The Experts below are selected from a list of 738 Experts worldwide ranked by ideXlab platform

Albrecht E. Melchinger - One of the best experts on this subject based on the ideXlab platform.

  • new insights into the genetics of in vivo induction of maternal haploids the backbone of doubled haploid technology in maize
    Genetics, 2012
    Co-Authors: Vanessa Prigge, Raman Babu, Shaojiang Chen, G N Atlin, Albrecht E. Melchinger
    Abstract:

    Haploids and doubled haploid (DH) inbred lines have become an invaluable tool for maize genetic research and hybrid breeding, but the genetic basis of in vivo induction of maternal haploids is still unknown. This is the first study reporting comparative quantitative trait locus (QTL) analyses of this trait in maize. We determined haploid induction rates (HIR) in testcrosses of a total of 1061 progenies of four segregating populations involving two temperate haploid inducers, UH400 (HIR = 8%) and CAUHOI (HIR = 2%), one temperate and two tropical inbreds with HIR = 0%, and up to three generations per population. Mean HIR of the populations ranged from 0.6 to 5.2% and strongly deviated from the Midparent values. One QTL (qhir1) explaining up to p^=66% of the genetic variance was detected in bin 1.04 in the three populations involving a noninducer parent and the HIR-enhancing allele was contributed by UH400. Segregation ratios of loci in bin 1.04 were highly distorted against the UH400 allele in these three populations, suggesting that transmission failure of the inducer gamete and haploid induction ability are related phenomena. In the CAUHOI × UH400 population, seven QTL were identified on five chromosomes, with qhir8 on chromosome 9 having p^>20% in three generations of this cross. The large-effect QTL qhir1 and qhir8 will likely become fixed quickly during inducer development due to strong selection pressure applied for high HIR. Hence, marker-based pyramiding of small-effect and/or modifier QTL influencing qhir1 and qhir8 may help to further increase HIR in maize. We propose a conceptual genetic framework for inheritance of haploid induction ability, which is also applicable to other dichotomous traits requiring progeny testing, and discuss the implications of our results for haploid inducer development.

  • the role of epistasis in the manifestation of heterosis a systems oriented approach
    Genetics, 2007
    Co-Authors: Albrecht E. Melchinger, Zhaobang Zeng, Hans-peter Piepho, C C Schon
    Abstract:

    Heterosis is widely used in breeding, but the genetic basis of this biological phenomenon has not been elucidated. We postulate that additive and dominance genetic effects as well as two-locus interactions estimated in classical QTL analyses are not sufficient for quantifying the contributions of QTL to heterosis. A general theoretical framework for determining the contributions of different types of genetic effects to heterosis was developed. Additive × additive epistatic interactions of individual loci with the entire genetic background were identified as a major component of Midparent heterosis. On the basis of these findings we defined a new type of heterotic effect denoted as augmented dominance effect di* that comprises the dominance effect at each QTL minus half the sum of additive × additive interactions with all other QTL. We demonstrate that genotypic expectations of QTL effects obtained from analyses with the design III using testcrosses of recombinant inbred lines and composite-interval mapping precisely equal genotypic expectations of Midparent heterosis, thus identifying genomic regions relevant for expression of heterosis. The theory for QTL mapping of multiple traits is extended to the simultaneous mapping of newly defined genetic effects to improve the power of QTL detection and distinguish between dominance and overdominance.

  • analysis of a triple testcross design with recombinant inbred lines reveals a significant role of epistasis in heterosis for biomass related traits in arabidopsis
    Genetics, 2007
    Co-Authors: Barbara Kusterer, Hans-peter Piepho, J Muminovic, Susanne Barth, Martin Heckenberger, Rhonda C Meyer, Thomas Altmann, Albrecht E. Melchinger
    Abstract:

    Primary causes of heterosis are still unknown. Our goal was to investigate the extent and underlying genetic causes of heterosis for five biomass-related traits in Arabidopsis thaliana. We (i) investigated the relative contribution of dominance and epistatic effects to heterosis in the hybrid C24 × Col-0 by generation means analysis and estimates of variance components based on a triple testcross (TTC) design with recombinant inbred lines (RILs), (ii) estimated the average degree of dominance, and (iii) examined the importance of reciprocal and maternal effects in this cross. In total, 234 RILs were crossed to parental lines and their F1's. Midparent heterosis (MPH) was high for rosette diameter at 22 days after sowing (DAS) and 29 DAS, growth rate (GR), and biomass yield (BY). Using the F2-metric, directional dominance prevailed for the majority of traits studied but reciprocal and maternal effects were not significant. Additive and dominance variances were significant for all traits. Additive × additive and dominance × dominance variances were significant for all traits but GR. We conclude that dominance as well as digenic and possibly higher-order epistatic effects play an important role in heterosis for biomass-related traits. Our results encourage the use of Arabidopsis hybrid C24 × Col-0 for identification and description of quantitative trait loci (QTL) for heterosis for biomass-related traits and further genomic studies.

