted in close cooperation with them. The characterization of breeding material for SR and LR infection, development of (new) mapping approaches, detection of resistance loci and marker candidates in the rye genome and finally the discussion of selection strategies provides a solid basis for breeders to develop the most durable SR and LR resistant rye cultivars. For scientists, new research topics could be, for example, the cloning of rye genes or a more thorough understanding of pathogen dynamics to finally achieve durable resistance in future.
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.
Optimum strategies to implement genomic selection in hybrid breeding
(2022) Marulanda Martinez, Jose Joaquin; Melchinger, Albrecht E.
To satisfy the rising demand for more agricultural production, a boost in the annual expected selection gain (ΔGa) of traits such as grain yield and especially yield stability has to be rapidly achieved. Hybrid breeding has contributed to a notable increment in performance for numerous allogamous species and has been proposed as a way to match the increased demand for autogamous cereals such as rice, wheat, and barley. An additional tool to increase the rate of annual selection gain is genomic selection (GS), a method to assess the merit of an individual by simultaneously accounting for the effects associated with hundreds to thousands of DNA markers. Successful integration of GS and hybrid breeding should go beyond the study of GS prediction accuracy and focus on the design of breeding strategies, for which GS maximizes ΔGa and optimizes the allocation of resources. The main goal of this thesis was to examine strategies for optimum implementation of GS in hybrid breeding with emphasis on estimation set design to perform GS within biparental populations and on the optimization of hybrid breeding strategies through model calculations. One strategy, GSrapid, with moderate nursery selection, one stage of GS, and one stage of phenotypic selection, reached the greatest ΔGa for single trait selection regardless of the budget, costs, variance components, and accuracy of genomic prediction. GSrapid was also the most efficient strategy for the simultaneous improvement of two traits regardless of the correlation between traits, selection index chosen, and economic weights assigned to each trait. The success of this strategy relies principally on the reduction of breeding cycle length and marginally on the increase in selection intensity. Moving from traditional breeding strategies based on phenotypic selection to strategies using GS for single trait improvement in hybrid breeding could lead not only to increments in ΔGa but also to large savings in the budget. The implementation of nursery selection in breeding strategies boosted the importance of efficient systems for inbred generation accompanied by improvements in the methods of hybrid seed production for experimental tests. When it comes to multiple trait improvement, the choice between optimum and base selection indices had minor impact on the net merit. However, considerable differences for ΔGa of single traits were observed when applying optimum or base indices if the variance components of the traits to be improved differed. The role of the economic weights assigned to each trait was determinant and small variations in the weights led to a remarkable genetic loss in one of the traits. The optimum design of estimation sets to perform GS within biparental populations should be based on phenotypic data, rather than molecular marker data. This finding poses major challenges for GS-based strategies aiming to select the best new inbreds within second cycle breeding populations, as breeding cycle length might not be reduced. Then, the ES design to optimize GS within biparental populations would have a defined application on the exploitation of within-family variation by increasing selection intensity in biparental populations with the largest potential of producing high-performing inbreds. Based on the results of this thesis, future challenges for the optimum implementation of GS in hybrid breeding strategies include (i) reductions in breeding cycle length and increments in selection intensity by refinements of DH technology or implementation of speed breeding, (ii) improvements in the methods for hybrid seed production, facilitating the reallocation of resources to the production of more candidates tested during the breeding cycle, and (iii) precise estimation of economic weights, reflecting the importance of the traits for breeding programs and farmers, and maximizing long term ΔGa for the most relevant traits.
