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Showing papers on "Plant breeding published in 2001"


Journal ArticleDOI

806 citations


Journal ArticleDOI
TL;DR: It is argued that exotic libraries, which consist of marker-defined genomic regions taken from wild species and introgressed onto the background of elite crop lines, provide plant breeders with an important opportunity to improve the agricultural performance of modern crop varieties.
Abstract: Naturally occurring variation among wild relatives of cultivated crops is an under-exploited resource in plant breeding. Here, I argue that exotic libraries, which consist of marker-defined genomic regions taken from wild species and introgressed onto the background of elite crop lines, provide plant breeders with an important opportunity to improve the agricultural performance of modern crop varieties. These libraries can also act as reagents for the discovery and characterization of genes that underlie traits of agricultural value.

659 citations


Journal ArticleDOI
TL;DR: The potential of somaclonal variation has yet to be fully exploited by breeders, even though a few cultivars have been developed in crops such as Brassica juncea, rice and others.
Abstract: Tissue culture generates a wide range of genetic variation in plant species which can be incorporated in plant breeding programmes By in vitro selection, mutants with useful agronomic traits, eg salt or drought tolerance or disease resistance, can be isolated in a short duration The successful use of somaclonal variation is very much dependent on its genetic stability in the subsequent generations for which molecular markers such as RAPDs, AFLPs, SSRs and others can be helpful The potential of somaclonal variation has yet to be fully exploited by breeders, even though a few cultivars have been developed in crops such as Brassica juncea, rice and others

457 citations


Journal ArticleDOI
TL;DR: The identification and analysis of mutants by using molecular techniques of DNA fingerprinting and mapping with PCR based markers, such as RAPDs, AFLP and STMS, and mutant tagging shall bring a new dimension in gene technology.
Abstract: The use of ionizing radiation, such as X-rays, gamma rays and neutrons and chemical mutagens for inducing variation, is well established. Induced mutations have been used to improve major crops such as wheat, rice, barley,cotton, peanuts, and beans, which are seed propagated. Since the establishment of the Joint FAO/IAEA Division of the Nuclear Techniques in Agriculture, more than 1800 cultivars obtained either as direct mutants or derived from their crosses have been released worldwide in 50 countries. In vegetatively propagated plants, many of mutants were derived from irradiating rooted stem cuttings, detached leaves, and dormant plants. According to the FAO/IAEA database, of the 465 mutants released among the vegetatively propagated plants, most are in the floricultural plants and a few in fruit trees. These include chrysanthemum, Alstroemeria, dahlia, bougainvillea, rose, Achimenes,begonia, carnation, Streptocarpus, and azalea. The irradiation of in vitro cultured date palm, apple, potato, sweet potato and pineapple now provides a means to treat large populations which would not have been possible before. Irradiation of micropropagated plants, axillary and adventitious buds, apical meristems, regenerative callus cultures, anthers and microspores, and somatic embryos provides a miniaturized version of trees and seeds in the Petridish instead of the field. During the last decade, the use of radio-actively labeled probes in recombinant DNA research for cloning and mapping plant genes and transgenesis, particularly for RFLP, micro satellite based DNA fingerprinting, has become a routine procedure. Many homeotic mutants that change floral development have been isolated in Arabidopsis, Petunia, Antirrhinum and Lycopersicon. Mutants of Arabidopsis are being used to analyze genes, which determine response to auxins, cytokinins, gibberellin, abscisic acid and ethylene in plant growth, floral development and senescence, fruit formation and ripening. These mutants are facilitating the isolation, identification and cloning of the genes, which would ultimately help in designing crops with improved yield, increased stress tolerance, longer shelf-life and reduced agronomic inputs. The identification and analysis of mutants by using molecular techniques of DNA fingerprinting and mapping with PCR based markers, such as RAPDs, AFLP and STMS, and mutant tagging shall bring a new dimension in gene technology. Already, mutations can be linked to changes in DNA sequences for some plant traits and to establish molecular maps in structural and functional genomics of crop plants. These in turn would lead to a rapid enhancement of crop yields and quality.

