Showing papers on "Plant breeding published in 1990"

Screening of rice (Oryza sativa L.) genotypes for physiological characters contributing to salinity resistance, and their relationship to overall performance

Abstract: Phenotypic resistance of salinity is expressed as the ability to survive and grow in a salinised medium. Some subjective measure of overall performance has normally been used in plant breeding programmes aimed at increasing salinity resistance, not only to evaluate progeny, but to select parents. Salinity resistance has, at least implicitly, been treated as a single trait. Physiological studies of rice suggest that a range of characteristics (such as low shoot sodium concentration, compartmentation of salt in older rather than younger leaves, tolerance to salt within leaves and plant vigour) would increase the ability of the plant to cope with salinity. We describe the screening of a large number of rice genotypes for overall performance (using an objective measure based on survival) and for the aforementioned physiological traits. There was wide variation in all the characters studied, but only vigour was strongly correlated with survival. Shoot sodium concentration, which a priori is expected to be important, accounted for only a small proportion of the variability in the survival of salinity. Tissue tolerance (the cellular component of resistance reflecting the ability to compartmentalise salt within leaves) revealed a fivefold range between genotypes in the tolerance of their leaves to salt, but this was not correlated positively with survival. On the basis of such (lack of) correlation, these traits would be rejected in normal plant breeding practice, but we discuss the fallacies involved in attempting correlation between individual traits and the overall performance of a salt-sensitive species in saline conditions. We conclude that whilst overall performance (survival) can be used to evaluate the salt resistance of a genotype, it is not the basis on which parents should be selected to construct a complex character through breeding. It was the norm for varieties which had one good characteristic affecting salt resistance to be unexceptional or poor in the others. This constitutes experimental evidence that the potential for salt resistance present in the rice genome has not been realised in genotypes currently extant. The results are discussed in relation to the use of physiological traits in plant breeding, with particular reference to environmental stresses that do not affect a significant part of a species' ecological range.

Principles and methods of plant breeding

Abstract: Shortened Contents: 1. Importance of Plant Breeding. 2. Phytogeographical Differentiation as a Basis of Plant Breeding. 3. Sources of Genetic Variability. 4. Genetic Basis of Breeding Self-Pollinated Plants. 5. Genetic Basis of Breeding Open Pollinated Plants. 6. Trait, Genotype and Phenotype. 7. Methodologies of Plant Breeding. 8. Concept of Development of Cultivars. 9. Selection of Material for Breeding. 10. Importance of Crossing Methods. 11. Number of Cross Combinations and Size of F 2 Population. 12. Methods of Selection. 13. Selection for Traits and Genetic Gain from Selection. 14. Plant Breeding for Resistance to Parasites. 15. Breeding for Yield. 16. Use of Heterosis. 17. Mutations in Plant Breeding. 18. Chromosome Engineering. 19. Genetic Engineering. 20. Breeding Vegetatively Propagated Plants. 21. Genetic Composition and Adaptability of the Cultivar. 22. Genetic Basis of Seed Production and Introduction of Cultivars into Practice. Author index. Subject index.[/cmt]

Somaclonal variation in Lotus corniculatus L. in relation to plant breeding purposes

Abstract: Seventy-two plants regenerated from leaf-derived calli of a single plant of Lotus corniculatus have been evaluated for several morphological and agronomical traits. The analysis of selfed and polycross progenies of the regenerants indicates that the variation among regenerants was, at least in part, of genetic origin. Most of the mutations induced by tissue culture were recessive and were detected only after sexual propagation. Although in vitro culture had a depressive effect for most of the traits, the selfed progenies of 2 regenerants displayed higher values for leaflet width and seed yield than the selfed progeny of the initial plant. However the somaclonal variation did not increase the variation for any trait with respect to the variation of the donor cultivar of the initial plant.

In Vitro Production of Haploids in Triticale

Abstract: In much of the contemporary discussion about the role of anther culture in fundamental genetics as well as plant breeding it has been assumed that what has been possible with model plants can also be accomplished with important cereals like triticale. Unfortunately, the fact is that severe difficulties have been faced in the application of anther culture techniques to most of the important cereals. Major problems must be resolved before haploid production via anther culture can be readily and effectively applied to triticale. Two of the basic requirements for the application of anther culture techniques to plant improvement are the induction of sporophytic development from each genotype and the regeneration of green plants.

Genotypic variation in plant productivity and consequences for breeding of ‘low-input cultivars’

Abstract: Important characteristics of low input genotypes are a high efficiency of nutrient and water use, of assimilation, a proper assimilate transport and distribution, less losses of assimilates through respiration and adequate nutrient acquisition by the root system The response of cultivars to inputs is under genetic control and therefore improved response is accessible via screening, selection and breeding

Impact of genetically modified crops in agriculture.

