Plant resistance to pathogens is one of the most important strategies of disease control. Knowledge of resistance mechanisms, and of how to exploit them, has made a significant contribution to agricultural productivity. However, the continuous evolution of new variants of pathogen, ana additional control problems posed by new crops and agricultural methods, creates a need for a corresponding increase in our understanding of resistance and ability to utilize it. The study of resistance mechanisms also has attractions from a purely academic point of view. First there is the breadth of the problem, which can be approached at the genetical, molecular, cellular, whole plant or population lev~ls. Often there is the possibility of productive exchange of ideas between different disciplines. Then there is the fact that despite recent advances, many of the mechanisms involved have still to be fully elucidated. Finally, and compared with workers in other areas of biology, the student of resistance is twice blessed in having as his subject the interaction of two or more organisms, with the intriguing problems of recognition, specificity and co-evolution which this raises.
1. Some Basic Concepts and Definitions in Resistance Studies.- 1.1. Why study resistance?.- 1.2. Some working definitions.- References.- 2. Host Range Control and Hon-Host Immunity to Viruses.- 2.1. Introduction.- 2.2. Host range control.- 2.3. Possible mechanisms in non-host immunity.- 2.4. Conclusion.- References.- 3. Non-Host Resistance to Fungi.- 3.1. Introduction: definitions and problems.- 3.2. Microscopy of non-host resistance to fungi.- 3.3. Mechanisms of non-host resistance: general considerations.- 3.4. Mechanisms of resistance dependent on an absence of factors in the potential host.- 3.5. Mechanisms of resistance dependent on the presence or production of factors by the potential host.- 3.6. Conclusions.- References.- 4. Genetics of Host Resistance to Viruses and of Virulence.- 4.1. Introduction.- 4.2. Genetics of resistance: many cases are under simple Mendelian control.- 4.3. Genetic determinants of virulence.- 4.4. Dominance, recessiveness and modifiers: theoretical considerations.- 4.5. Resistance and virulence: the gene-for-gene relationship.- References.- 5. The Genetic Bases of Relationships between Microbial Parasites and Their Hosts.- 5.1. Introduction: an overview of the genetics of hostmicrobial parasite associations.- 5.2. Types and stability of resistance.- 5.3. Detailed consideration of quantitatively inherited resistance and virulence.- 5.4. Detailed consideration of gene-for-gene relationships.- 5.5. Genetics of resistance and complementary virulence above the cultivar level.- 5.6. Conclusion.- References.- 6. Mechanisms Involved in Genetically Controlled Resistance and Virulence: Virus Diseases.- 6.1. Introduction.- 6.2. Disease avoidance.- 6.3. Resistance operating within the plant: virus localizing mechanisms.- 6.4. Resistance mechanisms permitting some spread of virus.- 6.5. Mechanisms of virulence.- References.- 7. Mechanisms by Which Genetically Controlled Resistance and Virulence Influence Host Colonization by Fungal and Bacterial Parasites.- 7.1. Introduction.- 7.2. Passive resistance mechanisms.- 7.3. Active resistance mechanisms.- 7.4. Induction of active resistance mechanisms.- 7.5. Receptors for elictors of active resistance mechanisms.- 7.6. Physiological models to explain gene-for-gene relationships.- 7.7. Conclusion: perspectives and challenges.- References.- 8. Resistance and Pathogenicity: Epidemiological and Ecological Mechanisms.- 8.1. Introduction.- 8.2. Resistance and pathogenicity.- 8.3. Population dynamics and the genetics of epidemics.- 8.4. Topics in resistance and pathogenicity.- 8.5. Topics in fungicide insensitivity.- 8.6. Ecological and evolutionary perspectives.- 8.7. Implications for agriculture.- References.- 9. Mechanisms of Induced Resistance to Virus Disease.- 9.1. Introduction.- 9.2. Resistance induced by localized infections and analogous effects.- 9.3. Resistance induced by systemic infection.- 9.4. Conclusion.- References.- 10. Induced Resistance to Fungal and Bacterial Diseases.- 10.1. Introduction.- 10.2. Inducers of local resistance.- 10.3. The protective response in induced local resistance.- 10.4. Inducers of systemic resistance.- 10.5. The protective response in induced systemic resistance.- References.- 11. Present and Future Prospects for Exploitation of Resistance in Crop Protection by Novel Means.- 11.1. Introduction.- 11.2. Mutagenesis and variation: techniques at the cell and tissue level.- 11.3. Recombinant DNA techniques.- 11.4. The future for chemical controls.- 11.5. Conclusion.- References.