423 citations



BookDOI
TL;DR: Part I Genomics, quantitative trait loci, and tissue culture: why quantitative geneticists should care about bioinformatics use of molecular markers in plant breeding - drought tolerance improvements in tropical maize tissue culture for crop improvement transferring genes from wild species into rice.
Abstract: 1: Vignettes of the history of genetics Part I: Genomics, Quantitative Trait Loci, and Tissue Culture 2: Quantitative genetics, genomics and the future of plant breeding 3: Why quantitative geneticists should care about bioinformatics 4: QTL analysis: problems and (possible) solutions 5: Association mapping in plant populations 6: Integrating molecular techniques into quantitative genetics and plant breeding 7: Use of molecular markers in plant breeding: drought tolerance improvements in tropical maize 8: Explorations with barley genome maps 9: Global view of QTS/QTLS: rice as a model 10: Marker-assisted backcross breeding: a case-study in genotype building theory 11: Complexity, quantitative traits and plant breeding: a role for simulation modelling in the genetic improvement of crops 12: Linking bio physical and genetic models to integrate physiology, molecular biology and plant breeding 13: Tissue culture for crop improvement 14: Transferring genes from wild species into rice 15: Genotype environment interaction: progress and prospects 16: Analysing QTL - by environment interaction by factorial regression, with an application to the CIMMYT drought and low-nitrogen stress programme in maize 17: Elements of genotype - environment interaction: genetic components of the photoperiod response in maize 18: Mechanisms of improved nitrogen use efficiency in cereals 19: Biplot analysis of multi-environment trial data 20: Linear-bilinear models for the analysis of genotype - environment interaction 21: Exploring variety - environment data using random effects AMMI models with adjustments for spatial field trend: Part 1: Theory 22: Exploring variety - environment data using random effects AMMI models with adjustments for spatial field trend: Part 2: Applications 23: Applications of mixed models in plant breeding 24: Defining adaptation strategies and yield stability targets in breeding programmes

212 citations


Journal ArticleDOI
TL;DR: The identification of QTL repeatable over seasons indicates the potential for marker-assisted selection in a wheat breeding program selecting for improved grain yield and weed competitiveness.
Abstract: As weeds develop resistance to a broad range of herbicides, wheat (Triticum aestivum L.) cultivars with superior weed competitive capacity are needed to complement integrated weed management strategies. In this study, agronomic and morphological traits that enable wheat to compete effectively with weeds were identified. Halberd, Cranbrook, and 161 Cranbrook x Halberd doubled haploid (DH) lines were examined in field experiments conducted over two growing seasons. The weed species Lolium rigidum L. (annual ryegrass) was sown in strips perpendicular to the direction of wheat seeding. Various traits were measured during each season with competitive ability determined by both percent loss in wheat grain yield and suppression of ryegrass growth. Width of leaf 2, canopy height, and light interception at early stem elongation (Z31), and tiller number, height at maturity, and days to anthesis were important for competitive ability in 1999. In the previous year, length of leaf 2 and size of the flag leaf contributed to competitiveness. Seasonal effects appeared to have some impact on the relative contribution of crop traits to competitive ability. The morphological traits involved in maintaining grain yield differed from those that contributed to the suppression of ryegrass growth. Development of the Cranbrook x Halberd chromosomal linkage map enabled the putative identification of quantitative trait loci (QTL) associated with competitive ability in the DH population. Many of the QTL were mapped to similar positions in both years. Further, several traits, including time to anthesis, flag leaf size, height at stem elongation, and the size of the first 2 leaves, were mapped to similar positions on chromosomes 2B and 2D. Narrow-sense heritabilities on an entry-mean basis were typically high within each year for traits associated with weed competitive ability. However, large genotype x year interactions reduced these heritabilities, making genetic gain through phenotypic selection difficult. The identification of QTL repeatable over seasons indicates the potential for marker-assisted selection in a wheat breeding program selecting for improved grain yield and weed competitiveness.

154 citations


Book ChapterDOI
TL;DR: Transgenic plants represent a new mechanism for generating novel phenotypes with improved forage nutritional value and appear to represent metabolic lesions that may also occur by natural mutations, but are more frequent within transgenic populations.
Abstract: Plant breeding is an extremely cost-effective mechanism for increasing the nutritional value of forage crops. Genetic gains in in vitro dry-matter digestibility (IVDMD) have averaged 0.7–4.7% year -1 , similar to long-term gains for grain yield of many cereal crops. Relatively small increases in IVDMD typically result in measurable improvements in animal performance. Gains in IVDMD result from changes in chemical, anatomical, and/or morphological traits of plants, but rarely from genetic shifts in timing of reproductive maturity. These genetic gains are both genetically and environmentally stable and, for perennial forage crops, require only a one-time investment by growers. Selection for increased forage nutritional value is often associated with reductions in agricultural fitness traits, such as forage yield, disease and/or insect resistance, and stress tolerance. These characteristics can often be corrected by concomitant selection pressure in field-oriented plant-breeding programs. Transgenic plants represent a new mechanism for generating novel phenotypes with improved forage nutritional value. Many of these phenotypes appear to represent metabolic lesions that may also occur by natural mutations, but are more frequent within transgenic populations. Transgenic technology appears capable of contributing novel phenotypes to improved forage cultivars, but only from collaboration between molecular biologists and plant breeders or agronomists with strong field-oriented programs.

