The Integrated Breeding Platform (IBP) of the CGIAR Generation Challenge Programme (GCP) provides... more The Integrated Breeding Platform (IBP) of the CGIAR Generation Challenge Programme (GCP) provides information, analytical tools and related services to plant breeders to design and conduct modern breeding programs. It is intended to boost crop productivity for smallholders in drought-prone environments. The IBP is accessed through the Integrated Breeding Portal and is being developed in collaboration with 14 initial ‘user cases’ – breeding projects for eight crops in 32 developing countries. This ensures IBP development is driven by breeder needs. IBP informatics tools are packaged into the Integrated Breeding Workflow System (IBWS). The first integrated version of the IBWS was released in June 2013 and this facilitates information management by following breeders’ workflows. Pedigree, phenotype and genotype data are stored in a modular database and data management and analytical tools access data via a middleware layer. A new phenotyping database module based on the CHADO Natural D...
We investigate the interplay between genetic diversity and recombination in maize (Zea mays ssp. ... more We investigate the interplay between genetic diversity and recombination in maize (Zea mays ssp. mays). Genetic diversity was measured in three types of markers: single-nucleotide polymorphisms, indels, and microsatellites. All three were examined in a sample of previously published DNA sequences from 21 loci on maize chromosome 1. Small indels (1-5 bp) were numerous and far more common than large indels. Furthermore, large indels (>100 bp) were infrequent in the population sample, suggesting they are slightly deleterious. The 21 loci also contained 47 microsatellites, of which 33 were polymorphic. Diversity in SNPs, indels, and microsatellites was compared to two measures of recombination: C (=4Nc) estimated from DNA sequence data and R based on a quantitative recombination nodule map of maize synaptonemal complex 1. SNP diversity was correlated with C (r = 0.65; P = 0.007) but not with R (r = -0.10; P = 0.69). Given the lack of correlation between R and SNP diversity, the corre...
A meta-analysis of quantitative trait loci (QTL) associated with plant digestibility and cell wal... more A meta-analysis of quantitative trait loci (QTL) associated with plant digestibility and cell wall composition in maize was carried out using results from 11 different mapping experiments. Statistical methods implemented in ''MetaQTL'' software were used to build a consensus map, project QTL positions and perform meta-analysis. Fiftynine QTL for traits associated with digestibility and 150 QTL for traits associated with cell wall composition were included in the analysis. We identified 26 and 42 metaQTL for digestibility and cell wall composition traits, respectively. Fifteen metaQTL with confidence interval (CI) smaller than 10 cM were identified. As expected from trait correlations, 42% of metaQTL for digestibility displayed overlapping CIs with metaQTL for cell wall composition traits. Coincidences were particularly strong on chromosomes 1 and 3. In a second step, 356 genes selected from the MAIZEWALL database as candidates for the cell wall biosynthesis pathway were positioned on our consensus map. Colocalizations between candidate genes and meta-QTL positions appeared globally significant based on v 2 tests. This study contributed in identifying key chromosomal regions involved in silage quality and potentially associated genes for most of these regions. These genes deserve further investigation, in particular through association mapping.
with ear relative position, hundred kernel weight and timing of male and female flowering, and en... more with ear relative position, hundred kernel weight and timing of male and female flowering, and encodes nAC domaincontaining protein 2, a transcription factor expressed in different tissues. These results provide some good information for understanding the genetic basis for drought tolerance and further studies on identified candidate genes should illuminate mechanisms of drought tolerance and provide tools for designing drought-tolerant maize cultivars tailored to different environmental scenarios.