Abstract: During the 1980s the research achievement with probably the greatest potential significance for plant breeding was the ability to insert DNA into plant cells and to recover an intact plant which ca...

Significant Higher Proportions of 1BL-1RS Wheat-Rye Translocation Lines Among Doubled Haploid Progenies Derived from F1 Hybrids between Translocated and Non-Translocated Wheat Cultivars

Abstract: Many plant breeding programmes have been using doubled haploid plants (DHs) for increasing their efficiency and/or for development and release of new cultivars. In common wheat, Triticum aestivum L., anther culture is the most efficient technique for obtaining haploids and DHs, and many efforts have been devoted to its improvement (for recent review, see 1). Genetic analyses have shown that male gametophyte-derived plant production is under the control of at least three independently inherited characters i.e. embryo induction rate, regeneration ability and the ratio of green to albino plants(2).

Genetic, cytological and physiological aspects of seed yield in perennial ryegrass (Lolium perenne L.)

Abstract: Seed yield in perennial ryegrass is low and unpredictable. Breeding for a high stable seed yield is difficult, as seed yield is a complex trait with a low heritability. The aims of this study were to identify selection criteria for high seed yield and to gain more insight in the biology of seed reproduction in perennial ryegrass. Genotypic and temperature effects on pollen tube growth rate were detected. Cytological studies of seed development, ovule degeneration and seed abortion demonstrated that non-productive florets occurred at all positions within the ear. Abscission layer development and the mechanism of seed shattering were similar in genotypes with different seed retention. Indirect selection for seed yield would be more efficient, if correlated traits with a high heritability could be identified, either in spaced plants or in crops grown in drilled plots. Significant and consistent differences for seed yield per plot were found among nine perennial ryegrass cultivars over three years at two locations. These differences were not correlated with thousand-grain weight, other seed yield components or crop physiological traits assessed in drilled plots. Spaced plants within each cultivar differed greatly for many traits. Broad-sense heritabilities were high for all spaced-plant traits, but narrow-sense heritabilities were only significant for some traits. No spaced-plant traits were identified that correlate with seed yield in drilled plots.

Somaclonal Variation for Nematode Resistance

Abstract: The development of disease-resistant cultivars through plant breeding depends on the extent of variability in a plant population with resistance-bearing traits that can be selected for transfer into new cultivars. Breeders have been relatively successful in transferring nematode resistance into some crop species. through selection of variants occurring in genotypes and through introgression. For some crop species. the gene base for nematode resistance is extremely wide, and resistance can be easily transferred when it is expressed by a single dominant gene; in others, the base is so narrow that nematode resistance is nonexistent (Fassuliotis 1987). To increase the natural variation in plant populations, mutation techniques have produced some lines with increased nematode resistance (Fassuliotis 1987). The use of wild species as parental sources for resistance has been extremely successful in some crops. The tomato (Lycopersicon esculentum). to which root-knot nematode (Meloidogyne spp.) resistance was transferred by introgression of genes from the wild species Lycopersicon peruvianum. is an excellent example. F1 hybrids were brought to maturity through embryo culture (Smith 1944). Eggplant, Solanum melongena lacks resistance to root-knot nematodes, and attempts to cross it with the resistant wild species, S. sisymbriifolium. have been unsuccessful (Fassuliotis 1975). In potato breeding Solanum vernei has served as an important source of resistance against the potato cyst nematode, Globodera pallida.

Breeding of new Hippeastrum cultivars using diploid species. I. The F-1 evaluation.

Abstract: An amaryllis breeding program using diploid species not well represented in current commercial tetraploid cultivars has been underway since 1988. Objectives are to develop evergreen cultivars with attractive foliage and fragrant flow ers of novel floral form and coloration. F-l progeny between Hippeastrum papilio (Amaryllis papilio Ravenna1) and, re spectively, H. lapacense (A. lapacensis Cardenas), H. cardenasianum (A. cardenasiana Traub & Doran), and H. vittatum Herbert 'Tweed ian urn' have been successfully produc ed, and selections made during their first flowering season (February through June, 1990). Over two hundred progeny have been evaluated. Sibling, interhybrid and new primary hybrid crosses with H. papilio, H. 'Tucamanii', H. brasilianum (A. brasiliana Traub & Doran), H. fragantissimum (Amaryllis fragrantissima Cardenas) [these latter three all white, heavily fragrant, trumpet-flowered species], and H. reticulatum Her bert var. striatifolium Herbert as the seed and pollen parents have been generated. Ten to twenty percent of the seedlings from all new crosses are being treated with colchicine in an attempt to induce polyploidy. Hippeastrum Herbert, the amaryllis, consists of ca. 60 entirely New World species (26). The species are concen trated in two main centers of diversity: in eastern Brazil and the centralsouthern Andes of Peru, Bolivia and Argentina, on the eastern slopes and adjacent foothills. Little of this genetic diversity is represented in modern amaryllis hybrids. Primary hybrids were produced from a relatively small number of species, mainly H. vittatum Her bert, H. leopoldii Dombrain, H. pardinum (Hook, f.) Lemaire, H. reginae Herbert, H. puniceum (Lam.) Kuntze and H. aulicum Herbert (2, 10, 21, 24, 25). Hippeastrum x Florida Agricultural Experiment Station Journal Series No. N-00319. This project was supported by the American Floral Endowment. ■Following the decision of the Nomenclature Committee of the Inter national Association for Plant Taxonomy, Hippeastrum Herbert is recog nized as properly applied to the neotropical genus discussed in this paper, and Amaryllis L. as a monotypic genus of South Africa. As formal transfers into Hippeastrum of many species described as Amaryllis have yet to be made, the valid name and authority is given in parenthesis wherever