147 citations


Journal ArticleDOI
TL;DR: The negative genetic effect of the Rht-B1b dwarfing gene on early growth of wheat confirms phenotypic evidence of a pleiotropic effect of Rht’s B1b on establishment and early vigour, and genetic increases in coleoptile length and early leaf area development are likely to be limited in wheat populations containing the Rh1b dwaring gene.
Abstract: The Norin-10 dwarfing genes, Rht-B1b (Rht1) and Rht-D1b (Rht2), are commonly used to reduce plant height and increase grain yield in wheat breeding programs. These dwarfing genes lower sensitivity of vegetative tissue to endogenous gibberellin to reduce cell and subsequent stem elongation. This reduction in cell elongation capacity reportedly results in a concomitant reduction in coleoptile length and early vigour (leaf area) thereby affecting seedling establishment and growth. A detailed genetic map from a cross between tall Halberd (Rht-B1a) and semidwarf Cranbrook (Rht-B1b) wheat cultivars was used to assess genetic factors affecting seedling growth. Parental and 150 doubled haploid progeny lines were characterised for seedling and height-related traits in controlled and field environments. Genotypic variation was large and predominantly under additive genetic control with evidence for transgressive segregation for some traits. Narrow-sense heritabilities were moderate to high (h2 = 0.31–0.91) indicating a strong genetic basis for differences between progeny. Molecular marker analyses identified a number of significant (P < 0.05) quantitative trait loci (QTL) for each trait. A major QTL, mapping directly to the Rht-B1 locus on chromosome arm 4BS, accounted for up to 49% of the genotypic variance in peduncle length and plant height, and 27–45% of the genotypic variance in coleoptile length across different temperatures. Another QTL, located close to the RFLP marker XksuC2 on the long arm of chromosome 4B, accounted for 15–27% of the genotypic variance in coleoptile length. The influence of the XksuC2-linked QTL on coleoptile length was greatest at 19˚C and decreased with cooler temperatures. The same QTL affected reductions in leaf size, and both coleoptile tiller size and presence to affect overall seedling vigour. There was also some evidence for epistatic interactions influencing coleoptile tiller growth. Reductions in plant size at the Rht-B1b and XksuC2 loci were associated with presence of the Cranbrook 4B allele. The negative genetic effect of the Rht-B1b dwarfing gene on early growth of wheat confirms phenotypic evidence of a pleiotropic effect of Rht-B1b on establishment and early vigour. Genetic increases in coleoptile length and early leaf area development are likely to be limited in wheat populations containing the Rht-B1b dwarfing gene.

135 citations


Journal ArticleDOI
TL;DR: These populations provide powerful tools for extensive mapping studies to determine the genetic factors controlling grain quality traits and other wheat characters of interest and are recognised in the models used.
Abstract: Doubled haploid populations from 5 carefully selected wheat (Triticum aestivum L.) crosses were established in order to produce genetic maps. The characterisation of the parental material included pedigree analyses to define the extent of the genetic relationships among the lines and to determine the occurrence of alien chromosome segments that may contribute to segregation distortion. The characterisation of the parents also defined the range of grain quality traits that could be examined in the lines derived from each cross. Populations of up to 321 lines were produced using wide cross-mediated doubled haploid production from F1 plants. Assessment of the lines for heterogeneity was carried out using readily identifiable phenotypic markers and electrophoresis of seed storage proteins, with 2.3–11.6% of the lines being removed from further analysis. Segregation distortion was estimated in several populations where sufficient information from genetic markers was available. In a Sunco/Tasman doubled haploid population, heterogeneity was detected between the first 51 lines and the remainder of the mapping population and this could be traced to F1 plants that were produced from an earlier set of crosses. χ2 tests on the mapping data available for the Cranbrook/Halberd, CD87/Katepwa, and Sunco/Tasman doubled haploid populations revealed segregation distortion at rates of 1.8%, 5.1%, and 12.5% respectively. Whereas the wide-cross doubled haploid protocol does not appear responsible for the bulk of the non-Mendelian segregation observed, several potential sources were identified. In particular, clustering of distorted loci at specific chromosome regions appeared to be associated with the presence of alien introgressions in one of the parents. This was especially marked in the Sunco/Tasman population. Providing such distortions are recognised in the models used, these populations provide powerful tools for extensive mapping studies to determine the genetic factors controlling grain quality traits and other wheat characters of interest.