  • genetic distance based on simple sequence repeats and heterosis in tropical maize populations
    Crop Science, 2003
    Co-Authors: Jochen C Reif, Albrecht E. Melchinger, Marilyn L Warburton, D A Hoisington, S K Vasal, G Srinivasan, Martin O Bohn, Matthias Frisch
    Abstract:

    Heterotic groups and patterns are of fundamental importance in hybrid breeding of maize (Zea mays L.). The major goal of this study was to investigate the relationship between heterosis and genetic distance determined with simple sequence repeat (SSR) markers. The objectives of our research were to (i) compare the genetic diversity within and between seven tropical maize populations, (ii) test alternative hypotheses on the relationship between panmictic Midparent heterosis (PMPH) and genetic distances determined with SSR markers, and (iii) evaluate the use of SSR markers for grouping of germplasm and establishing heterotic patterns in hybrid breeding of tropical maize. Published data of a diallel of seven tropical maize populations evaluated for agronomic traits in seven environments were reanalyzed to calculate PMPH in population hybrids. In addition, 48 individuals from each population were sampled and assayed with 85 SSR markers covering the entire maize genome. A total of 532 alleles in the 7 × 48 genotypes assayed were detected. The analysis of molecular variance (AMOVA) revealed that 89.8% of the variation was found within populations and only 10.2% between populations. The correlation between PMPH and the squared modified Roger's distance (MRD) based on SSR markers was significantly positive (P < 0.05) only for grain yield (r = 0.63). With SSR analyses, it was possible to assign Population 29 (Pop29) to the established Heterotic Group A and propose new heterotic groups (Pop25, Pop43). We conclude that SSR markers provide a powerful tool for grouping of germplasm and are a valuable complementation to field trials for identifying groups with satisfactory heterotic response.

Ana Butrón - One of the best experts on this subject based on the ideXlab platform.

  • qtl for maize Midparent heterosis in the heterotic pattern american dent european flint under corn borer pressure
    Frontiers in Plant Science, 2017
    Co-Authors: Luis Fernando Samayoa, R A Malvar, Ana Butrón
    Abstract:

    Despite the importance of heterosis and the efforts to comprehend this phenomenon, its molecular bases are still unknown. In this study, we intended to detect QTL for mid-parent heterosis under infestation with the Mediterranean corn borer (MCB, Sesamia nonagrioides Lef.) using a North Carolina design III approach with a RIL population derived from a European flint inbred (EP42) x American dent inbred (A637) cross. QTL for heterosis of kernel yield have been positioned in regions corresponding to previously identified QTL for the same trait in different backgrounds. These results reinforce the high congruency of genes controlling heterosis across populations, even when populations have been developed from different heterotic patterns. A high percentage of genetic variation for mid-parent heterosis (Z2 transformation) for kernel yield could not be explained. Furthermore, genomic regions involved in heterosis for yield and plant height were not found despite the high genetic correlation between Z2 transformations for kernel yield and plant height. The moderate power in detecting QTL for mid-parent heterosis suggests that many genes with low augmented dominance effects contribute to the genetic architecture of mid-parent heterosis; dominance and additive-additive epistatic effects could contribute to heterosis. However, results from this and previous studies suggest that the region 8.03-8.05 deserves special attention in future works in order to fine map loci involved in mid-parent heterosis for yield.

Jochen C Reif - One of the best experts on this subject based on the ideXlab platform.

  • a quantitative genetic framework highlights the role of epistatic effects for grain yield heterosis in bread wheat
    Nature Genetics, 2017
    Co-Authors: Yong Jiang, Renate Schmidt, Yusheng Zhao, Jochen C Reif
    Abstract:

    Analysis of a large bread-wheat genomic data set through a quantitative genetic framework designed to study the genetic basis of heterosis shows that hybrids outperform Midparents in grain yield by 10%. Genome-wide prediction and association mapping indicate that epistasis plays a significant role in heterosis of grain yield in wheat.

