12 Disease in populations- Epidemics - Copy

12 Disease in populations- Epidemics - Copy - PP 315 590J...

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PP 315 / 590J  Lecture 12 Disease in populations: Epidemics Review of the Gene-for-Gene Interaction Avirulence genes and resistance genes  - Genes that code for production of pathogen elicitors and  host receptors and result in a highly specific interaction. Results in an incompatible interaction.  One way to overcome the effects of resistance genes is to lose the avirulence gene or its product  that is recognized by the resistance- gene product. Quadratic Check  - Interaction of gene products of plant resistance genes and pathogen avirulence  genes Co-evolution of host and pathgen   Theory of stabilizing selection  theory that wild type isolates (strains of pathogen present prior to  introduction of resistance genes) are more fit than races that have mutated to overcome  resistance genes Key Terms Disease cycle  - steps in the development of a disease; sometimes is used as a synonym of life cycle  epidemic  - a widespread increase of disease in a population of plants  epidemiology  - study of epidemics (factors that affect plant disease development in a population of  plants)  endemic  - establishment of a pathogen and reoccurrence of a disease in an area each year  inoculation  - transfer of inoculum to an infection court  initial inoculum  - inoculum that causes first infections in an epidemic (often is the  overwintering  inoculum infection  - establishment of a food relationship between a parasite and host  incubation period  - period of time between infection and symptom development  latent period  - period of time between infection and reproduction by the pathogen (usually refers to the  time required for a certain percentage of lesions to sporulate, e. g. 50%) dispersal  (dissemination) - transfer of inoculum from its source Disease progress curve   - measure of disease intensity over time;  temporal  development of disease:
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Typical change in disease over time. the curve illustrated is  typical for disease increase in a polycyclic disease.  An epidemic denotes the dynamics of disease, that is, the change in the amount of disease with time. By  "the amount of disease" we mean either incidence (the number of plants or plant parts affected) or 
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This note was uploaded on 03/22/2008 for the course PP 315 taught by Professor Shew during the Spring '08 term at N.C. State.

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12 Disease in populations- Epidemics - Copy - PP 315 590J...

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