124 citations


Journal ArticleDOI
TL;DR: The current challenges for genetic engineering of plants will be to understand and control factors causing transgene silencing, instability and rearrangement, which are often seen in transgenic plants and highly undesirable in lines to be used for crop development.
Abstract: Genetic improvement of crops has traditionally been achieved through sexual hybridization between related species, which has resulted in numerous cultivars with high yields and superior agronomic performance. Conventional plant breeding, sometimes combined with classical cytogenetic techniques, continues to be the main method of cereal crop improvement. More recently, through the introduction of new tools of biotechnology, crossing barriers have been overcome, and genes from unrelated sources have become available to be introduced asexually into plants. Cereal crops were initially difficult to genetically engineer, mainly due to their recalcitrance to in vitro regeneration and their resistance to Agrobacterium infection. Systematic screening of cultivars and explant tissues for regeneration potential, development of various DNA delivery methods and optimization of gene expression cassettes have produced transformation protocols for the major cereals, although some elite cultivars still remain recalcitrant to transformation. Most of the transgenic cereals developed for commercial purpose exhibit herbicide and/or insect resistance; traits that are often controlled by a single gene. In recent years, more complex traits, such as dough functionality in wheat and nutritional quality of rice have been improved by the use of biotechnology. The current challenges for genetic engineering of plants will be to understand and control factors causing transgene silencing, instability and rearrangement, which are often seen in transgenic plants and highly undesirable in lines to be used for crop development. Further improvement of current cereal cultivars is expected to benefit greatly from information emerging from the areas of genomics, proteomics and bioinformatics.

Journal ArticleDOI
TL;DR: Using gene sequences initially isolated from the Cre3 locus, a DNA-based marker selection system was developed and applied to unambiguously identify wheat lines carrying resistance alleles at theCre1 and/orCre3 loci in breeding populations derived from diverse genetic backgrounds.
Abstract: The development of cultivars resistant to cereal cyst nematode (CCN) is a primary objective in wheat breeding in the southern wheatbelt of Australia. Nine CCN resistance genes have been identified in wheat and its relatives, some of which confer resistance to the Australian pathotype of CCN (Ha13). Cultivars released in Australia with CCN resistance carry either the Cre1 or CreF gene, with the Cre3 gene present in advanced breeding lines. The biological assay for CCN resistance screening in wheat is time-consuming, not reliable on a single-plant basis, and prone to inconsistencies, thus reducing the efficiency of selection amongst breeding lines. Using gene sequences initially isolated from the Cre3 locus, a DNA-based marker selection system was developed and applied to unambiguously identify wheat lines carrying resistance alleles at theCre1 and/or Cre3 loci in breeding populations derived from diverse genetic backgrounds. Homologues of sequences from the Cre3 locus, located elsewhere in the wheat genome, can also be used to select wheat lines with a newly identified CCN resistance gene (Cre6) introgressed from Aegilops ventricosa. Application of these markers has become an integral part of the southern Australian breeding programs.



Journal ArticleDOI
TL;DR: The high frequency of observed doubled haploid mutants indicates that anther culture applied in connection with gamma rays is an effective way to improve rice cultivars.
Abstract: Doubled haploids have long been recognized as a valuable tool in plant breeding since it not only offers the quickest method of advancing heterozygous breeding lines to homozygosity, but also increases the selection efficiency over conventional procedures due to better discrimination between genotypes within any one generation. Ten cultivars of japonica rice and nine cultivars of indica rice were evaluated for androgenic response. Various doses (10–50 Gy) of gamma rays were applied to investigate the effect of radiation on callus formation, green plant regeneration and the frequency of selected doubled haploid mutants. Similarly, the effects of colchicine concentration (10–200 mg/l) on callus induction, regeneration and fertility of green plants were observed. It was demonstrated that the dose of 20 Gy gamma rays and 30 mg/l concentration of colchicine have significant stimulation effect on regeneration of green plants from rice anther culture. The high frequency of observed doubled haploid mutants indicates that anther culture applied in connection with gamma rays is an effective way to improve rice cultivars.

