Showing papers on "Plant disease resistance published in 1983"

Induced Mutations in Plant Breeding

Abstract: 1 Introduction- 2 Methods for Inducing Mutations- 21 Mutagenic Agents and Related Problems- 22 The Chimerical Structure of the M1 Plants- 3 The Selection Value of Mutant Genes- 4 The Seed Production of Mutants and the Alteration of Quantitative Characters- 41 The Alteration of Quantitative Characters- 42 Mutants with Increased Seed Yield- 43 Released or Approved Mutant Varieties- 5 The Utilization of Mutants in Crossbreeding- 51 The Incorporation of Mutant Genes into the Genomes of Varieties or Strains- 52 The Joint Action of Mutant Genes- 521 Negative Interactions- 522 Positive Interactions- 6 The Alteration of the Shoot System by Means of Mutations- 61 Mutants with Reduced Plant Height: Erectoides Types, Semidwarfs, Dwarfs- 611 Barley- 612 Rice- 613 Bread and Durum Wheat Other Gramineae- 614 Dicotyledonous Crops- 62 Mutants with Increased Plant Height- 63 Mutants with Altered Stem Structure- 631 Branching, Tillering- 632 Stem Bifurcation- 6321 Bifurcated Mutants- 6322 Bifurcated Recombinants- 633 Stem Fasciation- 6331 Fasciated Mutants- 6332 Fasciated Recombinants- 634 Mutations in Fiber Plants- 7 Alterations of Flower Shape, Color and Function- 71 Flower Shapes and Flower Colors in Ornamentals- 72 Inflorescences- 73 Genetic Male Sterility- 8 Leaf Mutants of Agronomic Interest- 9 Mutations Affecting the Root System- 10 The Alteration of Flowering and Ripening Times- 101 Earliness- 102 Lateness- 103 Changes of the Photoperiodic Reaction- 11 Mutations in Vegetatively Propagated Crops and Ornamentals- 12 Heterosis- 13 Disease Resistance- 131 Resistance Against Fungi, Bacteria, and Viruses- 1311 Barley- 1312 Rice- 1313 Bread and Durum Wheat- 1314 Oats- 1315 Maize- 1316 Pearl Millet- 1317 Sugarcane- 1318 Dicotyledonous Crops- 132 Resistance Against Animal Pathogens- 133 Herbicide Tolerance- 14 Drought Resistance, Heat Tolerance, Winterhardiness- 15 Shattering and Shedding Resistance- 16 The Pleiotropic Gene Action as a Negative Factor in Mutation Breeding- 161 The Alteration of Pleiotropic Patterns Under the Influence of Changed Genotypic Background or Environment- 162 Mutations of Closely Linked Genes- 17 The Penetrante Behavior of Mutant Genes as a Negative Factor- 18 The Adaptability of Mutants to Altered Environmental Conditions- 181 The Reaction of Mutants to Different Natural Environments- 182 The Reaction of Mutants Under Controlled Phytotron Conditions- 19 The Alteration of Morphological and Physiological Seed Characters- 191 Seed Size- 192 Seed Shape- 193 Seed Color- 194 Physiological Seed Characters- 20 The Alteration of Seed Storage Substances- 201 Seed Proteins- 2011 The Characterization of Seed Proteins- 2012 Factors Influencing Protein Content and Composition- 20121 Environmental Factors- 20122 Endogenous Factors- 2013 Seed Protein Content of Different Varieties of the Same Species- 2014 Alteration of Seed Proteins Through Mutant Genes- 20141 Protein Mutants in Cereals- 20142 Protein Mutants in Legumes- 202 Seed Carbohydrates- 2021 Maize- 2022 Barley and Other Cereals- 2023 Peas- 203 Seed Lipids- 21 Other Plant Substances- 22 The Nutritional Value of Mutants- 221 Maize Mutants- 222 Barley Mutants- 223 Sorghum Genotypes- 224 Pea Mutants- 23 General Aspects of Mutation Breeding with Regard to the Improvement of Seed Storage Substances- References

Breeding for Immune Responsiveness and Disease Resistance

Abstract: Incorporation of disease resistance into breeding programmes would be enhanced by adequate methods. General disease resistance instead of resistance to specific diseases might be a useful concept.S...

