Ecology of Root Pathogens

List of contributors

Foreword

Chapter 1. Fungi: Pathogen or Host Dominance in Disease


1. Introduction


1.1. Root disease symptoms


1.2. Taxonomic groups


1.3. Host and type of parasitism


1.4. Ecological relations


1.5. Pathogen—host dominance system


2. Pathogen-dominant diseases; transitory relationship


2.1. Macerative pathogens


2.2. Toxicogenic pathogens


3. Host-dominant diseases; prolonged relationship


3.1. Tissue-nonspecific pathogens


3.2. Tissue-specific pathogens


4. Control principles based on pathogen- and host-dominant diseases


5. Summary


6. References

Chapter 2. Behavior of Plant Pathogenic Bacteria in Rhizosphere and Non-rhizosphere Soils


1. Introduction


2. Agrobacterium


2.1. Selective media for isolating Agrobacterium spp


2.2. Survival of A. rhizogenes


2.3. Survival of A. tumefaciens


2.4. infection


2.5. Control


3. Corynebacterium


3.1. Identification


3.2. Isolation


3.3. Survival in soil


3.4. Infection


4. Xanthomonas


4.1. Identification


4.2. Isolation


4.3. Survival of xanthomonads in soil


4.4. Survival in plant materials


4.5. Survival on roots of host plants


4.6. Survival on roots of non-host plants


5. Pseudomonas


5.1. Isolations


5.2. Identification


5.3. Survival in relation to seeds and propagative material


5.4. Survival in relation to plant residues


5.5. Survival in relation to roots


5.6. Root infections


6. Erwinia


6.1. Isolation


6.2. Survival in soil


6.3. Infection


7. Streptomyces


7.1. Infection symptoms


7.2. Isolation, identification and pathogenicity tests


7.3. Influence of environmental factors


7.4. Occurrence in virgin soil


7.5. Influence of cropping practices on disease severity and the development of scab suppressive soil


7.6. Influence of green manure on potato scab and the role of antagonists


7.7. Control


8. Discussion


9. References

Chapter 3. Some Interactions of Plant Parasitic Nematodes and Higher Plants


1. Introduction


2. The effects of plant-produced stimuli on plant parasitic nematodes


2.1. Hatching


2.2. Molting


2.3. Attraction


2.4. Initiation of the feeding process


2.5. Initiation of partial or full penetration


2.6. Emergence from roots


3. The effect of the host plant on the size and composition of the associated population of plant parasitic nematodes


3.1. Techniques


3.2. Moderate stress


3.3. Sex reversal and similar phenomena


3.4. Mineral nutrition of the host


4. Some ways in which nematodes affect higher plants


4.1. Introduction


4.2. Stimulation of growth


4.3. Alterations in chemical composition


4.4. Criticisms


4.5. Mechanisms of accumulation or alteration


5. References

Chapter 4. Viruses


1. Introduction


2. Morphology, classification, nomenclature, multiplication and translocation of viruses infecting plants


2.1. Morphology of viruses infecting plants


2.2. Classification and nomenclature of viruses


2.3. Infection of plants


2.4. Multiplication and translocation of viruses infecting plants


3. Symptoms of infection in roots


3.1. Location of virus in root tissue


3.2. Yield loss due to root infection


4. Release and survival of viruses in soil


4.1. Crop debris


4.2. Release of viruses into soil by living roots and the possibility of active uptake by roots


5. "Soil-borne viruses" and their biological vectors


5.1. Nematodes


5.2. Fungi


6. Interactions between virus-infected roots and other soil microorganisms


7. Control


7.1. Reducing and eliminating sources of viral inoculum


7.2. Limiting spread by vectors


7.3. Minimizing losses due to virus diseases


8. Discussion


9. References


10. Addendum

Chapter 5. Fundamentals of Biological Control


1. Introduction


2. The pathosystem concept


2.1. Energy flux


2.2. Quality of nutrients


2.3. Abiotic environmental factors


3. Behavior of the soil microflora in the soil


3.1. Behavior of saprophytic microflora


3.2. Behavior of pathogens in the soil


4. Reservoirs for infection


4.1. Plant residues


4.2. Conservation structures


5. Processes of pathogen decline


5.1. Fungistasis


5.2. The mechanisms of fungistasis


5.3. Antibiosis


5.4. Lysis


5.5. Hyperparasitism


5.6. Predation


6. Integrated effects on the decline of the pathogen


6.1. Consequences of fungistasis


6.2. Competition for infection sites


7. Natural biological control: suppressive soils


7.1. Biological origin of suppressiveness


7.2. The influence of the soil


7.3. Effect of crops


7.4. Mechanism of suppressivity


8. Artificially induced biological control


8.1. Modification of the biological balance in the soil


8.2. Biological control by introduced antagonists


9. Conclusion


10. References

Subject index