Development of new taro varieties through breeding.

Abstract: The production of new crop varieties through hybridization is the only stable method of crop improvement. As a program, crop improvement through breeding has been a major project of most research centers and institutes. An example of the value of plant breeding was demonstrated by the release of IR-8 or "miracle rice" by the International Rice Research Institute in the mid-1960's. Other crops like corn and wheat had similar dramatic and valuable contributions. In Hawaii, new variety development has been and continues to be an important and well supported program of the Hawaiian Sugar Planters Association. Although taro is considered to be one of the oldest cultivated crops, there has virtually been no research program aimed at improving the varieties existing throughout the world. Because of the importance of taro as a commercial and staple crop in Hawaii and many countries in Asia and the Pacific area, an organized crop improvement program through breeding should be established and supported. Some of the advantages, problems, and general method of hybridizing taro are discussed. Introduction Production of new varieties of plants through breeding is the only stable method of improving crops. Crop yields and quality can be improved through pest and disease control, fertilizer application and cultural manipulations but all these have to be repeated each time the crop is grown (Abbott and Atkin, 1987; Hawkes, 1987; Hayes and Immer, 1942; Martin and Leonard, 1949). There are three general methods of crop improvement and these are (1) Introduction, (2) Selection, and (3) Hybridization. Introduction sometimes replaces hybridization when a superior variety is introduced from another source but often introduction provides foundation materials for hybridization. Selection follows and/or precedes either introduction and hybridization. The process of developing new crop varieties or hybrids through breeding has been an important research program of the many international as well as national research centers and institutes. The International Rice Research Institute ORR}) has become well known very quickly because of the success in producing the famous "miracle rice" or IR-8, a short stature, high yielding variety developed by plant breeder Henry Beachell shortly after the institute opened ORRI, 1967). The com and wheat programs of the U.s. as well as that of CIMMYT in Mexico produced new com and wheat hybrids and varieties which gave similarly outstanding yield potentials and qualities. Aside from increasing yields, plant breeding has been used to produce new plants which have resistance to some pests and diseases. The California rice breeding program has as one of its objectives the production of new varieties with resistance to low temperatures at the time of flowering. Most tropical rice varieties to not produce grains when exposed to temperatures below 600 p at flowering. Eating and processing qualities are also very important characteristics that are incorporated in new varieties or cultivars. Taro, a crop of commercial importance in Hawaii and many Asian-Pacific countries is one of the oldest known cultivated food crops (de la Pena, 1970; Plucknett and de la Pena, 1971; Whitney, Bowers and Takahashi, 1939). In spite of its importance, there has virtually been no effort or work in improving its production potential through plant breeding. One reason for this lack of research activity is the difficulty of performing the work of cross-pollination due to the infrequent flowering habit of the taro plant. In its natural habitat, the taro plant rarely flowers and when it does, its flower anatomy discourages natural pollination (Plucknett, de la Pena and Obrero, 1970). The discovery of gibberellic acid as an aid in inducing flower formation in taro and the other edible aroids has encouraged some plant breeders to look at the possibility of producing new taro varieties or hybrids (Wilson and Cable, 1984). In a very limited breeding program at the University of the South Pacific in Apia, Western Samoa, Dr. J. Wilson was able to produce some hybrids and released a new variety which was named "Alafua Sunrise". This variety has a better yield potential than many of the commercial varieties in Western Samoa, however, its eating quality is not as good and acceptable as the popular variety, Niue. Aside from this breeding work, there has been little or no known breeding program in taro and the edible aroids elsewhere.