Proceedings of the National Academy of Sciences, 2001
We measured sequence diversity in 21 loci distributed along chromosome 1 of maize (Zea mays ssp. ... more We measured sequence diversity in 21 loci distributed along chromosome 1 of maize (Zea mays ssp. mays L.). For each locus, we sequenced a common sample of 25 individuals representing 16 exotic landraces and nine U.S. inbred lines. The data indicated that maize has an average of one single nucleotide polymorphism (SNP) every 104 bp between two randomly sampled sequences, a level of diversity higher than that of either humans or Drosophila melanogaster. A comparison of genetic diversity between the landrace and inbred samples showed that inbreds retained 77% of the level of diversity of landraces, on average. In addition, Tajima's D values suggest that the frequency distribution of polymorphisms in inbreds was skewed toward fewer rare variants. Tests for selection were applied to all loci, and deviations from neutrality were detected in three loci. Sequence diversity was heterogeneous among loci, but there was no pattern of diversity along the genetic map of chromosome 1. Nonetheless, diversity was correlated (r ؍ 0.65) with sequence-based estimates of the recombination rate. Recombination in our sample was sufficient to break down linkage disequilibrium among SNPs. Intragenic linkage disequilibrium declines within 100 -200 bp on average, suggesting that genome-wide surveys for association analyses require SNPs every 100 -200 bp.
Proceedings of the National Academy of Sciences, 2000
The maize genome is replete with chromosomal duplications and repetitive DNA. The duplications re... more The maize genome is replete with chromosomal duplications and repetitive DNA. The duplications resulted from an ancient polyploid event that occurred over 11 million years ago. Based on DNA sequence data, the polyploid event occurred after the divergence between sorghum and maize, and hence the polyploid event explains some of the difference in DNA content between these two species. Genomic rearrangement and diploidization followed the polyploid event. Most of the repetitive DNA in the maize genome is retrotransposable elements, and they comprise 50% of the genome. Retrotransposon multiplication has been relatively recent-within the last 5-6 million years-suggesting that the proliferation of retrotransposons has also contributed to differences in DNA content between sorghum and maize. There are still unanswered questions about repetitive DNA, including the distribution of repetitive DNA throughout the genome, the relative impacts of retrotransposons and chromosomal duplication in plant genome evolution, and the hypothesized correlation of duplication events with transposition. Population genetic processes also affect the evolution of genomes. We discuss how centromeric genes should, in theory, contain less genetic diversity than noncentromeric genes. In addition, studies of diversity in the wild relatives of maize indicate that different genes have different histories and also show that domestication and intensive breeding have had heterogeneous effects on genetic diversity across genes.
In the past few decades, a wealth of genomic data has been produced in a wide variety of species ... more In the past few decades, a wealth of genomic data has been produced in a wide variety of species using a diverse array of functional and molecular marker approaches. In order to unlock the full potential of the information contained in these independent experiments, researchers need efficient and intuitive means to identify common genomic regions and genes involved in the expression of target phenotypic traits across diverse conditions. To address this need, we have developed a Comparative Map and Trait Viewer (CMTV) tool that can be used to construct dynamic aggregations of a variety of types of genomic datasets. By algorithmically determining correspondences between sets of objects on multiple genomic maps, the CMTV can display syntenic regions across taxa, combine maps from separate experiments into a consensus map, or project data from different maps into a common coordinate framework using dynamic coordinate translations between source and target maps. We present a case study that illustrates the utility of the tool for managing large and varied datasets by integrating data collected by CIMMYT in maize drought tolerance research with data from public sources. This example will focus on one of the visualization features for Quantitative Trait Locus (QTL) data, using likelihood ratio (LR) files produced by generic QTL analysis software and displaying the data in a unique visual manner across different combinations of traits, environments and crosses. Once a genomic region of interest has been identified, the CMTV can search and display additional QTLs meeting a particular threshold for that region, or other functional data such as sets of differentially expressed genes located in the region; it thus provides an easily used means for organizing and manipulating data sets that have been dynamically integrated under the focus of the researcher's specific hypothesis.