Book
19 Nov 2001
TL;DR: This book discusses the origins, nature, and Significance of Variation in Tissue Culture, and the application of Molecular Markers in Plant Breeding.
Abstract: Contents * Foreword * Preface * Chapter 1. Introduction * Types of In Vitro Culture * Applications of Plant Tissue Culture * Chapter 2. Morphogenesis/Organogenesis * Introduction * Plant Growth * Cellular Differentiation * Morphogenesis * Chapter 3. Micropropagation * Definition * Stages in Micropropagation * Commercial Micropropagation * Applications of Micropropagation * Chapter 4. Haploid Plant Production In Vitro * Anatomy of Anther * Anther Culture * Androgenesis * Chapter 5. In Vitro Pollination and Fertilization * Development of Female Gametophyte * Pollination * Fertilization * Embryo Culture * Chapter 6. Somatic Hybridization Using Protoplast Technology * Introduction * Uses of Protoplast Technology * Obtaining Protoplasts * The Culture of Protoplasts * The Cytoplasmic Genomes * Common Potential of Protoplast Fusion * Chapter 7. Cell Culture and Selection of Desirable Traits * Selection of Naturally Occurring Variants in Culture * General Selection Strategies * Chapter 8. In Vitro Mutagenesis * Types of Mutagens * Determining the Type and Suitable Concentration of Mutagens * The Choice of Plant Tissues for In Vitro Mutagensis * Chapter 9. The Origin, Nature, and Significance of Variation in Tissue Culture * Introduction * The Basis of Somaclonal Variations * Causes of Somaclonal Variations * Use of Somaclonal Variation in Breeding * Prevention of Somaclonal Variation * Chapter 10. Cryopreservation and Plant Breeding * Introduction * Theory and Technology * Cryopreservation Protocols for Cold-Hardy and Non-Cold-Hardy Species * Storage and Thawing * Equipment for Cryopreservation * Practical Issues and Strategies Toward Improved Cryoprotection * Chapter 11. In Vitro Micrografting * Definition of Micrografting * Analysis of Compatibility and Incompatibility Phenomena * Chapter 12. In Vitro Flowering: Its Relevance to Plant Breeding * Factors Influencing In Vitro Flowering * Plant Growth Regulators * Mineral Nutrients and Other Medium Components * Explant, Light, and Other Variables * Application of In Vitro Flowering to Plant Breeding * Chapter 13. In Vitro Tuberization * Introduction * Factors Controlling Microtuber Production * Practical Aspects of In Vitro Tuberization * Chapter 14. Molecular Plant Breeding * Types of Molecular Markers * Major Objectives of Molecular Breeding * Applications of Molecular Markers in Plant Breeding * Case Study: Application of Molecular Markers in Barley (Hordeum vulgare) Breeding * References * Index


Journal ArticleDOI
TL;DR: In this article, the results of phenotypic measurements of genetic diversity in the world collection of flax maintained by Plant Gene Resources of Canada (PGRC) and compares the range of diversity observed in 19 Canadian registered flax cultivars are reported.
Abstract: This study reports results of phenotypic measurements of genetic diversity in the world collection of flax maintained by Plant Gene Resources of Canada (PGRC) and compares the range of diversity in the world collection with the diversity observed in 19 Canadian registered flax cultivars. Morphological and seed-oil characters were used to describe the phenotypic diversity in 2331 flax accessions. The plants were grown by PGRC at Saskatoon, Saskatchewan, Canada, in 1998 and 1999. The comparison between the Canadian cultivars and the world collection was based on single characters, as well as on character complexes by application of an existing intraspecific classification for the species. Considering single quantitative or qualitative character expressions, the Canadian cultivars represented a wide range in diversity for the species. The variation of characters Canadian plant breeders have selected for (e.g. plant height, seed weight, seed colour, petal colour, oil content) was reduced further than those characters not focused on by plant breeders (e.g. dotting of the sepals, style colour, ciliation of capsule septa, oil quality characters). A comparison of diversity based on the intraspecific classification proposed for flax by Kulpa and Danert, who described 28 botanical varieties, showed that all Canadian cultivars belong to two botanical varieties. This study demonstrates the usefulness of agrobotanical characterization of genebank collections for plant breeding and illustrates the application of the traditional method of intraspecific classification for comparison of gene pools.

