Showing papers on "Plant breeding published in 1996"

Genetic engineering for resistance to bacteria in transgenic plants by introduction of foreign genes

Abstract: Bacterial diseases are of high economic importance in many crop plant species including potato, different vegetable species, fruit trees, rice, cotton and grapevine. Conventional breeding efforts in potato has not resulted in the generation of varieties resistant to soft rot and black leg due to the lack of known resistance traits in lines or species which are sexually compatible with potato. Resistance traits known to be present in wild species often cannot be used for classical breeding programmes as these are genetically too distant from today’s cultivars. Similarly, in other plant species susceptible to bacterial pathogens often no valuable resistance or tolerance traits are known. Furthermore, chemical plant protection is not as evolved as for other pathogens. Actually, the most prominent means of prevention of bacterial infections are phytosanitary practices and highly developed harvesting techniques minimizing wounding as well as storage conditions reducing temperature and humidity. Genetic engineering allows a new approach to an old problem. Foreign proteins or peptides can be expressed in transgenic plants and might introduce new resistance factors or complement the natural mechanisms. An excellent model host-pathogen system of high economic importance is the interaction between Solanurn tuberosum and Etwinia carotovora. This bacterial species is the causative agent of soft rot and black leg in potato. Especially in tropical and subtropical climates the pathogen provokes severe damage and losses of harvest both in the field and during storage. Compared to other types of pathogens, efforts in genetic engineering allocated to the development of resistance to phytopathogenic bacteria in transgenic plants is quite small. In general, this work has focused mostly on potato or tobacco. This mini-review will summarize the different research approaches published so far.

Segregation distortion in androgenic plants

Abstract: Haplodiploidization through in vitro androgenesis allows the development of homozygous lines from heterozygous parents in one generation Hence, the production of doubled haploid (DH) lines is a powerful tool for plant breeding and genetic analyses The main use of haplodiploidization is to hasten the development of inbred lines combining the desired homozygous genes from genetically distinct populations For example, the technique has been used to obtain yellow mosaic virus resistant (Foroughi-Wehr and Friedt, 1984) and mildew resistant (Powell et al, 1984) barley lines and yellow seeded canola lines (Henderson and Pauls, 1992) Haplodiploidization could be of great value when applied in recurrent selection schemes (Patel et al, 1985; Gallais, 1986)

Inheritance of β-glucan content of oat grain

Abstract: β-Glucan in oat (Avena sativa L.) grain is primarily responsible for the beneficial effect of oat fiber on lowering blood serum cholesterol levels in humans. Plant breeding programs designed to genetically alter the β-glucan contents of oat germplasm would benefit from information on the inheritance of this trait. Two experiments were conducted to study the inheritance of β-glucan. Generation means analysis of five populations derived from biparental crosses between high and low β-glucan lines and cultivars was used to determine the genetic effects controlling β-glucan content in these populations. Parent-offspring regression was performed by using β-glucan data collected from individual plants of 166 oat lines and cultivars and their selfed offspring, allowing estimation of broad-sense heritability for β-glucan content in a diverse sample of oat germplasm. Additive gene effects were more important, and dominant gene effects were detected in only two of five biparental populations. No evidence of epistatic gene effects was found. Broad-sense heritability was estimated as 0.55 on an individual plant basis. This estimate is based on the covariance of inbred parents and their selfed progeny, which involves twice the additive gene action of the reference noninbred population, as well as nonadditive genetic effects. Selection based on replicated progeny families would involve a higher heritability. A positive correlation between grain yield and β-glucan was observed in the generation means analysis. These results suggest that plant breeders should be successful in altering β-glucan in oat through direct selection for this genetically variable trait.

