In the last decades procedures for obtaining protein isolates and concentrates derived from narro... more In the last decades procedures for obtaining protein isolates and concentrates derived from narrow-leafed lupins ( L. angustifolius ) for human nutrition have been developed. Since this processes starts with defatting of seeds, lupin oil is obtained in large quantities. Therefore, 50 genotypes of L. angustifolius were analysed regarding the fatty acid (FA) composition of seed oil and the environmental stability of fatty acid contents in order to get information on the application of lupin oil in the food industry. The results revealed an n-3/n-6 poly unsaturated fatty acid ratio of 0.13. Furthermore, the seed oil of L. angustifolius contains rather high amounts of saturated FAs (22%). Significant genotypic differences and a high heritability (h2>85%) for the content of all fatty acids are suggesting that the potential for genetic improvement of fatty acid composition by breeding is given. However, coefficients of variation below 10% for all considered traits point out that a rapi...
The combination of crops in mixed cropping systems can lead to a complementary utilization of gro... more The combination of crops in mixed cropping systems can lead to a complementary utilization of growing factors and in an increase of the nutrient and water use efficiency. Legumes as a cultivation partner are especially useful because of the additional fixation of nitrogen. The performance of different crops in sole and mixed cropping are investigated under controlled, semi-controlled and field conditions. In a field experiment, which was established in 1998 to investigate the effects of phosphorus (P) fertilizer strategies, the following crops were cultivated from 2013 till 2015: Maize (Zea mays), sorghum (Sorghum bicolor), maize + runner bean (Phaseolus coccineus) and Sorghum + blue lupin (Lupinus angustifolius) (2013) and Andean lupin (Lupinus mutabilis) (2014, 2015). Under optimal P supply maize and sorghum had higher biomass yields than the respective combinations with the legumes. However, under suboptimal P supply the mixtures of maize or sorghum with the legumes had comparati...
In order to identify improved sorghum varieties for smallholder farmers, 85 promising varieties w... more In order to identify improved sorghum varieties for smallholder farmers, 85 promising varieties were evaluated at three locations. Thirteen varieties were selected on the basis of grain yield, resistance to drought, aphids and stem borers, as well as seed characteristics such as seed and flour colour, endosperm texture, kernel hardness and seed mass. The selected varieties should be evaluated on-farm in order to test their adaptability under low-input farming conditions.
Understanding the adaptation mechanisms of sorghum to drought and the underlying genetic architec... more Understanding the adaptation mechanisms of sorghum to drought and the underlying genetic architecture may help to improve its production in a wide range of environments. By crossing a high yielding parent (HYP) and a drought tolerant parent (DTP), we obtained 140 recombinant inbred lines (RILs), which were genotyped with 120 DArT and SSR markers covering 14 linkage groups (LGs). A subset of 100 RILs was evaluated three times in control and drought treatments to genetically dissect their response to water availability. Plants with early heading date (HD) in the drought treatment maintained yield (YLD) level by reducing seed number SN and increasing hundred seed weight (HSW). In contrast, early HD in the control treatment increased SN, HSW and YLD. In total, 133 significant QTL associated with the measured traits were detected in ten hotspot regions. Antagonistic, pleiotropic effects of a QTL cluster mapped on LG-6 may explain the observed trade-offs between SN and HSW: Alleles from DTP reduced SN and the alleles from HYP increased HSW under drought stress, but not in the control treatment. Our results illustrate the importance of considering genetic and environmental factors in QTL mapping to better understand plant responses to drought and to improve breeding programs.