Book ChapterDOI
01 Jan 2001
TL;DR: In outbreeding forage species such as perennial ryegrass and white clover, natural and synthetic populations are genetically heterogeneous and show a high degree of developmental plasticity, so strategies for molecular marker development, genetic mapping, QTL detection and marker assisted selection must be designed in the context of these constraints.
Abstract: A number of plant species are used individually and in combination in pastures for the grazing of livestock. Temperate forages include grasses such as perennial ryegrass, tall fescue and phalaris and legumes such as white clover, red clover and alfalfa. Tropical forages include grasses such as buffelgrass and brachiaria and legumes such as cassia, siratro and stylo. Temperate and warm-season grass species are also important for turf and amenity purposes. In outbreeding forage species such as perennial ryegrass and white clover, natural and synthetic populations are genetically heterogeneous and show a high degree of developmental plasticity. Strategies for molecular marker development, genetic mapping, QTL detection and marker assisted selection must be designed in the context of these constraints. The current status of molecular marker technology with regard to genetic mapping, marker assisted selection, DNA profiling and molecular taxonomy is reviewed. The development of framework genetic maps based on highly informative co-dominant genetic markers (anchor RFLPs and SSRs) is described. Innovative strategies for implementation will be applied to these efficient marker systems in order to enhance forage breeding.

Journal ArticleDOI
TL;DR: Selections for the measured traits in this study appear to be most effective during the first and second years of growth, with effectiveness diminishing during the third year, thus suggesting one reason for the lack of significant progress in most breeding programs.

Journal ArticleDOI
TL;DR: The use of molecular markers in plant breeding has become very commonplace and has given rise to “molecular breeding”.
Abstract: Markers are of interest to plant breeders as a source of genetic information on crops and for use in indirect selection of traits to which the markers are linked. In the classic breeding approach, the markers were invariably the visible morphological and other phenotypic characters, and the breeders expended considerable effort and time in refining the crosses as the tight linkage or association of the desired characters with the obvious phenotypic characters was never unequivocally established. Furthermore, indirect selection for a trait using such morphological markers was not practical due to (1) a paucity of suitable markers, (2) the undesirable pleiotropic effects of many morphological markers on plant phenotype, and (3) the inability to score multiple morphological mutant traits in a single segregating population. With the advancement in molecular biology, the use of molecular markers in plant breeding has become very commonplace and has given rise to “molecular breeding”. Molecular breeding involve...

01 Jan 2001
TL;DR: Article available on line / Article disponible en ligne à l’adresse : http://om.ciheam.org/article.php?IDPDF=1600050
Abstract: Article available on line / Article disponible en ligne à l’adresse : -------------------------------------------------------------------------------------------------------------------------------------------------------------------------http://om.ciheam.org/article.php?IDPDF=1600050 --------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Reference EntryDOI
19 Apr 2001
TL;DR: To respond to the increasing need to feed the world's population, standing at 7.2 billion in 2013 and predicted to reach over 9 billion by 2050, as well as an ever greater demand for a balanced and healthy diet, there is a continuing need to produce improved new cultivated varieties of crop plants.
Abstract: To respond to the increasing need to feed the world's population, standing at 71–72 billion in 2013 and predicted to reach over 9 billion by 2050, as well as an ever greater demand for a balanced and healthy diet, there is a continuing need to produce improved new cultivated varieties of crop plants Land available for crop production is limited and has stayed at 660 million hectares for the past 50 years Much of the world's best soils are already in use and others are protected, for example, for environmental concerns The demand for food brings marginal lands into play for which stress-tolerant crops need to be developed Climate variation is yet another challenge breeders have to respond to In short, more food, fibre, fuel and forage need to be produced per unit of land, and time is of the essence The strategies used to meet these demands are increasingly based on our knowledge of relevant science, particularly genetics and reproductive biology Success is gained by a multidisciplinary understanding and the deployment of relevant science and technology Key Concepts Plant breeders must have access to genetic variation in crop species Plant breeders must be equipped with the tools to respond quickly to new demands by developing accelerated breeding techniques and the ability to screen for traits of interest rapidly among progeny Yield and yield stability remain the top priorities for breeders Increasing production of plant products is essential for food, feed and fibre for the increasing World population Breeders must be visionary in planning for requirements in the future, at least 7–20 years ahead, as this is the timescale from initiating the breeding programme to release cultivars Keywords: crossing; sexual reproduction; selection; multiplication; varieties; cultivars; plant breeding; plant improvement; genetic variation