In maize, water stress at flowering causes loss of kernel set and productivity. While changes in ... more In maize, water stress at flowering causes loss of kernel set and productivity. While changes in the levels of sugars and abscisic acid (ABA) are thought to play a role in this stress response, the mechanistic basis and genes involved are not known. A candidate gene approach was used with association mapping to identify loci involved in accumulation of carbohydrates and ABA metabolites during stress. A panel of single nucleotide polymorphisms (SNPs) in genes from these metabolic pathways and in genes for reproductive development and stress response was used to genotype 350 tropical and subtropical maize inbred lines that were well watered or water stressed at flowering. Pre-pollination ears, silks, and leaves were analysed for sugars, starch, proline, ABA, ABA-glucose ester, and phaseic acid. ABA and sugar levels in silks and ears were negatively correlated with their growth. Association mapping with 1229 SNPs in 540 candidate genes identified an SNP in the maize homologue of the Arabidopsis MADS-box gene, PISTILLATA, which was significantly associated with phaseic acid in ears of well-watered plants, and an SNP in pyruvate dehydrogenase kinase, a key regulator of carbon flux into respiration, that was associated with silk sugar concentration. An SNP in an aldehyde oxidase gene was significantly associated with ABA levels in silks of water-stressed plants. Given the short range over which decay of linkage disequilibrium occurs in maize, the results indicate that allelic variation in these genes affects ABA and carbohydrate metabolism in floral tissues during drought.
Page 1. Genetic Diversity in Seven Perennial Ryegrass (Lolium perenne L.) Cultivars Based on SSR ... more Page 1. Genetic Diversity in Seven Perennial Ryegrass (Lolium perenne L.) Cultivars Based on SSR Markers Christine Kubik, Mark Sawkins, William A. Meyer, and Brandon S. Gaut* ABSTRACT (AFLP) markers, to measure ...
Understanding the extent and distribution of genetic diversity within a species is essential for ... more Understanding the extent and distribution of genetic diversity within a species is essential for the development of effective conservation strategies. The objective of this study was to assess genetic variation using amplified fragment length polymorphisms (AFLP) in two species of the tropical legume genus Stylosanthes Sw. Annual, S. humilis (2 n = 20) and perennial, S. viscosa (2n = 20) are found throughout tropical America, and are sympatric for much of their range of distribution. One hundred and eleven accessions, covering a wide geographical range, were selected for AFLP analysis. Binary data matrices derived from DNA banding patterns were analysed using the software programs NTSYS -PC and ARLEQUIN . Several accessions were found to be misidentified. Of the S. humilis accessions, the overall average similarity value was (0.72) slightly higher than the value obtained for S. viscosa (0.67). Cluster analysis and principal coordinate analysis grouped accessions from both species by geographical origin, with a few exceptions. Analysis of molecular variance ( AMOVA ) in S. humilis revealed 59.4% of the variation among groups formed from the cluster analysis. This was highly significant ( P < 0.001). For S. viscosa AMOVA also revealed more variation among than within groups (66.5%). This was also highly significant ( P < 0.001). The majority of accessions of both species conserved ex situ are of Brazilian and Venezuelan origin. This study has identified areas in Central America and Mexico for which novel genetic variation may be found and where conservation activities should be focused.
Breeding for adaptation to abiotic stress is extremely challenging due to the complexity of the t... more Breeding for adaptation to abiotic stress is extremely challenging due to the complexity of the target environments as well as that of the stress-adaptive mechanisms adopted by plants. While many traits have been reported in the literature, these must be considered with respect to the type of environment for which a cultivar is targeted. In theory, stress-adaptive traits can be divided into groups whose genes and/or physiological effects are likely to be relatively independent such that when parents with contrasting traits are crossed, adaptive genes will be pyramided. Currently the following groups of candidate traits are being considered for drought adaptation in wheat: traits relating to: (i) pre-anthesis growth, (ii) water extraction, (iii) water use effi ciency, (iv) photo-protection. A number of mechanisms relating to root function have potential to ameliorate drought stress. Hydraulic redistribution (HR) of water by roots of dryland shrubs enables even relatively small amounts of rainwater to be moved down into the soil profi le actively by the root system before it evaporates from the soil surface. Another example is the symbiotic relationship of plants with mycorrhizal fungi that produce a glycoprotein that has a positive effect on soil structure and moisture characteristics. From an agronomic point of view, crop water use effi ciency can be increased by exploiting the stress-adaptive mechanism whereby leaves reduce transpiration rate in response to a chemical root signal in response to drying soil. While there is limited genetic diversity for adaptation to salinity in wheat, tolerance has been found in the ancestral genomes of polyploid wheat and their relatives associated with sodium exclusion into the xylem. Wide crossing techniques such as production of synthetic hexaploids are being exploited to tap into this source of genetic diversity. Looking further into the future, progress is being made into understanding the regulatory mechanisms that are expressed under abiotic stress to maintain cellular homeostasis, as well as in the ability to genetically transform crop plants with genes from alien species.
