Browsing by Subject "Quality traits"

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Application of Near-Infrared Spectroscopy in Plant Breeding Programs
(2006) Montes, Juan Manuel; Melchinger, Albrecht E.
The success of plant breeding programs depends on the availability of genetic variation and efficient data collection processes that allow large-scale screenings of genotypes. When genetic variation is present, the goal is to identify those genotypes that are closest to the breeding objectives. In this context, the evaluation of a large number of genotypes requires optimization of the data collection process in order to provide reliable information for making selection decisions. The process of data collection must yield an accurate and precise assessment of genotypes timely because the information is needed to plan the next generation for breeding and cultivar development. Laboratory NIRS is routinely used in the data collection process of many breeding programs, but it requires the withdrawal of field plot samples and involves manual work. Applications of the near-infrared spectroscopy on choppers (NOC) and near-infrared spectroscopy on combine harvester (NOCH) are a step forward to the automation of data collection processes, by which sampling, labor, and sources of error in the data can be reduced. The objective of this thesis research was to assess the potential of NOC and NOCH for application in breeding programs of grain maize, rapeseed, and silage maize. Plot combine harvesters and choppers were equipped with diode-array spectrometers for collection of near-infrared plot spectra, and used to harvest experimental varieties of breeding programs in Central Europe. Two alternative sample presentation designs (conveyor belt and spout) were used for the NOC systems. The NOCH systems used the conveyor belt as sample presentation design. NOCH showed a high potential for determination of dry matter (DM), crude protein (CP), and starch (ST) contents of maize grain. NOCH calibration models yielded standard errors of prediction (SEP) and coefficients of determination of validation (R2V) of 1.2% and 0.95 for DM, 0.3% and 0.88 for CP, and 1.0% and 0.79 for ST, respectively. The potential of NOCH for determination of DM, CP, oil and glucosinolate contents of rapeseed was also high. NOCH calibration models yielded standard errors of cross validation (SECV) and coefficients of determination of cross validation (R2CV) of 0.3% and 0.96 for DM, 0.6% and 0.69 for CP, 0.9% and 0.71 for oil, and 2.2 μmol/g and 0.40 for glucosinolate, respectively. The NOC systems showed high potential for the determination of DM, ST, and soluble sugars (SS) content of silage maize hybrids. The NOC system equipped with a conveyor belt design yielded calibration models with SEP and R2V of 0.9% and 0.93 for DM, and 2.1% and 0.78 for ST, respectively. For the NOC system equipped with the spout design, the SEP and R2V amounted to 1.4% and 0.84 for DM, 2.3% and 0.75 for ST, and 0.9% and 0.81 for SS. The potential of both NOC systems for determination of fiber contents (CF, ADF, and NDF), digestibility and energy-related traits was lower than for DM, ST, and SS. The precision of NOCH for the determination of DM content in maize grain was higher than by traditional drying-oven method. A higher precision of NOCH is also expected for other traits and may also be extended to the NOC systems because the sampling error associated with traditional processes of data collection is reduced drastically by NOC and NOCH. The investigation of the effects caused by the calibration technique, mathematical transformation of the near-infrared spectra, and scatter correction on the development of NOCH calibration models for the prediction of DM, CP, and ST content in maize grain revealed that calibration technique was the most important factor affecting the prediction ability, whereas the importance of mathematical transformation and scatter correction depended on the particular constituent considered. Presently, there exists high uncertainty about the optimal NOC and NOCH sample presentation designs for agricultural harvesters. The dynamic signal range, i.e., the range of spectral values on which predictions are based, and the amount of plot material measured were identified as guide parameters for optimization of sample presentation designs. In addition, calibration transferability between NOC systems with different sample presentation designs proved to be feasible after merging spectra from both NOC systems in the calibration set. In conclusion, NOC and NOCH show high potential for replacing laboratory NIRS analysis of several traits in a plant breeding context and yield a more accurate and precise evaluation of field plot characteristics. Therefore, technological applications of the electromagnetic radiation is predicted to have a high impact in plant breeding, precision farming, and agriculture.