Ruminal degradation characteristics of barley, rye, and triticale grains assayed in situ and in vitro, and by near-infrared spectroscopy
(2017) Krieg, Jochen; Rodehutscord, Markus
The milk yield of dairy cows and related energy and protein requirements have steadily increased in the last few decades. Since feed intake has not increased to the same extent as nutritional requirements, the concentration of nutrients in mixed rations had to be increased. An increase in energy concentration is often achieved by the inclusion of high levels of cereal grains. In the EU—apart from wheat—barley, rye, and triticale are widely cultivated cereal grains. Starch (ST), followed by crude protein (CP), is the main constituent of cereal grains. The rate and extent of ruminal CP and ST degradation can influence the performance and health of dairy cows, but data that can enable the comparison of ruminal degradation within and between barley, rye, and triticale grains are scarce. Commonly used techniques to explore ruminal degradation of feed are in situ and in vitro incubations. Both techniques require ruminal-fistulated animals, but alternative methods are being demanded by the community, in order to reduce the number of animal trials. An approach with the potential to estimate the nutritional value of various feeds is near-infrared spectroscopy (NIRS). The present thesis has two major parts. In the first part, ruminal degradation parameters and the effective degradability (ED) of DM, CP, and ST from barley, rye, and triticale grains are investigated using standardised in situ and in vitro incubation techniques. A total of 20 genotypes per grain species were used. In the second part, NIRS calibrations were developed with the aim of estimating the CP and ST concentrations of cereal grains and their incubation residues. Subsequently, data from in situ experiments were used to establish the calibrations for estimating the ruminal in situ degradation of cereal grains from their spectral data. In situ degradation studies have been conducted by ruminal incubation, utilising three lactating cows. Ruminal degradation parameters and ED (ruminal passage rate = 8%//h) were calculated. For in vitro incubations, the samples were incubated in a rumen fluid-buffer mixture (‘Hohenheim Gas Test’). The gas production was recorded for estimating gas production kinetics. In vitro gas production—in combination with crude nutrient concentrations—was used to estimate the metabolisable energy concentration (ME) and digestibility of organic matter (dOM). The degradation rates differed between and within the grain species for DM, CP, and ST. The variation within grain species was not reflected in the ED of CP and ST, due to the relatively fast and almost complete degradation of the grains. The ED of CP was 77% (69–80%) for barley, 85% (83–86%) for rye, and 82% (79–84%) for triticale. The corresponding ED of ST was 86% (82–88%), 95% (92–96%), and 94% (90–95%). Accordingly, the estimated ME (barley: 13.5 MJ/kg DM, rye: 13.9 MJ/kg DM, triticale: 13.5 MJ/ kg DM) showed only relatively minor variation within one grain species. The dOM was overall at a high level (barley: 91.3%, rye: 95.3%, triticale: 95.8%). The relatively small variation within one grain species could not be explained by the chemical and physical characteristics of the samples. Hence, it was concluded that it is feasible to use mean values for every species in feed formulation and ration planning. In the second part of this thesis, it was shown that it is possible to replace chemical CP and ST analyses of samples from in situ studies by NIRS without affecting the calculated ruminal degradation characteristics. NIRS could be used to estimate the ED of CP and ST from cereal grains. The sample set to establish the calibrations included barley, durum, maize, rye, triticale, and wheat grains. Calibrations for the CP and ST concentration were extended to pea samples. The calibrations with the best validation performance for CP and ST concentration were obtained by using the wavelength segment of 1250 to 2450 nm and the first derivative of the spectra (CP: R2 = 0.99; SEP = 0.46% DM. ST: R2 = 0.99; SEP = 2.10% DM). The results of in situ studies did not differ, irrespective of whether chemical or NIRS analysis was used. Like the CP and ST concentration, the ED was estimated with a high accuracy (ED8 CP: R2 = 0.95; SEP = 2.43%. ED8 ST: R2 = 0.97; SEP = 2.45%). However, calibrations need to be extended before they can be recommended for routine use. The present thesis demonstrates that the ED of CP and ST of barley, rye, and triticale grains differ between the species, but variation within one grain species is relatively small and not related to the chemical and physical characteristics of the grain. Hence, under the prevailing cultivation conditions, the mean values for each grain species in feed evaluation are deemed adequate. It was demonstrated that NIRS has the potential to facilitate the evaluation of the nutritive value of cereal grains for ruminants.
