Showing papers on "Plant breeding published in 1998"

In-vitro Techniques and Mutagenesis for the Improvement of Vegetatively Propagated Plants

Abstract: Conventional plant breeding is based on genetic variation and selection of the desired genotypes. The availability of genetic diversity and genetic variation is the starting point of any breeding programme. In most crops, sufficient genetic variation is present among land races, cultivars and their wild relatives. In conventional plant breeding programmes this is followed by several years of selection and field evaluation before a desired genotype is released as an improved cultivar. In many sexually propagated crops, e.g., rice, wheat, maize, barley, the genetic variability is usually recombined through hybridization. The desired recombinants are then selected from the segregating populations in the subsequent generations which are tested, multiplied and released as improved cultivars. However, a number of important crops such as banana, plantain, date palm, citrus, potato, sweet potato, pineapple, apple, and pear are propagated from vegetative parts, and are not amenable to improvement in the same manner as sexually propagated plants. Many of these plants are complex polyploids, take several years to flower and fruit, some are self-incompatible. In others, such as banana and plantain, there is little or no seed formation. Often the propagule size is too big and bulky to handle and to grow large populations. Hence, it is not possible to produce sufficiently large populations required to obtain the desired recombinant in a short duration. In these plants, mutation induction offers the possibility to alter a few characters without disrupting the genome while retaining all the other characters of clones.

Qtl mapping in plant breeding populations

Abstract: This invention relates to a method for improving the efficacy of a plant breeding program by selectively altering the average of a quantitative phenotypic trait in a plant population. The method employs statistical models to predict the association of genetic markers with a desired phenotypic trait. These models allow the association to be extrapolated to the progeny of the plants tested as well as plants in other families within the breeding population. After the statistical association has been determined, the genetic markers which associate with quantitative trait loci can be used to screen for plants with the desired genetic markers to use as progenitors of an F1 seed population. Alternatively, after the alleles which associate with a QTL have been identified, the coding sequences of at least one of the alleles can be cloned and introduced into a plant to create a transgenic plant line.

Pollen control during transgenic hybrid maize development in mexico

Abstract: Pollen containment may be necessary to prevent the dissemination of novel genes from transgenic crops into sexually compatible land races or wild relatives in locations where these are grown or occur naturally in the same vicinity. Routine maize (Zea maps L.) breeding activities employ controlled pollinations and are sometimes done in areas where land races or wild relatives are known to occur. The ability of researchers to control pollen movement and to thereby control the potential flow of novel genes from transgenic maize to land races or wild relatives was investigated. Using white- and yellow-seeded inbreds, pollen control was measured in two mating designs. The ability to control pollen was assessed by observing seed color in pollinations on adjacent plantings intended to trap uncontrolled pollen. In one experiment, the yellow-seeded maize contained a transgene. In this experiment contaminant seeds observed in the white maize were analyzed for the presence of recombinant DNA and the gene expression product. The results from these experiments indicated that routine plant breeding activities can he conducted with completely effective pollen containment if the transgenic line is detasseled and serves as the female for pollination with a nontransgenic male inbred. However, precautions in addition to those used in these experiments are necessary to provide complete control of pollen dissemination if a transgenic male is used to make crosses and 0.1% outcrossing to adjacent rows is deemed unacceptable.

DNA analysis of turfgrass genetic diversity

Abstract: Turfgrasses constitute an heterogeneous group of species differing widely in reproductive strategy, genome organization, and evolutionary history, Cultivars derived from vegetative propagation or from apomictic or self-pollinated species can be homogeneous at the genetic level, exhibiting little genetic variation. Alternatively, cultivars with an outcrossing breeding system can he genetically heterogeneous, such as those from open-pollinated seeded species. A careful study of the degree and distribution of turfgrass genetic variation is therefore essential for the efficient selection of superior plant material for breeding, an adequate management of genetic resources, and the effective preservation of biodiversity. An array of molecular techniques have targeted nucleic acids to evaluate molecular diversity at the species, population, and within-population levels. These techniques have only recently been applied to the breeding and management of turfgrass germplasm. Using the hybridization and amplification of nucleic acids, DNA profiling techniques have established patterns of genetic variation at the species level in grass systematics, and at the subspecies level in the study of natural populations, breeding lines, cultivars, and accessions. In some cases, chromosome analysis by flow cytometry and genomic in situ hybridization have notably complemented the use of nucleic acid markers. DNA profiling techniques have also assessed the genetic stability of cultivars and the appearance of off-types, and have provided molecular estimates of turfgrass evolution. The review of current efforts to evaluate turfgrass genetic diversity clearly indicates that the application of the tools of genome analysis to the study of germplasm diversity may finally unlock the genetic potential of wild and cultivated turfgrass resources.