  • genetic distance based on simple sequence repeats and heterosis in tropical maize populations
    Crop Science, 2003
    Co-Authors: Jochen C Reif, Albrecht E. Melchinger, Marilyn L Warburton, D A Hoisington, S K Vasal, G Srinivasan, Martin O Bohn, Matthias Frisch
    Abstract:

    Heterotic groups and patterns are of fundamental importance in hybrid breeding of maize (Zea mays L.). The major goal of this study was to investigate the relationship between heterosis and genetic distance determined with simple sequence repeat (SSR) markers. The objectives of our research were to (i) compare the genetic diversity within and between seven tropical maize populations, (ii) test alternative hypotheses on the relationship between panmictic Midparent heterosis (PMPH) and genetic distances determined with SSR markers, and (iii) evaluate the use of SSR markers for grouping of germplasm and establishing heterotic patterns in hybrid breeding of tropical maize. Published data of a diallel of seven tropical maize populations evaluated for agronomic traits in seven environments were reanalyzed to calculate PMPH in population hybrids. In addition, 48 individuals from each population were sampled and assayed with 85 SSR markers covering the entire maize genome. A total of 532 alleles in the 7 × 48 genotypes assayed were detected. The analysis of molecular variance (AMOVA) revealed that 89.8% of the variation was found within populations and only 10.2% between populations. The correlation between PMPH and the squared modified Roger's distance (MRD) based on SSR markers was significantly positive (P < 0.05) only for grain yield (r = 0.63). With SSR analyses, it was possible to assign Population 29 (Pop29) to the established Heterotic Group A and propose new heterotic groups (Pop25, Pop43). We conclude that SSR markers provide a powerful tool for grouping of germplasm and are a valuable complementation to field trials for identifying groups with satisfactory heterotic response.

Luis Fernando Samayoa - One of the best experts on this subject based on the ideXlab platform.

  • qtl for maize Midparent heterosis in the heterotic pattern american dent european flint under corn borer pressure
    Frontiers in Plant Science, 2017
    Co-Authors: Luis Fernando Samayoa, R A Malvar, Ana Butrón
    Abstract:

    Despite the importance of heterosis and the efforts to comprehend this phenomenon, its molecular bases are still unknown. In this study, we intended to detect QTL for mid-parent heterosis under infestation with the Mediterranean corn borer (MCB, Sesamia nonagrioides Lef.) using a North Carolina design III approach with a RIL population derived from a European flint inbred (EP42) x American dent inbred (A637) cross. QTL for heterosis of kernel yield have been positioned in regions corresponding to previously identified QTL for the same trait in different backgrounds. These results reinforce the high congruency of genes controlling heterosis across populations, even when populations have been developed from different heterotic patterns. A high percentage of genetic variation for mid-parent heterosis (Z2 transformation) for kernel yield could not be explained. Furthermore, genomic regions involved in heterosis for yield and plant height were not found despite the high genetic correlation between Z2 transformations for kernel yield and plant height. The moderate power in detecting QTL for mid-parent heterosis suggests that many genes with low augmented dominance effects contribute to the genetic architecture of mid-parent heterosis; dominance and additive-additive epistatic effects could contribute to heterosis. However, results from this and previous studies suggest that the region 8.03-8.05 deserves special attention in future works in order to fine map loci involved in mid-parent heterosis for yield.

Hans-peter Piepho - One of the best experts on this subject based on the ideXlab platform.

  • comparison of maize zea mays l f1 hybrid and parental inbred line primary root transcriptomes suggests organ specific patterns of nonadditive gene expression and conserved expression trends
    Genetics, 2008
    Co-Authors: Nadine Hoecker, Hans-peter Piepho, Barbara Keller, Nils Muthreich, Didier Chollet, Patrick Descombes, Frank Hochholdinger
    Abstract:

    The phenomenon of heterosis describes the increased agronomic performance of heterozygous F1 plants compared to their homozygous parental inbred plants. Heterosis is manifested during the early stages of root development in maize. The goal of this study was to identify nonadditive gene expression in primary roots of maize hybrids compared to the average expression levels of their parental inbred lines. To achieve this goal a two-step strategy was used. First, a microarray preselection of nonadditively expressed candidate genes was performed. Subsequently, gene expression levels in a subset of genes were determined via high-throughput quantitative real-time (qRT)–PCR experiments. Initial microarray experiments identified 1941 distinct microarray features that displayed nonadditive gene expression in at least 1 of the 12 analyzed hybrids compared to the Midparent value of their parental inbred lines. Most nonadditively expressed genes were expressed between the parental values (>89%). Comparison of these 1941 genes with nonadditively expressed genes identified in maize shoot apical meristems via the same experimental procedure in the same genotypes revealed significantly less overlap than expected by pure chance. This finding suggests organ-specific patterns of nonadditively expressed genes. qRT–PCR analyses of 64 of the 1941 genes in four different hybrids revealed conserved patterns of nonadditively expressed genes in different hybrids. Subsequently, 22 of the 64 genes that displayed nonadditive expression in all four hybrids were analyzed in 12 hybrids that were generated from four inbred lines. Among those genes a superoxide dismutase 2 was expressed significantly above the Midparent value in all 12 hybrids and might thus play a protective role in heterosis-related antioxidative defense in the primary root of maize hybrids. The findings of this study are consistent with the hypothesis that both global expression trends and the consistent differential expression of specific genes contribute to the organ-specific manifestation of heterosis.