Towards sustainable chemical fertilizer management in China : from theory to farm household
(2023) Yu, Xiaomin; Doluschitz, Reiner
Over the past few decades, China’s grain production has expanded drastically. On the one hand, this has eliminated food shortages and allowed China to feed its huge and still growing population. On the other hand, the rapid growth in grain productivity has come at a heavy cost. Excessive fertilizer use has led to a variety of negative consequences that threaten national food security and environmental sustainability. Since the 2010s, the Chinese government and academia have made considerable efforts to reduce the consumption of chemical fertilizers and improve nutrient management. These include a wide range of regulations to control or guide chemical fertilizer use, policies to eliminate subsidies for the fertilizer industry, and nationwide promotion of scientific fertilizer application methods. In response to these efforts, Chinas overall fertilizer application rate has been declining since 2016. However, China still applies far more fertilizers than its crops need, and the current crop Nitrogen Use Efficiency (NUE) and Phosphorus Use Efficiency (PUE) in China are both below the global average. Therefore, reducing dependence on chemical fertilizers for crop production and sustainably feeding a large population remains a key challenge for China. This dissertation aims to contribute to sustainable nutrient management in China by providing a comprehensive and in-depth understanding of fertilizer use and management at the national, regional, farm and household levels. In the first study (Chapter 2), a systematic review of the historical development and current status of chemical fertilizer use and management in China at the national level is presented. In addition, fertilizer nutrient surpluses are estimated for 30 provinces in China and the regional and temporal variations are visualized. In the second study (Chapter 3), the relationship between fertilizer nutrient surpluses and the regional economy at the provincial level is examined within the framework of the Environmental Kuznets curve (EKC) hypothesis. A panel cointegration approach is employed, using time-series data from 1988 to 2019. In the third study (Chapter 4), the research focus is further narrowed to the farm household resolution. Using cross-sectional survey data from 774 maize-growing farms in northern China in 2019, the study investigates the role of farm characteristics, farmers knowledge, perceptions, and socioeconomic context in farmers fertilizer use strategies. The studies confirm that by 2021, China has reached zero growth in fertilizer use and fertilizer nutrient surpluses at the national and regional level. However, regions with a high proportion of cash crops, such as the southeast coast and northwest, still suffer from high nutrient surpluses. Furthermore, in circa 2012, China has reached its EKC turning point between fertilizer nutrient surpluses and GDP per capita. With further economic growth, the fertilizer surpluses in most Chinese provinces will decrease, indicating a moderating of the tension between economic development and the environment. Looking at the farm and household level, the study shows that in northern China, small farms are more likely to overuse fertilizers in maize cultivation without further yield improvement. Current extension programs have had a positive impact on farmers’ fertilizer use strategies and environmental awareness; nevertheless, the coverage and effectiveness of trainings should be improved. In summary, the dissertation identifies the following key factors that impede sustainable chemical fertilizer management in China: small farm size; regional economic dependence on cash crops; the large discrepancy between farmers practices and scientific production guidelines; and the shrinking and aging of Chinas rural labor force. To address these aspects, the dissertation proposes recommendations at the national strategic level, policy level and implementation level, respectively. The findings and recommendations of this dissertation can serve as a robust decision support and scientific basis for policy makers, stakeholders and researchers in the field of sustainable nutrient management in China.
Untersuchungen und Verbesserungen der Querstromtrocknung von Getreide
(1980) Kuppinger, Heinz; Kutzbach, Heinz Dieter
Das Querstromtrocknungsverfahren findet weit verbreitete Anwendung zur Getreidetrocknung. Allerdings hat dieses Trocknungsverfahren den Nachteil der geringen Trocknungsleistung, des hohen Wärmebedarfs und der ungleichmäßigen Trocknung der Körnerschüttung.. Ziel der vorliegenden Arbeit war es daher, zu untersuchen, inwieweit durch eine Variation der das Trocknungsverhalten beeinflussenden Trocknungsparameter und durch eine Modifikation des Querstromverfahrens Verbesserungen der Querstromtrocknung zu erreichen sind.