The development of cauliflower (Brassica oleracea var. botrytis) is highly dependent on temperatu... more The development of cauliflower (Brassica oleracea var. botrytis) is highly dependent on temperature due to vernalization requirements, which often causes delay and unevenness in maturity during months with warm temperatures. Integrating quantitative genetic analyses with phenology modeling was suggested to accelerate breeding strategies toward wide-adaptation cauliflower. The present study aims at establishing a genome-based model simulating the development of doubled haploid (DH) cauliflower lines to predict time to curd induction of DH lines not used for model parameterization and test hybrids derived from the bi-parental cross. Leaf appearance rate and the relation between temperature and thermal time to curd induction were examined in greenhouse trials on 180 DH lines at seven temperatures. Quantitative trait loci (QTL) analyses carried out on model parameters revealed ten QTL for leaf appearance rate (LAR), five for the slope and two for the intercept of linear temperature-response functions. Results of the QTL-based phenology model were compared to a genomic selection (GS) model. Model validation was carried out on data comprising four field trials with 72 independent DH lines, 160 hybrids derived from the parameterization set, and 34 hybrids derived from independent lines of the population. The QTL model resulted in a moderately accurate prediction of time to curd induction (R 2 = 0.42-0.51) while the GS model generated slightly better results (R 2 = 0.52-0.61). Predictions of time to curd induction of test hybrids from independent DH lines were less precise with R 2 = 0.40 for the QTL and R 2 = 0.48 for the GS model. Implementation of juvenile-to-adult phase transition is proposed for model improvement.
Potato is considered to have a low phosphorus (P) efficiency compared to other crops. Therefore, ... more Potato is considered to have a low phosphorus (P) efficiency compared to other crops. Therefore, P fertilization requirements are high. New cultivars with improved P efficiency may contribute to save limited mineral P sources and to reduce eutrophication of surface water bodies. The present study aims to characterize the P efficiency of different potato genotypes and to identify mechanisms that improve P efficiency in cultivated potato. A diversity set of 32 potato accessions was used to assess their P efficiency. From this set, five cultivars were selected and two pot experiments with different P-fertilization strategies including a non-fertilized control were conducted to estimate effects of P deficiency on general agronomic and P related traits, root development, phosphatase activity and micro RNA 399 (miR399) expression. Significant differences between the 32 genotypes were found for P utilization efficiency (PUtE). P acquisition efficiency (PAE) as P content in low P in relation to P content in high P was positively correlated to relative biomass production while PUtE was not. Selected genotypes displayed a strong relation between total root length and P content. Root phosphatase activity and miR399 expression increased under P deficiency. However, tuber yields of four cultivars, grown on a soil with suboptimal content of plant available P, were not significantly affected in comparison to yields of wellfertilized plots. We conclude from the present study that PUtE and PAE are important traits when selecting for plants requiring less fertilizer inputs but PAE might be more important for cropping on deficient soils. A large root system might be the most important trait for P acquisition on such soils and therefore in breeding for P efficient crops. Lowering P fertilizer inputs might not necessarily reduce tuber yields.
Background and Aims Roots facilitate acquisition of macro- and micronutrients, which are crucial ... more Background and Aims Roots facilitate acquisition of macro- and micronutrients, which are crucial for plant productivity and anchorage in the soil. Phosphorus (P) is rapidly immobilized in the soil and hardly available for plants. Adaptation to P scarcity relies on changes in root morphology towards rooting systems well suited for topsoil foraging. Root-system architecture (RSA) defines the spatial organization of the network comprising primary, lateral and stem-derived roots and is important for adaptation to stress conditions. RSA phenotyping is a challenging task and essential for understanding root development. Methods In this study, 19 traits describing RSA were analysed in a diversity panel comprising 194 sorghum genotypes, fingerprinted with a 90-k single-nucleotide polymorphism (SNP) array and grown under low and high P availability. Key Results Multivariate analysis was conducted and revealed three different RSA types: (1) a small root system; (2) a compact and bushy rooting type; and (3) an exploratory root system, which might benefit plant growth and development if water, nitrogen (N) or P availability is limited. While several genotypes displayed similar rooting types in different environments, others responded to P scarcity positively by developing more exploratory root systems, or negatively with root growth suppression. Genome-wide association studies revealed significant quantitative trait loci (P < 2.9 × 10-6) on chromosomes SBI-02, SBI-03, SBI-05 and SBI-09. Co-localization of significant and suggestive (P < 5.7 × 10-5) associations for several traits indicated hotspots controlling root-system development on chromosomes SBI-02 and SBI-03. Conclusions Sorghum genotypes with a compact, bushy and shallow root system provide potential adaptation to P scarcity in the field by allowing thorough topsoil foraging, while genotypes with an exploratory root system may be advantageous if N or water is the limiting factor, although such genotypes showed highest P uptake levels under the artificial conditions of the present study.