The signing and ratification of the Convention on Biological Diversity has resulted in increased ... more The signing and ratification of the Convention on Biological Diversity has resulted in increased scientific and public interest in the conservation and utilisation of biological diversity. This has in turn triggered the need to develop more effective methodologies to conserve biological diversity for the benefit of all humanity. One of the first factors to be considered when conserving botanical diversity is the efficient and effective selection of the target taxa. The aim of this paper is not to set detailed priorities for the genetic ...
The Integrated Breeding Platform (IBP) is a public web-based one-stop shop for information, analy... more The Integrated Breeding Platform (IBP) is a public web-based one-stop shop for information, analytical tools and related services to design and efficiently conduct molecular-assisted breeding experiments. The IBP aims to leverage advanced information and communication technologies to enable breeding programmes in the public and private sectors to accelerate variety development for developing countries using marker technologies for various breeding purposes. These include major gene or transgene introgression, gene pyramiding and complex marker-assisted recurrent selection (MARS) and – in the near future – genome-wide marker-assisted selection (GWMAS). The IBP gives access to marker services such as SNP genotyping. The platform also delivers support services to guide and train developing-country breeders in accessing and using marker technologies. Critical for the adoption of modern breeding technologies in developing countries will be supporting communities of practice on molecular ...
The Integrated Breeding Platform (IBP) of the CGIAR Generation Challenge Programme (GCP) provides... more The Integrated Breeding Platform (IBP) of the CGIAR Generation Challenge Programme (GCP) provides information, analytical tools and related services to plant breeders to design and conduct modern breeding programs. It is intended to boost crop productivity for smallholders in drought-prone environments. The IBP is accessed through the Integrated Breeding Portal and is being developed in collaboration with 14 initial ‘user cases’ – breeding projects for eight crops in 32 developing countries. This ensures IBP development is driven by breeder needs. IBP informatics tools are packaged into the Integrated Breeding Workflow System (IBWS). The first integrated version of the IBWS was released in June 2013 and this facilitates information management by following breeders’ workflows. Pedigree, phenotype and genotype data are stored in a modular database and data management and analytical tools access data via a middleware layer. A new phenotyping database module based on the CHADO Natural D...
We investigate the interplay between genetic diversity and recombination in maize (Zea mays ssp. ... more We investigate the interplay between genetic diversity and recombination in maize (Zea mays ssp. mays). Genetic diversity was measured in three types of markers: single-nucleotide polymorphisms, indels, and microsatellites. All three were examined in a sample of previously published DNA sequences from 21 loci on maize chromosome 1. Small indels (1-5 bp) were numerous and far more common than large indels. Furthermore, large indels (>100 bp) were infrequent in the population sample, suggesting they are slightly deleterious. The 21 loci also contained 47 microsatellites, of which 33 were polymorphic. Diversity in SNPs, indels, and microsatellites was compared to two measures of recombination: C (=4Nc) estimated from DNA sequence data and R based on a quantitative recombination nodule map of maize synaptonemal complex 1. SNP diversity was correlated with C (r = 0.65; P = 0.007) but not with R (r = -0.10; P = 0.69). Given the lack of correlation between R and SNP diversity, the corre...