Phenotypic and molecular analyses of grain and biomass productivity under irrigated and rainfed conditions in hybrid rye
(2014) Gottwald, Marlen; Miedaner, Thomas
Rye (Secale cereale L.) is a small grain cereal used for bread making, livestock feeding and as renewable energy source. These types of usages are leading to different breeding goals. Rye growing regions are affected by climate change and consequently by drought. Germany is touched by rainless periods in spring and early summer in the last years. Again, in spring 2012 farmers in Brandenburg and Lower Saxony were affected by drought periods. Yield losses in those regions, especially in combination with sandy soils are expected. Therefore much attention is paid for breeding of drought resistant germplasm. Briefly, our objectives of this study were to (1) estimate the biomass and biogas potential of different plant materials, their quantitative genetic parameters and biogas-related traits, (2) analyze two recombinant inbred lines and differences in their yield potential between irrigated and rainfed regime, as well as the relative efficiency for indirect selection for drought resistance in irrigated regime, and (3) investigate the phenotypic performance for ten agronomic and quality traits across multiple environments and estimated the number and effects underlying QTL. For the biomass-/ biogas analyses a wide range of plant material was analysed. Germplasm resources, full-sib families selected for grain and forage use were tested for their per se and testcross performance and experimental hybrids selected for grain use and population cultivars selected for grain and forage use were analyzed. Dry matter yields varying across environments from 106 to 177 dt/ha for per se and testcross performance, respectively. For testcross performance, germplasm resources showed similar values to forage rye. The later the maturity stage, the more dry matter yield on the whole plant level was achieved. Estimates of genotypic variances for biomass yield were significant for all rye materials, whereas the variances per se and for testcrosses were for germplasm resources exorbitant higher than for forage and grain rye. Typical cumulative methane production curves were obtained for the whole plant material from the Hohenheim biogas yield test. Methane yield showed large differences between second and third harvest date for individual plant fractions. Differences between genotypes were not substantial for methane yield although significant in some instances. At EC77/83 hybrids and forage rye reached similar methane yield of about 5000 m3/ha. A high correlation between dry matter yield and methane yield was observed (r=0.95). Concerning high cost and time consuming analysis of biogas tests, for breeders the main breeding goal should be maximum dry matter yield. Direct selection on dry matter yield should indirect improve methane yield. Two biparental populations were used for the analysis of drought tolerance. The analysis was performed in duplicate. Both populations were grown under irrigated and rainfed regimes. Striking less rainfall compared to long-term precipitation occurred between April and July, during critical phases of plant development. Grain yield reduction between irrigated and non-irrigated regime ranged from 2% to 29.6% for population A and 2% to 40% for population B, whereas differences between both regimes were significant (P<0.05) for five and four environments, respectively. Genotypic variances of grain yield were significant in all instances, whereas genotype by irrigation interaction variance between both regimes being significant only in three and four environments for population A and B, respectively. Analysis across those environments revealed significant difference for genotype by irrigation interaction variance and the three-way interaction variance in both populations. Heritability estimates were higher for the irrigated than for the rainfed regime. High interaction variance with environment and no clustering of the two regimes in a multi-dimensional analysis were found. This illustrates the different soil and whether conditions between locations and additionally every location suffered from a different drought stress. The correlation between both regimes was significant but moderate, but genotypic coefficients considerably higher (Pop-A: 0.86, Pop-B: 0.84), which could be substantiated that testcrosses differed not substantially in drought-resistance. Indirect selection for drought in the irrigated regime was predicted to be equally or more efficient than direct selection in the non-irrigated regime. Phenotypic and genotypic analysis was done across ten environments for both biparental populations for the general improvement of agronomic and quality traits in rye. Population A were genotyped with a Rye5K SNP array and for population B DArT genotyping was done with a 3K rye array. Additionally both populations were genotyped with about 150 SSRs. The genetic linkage maps comprised 1,819 and 1,265 markers for population A and B, respectively and were used for the QTL analysis for ten agronomic and quality traits. Phenotyping revealed large genetic variation for ten agronomic and quality traits. Intensive phenotyping at up to ten environments led to moderate to high heritabilities. Across environments explained genotypic variance of the individual QTL ranged from 5 to 55%. For 1000-kernel weight, test weight, falling number, and starch content, several QTL with high effects and a frequency of recovery of about 90% were identified in both population. Rye suffered from drought stress in the last decade. Focusing on general improvement of rye regarding yield and quality, as well as improving rye regarding drought-resistance is important. Future research should be done in fine mapping and validation of the detected QTLs, for exploiting their potential in marker assisted breeding.