Abstract Phenotype by genotype prediction based on ecophysiological models, which account for all... more Abstract Phenotype by genotype prediction based on ecophysiological models, which account for allelic gene, QTL, or marker effects, have many possible applications in plant breeding programs. The goal of the present study was to predict heading date of individual lines of a Hordeum vulgare x H. vulgare ssp. spontaneum BC2DH-population using a phenology model parameterized with marker effects derived from ridge regression best linear unbiased prediction. The genetic linkage map included SSR markers and flowering-time genes. Effects of photoperiod and temperature on heading date were measured under controlled conditions on a subset of the population comprising the recurrent parent and 36 BC2DH candidate introgression lines covering the H. spontaneum genome. Marker effects, which were subsequently used for model parameterization, were estimated. Model evaluation was carried out on already published field trial data comprising the 36 BC2DH lines and 266 independent BC2DH lines from the same cross. Applying the model on the lines used for model parameterization explained 33–51% of heading-date variation in three of the four evaluation environments but only 20% of the variation in the fourth environment. Heading dates of the 266 independent lines were predicted with less accuracy. Between 20 and 25% of phenotypic variation was explained by the model in three environments and only 8% of heading date variation in the fourth environment. The root mean squared error (RMSE) was slightly higher for independent lines than for the lines used for model parameterization. Dissecting RMSE into its components revealed that RMSE was largely influenced by a systematic bias in most environments and by the missing ability of the model to describe the observed variation within the set of genotypes in all environments. Comparing the combined genome-wide prediction (GWP) and phenology model with a conventional GWP model gave similar prediction accuracies if the training set had the same size.
Journal of the American Society for Horticultural Science, 2009
The combination of quantitative trait loci (QTL) analysis and ecophysiological modeling has been ... more The combination of quantitative trait loci (QTL) analysis and ecophysiological modeling has been suggested as an approach to reveal the genetic basis of complex traits since phenotypes change with time and environmental conditions and the variation within populations can be described by genotype-specific parameterization of response curves on time and influential environmental factors. The objectives of the present study are a genotype-specific parameterization of a model describing leaf area development under well-watered and drought stress conditions, the use of QTL for estimating model input parameters, an evaluation of the model, and a comparison of the genotype-specific and QTL-based model parameterization. We used a two-phase linear function to describe preflowering leaf area development in a Brassica oleracea L. doubled haploid population. To illustrate effects of drought on leaf growth, the function was combined with a plateau function, which estimates the soil water status ...
Water and nitrogen (N) management is a key factor in starch potato (Solanum tuberosum L.) product... more Water and nitrogen (N) management is a key factor in starch potato (Solanum tuberosum L.) production to ensure good yield and quality. Due to its shallow root system, potato is sensitive to drought and N uptake is limited to the upper soil layer resulting in leaching of nitrate. Efficient utilization of N and water can be optimized by adaptation of the cropping system and by selection of improved genotypes. A 2-year pot experiment with 14 modern starch and 3 table potato cultivars was conducted under controlled conditions in a rain-out shelter in order to investigate genotype-dependent responses to N deficiency and drought stress with regard to yield and yield components. Plants were grown at two N levels and a short-term drought-stress period during the sensitive tuber initiation stage was applied. Starch yield under control condition reached an average of 80.2 g plant −1 , which was reduced under drought stress by 18% at sufficient N supply and by 23% at N deficiency. Sufficient N fertilization improved the water use efficiency under both continuous water supply and drought stress. N limitation increased the N use efficiency (NUE) at continuous watering, while NUE was not affected by drought stress at sufficient N supply but decreased under N deficiency. Genotype and drought as well as genotype and N level interactions were significant for all investigated traits, i.e. tuber yield (fresh and dry matter), starch and N Kjeldahl contents, starch yield and water consumption.