A meta-analysis of quantitative trait loci (QTL) associated with plant digestibility and cell wal... more A meta-analysis of quantitative trait loci (QTL) associated with plant digestibility and cell wall composition in maize was carried out using results from 11 different mapping experiments. Statistical methods implemented in ''MetaQTL'' software were used to build a consensus map, project QTL positions and perform meta-analysis. Fiftynine QTL for traits associated with digestibility and 150 QTL for traits associated with cell wall composition were included in the analysis. We identified 26 and 42 metaQTL for digestibility and cell wall composition traits, respectively. Fifteen metaQTL with confidence interval (CI) smaller than 10 cM were identified. As expected from trait correlations, 42% of metaQTL for digestibility displayed overlapping CIs with metaQTL for cell wall composition traits. Coincidences were particularly strong on chromosomes 1 and 3. In a second step, 356 genes selected from the MAIZEWALL database as candidates for the cell wall biosynthesis pathway were positioned on our consensus map. Colocalizations between candidate genes and meta-QTL positions appeared globally significant based on v 2 tests. This study contributed in identifying key chromosomal regions involved in silage quality and potentially associated genes for most of these regions. These genes deserve further investigation, in particular through association mapping.
with ear relative position, hundred kernel weight and timing of male and female flowering, and en... more with ear relative position, hundred kernel weight and timing of male and female flowering, and encodes nAC domaincontaining protein 2, a transcription factor expressed in different tissues. These results provide some good information for understanding the genetic basis for drought tolerance and further studies on identified candidate genes should illuminate mechanisms of drought tolerance and provide tools for designing drought-tolerant maize cultivars tailored to different environmental scenarios.
Proceedings of the National Academy of Sciences, 2001
We measured sequence diversity in 21 loci distributed along chromosome 1 of maize (Zea mays ssp. ... more We measured sequence diversity in 21 loci distributed along chromosome 1 of maize (Zea mays ssp. mays L.). For each locus, we sequenced a common sample of 25 individuals representing 16 exotic landraces and nine U.S. inbred lines. The data indicated that maize has an average of one single nucleotide polymorphism (SNP) every 104 bp between two randomly sampled sequences, a level of diversity higher than that of either humans or Drosophila melanogaster. A comparison of genetic diversity between the landrace and inbred samples showed that inbreds retained 77% of the level of diversity of landraces, on average. In addition, Tajima's D values suggest that the frequency distribution of polymorphisms in inbreds was skewed toward fewer rare variants. Tests for selection were applied to all loci, and deviations from neutrality were detected in three loci. Sequence diversity was heterogeneous among loci, but there was no pattern of diversity along the genetic map of chromosome 1. Nonetheless, diversity was correlated (r ؍ 0.65) with sequence-based estimates of the recombination rate. Recombination in our sample was sufficient to break down linkage disequilibrium among SNPs. Intragenic linkage disequilibrium declines within 100 -200 bp on average, suggesting that genome-wide surveys for association analyses require SNPs every 100 -200 bp.
Proceedings of the National Academy of Sciences, 2000
The maize genome is replete with chromosomal duplications and repetitive DNA. The duplications re... more The maize genome is replete with chromosomal duplications and repetitive DNA. The duplications resulted from an ancient polyploid event that occurred over 11 million years ago. Based on DNA sequence data, the polyploid event occurred after the divergence between sorghum and maize, and hence the polyploid event explains some of the difference in DNA content between these two species. Genomic rearrangement and diploidization followed the polyploid event. Most of the repetitive DNA in the maize genome is retrotransposable elements, and they comprise 50% of the genome. Retrotransposon multiplication has been relatively recent-within the last 5-6 million years-suggesting that the proliferation of retrotransposons has also contributed to differences in DNA content between sorghum and maize. There are still unanswered questions about repetitive DNA, including the distribution of repetitive DNA throughout the genome, the relative impacts of retrotransposons and chromosomal duplication in plant genome evolution, and the hypothesized correlation of duplication events with transposition. Population genetic processes also affect the evolution of genomes. We discuss how centromeric genes should, in theory, contain less genetic diversity than noncentromeric genes. In addition, studies of diversity in the wild relatives of maize indicate that different genes have different histories and also show that domestication and intensive breeding have had heterogeneous effects on genetic diversity across genes.