Journal ArticleDOI
TL;DR: Populations collected from southern latitudes (56°–60°N) in general showed better values than the northern populations for horticulturally important traits, and significant genetic variation among populations in nearly all traits investigated.
Abstract: Plant breeding of lingonberry (Vaccinium vitis-idaea L.) is still in its infancy. In order to optimize sampling strategy to broaden the genetic base and to improve horticulturally important traits, we need more information about the genetic structure of wild populations. In a field study, seeds were collected from thirteen widely spaced lingonberry populations in Sweden, from one in Estonia and from one in Japan. The resulting seedlings were subsequently transferred into a field with a randomized design and were investigated regarding horticulturally important traits (growth, flowering, phenology and cropping performance). Common for all traits was that the amount of variation (mean for 17 traits: 21.8% ± 11.2) was smaller among populations than within populations. In spite of this low variation, the study revealed significant genetic variation (p<0.05) among populations in nearly all traits investigated. Significant correlations were found between several traits: between plant width and plant height (r=0.516, p<0.001),between plant height and total fruit yield (r=0.253, p<0.001),between number of rhizome-derived daughter plants and total fruit yield (r=–0.189, p<0.001) and between the beginning of spring flowering and the duration of repeat flowering (r=–0.354, p<0.001). Many traits were associated with the latitude of the sample location, e.g. duration of flowering (r=–0.620, p<0.05) and total fruit yield (r=–0.580, p<0.05). Populations collected from southern latitudes (56°–60°N) in general showed better values than the northern populations for horticulturally important traits. The Japanese population, which belongs to the subspecies minus, differed in many traits from all the other populations which belong to the subspecies vitis-idaea.

Journal ArticleDOI
TL;DR: Observations indicate that it may be possible to increase both the symbiotic N2-fixation and seed yield through plant breeding.
Abstract: Common bean (Phaseolus vulgaris L.), an important food crop in Europe, America, Africa and Asia, is thought to fix only small amounts of atmospheric nitrogen. It contributes significantly to the sustainability of traditional cropping systems because of the predominance of small-scale farmers who cultivate beans in those areas. The objectives of this work were to evaluate bush bean varieties under common agronomic cropping systems and to evaluate breeding lines under low N-fertility sole cropping and intercropping systems. The purpose of the study was to characterize the genotype and cropping system's variability in symbiotic and plant characters and to identify the most suitable genotypes to establish an effective symbiosis with indigenous strains of Rhizobium. No significant differences among the bush bean varieties evaluated under typical fertilization practices were observed for N2-fixation and plant traits except for seed nitrogen. Significant differences among the bean lines studied under low N-fertilization conditions were detected for plant growth,plant component and N2-fixation traits. A significant interaction of bean genotype x cropping system was found for number of nodules per plant and nodule moisture on the bush bean varieties studied, and for days to emergence, days to flowering, end of flowering, shoot length, root dry weight and shoot nitrogen on the bean lines evaluated. Nodulation parameters were correlated positively with the yield components, shoot and root parts and duration of flowering, and correlated negatively with seed crude protein, pod and seed dimensions and seed dry weight. These observations indicate that it may be possible to increase both the symbiotic N2-fixation and seed yield through plant breeding.

Book ChapterDOI
01 Jan 2001
TL;DR: Transgenic white clover plants expressing a modified crylBa gene, altered to give an increased proportion of G/C bases and mimic the codon use of plant genes, were toxic to feeding Wiseana larvae, and expressing a mutated form of the WC1MV 13K movement protein gene resulted in plants with a high level of resistance and restricted systemic spread of the virus.
Abstract: Both insect pests and viral diseases have significant negative impacts on the yield and persistence of forage legumes, and often it is difficult to develop resistant germplasm using traditional plant breeding approaches. We illustrate some of the principles for the molecular breeding of forage legumes, by demonstrating how cloned resistance genes can be used to produce transgenic white clover plants, resistant to either an insect pest (Wiseana spp.) or white clover mosaic virus (WC1MV). Insect bioassays identified a Bacillus thuringiensis Cry1Ba toxin and the proteinase inhibitor, BPTI, as possible resistance factors for Wiseana larvae. Transgenic white clover plants expressing a modified crylBa gene, altered to give an increased proportion of G/C bases and mimic the codon use of plant genes, were toxic to feeding Wiseana larvae. While larvae feeding on white clover expressing the BPTI transgene survived, their growth rate was significantly reduced. Our strategy to develop resistance to WC1MV has been to express individual WC1MV genes in transgenic white clover plants. Expression of the coat protein gene of WC1MV in white clover gave low levels of resistance to the virus, but a substantial delay to systemic infection. Expression of a mutated form of the WC1MV 13K movement protein gene in white clover, resulted in plants with a high level of resistance and restricted systemic spread of the virus. Five of 22 transgenic white clover plants designed to express the WC1MV replicase gene showed immunity to WC1MV infection.