Grafting tomato (Solanum lycopersicum L.) onto introgression lines (ILs) derived from S. habrocha... more Grafting tomato (Solanum lycopersicum L.) onto introgression lines (ILs) derived from S. habrochaites with introgression of a quantitative trait locus (QTL), stm9, for shoot turgor maintainer located on chromosome 9 has been suggested for improving yield under abiotic stresses. However, the physiological and agronomic responses of grafts with IL rootstocks to low rootzone temperature (RZT) and drought stresses are not yet clearly understood. Therefore, recurrent parent (RP) grafted onto IL and donor (D) rootstocks, and self-grafted IL and RP were examined at different combinations of optimal (20°-26°C RZT and well-watered) and suboptimal (10°C RZT and wellwatered, and 20°-26°C RZT and cyclic drought) temperatures. Graft combinations were compared with self-grafted controls for dry weights, stomatal conductance (g s), leaf parameters, osmotic adjustment, and stress tolerance index. The RP grafted onto IL rootstocks regulated g s efficiently, retained the green trait, and produced higher biomass than the self-grafted RP. The IL rootstocks improved tolerance of the scion to drought and low RZT. Potential of IL rootstocks for improving tomato production under stressed conditions is discussed.
Comparative shoot proteome analysis of two potato (Solanum tuberosum L.) genotypes contrasting in... more Comparative shoot proteome analysis of two potato (Solanum tuberosum L.) genotypes contrasting in nitrogen deficiency responses in vitro
Roots are of immense importance for environmental adaptation, but are largely unexplored in major... more Roots are of immense importance for environmental adaptation, but are largely unexplored in major crops. Via high-resolution linkage disequilibrium mapping, we discovered strong linkage drag in European wheat between a haplotype variant controlling heading date and two flanking loci carrying alleles that constrain root biomass. Investigation of genes within the region of interest could help breeders to recover root diversity for future food production in fluctuating environments.
In order to get an overview on the genetic relatedness of sorghum (Sorghum bicolor) landraces and... more In order to get an overview on the genetic relatedness of sorghum (Sorghum bicolor) landraces and cultivars grown in low-input conditions of small-scale farming systems, 46 sorghum accessions derived from Southern Africa were evaluated on the basis of amplified fragment length polymorphism (AFLPs), random amplified polymorphic DNAs (RAPDs) and simple sequence repeats (SSRs). By this approach all sorghum accessions were uniquely fingerprinted by all marker systems. Mean genetic similarity was estimated at 0.88 based on RAPDs, 0.85 using AFLPs and 0.31 based on SSRs. In addition to this, genetic distance based on SSR data was estimated at 57 according to a stepwise mutation model (Dm-SSR). All UPGMA-clusters showed a good fit to the similarity estimates (AFLPs: r = 0.92; RAPDs: r = 0.88; SSRs: r = 0.87; Dm-SSRs: r = 0.85). By UPGMA-clustering two main clusters were built on all marker systems comprising landraces on the one hand and newly developed varieties on the other hand. Further sub-groupings were not unequivocal. Genetic diversity (H, DI) was estimated on a similar level within landraces and breeding varieties. Comparing the three approaches to each other, RAPD and AFLP similarity indices were highly correlated (r = 0.81), while the Spearman's rank correlation coefficient between SSRs and AFLPs was r = 0.57 and r = 0.51 between RAPDs and SSRs. Applying a stepwise mutation model on the SSR data resulted in an intermediate correlation coefficient between Dm-SSRs and AFLPs (r = 0.66) and RAPDs (r = 0.67), respectively, while SSRs and Dm-SSRs showed a lower correlation coefficient (r = 0.52). The highest bootstrap probabilities were found using AFLPs (56% on average) while SSR, Dm-SSR and RAPD-based similarity estimates had low mean bootstrap probabilities (24%, 27%, 30%, respectively). The coefficient of variation (CV) of the estimated genetic similarity decreased with an increasing number of bands and was lowest using AFLPs.