In the past few decades, a wealth of genomic data has been produced in a wide variety of species ... more In the past few decades, a wealth of genomic data has been produced in a wide variety of species using a diverse array of functional and molecular marker approaches. In order to unlock the full potential of the information contained in these independent experiments, researchers need efficient and intuitive means to identify common genomic regions and genes involved in the expression of target phenotypic traits across diverse conditions. To address this need, we have developed a Comparative Map and Trait Viewer (CMTV) tool that can be used to construct dynamic aggregations of a variety of types of genomic datasets. By algorithmically determining correspondences between sets of objects on multiple genomic maps, the CMTV can display syntenic regions across taxa, combine maps from separate experiments into a consensus map, or project data from different maps into a common coordinate framework using dynamic coordinate translations between source and target maps. We present a case study that illustrates the utility of the tool for managing large and varied datasets by integrating data collected by CIMMYT in maize drought tolerance research with data from public sources. This example will focus on one of the visualization features for Quantitative Trait Locus (QTL) data, using likelihood ratio (LR) files produced by generic QTL analysis software and displaying the data in a unique visual manner across different combinations of traits, environments and crosses. Once a genomic region of interest has been identified, the CMTV can search and display additional QTLs meeting a particular threshold for that region, or other functional data such as sets of differentially expressed genes located in the region; it thus provides an easily used means for organizing and manipulating data sets that have been dynamically integrated under the focus of the researcher's specific hypothesis.
In maize, water stress at flowering causes loss of kernel set and productivity. While changes in ... more In maize, water stress at flowering causes loss of kernel set and productivity. While changes in the levels of sugars and abscisic acid (ABA) are thought to play a role in this stress response, the mechanistic basis and genes involved are not known. A candidate gene approach was used with association mapping to identify loci involved in accumulation of carbohydrates and ABA metabolites during stress. A panel of single nucleotide polymorphisms (SNPs) in genes from these metabolic pathways and in genes for reproductive development and stress response was used to genotype 350 tropical and subtropical maize inbred lines that were well watered or water stressed at flowering. Pre-pollination ears, silks, and leaves were analysed for sugars, starch, proline, ABA, ABA-glucose ester, and phaseic acid. ABA and sugar levels in silks and ears were negatively correlated with their growth. Association mapping with 1229 SNPs in 540 candidate genes identified an SNP in the maize homologue of the Arabidopsis MADS-box gene, PISTILLATA, which was significantly associated with phaseic acid in ears of well-watered plants, and an SNP in pyruvate dehydrogenase kinase, a key regulator of carbon flux into respiration, that was associated with silk sugar concentration. An SNP in an aldehyde oxidase gene was significantly associated with ABA levels in silks of water-stressed plants. Given the short range over which decay of linkage disequilibrium occurs in maize, the results indicate that allelic variation in these genes affects ABA and carbohydrate metabolism in floral tissues during drought.
Page 1. Genetic Diversity in Seven Perennial Ryegrass (Lolium perenne L.) Cultivars Based on SSR ... more Page 1. Genetic Diversity in Seven Perennial Ryegrass (Lolium perenne L.) Cultivars Based on SSR Markers Christine Kubik, Mark Sawkins, William A. Meyer, and Brandon S. Gaut* ABSTRACT (AFLP) markers, to measure ...