  • the role of epistasis in the manifestation of heterosis a systems oriented approach
    Genetics, 2007
    Co-Authors: Albrecht E. Melchinger, Zhaobang Zeng, Hans-peter Piepho, C C Schon
    Abstract:

    Heterosis is widely used in breeding, but the genetic basis of this biological phenomenon has not been elucidated. We postulate that additive and dominance genetic effects as well as two-locus interactions estimated in classical QTL analyses are not sufficient for quantifying the contributions of QTL to heterosis. A general theoretical framework for determining the contributions of different types of genetic effects to heterosis was developed. Additive × additive epistatic interactions of individual loci with the entire genetic background were identified as a major component of Midparent heterosis. On the basis of these findings we defined a new type of heterotic effect denoted as augmented dominance effect di* that comprises the dominance effect at each QTL minus half the sum of additive × additive interactions with all other QTL. We demonstrate that genotypic expectations of QTL effects obtained from analyses with the design III using testcrosses of recombinant inbred lines and composite-interval mapping precisely equal genotypic expectations of Midparent heterosis, thus identifying genomic regions relevant for expression of heterosis. The theory for QTL mapping of multiple traits is extended to the simultaneous mapping of newly defined genetic effects to improve the power of QTL detection and distinguish between dominance and overdominance.

  • analysis of a triple testcross design with recombinant inbred lines reveals a significant role of epistasis in heterosis for biomass related traits in arabidopsis
    Genetics, 2007
    Co-Authors: Barbara Kusterer, Hans-peter Piepho, J Muminovic, Susanne Barth, Martin Heckenberger, Rhonda C Meyer, Thomas Altmann, Albrecht E. Melchinger
    Abstract:

    Primary causes of heterosis are still unknown. Our goal was to investigate the extent and underlying genetic causes of heterosis for five biomass-related traits in Arabidopsis thaliana. We (i) investigated the relative contribution of dominance and epistatic effects to heterosis in the hybrid C24 × Col-0 by generation means analysis and estimates of variance components based on a triple testcross (TTC) design with recombinant inbred lines (RILs), (ii) estimated the average degree of dominance, and (iii) examined the importance of reciprocal and maternal effects in this cross. In total, 234 RILs were crossed to parental lines and their F1's. Midparent heterosis (MPH) was high for rosette diameter at 22 days after sowing (DAS) and 29 DAS, growth rate (GR), and biomass yield (BY). Using the F2-metric, directional dominance prevailed for the majority of traits studied but reciprocal and maternal effects were not significant. Additive and dominance variances were significant for all traits. Additive × additive and dominance × dominance variances were significant for all traits but GR. We conclude that dominance as well as digenic and possibly higher-order epistatic effects play an important role in heterosis for biomass-related traits. Our results encourage the use of Arabidopsis hybrid C24 × Col-0 for identification and description of quantitative trait loci (QTL) for heterosis for biomass-related traits and further genomic studies.

  • manifestation of heterosis during early maize zea mays l root development
    Theoretical and Applied Genetics, 2006
    Co-Authors: Nadine Hoecker, Hans-peter Piepho, Barbara Keller, Frank Hochholdinger
    Abstract:

    Heterosis is typically detected in adult hybrid plants as increased yield or vigor compared to their parental inbred lines. Only little is known about the manifestation of heterosis during early postembryonic development. Objective of this study was to identify heterotic traits during early maize root development. Four German inbred lines of the flint (UH002 and UH005) and dent (UH250 and UH301) pool and the 12 reciprocal hybrids generated from these inbred lines were subjected to a morphological and histological analysis during early root development. Primary root length and width were measured daily in a time course between 3 and 7 days after germination (DAG) and displayed average Midparent heterosis (MPH) of 17–25% and 1–7%, respectively. Longitudinal size of cortical cells in primary roots was determined 5 DAG and displayed on average 24% MPH thus demonstrating that enlarged primary roots of hybrids can mainly be attributed to elongated cortical cells. The number of seminal roots determined 14 DAG showed on average 18% MPH. Lateral root density of all tested hybrids was determined 5 DAG. This root trait showed the highest degree of heterosis with an average MPH value of 51%. This study demonstrated that heterosis is already manifesting during the very early stages of root development a few days after germination. The young root system is therefore a suitable model for subsequent molecular studies of the early stages of heterosis manifestation during seedling development.