In the last decades procedures for obtaining protein isolates and concentrates derived from narro... more In the last decades procedures for obtaining protein isolates and concentrates derived from narrow-leafed lupins ( L. angustifolius ) for human nutrition have been developed. Since this processes starts with defatting of seeds, lupin oil is obtained in large quantities. Therefore, 50 genotypes of L. angustifolius were analysed regarding the fatty acid (FA) composition of seed oil and the environmental stability of fatty acid contents in order to get information on the application of lupin oil in the food industry. The results revealed an n-3/n-6 poly unsaturated fatty acid ratio of 0.13. Furthermore, the seed oil of L. angustifolius contains rather high amounts of saturated FAs (22%). Significant genotypic differences and a high heritability (h2>85%) for the content of all fatty acids are suggesting that the potential for genetic improvement of fatty acid composition by breeding is given. However, coefficients of variation below 10% for all considered traits point out that a rapi...
The combination of crops in mixed cropping systems can lead to a complementary utilization of gro... more The combination of crops in mixed cropping systems can lead to a complementary utilization of growing factors and in an increase of the nutrient and water use efficiency. Legumes as a cultivation partner are especially useful because of the additional fixation of nitrogen. The performance of different crops in sole and mixed cropping are investigated under controlled, semi-controlled and field conditions. In a field experiment, which was established in 1998 to investigate the effects of phosphorus (P) fertilizer strategies, the following crops were cultivated from 2013 till 2015: Maize (Zea mays), sorghum (Sorghum bicolor), maize + runner bean (Phaseolus coccineus) and Sorghum + blue lupin (Lupinus angustifolius) (2013) and Andean lupin (Lupinus mutabilis) (2014, 2015). Under optimal P supply maize and sorghum had higher biomass yields than the respective combinations with the legumes. However, under suboptimal P supply the mixtures of maize or sorghum with the legumes had comparati...
In order to identify improved sorghum varieties for smallholder farmers, 85 promising varieties w... more In order to identify improved sorghum varieties for smallholder farmers, 85 promising varieties were evaluated at three locations. Thirteen varieties were selected on the basis of grain yield, resistance to drought, aphids and stem borers, as well as seed characteristics such as seed and flour colour, endosperm texture, kernel hardness and seed mass. The selected varieties should be evaluated on-farm in order to test their adaptability under low-input farming conditions.
Understanding the adaptation mechanisms of sorghum to drought and the underlying genetic architec... more Understanding the adaptation mechanisms of sorghum to drought and the underlying genetic architecture may help to improve its production in a wide range of environments. By crossing a high yielding parent (HYP) and a drought tolerant parent (DTP), we obtained 140 recombinant inbred lines (RILs), which were genotyped with 120 DArT and SSR markers covering 14 linkage groups (LGs). A subset of 100 RILs was evaluated three times in control and drought treatments to genetically dissect their response to water availability. Plants with early heading date (HD) in the drought treatment maintained yield (YLD) level by reducing seed number SN and increasing hundred seed weight (HSW). In contrast, early HD in the control treatment increased SN, HSW and YLD. In total, 133 significant QTL associated with the measured traits were detected in ten hotspot regions. Antagonistic, pleiotropic effects of a QTL cluster mapped on LG-6 may explain the observed trade-offs between SN and HSW: Alleles from DTP reduced SN and the alleles from HYP increased HSW under drought stress, but not in the control treatment. Our results illustrate the importance of considering genetic and environmental factors in QTL mapping to better understand plant responses to drought and to improve breeding programs.