Haploidy and mutation techniques

Abstract: Mutation techniques have already proven their potential for generating useful variability for plant breeding (Micke et al.,1990; Sigurbjornsson, 1983). The FAO/IAEA Mutant Varieties Database now lists almost 1800 officially released mutant cultivars in more than 150 plant species (Maluszynski et al.,1991, 1992). Mutant cultivars or mutated genes have significantly contributed to the economy of many countries. One example is X-ray induced semidwarfness in the barley variety “Diamant” in Central Europe; another is gamma ray induced semidwarfness in the barley cultivar “Golden Promise” in the UK as well as in the durum wheat cultivar “Creso” in Italy. A significant economic impact also resulted from the cultivation of the cotton mutant cultivars “NIAB 78” and “Lu Mian No. 1” in Pakistan and China, respectively (Maluszynski, 1990). Rutger (1992) listed 11 rice mutant cultivars in Japan and China, each of which has been grown annually on 100,000 or more hectares. In ornamentals, induced mutations are now routinely used to develop new, more attractive cultivars (Broertjes and Van Harten, 1988). The development of efficient in vitro culture methods offers new, effective ways of overcoming difficulties in using induced mutations to generate desired variability in crops, particularly in vegetatively propagated crops. Among in vitro systems, doubled haploidy can be considered as an efficient tool for facilitating application of mutation techniques. The main advantages for sexually- and asexually-propagated plants are in facilitating screening for both dominant and recessive mutants which are homozygous early in the programme, in avoiding chimerism and in reducing the number of generations of progeny testing thus shortening the breeding cycle. The value of this methodology has already been clearly demonstrated in rapeseed breeding. This review will deal with the main theoretical considerations of these approaches, their development and applications.

Hybrids of crosses between oat and andropogoneae or paniceae species

Abstract: Plant breeders are interested in enlarging the genetic variability within a species of interest and in improving breeding strategies. A wide hybridization program was conducted from 1990 to 1994 in Germany to determine the prospects for sexual gene transfer or haploid production in oat (Avena sativa L.). Five cultivars of oat were pollinated with pearl millet [Pennisetum americanum (L.) Leecke], eastern gamagrass [Tripsacum dactyloides (L.) L.], and maize (Zea mays L. ; 2x and 4x) in the greenhouse. Exogenous auxin application, embryo rescue, and early colchicine-mediated doubling of chromosomes were used to overcome postzygotic barriers. The recovered plants were analyzed cytologically and phenotypically under greenhouse and field conditions. Depending on the pollinator species, the embryo frequencies varied from 0.4% (Z. mays 4x) to 9.8% (pearl millet). In embryo rescue, initial growth occurred frequently, but many plantlets died. Chromosomes of the pollinator species were lost late in embryo and plant development. One to four chromosomes of the pollinator species were found at the tillering stage in root tip cells. Overall, four viable plants were produced, among them hybrids with pearl millet and eastern gamagrass for the first time. The efficiency of haploid production (<0.1%) was too low in all combinations for application in plant breeding programs ; however, the transfer of genes or chromosomes appears promising in crosses of oat with maize and pearl millet.

Lily breeding research in the Netherlands

Abstract: At the Centre for Plant Breeding and Reproduction Research (CPRO-DLO) in Wageningen lily breeding research in the Netherlands is concentrated. To this end sources of germplasm (genetic material) are maintained in a lily species and cultivar collection. Research is done on long term storage of this collection by use of low temperature and minimal growth conditions in vitro. Main themes of our breeding research are breeding for resistance (to Fusarium oxysporum, Pythium and virus diseases), breeding for quality traits (flower longevity lily; forcing ability; bulbgrowth of Lilium longiflorum), interspecific hybridization and genetic modification. A molecular marker system using RAPD's is developed in lily to link Fusarium resistance with molecular markers and to construct a genetic map of lily. A system for in vitro pollination, fertilization and embryo rescue has been developed for lily. By combining pollination techniques to overcome prefertilization barriers with in vitro methods to overcome postfertilization barriers, wide interspecific crosses could be made more efficiently. This resulted into a range of new interspecific hybrids, which have led to completely new hybrid groups in the lily assortment. To overcome F1-sterility of interspecific hybrids, owing to lack of chromosome pairing during meiosis, colchicine and oryzalin are used for the induction of mitotic tetraploids. Interspecific crosses at tetraploid level between complex hybrids of L. longiflorum, L. henryi, L. candidum, Asiatic and Oriental hybrid lilies have been made. To develop efficient methods for breeding at tetraploid level, meiotic polyploidization is investigated. Procedures of genetic modification of lily are developed in several directions. At the University of Leiden, for the introduction of virus resistances a transformation technique is in development by particle bombardment on bulb-scale explants. An approach followed by CPRO-DLO is pollen transformation: isolated pollen bombarded with particles coated with DNA containing the kanamycin resistance gene and the B-glucuronidase gene are used to obtain transgenic plants. Other biotechnological techniques are based on protoplast regeneration for either somatic hybridization or direct DNA transfer and microspore culture for the induction of haploidy.