Dissertation
01 Jan 2001
TL;DR: In the present thesis, both RAPD markers and morphology were successfully used to identify twelve cultivars of rhubarb, and RAPD was used to search for a marker linked to sex determi- nation in sea bucktho.
Abstract: Domestication may be viewed as an evolutionary process, involving mechanisms like muta- tion, selection, genetic drift, hybridization and polyploidization, and in the end resulting in individuals with traits profitable for man. The advent of modern plant breeding has acceler- ated the domestication of plants considerably. Plant breeding is essentially a selection of plant material based on the existence of genetic variation. Genetic variation within species has been assessed by many methods and from several perspectives. In the present thesis, I study some genetical aspects in five crop species at different stages of domestication, using RAPD and morphological characters. The very first step in the domestication process in- volves selection of plant material in nature. Often, only a small amount of the variation present in the source material is represented in the samples taken. Domesticated populations of Turk‘s-cap lily proved, however, to contain as high levels of genetic variation as native populations. A totally different pattern was found in black chokeberry, as no variation at all could be found in cultivated material. In such a case, it is of vital importance to broaden the genetic basis within the crop, and this may be accomplished by incorporation of new selec- tions from nature. In order to optimize collection strategies, information must be aquired about genetic structure in these populations. Native plant material of black chokeberry turned out to contain substantial amounts of variation, however tetraploid and presumably apomic- tic plants produced progeny groups with much less variability than progeny groups derived from diploid plants. In native populations of lingonberry, individual clones extended at least 30m, which gives an indication of how to collect plants for maximizing the genetic variation within the material. In crops where valuable cultivars already have been developed, tools for simple and fast identification of these cultivars are needed. In the present thesis, both RAPD markers and morphology were successfully used to identify twelve cultivars of rhubarb. Moreover, to facilitate the breeding work, molecular markers linked to traits of interest are highly desirable. In this thesis, RAPD was used to search for a marker linked to sex determi- nation in sea bucktho


Book ChapterDOI
01 Jan 2001
TL;DR: Methods and techniques developed in molecular biology in recent years are providing tools to support plant breeding strategies and allowing scientists to tackle as yet unsolved problems or to speed up breeding programmes, which will extend plant breeding by introducing new, unanticipated traits.
Abstract: The goals of agricultural plant science are to increase crop productivity and the quality of agricultural products and to protect the environment by maintaining a system of sustainable agriculture that preserves the ecological basis of plant production. These goals have significant economic implications, which are affected by environmental conditions. The inherent diversity among plant species demonstrates clearly that plants are able to adapt to environmental stresses using genetically based programs Crop improvement, i.e. the optimisation of plant features and performance according to agricultural needs, has been undertaken for hundred’s of years: agronomists, breeders, and gardeners have used classical plant breeding methods based on selection of natural variants to improve genetic sources. Methods and techniques developed in molecular biology in recent years, especially reliable transformation systems for essentially all crops and growing numbers of complete genome sequences of higher plants, are providing tools to support plant breeding strategies and allowing scientists to tackle as yet unsolved problems or to speed up breeding programmes. Such tools will extend plant breeding by introducing new, unanticipated traits, in order to develop plants in which both crop productivity and stress tolerance are enhanced.

01 Jan 2001
TL;DR: The efficiency of some rnicrosatellite primers to generate polymorphic and easily scorable markers in sugar cane is reported.
Abstract: Sugar cane microsatellite libraries have recently been developed. Here, we report the efficiency of some rnicrosatellite primers to generate polymorphic and easily scorable markers in sugar cane. Primers selected proved to be very efficient when applied to test for legitimacy of clones, to identify contaminants in nurseries and for diversity studies. We also investigated the amplification of microsatellite primers on DNA extracted using an alkaline treatment method, and this technique looks promising.