Understanding the extent and distribution of genetic diversity within a species is essential for ... more Understanding the extent and distribution of genetic diversity within a species is essential for the development of effective conservation strategies. The objective of this study was to assess genetic variation using amplified fragment length polymorphisms (AFLP) in two species of the tropical legume genus Stylosanthes Sw. Annual, S. humilis (2 n = 20) and perennial, S. viscosa (2n = 20) are found throughout tropical America, and are sympatric for much of their range of distribution. One hundred and eleven accessions, covering a wide geographical range, were selected for AFLP analysis. Binary data matrices derived from DNA banding patterns were analysed using the software programs NTSYS -PC and ARLEQUIN . Several accessions were found to be misidentified. Of the S. humilis accessions, the overall average similarity value was (0.72) slightly higher than the value obtained for S. viscosa (0.67). Cluster analysis and principal coordinate analysis grouped accessions from both species by geographical origin, with a few exceptions. Analysis of molecular variance ( AMOVA ) in S. humilis revealed 59.4% of the variation among groups formed from the cluster analysis. This was highly significant ( P < 0.001). For S. viscosa AMOVA also revealed more variation among than within groups (66.5%). This was also highly significant ( P < 0.001). The majority of accessions of both species conserved ex situ are of Brazilian and Venezuelan origin. This study has identified areas in Central America and Mexico for which novel genetic variation may be found and where conservation activities should be focused.
Breeding for adaptation to abiotic stress is extremely challenging due to the complexity of the t... more Breeding for adaptation to abiotic stress is extremely challenging due to the complexity of the target environments as well as that of the stress-adaptive mechanisms adopted by plants. While many traits have been reported in the literature, these must be considered with respect to the type of environment for which a cultivar is targeted. In theory, stress-adaptive traits can be divided into groups whose genes and/or physiological effects are likely to be relatively independent such that when parents with contrasting traits are crossed, adaptive genes will be pyramided. Currently the following groups of candidate traits are being considered for drought adaptation in wheat: traits relating to: (i) pre-anthesis growth, (ii) water extraction, (iii) water use effi ciency, (iv) photo-protection. A number of mechanisms relating to root function have potential to ameliorate drought stress. Hydraulic redistribution (HR) of water by roots of dryland shrubs enables even relatively small amounts of rainwater to be moved down into the soil profi le actively by the root system before it evaporates from the soil surface. Another example is the symbiotic relationship of plants with mycorrhizal fungi that produce a glycoprotein that has a positive effect on soil structure and moisture characteristics. From an agronomic point of view, crop water use effi ciency can be increased by exploiting the stress-adaptive mechanism whereby leaves reduce transpiration rate in response to a chemical root signal in response to drying soil. While there is limited genetic diversity for adaptation to salinity in wheat, tolerance has been found in the ancestral genomes of polyploid wheat and their relatives associated with sodium exclusion into the xylem. Wide crossing techniques such as production of synthetic hexaploids are being exploited to tap into this source of genetic diversity. Looking further into the future, progress is being made into understanding the regulatory mechanisms that are expressed under abiotic stress to maintain cellular homeostasis, as well as in the ability to genetically transform crop plants with genes from alien species.
The signing and ratification of the Convention on Biological Diversity has resulted in increased ... more The signing and ratification of the Convention on Biological Diversity has resulted in increased scientific and public interest in the conservation and utilisation of biological diversity. This has in turn triggered the need to develop more effective methodologies to conserve biological diversity for the benefit of all humanity. One of the first factors to be considered when conserving botanical diversity is the efficient and effective selection of the target taxa. The aim of this paper is not to set detailed priorities for the genetic ...
The Integrated Breeding Platform (IBP) is a public web-based one-stop shop for information, analy... more The Integrated Breeding Platform (IBP) is a public web-based one-stop shop for information, analytical tools and related services to design and efficiently conduct molecular-assisted breeding experiments. The IBP aims to leverage advanced information and communication technologies to enable breeding programmes in the public and private sectors to accelerate variety development for developing countries using marker technologies for various breeding purposes. These include major gene or transgene introgression, gene pyramiding and complex marker-assisted recurrent selection (MARS) and – in the near future – genome-wide marker-assisted selection (GWMAS). The IBP gives access to marker services such as SNP genotyping. The platform also delivers support services to guide and train developing-country breeders in accessing and using marker technologies. Critical for the adoption of modern breeding technologies in developing countries will be supporting communities of practice on molecular ...
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Papers by Mark Sawkins