Hybrid cultivar development

Abstract: Heterosis: An Introduction / Male Sterility: Classfication and Concept / Male Sterility: Molecular Characterisation / Self-Incompatibility / Monoecious and Dioecious Floral Morphologies / Chemical Hybridizing Agents / Biotechnology and Hybrid Breeding/ Molecular Genetic Markers / Rice / Wheat / Maize / Barley / Pearl Millet / Sorghum / Cotton / Sunflower / Rapeseed and Mustard / Castor/ Pigeonpea / Tomato / Onion / Cole Crops / Capsicum / Muskmelon/ Watermelon.

Plant breeding and whole-system crop physiology : improving crop maturity, adaptation, and yield

Abstract: 1: Shifts from Current Paradigms Suggested by Near-whole and Whole-system Research 2: The Beginning of Systems Thinking about Breeding for Yield 3: Biomass Accumulation: The First Major Physiological Genetic Component of Yield 4: Partitioning of Photosynthate: The Second Major Physiological Genetic Component of Yield 5: Days to Maturity: The Third Major Physiological Genetic Component of Yield 6: A Model of Photoperiod x Temperature Interaction Effects on Plant Development 7: Prediction of Phenology by the Genotype x Photoperiod x Temperature Interaction Model 8: Interactive Control over Plant Development by Vernalization, Photoperiodism and Temperature 9: Yield System Analysis: An Adjunct to Yield Trials 10: Interplant Competition and Breeding for Higher Yield 11: System-established Interconnections among Plant Traits and Implications for Plant Breeding Strategies 12: Maximising Efficiency of Breeding for Higher Crop Yield 13: Systems Thinking Requires Multidisciplinary Expertise and Collaboration

Variation in resistance to the grain aphid, Sitobion avenae (Sternorhynca: Aphididae), among diploid wheat genotypes: Multivariate analysis of agronomic data

Abstract: A collection of 87 ancient wheat genotypes, 67 Triticum monococcum, 13 Triticum boeoticum, seven Triticum urartu and one cultivar of the modern wheat Triticum aestivum (variety 'Arminda') were evaluated for resistance to the cereal aphid Sitobion avenae, the main damaging aphid pest on winter wheat in Europe. The intrinsic rate of natural increase (r m ), which is regarded as a good estimate of the fitness of an aphid population, was used as an indicator for the level of plant resistance. Differentiation of the 88 plant genotypes into four distinct groups was achieved with a cluster analysis of the r m values. The modern wheat 'Arminda' was more susceptible than any of the ancient wheat genotypes tested (r m = 0.24, i.e. the aphid population doubled every 2.6 days). A second group of 19 plants ranged from relatively susceptible to moderately resistant (0.17 < r m < 0.21). Fifty-one plants were allocated to a third group and classified as resistant (0.09 < r m < 0.16). The last group contained 17 genotypes with a high level of resistance where aphid fitness was greatly reduced (0.02 < r m < 0.09, i.e. the aphid population doubled every 11.4 days or 7.7 days, respectively). Clustering of the accessions into the different phenetic groups did not follow the geographical origin of the wheat genotypes or the species to which they belong. These results show that ancient diploid wheats, all characterized by the genome A, present considerable interest for plant breeding for resistance to S. avenae in modern wheat. The potential use of these strong and partial sources of resistance for introduction of a stable and durable form of resistance to S. avenae in wheat is discussed.

The influence of auxin type on the array of somaclonal variants generated from somatic embryogenesis of eggplant, Solanum melongena L.

Abstract: Somaclonal variation is a possible source of variation in plant breeding. To apply this approach to eggplant breeding, somaclonal variations were observed among plants regenerated through somatic embryogenesis induced by 1-naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). Variations including leaf shape, plant height, flower number per cluster, fruit shape, anther number per flower and pollen fertility were compared among 300 plants (R 0 ). Although these variations were confirmed among plants regenerated using both auxins, the frequencies of somaclonal variations in leaf shape, plant height, fruit shape and pollen fertility in the NAA experiment were higher than those in the 2,4-D experiment. Variations in flower number and anther number were also confirmed among plants from both experiments, although no significant differences in their frequency were observed. Subsequently, the inheritance of variations (leaf shape, fruit shape, and flower number) observed in R 0 was investigated from generation to generation (R 1 ). Variations in leaf shape and fruit shape were inherited while those in flower number were not. From these results we concluded that, although a high frequency of somaclonal variations were observed among plants from both methods, embryogenesis with NAA was more efficient than 2,4-D in eggplant.

Use of seed protein polymorphism for discrimination of improvement level and geographic origin of upland rice cultivars

Abstract: Grain proteins from 58 Brazilian and nine Japanese upland rice cultivars (Oryza sativa L.) were electrophoretically separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Densitometric scanning of the electrophoretic profiles permitted the estimation of the relative concentration of 16 protein fractions, which were used as variables for the calculation of Fisher's canonical discriminating functions. Significant differences between mean values of protein fractions were useful in distinguishing Brazilian and Japanese cultivars, as well as improved and non-improved Brazilian rice cultivars in scattered plots. Electrophoretically detectable protein polymorphism in rice grain can indicate geographic origin as well as breeding improvement level of a cultivar. Improved cultivars were those released by plant breeding institutes.