Triticale × Wheat Hybrids

Abstract: Wheat (Triticum aestivum L. em Thell) is the most important temperate cereal crop grown in the world. It is the end product of several thousand years of selection and 100 years or so of applied plant breeding. It is well documented that bread wheat is the result of natural hybridizations between diploid (2n = 2x = 14) and tetraploid (2n = 4x = 28) progenitor species, some of which are themselves important cereals, so that hexaploid wheat (2n = 6x = 42) can be regarded as a tetraploid wheat to which seven pairs of chromosomes from T. tauschii (Coss.) Schmal have been added. The man-made hybrid triticale (× Triticosecale Wittmack), on the other hand, has had a total history of only 100 years and has only been investigated seriously for the last 40 years. As the name implies, triticales are hybrids between hexaploid or tetraploid Triticum species and diploid species of Secale, cereal rye. To some extent, therefore, triticales can be regarded as wheat plants to which rye chromosomes have been added.

Sugarbeet germplasm selected from the USDA collection.

Abstract: This article addresses the consequences of selective breeding narrowing down the genetic diversity of sugar beet crops. The reasoning behind selective breeding attempting to produce those sugar beet lines with superior processing qualities is addressed. This narrowing resulted in reduced crop yields and lowered sucrose levels. Advancements in technology aided in the improvement of higher extractible sucrose content

Importance of flowering interval on breeding for drought resistance in tropical maize.

Abstract: espanolLa longitud de intervalo entre la aparicion de estigmas y antesis se incrementa cuando la sequia coincide con la epoca de floracion del maiz (Zea mays L.). Cuatro poblaciones elite de maiz tropical del CIMMYT estan siendo mejoradas para resistencia a sequia por esquemas de seleccion recurrente (S1 o hermanos completos) para rendimiento de grano y varias otras caracteristicas, tanto bajo estres de sequia, como bajo condiciones de buena humedad. Los datos recolectados de mas de 2,000 famillas por poblacion evaluadas en parcelas de un solo surco, bajo tres niveles de estres de humedad de suelo (1. estres severo durante el periodo de pre y postfloracion; 2. estres intermedio durante el llenado de grano; y 3. irrigacion normal, todos en ausencia de lluvia), mostraron correlacion debil o ausencia de esta entre el rendimiento de grano y otras caracteristicas relacionadas al balance hidrico de la planta, tales como: enrollamiento foliar y senescencia, foto-oxidacion, concentracion foliar de clorofila, tasa de elongacion vegetativa, temperatura foliar y potencial hidrico matutino. El rendimiento bajo todos los niveles de estres fue correlacionado negativamente con el intervalo de floracion y el intervalo de floracion se incremento debido a la sequia. Asimismo, los granos y mazorcas por plantase redujeron significativamente. En todas las poblaciones el rendimiento disminuyo aproximadamente 10% por dia de incremento en el intervalo de floracion y hasta 8 dias. En varias situaciones de estres, la heredabilidad de sentido amplio para el intervalo de floracion fue mayor que aquella del rendimiento de grano y la correlacion genetica entre rendimiento de grano y el intervalo de floracion aproximadamente -1.00. Los sinteticos formados a partir de una de las poblaciones, seguidos de seleccion bidireccional y evaluados bajo sequia, demostraron ventajas adaptativas como baja temperatura foliar, baja senescencia foliar, un intervalo de floracion reducido y hojas erectas, especialmente, cuando todas estas caracteristicas fueron combinadas en un indice de seleccion. La seleccion por intervalo de floracion corto y alto rendimiento de grano puede ser un medio eficaz de mejorar la tolerancia a la sequia en maiz tropical. EnglishThe length of the Interval between anthesis and silking (ASI) is increased by drought which coincides with flowering. Four elite CIMMYT lowland tropical populations are undergoing recurrent selection (S1 or full-sib) for improved grain yield and several other traits under drought and well watered conditions. Data collected from more than 200 families per population grown In single row plots under three water stress levels (pre and post-flowering stress; post-flowering stress; normal irrigation, all in the absence of rain) showed weak or no correlation between grain yield and traits related to plant water status, such as leaf rolling and senescence, photooxidation, leaf chlorophyll concentration, shoot elongation rate, canopy temperature and predawn water potential. Yield under all levels of stress was significantly negatively correlated with AST, and as AST increased due to drought, kernels and ears per plant were significantly reduced. In all populations yield decreased by approximately 10 % per day increase in AST up to 8 days. In several stress situations broad-sense heritability of AST was greater than that of grain yield and the genetic correlation between grain yield and AST approached -1.00. Synthetics formed from one population following bidirectional selection and tested under drought showed adaptive advantage of cool canopy temperature, delayed leaf senescence, reduced AST and erect leaves, especially when all were combined with grain yield in a single index during selection. Selection for reduced AST and high grain yield under drought can be an effective means of improving drought tolerance in tropical maize.