The development of cauliflower (Brassica oleracea var. botrytis) is highly dependent on temperatu... more The development of cauliflower (Brassica oleracea var. botrytis) is highly dependent on temperature due to vernalization requirements, which often causes delay and unevenness in maturity during months with warm temperatures. Integrating quantitative genetic analyses with phenology modeling was suggested to accelerate breeding strategies toward wide-adaptation cauliflower. The present study aims at establishing a genome-based model simulating the development of doubled haploid (DH) cauliflower lines to predict time to curd induction of DH lines not used for model parameterization and test hybrids derived from the bi-parental cross. Leaf appearance rate and the relation between temperature and thermal time to curd induction were examined in greenhouse trials on 180 DH lines at seven temperatures. Quantitative trait loci (QTL) analyses carried out on model parameters revealed ten QTL for leaf appearance rate (LAR), five for the slope and two for the intercept of linear temperature-response functions. Results of the QTL-based phenology model were compared to a genomic selection (GS) model. Model validation was carried out on data comprising four field trials with 72 independent DH lines, 160 hybrids derived from the parameterization set, and 34 hybrids derived from independent lines of the population. The QTL model resulted in a moderately accurate prediction of time to curd induction (R 2 = 0.42-0.51) while the GS model generated slightly better results (R 2 = 0.52-0.61). Predictions of time to curd induction of test hybrids from independent DH lines were less precise with R 2 = 0.40 for the QTL and R 2 = 0.48 for the GS model. Implementation of juvenile-to-adult phase transition is proposed for model improvement.
Potato is considered to have a low phosphorus (P) efficiency compared to other crops. Therefore, ... more Potato is considered to have a low phosphorus (P) efficiency compared to other crops. Therefore, P fertilization requirements are high. New cultivars with improved P efficiency may contribute to save limited mineral P sources and to reduce eutrophication of surface water bodies. The present study aims to characterize the P efficiency of different potato genotypes and to identify mechanisms that improve P efficiency in cultivated potato. A diversity set of 32 potato accessions was used to assess their P efficiency. From this set, five cultivars were selected and two pot experiments with different P-fertilization strategies including a non-fertilized control were conducted to estimate effects of P deficiency on general agronomic and P related traits, root development, phosphatase activity and micro RNA 399 (miR399) expression. Significant differences between the 32 genotypes were found for P utilization efficiency (PUtE). P acquisition efficiency (PAE) as P content in low P in relation to P content in high P was positively correlated to relative biomass production while PUtE was not. Selected genotypes displayed a strong relation between total root length and P content. Root phosphatase activity and miR399 expression increased under P deficiency. However, tuber yields of four cultivars, grown on a soil with suboptimal content of plant available P, were not significantly affected in comparison to yields of wellfertilized plots. We conclude from the present study that PUtE and PAE are important traits when selecting for plants requiring less fertilizer inputs but PAE might be more important for cropping on deficient soils. A large root system might be the most important trait for P acquisition on such soils and therefore in breeding for P efficient crops. Lowering P fertilizer inputs might not necessarily reduce tuber yields.
Background and Aims Roots facilitate acquisition of macro- and micronutrients, which are crucial ... more Background and Aims Roots facilitate acquisition of macro- and micronutrients, which are crucial for plant productivity and anchorage in the soil. Phosphorus (P) is rapidly immobilized in the soil and hardly available for plants. Adaptation to P scarcity relies on changes in root morphology towards rooting systems well suited for topsoil foraging. Root-system architecture (RSA) defines the spatial organization of the network comprising primary, lateral and stem-derived roots and is important for adaptation to stress conditions. RSA phenotyping is a challenging task and essential for understanding root development. Methods In this study, 19 traits describing RSA were analysed in a diversity panel comprising 194 sorghum genotypes, fingerprinted with a 90-k single-nucleotide polymorphism (SNP) array and grown under low and high P availability. Key Results Multivariate analysis was conducted and revealed three different RSA types: (1) a small root system; (2) a compact and bushy rooting type; and (3) an exploratory root system, which might benefit plant growth and development if water, nitrogen (N) or P availability is limited. While several genotypes displayed similar rooting types in different environments, others responded to P scarcity positively by developing more exploratory root systems, or negatively with root growth suppression. Genome-wide association studies revealed significant quantitative trait loci (P < 2.9 × 10-6) on chromosomes SBI-02, SBI-03, SBI-05 and SBI-09. Co-localization of significant and suggestive (P < 5.7 × 10-5) associations for several traits indicated hotspots controlling root-system development on chromosomes SBI-02 and SBI-03. Conclusions Sorghum genotypes with a compact, bushy and shallow root system provide potential adaptation to P scarcity in the field by allowing thorough topsoil foraging, while genotypes with an exploratory root system may be advantageous if N or water is the limiting factor, although such genotypes showed highest P uptake levels under the artificial conditions of the present study.