Reflections on doubled haploids in plant breeding

Abstract: Doubled haploid breeding has intrigued plant breeders for the past thirty years. The breeding method involves: 1. making haploid tissues or plants (1n) from heterozygous parents, and 2. doubling the chromosomes in the tissues (followed by regenerating plants) or plants to obtain diploid plants (2n) which are referred to as doubled haploids. At the haploid level, every gene is hemizygous. After chromosome doubling, which in theory makes an identical copy of each haploid chromosome, every gene is homozygous. Hence, the doubled haploid plant is completely homozygous. Occasionally doubled haploid plants have also been referred to as dihaploid plants, however, the classical definition of dihaploid is the haploid plant (1n = 2x) of an autotetraploid (2n = 4x). To avoid confusion, doubled haploid is preferred to dihaploid.

Genetics of green plant regeneration from anther culture in cereals

Abstract: The potential uses of doubled haploids in plant breeding and genetic studies have been well documented in the past two decades (Chen, 1986; De Buyser et al., 1987; Graner et al., 1991). There are at least three doubled haploid systems. They are anther or isolated microspore culture (Charmet and Bernard, 1984; Dunwell et al., 1987; Zhou and Konzak, 1989; Ziauddin et al., 1990), ovary culture (Wang and Kuang, 1981; Castillo and Cistue, 1993), and embryo rescue following interspecific crosses, such as the Hordeum bulbosum system (Kasha and Kao, 1970) and the wheat × maize hybridization method (Amrani et al., 1993). The anther culture system has been a favorable choice by many researchers because of the availability of a large number of microspores within each anther that could potentially produce doubled haploid plants. For many plant species, anther culture is the most efficient means to obtain ample haploid plants for selecting desirable F1 combinations in plant breeding.

QTL for insect resistance and drought tolerance in tropical maize: prospects for marker assisted selection

Abstract: Insects and drought cause severe losses in the production of maize in many developing countries Conventional breeding efforts to enhance the level of resistance to a number of insect pests and tolerance to drought have been successful, although only through large efforts of many breeders and over a large period of time Continued improvements will only be possible through substantial investment of resources Recently, success in identifying quantitative trait loci (QTL) in several plant species using various molecular marker systems offers alternative methods for accelerating conventional breeding programs As the first step towards using molecular markers in CIMMYT's maize breeding program, restriction fragment length polymorphisms (RFLPs) have been used to understand the genetic basis of resistance to two corn borer species, southwestern corn borer and sugarcane borer, and to one major component of drought tolerance, anthesis-silking interval A number of QTL with effects large enough to be regarded as significant in breeding were detected for each of these traits and many of them presented stable effects over environments While variability in the number and location of QTL has been found when compared across populations, several loci were found to be quite consistent Simple calculations can be made which estimate that the total genetic potential in maize for these traits is high It is argued that to ultimately access and manipulate this potential, the use of linked molecular markers as indirect selectable markers is both feasible and necessary

Comparative genetic and QTL mapping in sorghum and maize.

Abstract: DNA markers and genetic maps will be important tools for direct investigations of several facets of crop improvement and will provide vital links between plant breeding and basic plant biology. The markers and maps will become more important for increased crop production because plant genetics will be required to extend or replace extant management practices such as chemical fertilizers, pesticides, and irrigation (Lee, 1995). Despite the importance of the sorghum crop, comprehensive genetic characterization has been limited. Therefore, the primary goal of this research program was to develop basic genetic tools to facilitate research in the genetics and breeding of sorghum. The first phase of this project consisted of constructing a genetic map based on restriction fragment length polymorphisms (RFLPs). The ISU sorghum map was created through linkage analysis of 78 F2 plants of an intraspecific cross between inbred CK60 and accession P1229828 (Pereira et al., 1994). The map consists of 201 loci distributed among 10 linkage groups covering 1,299 cM. Comparison of sorghum and maize RFLP maps on the basis of common sets of DNA probes revealed a high degree of conservation as reflected by homology, copy number, and collinearity. Examples of conserved and rearranged locus orders were observed. The same sorghum population was used to map genetic factors (mutants and QTL) for several traits including vegetative and reproductive morphology, maturity, insect, and disease resistance. This presentation will emphasize analysis of genetic factors affecting plant height, an important character for sorghum adaptation in temperate latitudes for grain production. Four QTL for plant height were identified in a sample of 152 F2 plants (Pereira and Lee, 1995) whereas 6 QTL were detected among their F3 progeny. These observations and assessments of other traits at 4 QTL common to F2 plants and their F3 progeny indicate some of these regions correspond to loci (dw) previously identified on the basis of alleles with highly qualitative effects. Four of the six sorghum plant height QTL seem to be orthologous to plant height QTL in maize. Other possible instances of orthologous QTL included regions for maturity and tillering. These observations suggest that the conservation of the maize and sorghum genomes encompasses sequence homology, collinearity, and function. The genetic information and technology developed on the basis of DNA markers could be used in several facets of breeding, genetics, and other basic biological investigations. In addition, DNA markers have been used to survey large collections of elite sorghum germ plasm to determine the degree of genetic relationships and genetic diversity (Ahnert et al., 1996). RFLP data seem to portray genetic relationships more accurately than the methods based exclusively on the coancestry coefficient. This information provides the basis for more accurate perceptions of genetic relationships and diversity.