Resistant tobacco plants from protoplast-derived calluses selected for their resistance to Pseudomonas and Alternaria toxins.

Abstract: Protoplast-derived calluses of tobacco (Nicotiana tabacum cv. ‘Samsun’) were selected for their resistance to toxins from Pseudomonas syringae pv. tabaci, which causes wildfire disease, and from Alternaria alternata pathotype tobacco, which causes brown spot. A number of plants were regenerated from each of the toxin-selected protoplast-derived calluses. A large percentage of the plants obtained from the second selection cycle calluses were resistant to infection by these pathogens. Resistance to wildfire disease, however, seems to be unrelated to resistance to brown spot disease. Variations in the morphological characteristics of the regenerated plants were found. Results of an assay of the R1 generation indicate that the resistance shown by R0 plants against both disease is heritable.

Genetic Background of Durable Resistance

Abstract: Durable disease resistance is defined as resistance that has remained effective while a cultivar possessing it has been widely cultivated in an environment favoring the disease. This characteristic of resistance is recognised retrospectively, as are all other characteristics of interactions between hosts and pathogens. Resistance that has been shown to be durable should be considered as a valuable resource for further breeding and for investigation of the causes of durability. Durable resistance is often achieved against diseases that show little or no specialisation into races pathogenic to particular cultivars. For such diseases, the control of resistance may be by single genes or by several genes, each of small effect, and the resistance may be either complete or incomplete (quantitative). For pathogens that possess pathogenicity specific for particular cultivars, failures of resistance can often be shown to be due to race-specificity of resistance genes and the evolution and spread of pathogen races with matching pathogenicity. These race-specific genes may have large (major) or small (minor) effects, giving either complete or quantitative resistance, and may operate at any stage of host development. Despite failures of resistance due to race-specificity in some cultivars, other cultivars remain resistant for relatively long periods, though this does not prove that their resistance will be permanent. For some diseases such durable resistance may be controlled by one or few genes of large effect. More usually a number of genes, not necessarily a large number, giving cumulative and often quantitative resistance, may appear to control durable resistance. Breeding programs should be modified to increase the chance of incorporating genetic components that appear to be related to durable resistance. However, breeding involves the selection of new genotypes, and the achievement of durable resistance in new cultivars, whatever the breeding method,. will only be proved by a widespread and prolonged test.

The Genes of Lettuce and Closely Related Species

Abstract: Nomenclature rules are proposed for naming and symbolizing genes for lettuce (Lactuca sativa L.). To date, 59 loci have been identified, including 6 influencing anthocyanin, 10 chlorophyll genes, 11 affecting leaf morphology, 4 genes influencing heading, 7 genes for flower and seed characteristics, 7 male sterile genes, 1 gene affecting sensitivity to chemicals, and 13 genes for disease resistance. Several cases of multiple alleles and gene linkage are known.

Evolution of resistance to scald, powdery mildew, and net blotch in barley composite cross II populations.

Abstract: Progenies of barley plants taken at random from generations F8, F13, F23, and F45 of Composite Cross II were tested for reaction to three barley pathogens, Helminthosporium teres, Erysiphe graminis, and Rhynchosporium secalis (four races) The frequency of families resistant to each of the three pathogens (excepting one race of R secalis) increased from early to later generations Many families carrying combinations of multiple resistance not observed among the parents were found in the later generations; one-half of the parents were susceptible to all three diseases but only 4% of the families in generation F45 were of this phenotype The frequency of multiply resistant families also increased sharply over generations Among the parents the greatest concentration of resistant reactions observed was triple resistance: 14% were triply resistant; none were quadruply resistant; nor were any resistant to all three pathogens In generation F43 36% of the families were triply resistant, 32% were quadruply resistant and 6% were resistant in five of the six disease reactions The value of later generations of Composite Cross II for breeding against pathogens thus appears to have been increased by recombination and natural selection Significant positive correlations were found for resistance to races 40, 61, and 74 of R secalis whereas correlations between resistance to R secalis, E graminis, and H teres were generally nonsignificant Use of these multiply resistant genotypes in breeding is thus unlikely to be hindered by negative associations between resistance to the three diseases