Abstract Phenotype by genotype prediction based on ecophysiological models, which account for all... more Abstract Phenotype by genotype prediction based on ecophysiological models, which account for allelic gene, QTL, or marker effects, have many possible applications in plant breeding programs. The goal of the present study was to predict heading date of individual lines of a Hordeum vulgare x H. vulgare ssp. spontaneum BC2DH-population using a phenology model parameterized with marker effects derived from ridge regression best linear unbiased prediction. The genetic linkage map included SSR markers and flowering-time genes. Effects of photoperiod and temperature on heading date were measured under controlled conditions on a subset of the population comprising the recurrent parent and 36 BC2DH candidate introgression lines covering the H. spontaneum genome. Marker effects, which were subsequently used for model parameterization, were estimated. Model evaluation was carried out on already published field trial data comprising the 36 BC2DH lines and 266 independent BC2DH lines from the same cross. Applying the model on the lines used for model parameterization explained 33–51% of heading-date variation in three of the four evaluation environments but only 20% of the variation in the fourth environment. Heading dates of the 266 independent lines were predicted with less accuracy. Between 20 and 25% of phenotypic variation was explained by the model in three environments and only 8% of heading date variation in the fourth environment. The root mean squared error (RMSE) was slightly higher for independent lines than for the lines used for model parameterization. Dissecting RMSE into its components revealed that RMSE was largely influenced by a systematic bias in most environments and by the missing ability of the model to describe the observed variation within the set of genotypes in all environments. Comparing the combined genome-wide prediction (GWP) and phenology model with a conventional GWP model gave similar prediction accuracies if the training set had the same size.
Journal of the American Society for Horticultural Science, 2009
The combination of quantitative trait loci (QTL) analysis and ecophysiological modeling has been ... more The combination of quantitative trait loci (QTL) analysis and ecophysiological modeling has been suggested as an approach to reveal the genetic basis of complex traits since phenotypes change with time and environmental conditions and the variation within populations can be described by genotype-specific parameterization of response curves on time and influential environmental factors. The objectives of the present study are a genotype-specific parameterization of a model describing leaf area development under well-watered and drought stress conditions, the use of QTL for estimating model input parameters, an evaluation of the model, and a comparison of the genotype-specific and QTL-based model parameterization. We used a two-phase linear function to describe preflowering leaf area development in a Brassica oleracea L. doubled haploid population. To illustrate effects of drought on leaf growth, the function was combined with a plateau function, which estimates the soil water status ...
Water and nitrogen (N) management is a key factor in starch potato (Solanum tuberosum L.) product... more Water and nitrogen (N) management is a key factor in starch potato (Solanum tuberosum L.) production to ensure good yield and quality. Due to its shallow root system, potato is sensitive to drought and N uptake is limited to the upper soil layer resulting in leaching of nitrate. Efficient utilization of N and water can be optimized by adaptation of the cropping system and by selection of improved genotypes. A 2-year pot experiment with 14 modern starch and 3 table potato cultivars was conducted under controlled conditions in a rain-out shelter in order to investigate genotype-dependent responses to N deficiency and drought stress with regard to yield and yield components. Plants were grown at two N levels and a short-term drought-stress period during the sensitive tuber initiation stage was applied. Starch yield under control condition reached an average of 80.2 g plant −1 , which was reduced under drought stress by 18% at sufficient N supply and by 23% at N deficiency. Sufficient N fertilization improved the water use efficiency under both continuous water supply and drought stress. N limitation increased the N use efficiency (NUE) at continuous watering, while NUE was not affected by drought stress at sufficient N supply but decreased under N deficiency. Genotype and drought as well as genotype and N level interactions were significant for all investigated traits, i.e. tuber yield (fresh and dry matter), starch and N Kjeldahl contents, starch yield and water consumption.