Untersuchungen zum Dresch- und Trennvorgang von Getreide in einem Axialdreschwerk
(1985) Wacker, Peter; Kutzbach, Heinz Dieter
In der vorliegenden Arbeit werden die für Axialdreschwerke weitgehend ungeklärten funktionellen Zusammenhänge zwischen verschiedenen Parametern und verschiedenen für die Bewertung der Arbeitsqualität maßgeblichen Kenngrößen für Getreide theoretisch ermittelt und an einer Versuchseinrichtung mit zylindrischem Rotor und feststehendem Außenmantel untersucht.
Variability of amino acid digestibility of cereal grains in laying hens
(2017) Zuber, Tobias; Rodehutscord, Markus
It was the objective of this doctoral thesis to generate a comprehensive data set of AA digestibility values of cereal grains in laying hens by using a strictly standardized assay procedure. Additionally, the suitability of two approaches to predict AA digestibility was examined. For this purpose, 80 genotypes of triticale, rye, corn, and wheat grains (n = 20 each) were grown as part of the “GrainUp” project. Apart from corn, the cereal species were grown under identical environmental conditions. The grain samples were comprehensively analyzed according to their physical properties, chemical composition, and gross energy concentration. The concentration of crude protein in the grain samples of triticale, rye, corn, and wheat was in the range of 113-138, 108-127, 78-112, and 125-162 g/kg dry matter, respectively. Additionally, the in vitro solubility of nitrogen (N) was determined in the grains after pretreatment with porcine pepsin and pancreatin. The animal trial comprised 16 Latin Squares (6x6), distributed among six subsequent runs. Thus, each run contained two to three Latin Squares. Cecectomized laying hens were individually housed in metabolism cages and fed either on a basal diet containing 500 g/kg cornstarch or one of the 80 cereal diets, with the cornstarch being replaced with a grain sample, for eight days. During the last four days, feed intake was recorded and excreta were collected quantitatively twice daily. After each collection period, the hens were group-housed in a floor pen for two days and offered a conventional layer diet. Amino acid digestibility of the grain samples was calculated using a linear regression approach. Relationships between AA digestibility and single analyzed fractions or the in vitro solubility of N of the cereal grains were examined by calculating Pearson product-moment correlation coefficients. Prediction equations to estimate AA digestibility were calculated by multiple regression analysis using a stepwise selection approach. Therefore, the variables were pooled according to their characteristics, and the prediction equations were calculated for the digestibility of each AA using each pool. The variables were offered in a linear or linear plus quadratic fashion and classified as significant predictors at P<0.10. The equations were assessed based on the adjusted R² and the root-mean-square error. The AA digestibility varied widely within and among the cereal species. The mean digestibility of lysine was 74% (digestibility range: 68-80%), 49% (35-59%), 79% (64-85%), and 80% (69-87%) for triticale, rye, corn, and wheat grains, respectively. A similar ranking was observed for methionine with a mean digestibility of 83% (digestibility range: 77-86%), 67% (57-75%), 91% (86-94%) and 84% (70-93%) for triticale, rye, corn, and wheat grains, respectively. Correlation analysis showed inconsistent results within and across the cereal species. Among the physical characteristics, significant correlations were detected for the thousand seed weight and the digestibility of a few AA in wheat, and for the test weight and the digestibility of a few AA in rye and corn. Significant correlations between NSP fractions and the digestibility of essential AA were detected only for rye grains. In this crop, the concentration of arabinoxylans and total NSP in the grains was negatively correlated with the digestibility of arginine, leucine, phenylalanine, and threonine. The concentration of crude protein in corn grains was positively correlated with the digestibility of essential AA, except isoleucine, tryptophan, and valine. In contrast, only a few significant positive correlations between crude protein concentration and essential AA digestibility were found for triticale and rye grains. No significant correlations were found for wheat grains in this regard. The in vitro solubility of N was negatively and positively correlated with the digestibility of a few AA in triticale and rye grains, respectively. The accuracy of the predictive equations was generally low (adjusted R² below 0.7 in most cases), and varied considerably between both pools of variables for the same AA and the same pool of variables for different AA. Thus, single or several physical or chemical characteristics could not explain the variation in AA digestibility in laying hens and the development of prediction equations sufficiently precise for the practical application was not possible.