Fast resolution of identification problems in seed production and plant breeding using molecular markers

Abstract: Summary. Polymerase chain reaction (PCR) analysis confusion in the identity of seed lots of an advanced with specific and arbitrary primers was used to identify breeding line was resolved and off-type barley plants germplasm from a barley breeding program. Through were identified in a seed increase block. This illustrated practical application of the technology, an F1 plant's the value of PCR-based genotype analysis in plant identity was confirmed, the correct pedigrees 'of breeding programs. 2 incorrectly labelled F2 populations were determined,

Somaclonal Variation for Salt Tolerance in Tomato and Potato

Abstract: Currently, genetic improvement of crop tolerance to salinity (and to other prevailing stresses) is considered a major practical alternative for improving agricultural productivity in many arid and semiarid areas in both developed and developing countries. A great effort has been directed toward the development of salt-tolerant crop plants principally through: (1) use of conventional plant breeding (Epstein et al. 1980; Saranga et al. 1992) as well as by more modern molecular techniques (Winicov 1994), both involving the transfer of genes from salt-tolerant plants into the relatively more sensitive ones; (2) use of variability existing or produced in tissue and cell culture.

Future prospects for crop improvement through anther and microspore culture

Abstract: Plant breeders are keenly interested in haploid sporophytes because using the conventional method of plant breeding, a considerable number of generations are needed to create pure lines from a heterozygous population. However, if the chromosomes of haploids are doubled, completely homozygous lines can be obtained in one or two generations. The genetic factors in doubled haploid plants are fixed and will be identical in future generations, making it possible for a plant breeder to evaluate quantitative characters such as yield and quality early in the breeding process. Furthermore, a much smaller population may be needed using the haploid method than that required when employing the diploid method (Nei, 1963; Baenziger et al., 1984).

Field evaluation and selection of rice somaclonal variants at different altitudes

Abstract: A field experiment was designed to compare control with tissue culture-derived plants of rice, and to study the effects of natural selection pressure applied to the first generation (R0) of in vitro plants on the performance of their progeny. Control- and R0 in vitro plants of four rice varieties from middle altitude in Burundi, i.e. 'Facagro 57','Facagro 76','Kirundo 3' and 'Kirundo 9', were cultivated at four different altitudes (800, 1380, 1650 and 1900 m). Several parameters concerning tillering capacity, plant height development and seed production were measured. The means for most measured parameters were higher in control plants than in the in vitro plants, while the higher variation coefficients and most extreme values were usually found in the in vitro plants. For each variety, the 20 control plants and 20 in vitro plants having the highest production were selected at each altitude of 1380 and 1650 m, and their progenies were cultivated on the same site at 1580 m. Among the plants arising from 1650 m, most maximum values, higher variation coefficients and, in some cases, higher means were found in the in vitro plants. In contrast, among the plants arising from 1350 m, higher means most usually corresponded to control plants, while the tendency for maximum values and variation coefficients were unclear. These results indicate the positive effect of natural selection pressure applied in the first generation to plants rising from tissue culture. They also demonstrate that considerable variation may be generated in vitro. The interest for plant breeding purposes is discussed.

Some remarks on triticale breeding evolution in Portugal: (A) role played by the National Plant Breeding Station.

Abstract: The main steps of the triticale breeding evolution at NPBS are referred, showing its impact on the triticale utilization by the portuguese farmers.

Genetic gain for seed yield in soybean populations by recurrent selection

Abstract: iv INTRODUCTION 1