Grafting tomato (Solanum lycopersicum L.) onto introgression lines (ILs) derived from S. habrocha... more Grafting tomato (Solanum lycopersicum L.) onto introgression lines (ILs) derived from S. habrochaites with introgression of a quantitative trait locus (QTL), stm9, for shoot turgor maintainer located on chromosome 9 has been suggested for improving yield under abiotic stresses. However, the physiological and agronomic responses of grafts with IL rootstocks to low rootzone temperature (RZT) and drought stresses are not yet clearly understood. Therefore, recurrent parent (RP) grafted onto IL and donor (D) rootstocks, and self-grafted IL and RP were examined at different combinations of optimal (20°-26°C RZT and well-watered) and suboptimal (10°C RZT and wellwatered, and 20°-26°C RZT and cyclic drought) temperatures. Graft combinations were compared with self-grafted controls for dry weights, stomatal conductance (g s), leaf parameters, osmotic adjustment, and stress tolerance index. The RP grafted onto IL rootstocks regulated g s efficiently, retained the green trait, and produced higher biomass than the self-grafted RP. The IL rootstocks improved tolerance of the scion to drought and low RZT. Potential of IL rootstocks for improving tomato production under stressed conditions is discussed.
Comparative shoot proteome analysis of two potato (Solanum tuberosum L.) genotypes contrasting in... more Comparative shoot proteome analysis of two potato (Solanum tuberosum L.) genotypes contrasting in nitrogen deficiency responses in vitro
Roots are of immense importance for environmental adaptation, but are largely unexplored in major... more Roots are of immense importance for environmental adaptation, but are largely unexplored in major crops. Via high-resolution linkage disequilibrium mapping, we discovered strong linkage drag in European wheat between a haplotype variant controlling heading date and two flanking loci carrying alleles that constrain root biomass. Investigation of genes within the region of interest could help breeders to recover root diversity for future food production in fluctuating environments.
In order to get an overview on the genetic relatedness of sorghum (Sorghum bicolor) landraces and... more In order to get an overview on the genetic relatedness of sorghum (Sorghum bicolor) landraces and cultivars grown in low-input conditions of small-scale farming systems, 46 sorghum accessions derived from Southern Africa were evaluated on the basis of amplified fragment length polymorphism (AFLPs), random amplified polymorphic DNAs (RAPDs) and simple sequence repeats (SSRs). By this approach all sorghum accessions were uniquely fingerprinted by all marker systems. Mean genetic similarity was estimated at 0.88 based on RAPDs, 0.85 using AFLPs and 0.31 based on SSRs. In addition to this, genetic distance based on SSR data was estimated at 57 according to a stepwise mutation model (Dm-SSR). All UPGMA-clusters showed a good fit to the similarity estimates (AFLPs: r = 0.92; RAPDs: r = 0.88; SSRs: r = 0.87; Dm-SSRs: r = 0.85). By UPGMA-clustering two main clusters were built on all marker systems comprising landraces on the one hand and newly developed varieties on the other hand. Further sub-groupings were not unequivocal. Genetic diversity (H, DI) was estimated on a similar level within landraces and breeding varieties. Comparing the three approaches to each other, RAPD and AFLP similarity indices were highly correlated (r = 0.81), while the Spearman's rank correlation coefficient between SSRs and AFLPs was r = 0.57 and r = 0.51 between RAPDs and SSRs. Applying a stepwise mutation model on the SSR data resulted in an intermediate correlation coefficient between Dm-SSRs and AFLPs (r = 0.66) and RAPDs (r = 0.67), respectively, while SSRs and Dm-SSRs showed a lower correlation coefficient (r = 0.52). The highest bootstrap probabilities were found using AFLPs (56% on average) while SSR, Dm-SSR and RAPD-based similarity estimates had low mean bootstrap probabilities (24%, 27%, 30%, respectively). The coefficient of variation (CV) of the estimated genetic similarity decreased with an increasing number of bands and was lowest using AFLPs.
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Papers by Ralf Uptmoor