Incomplete resistance to coffee leaf rust (Hemileia vastatrix)

Abstract: Incomplete resistance to coffee leaf rust ( Hemileia vastatrix ) may be of value in obtaining durable resistance, which is of great importance for the perennial coffee crop. Methods were developed to assess incomplete resistance to coffee leaf rust by using illustrated scales ranging from 0 to 9 (Chapter 1). A laboratory screening method, which uses leaf disks, has been standardized. The method is satisfactory for the assessment of complete and incomplete resistance (Chapter 2). Resistance to coffee leaf rust appeared to be affected by light intensity and leaf age (Chapters 3 and 4). In general, coffee leaves were more resistant under low than under high light intensities. The effect of leaf age varied with the coffee genotype. In general, however, old leaves were more susceptible than adult or young leaves. From 1976 to 1980, seven new races of H. vastatrix were found in breeding plots in Campinas (Chapter 5). Four races overcome combinations of known resistance genes in Coffea arabica and three races overcome yet unidentified resistances from C. canephora . Three other rust genotypes were found with intermediate virulence to certain resistance genes. Possibilities for obtaining durable resistance based on major genes are discussed. In Chapters 6, 7 and 8 a characterization is given of incomplete resistance in C. arabica , C. canephora cv. 'Kouillou' and in the 'Icatu' population. Icatu derives from a cross between C. canephora and C. arabica . In C. arabica , the period between the onset of sporulation till leaf abscission (leaf retention period) appeared to be an important determinant of the disease level in the field. Significant variation for latency period and lesion density was observed, but results were fairly inconsistent. Disease level in the field was positively correlated with productivity. In 'Kouillou' large variation for incomplete resistance was found. Genotypes were detected with high resistance expressed by a low lesion density and a quite high reaction type. These genotypes may have value for obtaining durable resistance to coffee leaf rust. Incomplete resistance in Icatu was mainly expressed by heterogeneous reaction types. Components of resistance were related to reaction type. Incomplete resistance of varying degrees was race-specific. In the general discussion the relevance of the findings for coffee breeding and the links to resistance theories are pointed out.

Plant Regeneration from Protoplasts of Different Potato Genotypes

Abstract: The Dutch commercial tetraploid potato “Bintje” is by far the most important cultivar in The Netherlands because of several good properties and despite its susceptibility to many potato diseases. During the last 80 years it has been unsuccessfully attempted in many breeding programmes to transfer disease resistance to “Bintje”, while preserving its agronomically important qualities. Therefore, the cultivar Bintje in particular, and the potato in general were chosen for genetic manipulation aiming at the addition of one or a few selected characters to the genome of a specific genotype by means of chromosome transplantation and/or DNA transformation.

Novas linhagens do feijoeiro resistentes ao crestamento bacteriano comum

Abstract: With the objective of incorporation of genetic resistance for common bacterial blight in commercial cultivars of bean, cultivars Carioca, Rosinha, Moruna, Rio Tibagi and Iguacu, susceptible to the disease, were crossed with moderately resistant Great Northern Nebraska 1 sel. 27. Some of the crosses yielded segregates with levels of resistance superior to the source employed. Subsequently, these selections were intercrossed among themselves and with another blight resistant source P.I. 207-262 with the objective of accumulating and stabilizing higher levels of resistance, thus resulting in several lines with high levels of foliage resistance, in some cases accompanied by pod resistance and desirable agronomic characters.