Genetic Fidelity of Plants Regenerated from Somatic Embryos of Cereals

Abstract: In-vitro somatic cell and tissue culture technologies have been developed to assist plant breeding. Since the first report on immature embryo culture of maize (Green and Phillips, 1975), extensive documented reports in a whole range of species (Larkin and Scowcroft, 1981; Evans et al., 1984; Maddock and Semple, 1986; Lee and Phillips, 1988; Brown, 1991; Karp, 1991, 1995) have shown undesirable genetic and cytogenetic variation between regenerated plants and the starting material. However, some papers gave the details on the production of agriculturally useful in-vitro selected traits of agronomic values. Regenerated plants varied for a wide range of agro-morphological characters. The variability associated with cell and tissue culture has been termed ‘somaclonal variation’ by Larkin and Scowcroft (1981), which is defined as ‘the variation displayed amongst plants derived from any form of cell culture’.

Soybean having epistatic genes affecting yield

Abstract: A method of plant breeding applicable to self-pollinating plants, and plants produced by use of the method, includes the use of molecular markers linked to interacting loci that affect traits of agronomic value. The method allows one to identify a first molecular marker linked to a quantitative trait locus (QTL) and a second molecular marker linked to a modifying locus having an epistatic effect in combination with the QTL. Conventional breeding steps can then be used to introgress the interacting loci into other plant varieties.

Mutation Breeding in Cereals and Legumes

Abstract: During the past more than 50 years, mutation breeding has been successfully utilized for crop improvement, to supplement the efforts made using conventional methods of plant breeding. As early as 1942, the first mutant for disease resistance was reported in barley showing resistance to powdery mildew (Freisleben and Lein, 1942). This encouraged further work on mutation breeding, leading to the release of mutant cultivars in several crops. The FAO/IAEA Mutant Varieties Database contained 1790 accessions in June 1996. Among these varieties, 854 were of cereals and 216 of legumes. The majority of varieties among the cereals came from rice (324), barley (256) and bread wheat (146). Many of these mutant varieties were released during the past 10 years (Maluszynski et al., 1991, 1992, 1995). Although, one may not accept that all the listed mutant cultivars really resulted from induced mutations, there is no doubt about the potential which mutation breeding offers for crop improvement. The attributes which are reported to have been improved by mutation breeding include a wide range of characters, including tolerance to biotic and abiotic stresses, duration of flowering and maturity, and other yield-contributing characters (Micke, 1984, 1988, 1991). Due to recent interest in new biotechnology, induced mutations have also proved useful in the preparation of genetic maps (Schwarzacher, 1994) that will facilitate molecular marker-assisted plant breeding in the future.

Somaclonal Variation in Solanaceous Medicinal Plants

Abstract: A wide range of pharmaceutical secondary metabolites, derived from several higher plants, have been used to benefit mankind for many thousands of years. Many of these compounds have been known for years, and are still being used as the drugs of choice for specific therapy, e.g. Digitalis cardiac glycosides such as digoxin (Parr, 1989). Furthermore, new compounds are being isolated from the plant kingdom, and are actively screened. The chemical synthesis of most of the plant-derived compounds is possible; however, it is usually complicated, requires several steps in the biosynthetic pathway, and is thus uneconomical. Plant cell cultures offer an alternative approach to produce valuable plant compounds and they can also be used in plant breeding (Verpoorte et al., 1993). Plant tissue culture-derived variation among regenerated plants, or somaclonal variation, has been extensively studied, especially in crop plants such as sugarcane, tobacco, rice, maize and barley (Larkin and Scowcroft, 1981; Peschke and Phillips, 1992). However, surprisingly little information is available on the applications of somaclonal variation in medicinal plants and their cell cultures.

Methods for Plant Genetic Transformation

Abstract: During the past three decades phytogeneticists have obtained important crop varieties of high yield and quality by means of traditional plant breeding. Natural genetic diversity present in the plants has permitted the selection of the best individuals for use as parents in improvement programs, which after several years of crossbreeding has led to new varieties with desirable traits of agronomic importance.

DNA Amplification Fingerprinting of Mycorrhizal Fungi and Associated Plant Materials Using Arbitrary Primers

Abstract: Plant genetics and, by association, plant breeding, is based on the analysis of inheritance of characteristics and traits, and elucidation of gene expression as related to the genotype and environmental interaction. Biochemistry and molecular biology have impacted these activities through the application of molecular markers. Table 33.1 lists commonly used molecular markers. Initially, molecular markers were based on isozymes (i.e., polymorphic mobility variants of enzymes detected usually in starch gels using activity staining), which are valuable but not numerous enough to cover the extensive regions of genome found in most plants.

QTL Mapping Associated to Photosynthesis in Bean (Phaseolus vulgaris L.)

Abstract: The genetic control of agronomic traits associated with yield, including complex metabolic processes such as photosynthesis, is an important goal for plant breeders because photosynthesis is the major determinant of biomass production in plants (1). Research has shown the existence of genetic variability in net photosynthesis among species and among cultivars (2), however there has been no utilization of these differences in plant breeding programs.