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Population Genetics of Plant Pathogens
Knowledge Tests


Knowledge Test on Population Biology and Coevolution

  1. What is a population and what is population genetics?
  2. Why is population biology important for plant pathologists?
  3. What is coevolution?
  4. Why don’t agroecosystems exhibit coevolution?
  5. What are the five evolutionary factors most commonly considered by population geneticists?

Knowledge Test on Mutation

  1. Why is mutation important in the population genetics of organisms?
  2. Does mutation acting alone cause changes in allele frequencies?
  3. Why do large populations have more alleles than small populations?
  4. Why do plant breeders seek the center of origin to find resistant germplasm?
  5. What is a resistance gene pyramid?
  6. How many resistance genes would a plant breeder need if a pathogen has a very large population size (>1012 individuals per field)?
  7. How many resistance genes would a plant breeder need if a pathogen has a relatively small population size (<105 individuals per field)?

Knowledge Test on Genetic Drift

  1. What is genetic drift? Name three processes that cause genetic drift.
  2. What is a genetic bottleneck and what is a founder effect?
  3. How does genetic drift affect the distribution of genetic diversity among populations?
  4. Why is genetic drift important in agroecosystems?
  5. How can you calculate the predicted effect of genetic drift?

Knowledge Test on Gene/Genotype Flow

  1. What is gene flow and how does it differ from genetic drift?
  2. How does gene flow differ from genotype flow?
  3. Why is gene flow important in agricultural ecosystems?
  4. How does Nem relate genetic drift to gene flow?
  5. What is a metapopulation and how is it relevant to agroecosystems?

Knowledge Test on Reproductive/Mating System

  1. What is the difference between genetic assortative and genetic disassortative mating?
  2. What is the difference between gene and genotype diversity? How do you measure them?
  3. Is gene diversity affected by mating system? How?
  4. Is genotype diversity affected by mating system? How?
  5. Why is mating/reproduction system relevant to plant pathology?

Knowledge Test on Natural Selection

  1. What is the difference between the balance model and the neutral mutation model for explaining genetic variation in populations?
  2. What is the difference between directional selection and stabilizing selection?
  3. Define pathogen fitness. Name as many fitness parameters as you can imagine for a pathogen in an agricultural ecosystem.
  4. What is Fisher’s Fundamental Theorem of Natural Selection?
  5. What happens to the frequency of pathogen virulence alleles if there is no fitness cost associated with having unneeded virulence?
  6. Have plant pathologists found evidence of selection against unneeded virulence genes?

Knowledge Test on Interactions/Genetic Structure

  1. What is a “boom-and-bust cycle”? How do they develop and why do they persist?
  2. Why did the Puccinia graminis f. sp. tritici population stabilize in North America?
  3. What is genetic structure?
  4. Does gene flow make populations more genetically similar or more different?
  5. How does sexual reproduction affect the genetic structure of populations?
  6. Describe the evolutionary forces that affected Phytophthora infestans populations in Europe before 1960. Now describe the evolutionary forces that affect P. infestans populations in Europe in 2000. Which population poses a greater threat to potato production and why is the threat greater?