Protoplast Fusion: Agricultural Applications of Somatic Hybrid Plants

Abstract: Interspecific sexual hybridization has, been important both in the evolution of cultivated crops (1) and for the development of new cultivated varieties. Several cultivated crops are allopolyploids that were originally derived through sexual hybridization, chromosome doubling, and subsequent diploidization (2). Hence, the historical value of interspecific hybridization is well documented. Interspecies hybrids have been extremely useful for transfer of genes into cultivated crops (3). Several plant varieties have been released that express traits derived from wild species. These include varieties of tomato, tobacco, barley, potato, wheat, etc. For example, resistance to several diseases has been transferred from Solanum demissum into cultivated potatoes (4). One variety of tobacco has resistance to three diseases derived from three different wild Nicotiana species (5). Disease resistance often may be controlled by a single gene and is relatively easy to transfer by hybridization. However, traits traditionally viewed as more complex have also been transferred into cultivated crops using sexual hybridization. For example, interspecies hybrids of oats (6) and tobacco (7) have been identified with improved yield. Novel variation, not expressed in either parent species, has also been observed in some interspecies sexual hybrids, such as cytoplasmically controlled male sterility in tobacco and improved fruit pigmentation in tomato.

Screening rice varieties for resistance to rice yellow mottle virus disease

Abstract: Rice yellow mottle virus (RYMV) is one of the major constraints to rice production in Kenya. The reactions of 30 varieties of rice to an isolate of RYMV were studied. The appearance and development of symptoms in the various varieties were scored on a 0–5 scale. The observed reactions ranged from highly susceptible to highly resistant. Thirty‐six per cent of the varieties showed a high level of resistance while 23.3% were highly susceptible. The intermediate reactions were 16.7% resistant, 6.6% susceptible and 16.7% moderately susceptible.

Breeding for Disease Resistance in Wheat; the Brazilian Experience

Abstract: A description is given of a program on horizontal resistance in wheat which was conducted at Passo Fundo, Brazil. The objective of the program was to determine the feasibility of accumulating useful levels of horizontal resistance to all locally important pests and diseases. The breeding and selection methods that were applied are described and results of trials to evaluate the program are presented. From these results, it is concluded that this new breeding approach is very suitable for the conditions at Passo Fundo, where many diseases have to be over-come and where stability of crop yield is the main interest.

Stability of host plant resistance to sorghum charcoal rot

Abstract: The 29 entries, including elite hybrids, cultivars, parents and resistant stocks, were evaluated for resistance to Macrophomina phaseolina in 4 environments covering rabi and kharif seasons. Artificial epiphytotic conditions were created by the tooth-pick method. Despite significant genotype × environment interactions varietal differences persisted. There was no host immunity but SPV-34, CSH-9 and 36B among the improved lines developed at the All-India Coordinated Sorghum Improvement Project and 6-39, 8-55 and SC 120-14 among the basic stocks were highly resistant. CSH-9, 36B and 6-39 were av. and 8-55 and SC 120-14 were above av. in stability of disease resistance. The seasonal change in host plant resistance of some of the cultivars appears due to their photoperiodic sensitivity

Changing Gene Frequencies in Populations

Abstract: Recurrent selection populations (RSP’s) have been effectively utilized for changing gene frequencies in populations of various crop plants and for pyramiding genes for resistance to specific plant diseases. The method has been particularly adapted for cross-pollinated crops and has been especially successful in developing disease resistance in maize and alfalfa. In regard to these two crops broad-based resistance to both fungus and bacterial diseases has been obtained. The method has also been used for developing resistance to various insect problems in maize and alfalfa. Among the self-pollinated crops barley is particularly suitable for improvement by RSP’s due to numerous genetic male sterility genes. In a program at Montana State University to improve the control of barley diseases for the semi-arid areas of the world, the method is being used with the major diseases of barley. The objective is to pyramid genes for resistance into suitable agronomic backgrounds for both 2 row and 6 row barley. Separate RSP’s are being developed with major and minor gene resistance. The base cultivars containing one male sterile entry were selected for their genetic diversity and general adaptability. Each cycle of recurrent selection in each year consisted of two generations: a selection for resistance and a recombination generation. In the latter, seeds were harvested only from male sterile plants to assure recombinations. The populations for resistance to specific diseases were grown each year in several locations and resistant-plants were selected for further cycling. At the same time new resistance sources, as identified, were added into the population. The RSP’s for scald and net blotch have shown a high percentage of resistant plants wherever grown and have been combined into one population. Significant progress has also been obtained on some of the RSP’s containing only minor effect additive genes for specific barley diseases.