EXAM 3- 50 pts.
1. What are 2 sources of genetic variation that exist in both fungi and plants?
Do fungi or plants have the advantage in terms of genetic variation? Explain your answer. (4 pts.)
2. What are 2 ways to prolong the usefulness of a resistance gene in an annual crop? (2 pts.)
3. What are 3 limitations (biological or agricultural) to the use of crop rotation?
Explain why crop rotation works so well to reduce the populations of many soilborne pathogens. (5 pts.)
4. Briefly, explain how government regulations minimize pesticide residues at the time of harvest. (3 pts.)
5. What are 2 ways that heat can be used to reduce pathogen inoculum? (2 pts.)
6. What is an advantage and a disadvantage to the use of meristem culture for the production of propagative plant material (2 pts.)
7. Penetrant/systemic fungicides are more subject to resistance than contact/protectant fungicides. What are 2 advantages to penetrants that make them attractive for disease management? (2 pts.)
8. The following statements are false. Write a correct statement. (10 pts.)
When genetically-resistant plants develop disease, the resistance gene has “broken down” and no longer functions.
Because of the intense movement of plants and people around the world, quarantines are no longer needed.
If a compound has a high LD50, it is relatively nontoxic and people should not be concerned about their exposure to it.
All fungicides are equally likely to result in the development of resistant fungal strains with intensive use.
All pesticides are equally likely to be groundwater contaminants.
ESSAY QUESTIONS. Choose only 2. 10 pts. each.
The genetic interaction between hosts and parasites has been described as a “chess game.” Explain this analogy. Then, explain how cultural practices and environmental conditions can modify the outcome of such an interaction.
You have a plant with genetic resistance conferred by a single gene for tomato yucky spot, a new and devastating polycyclic fungal disease. You also have a contact/protectant fungicide that is effective against the fungus that causes yucky spot. Describe a management plan that will provide good stewardship of the resistance gene and the afailable fugnicides and also provide reliable tomato crops in the coming years.
Integrated pest management (IPM) is the mainstay of modern agriculture. Explain how an understanding of monocyclic and polycyclic pathogens and the relative effect of reducing initial inoculum and epidemic rate can be used to create effective integrated disease management programs. Use graphs to illustrate your answer.
Extra credit:
Who provided the experimental evidence that led to the gene-for-gene theory?
Name any of the 3 diseases that led to the first US quarantine legislation in 1912.
