EPWS 310 PLANT PATHOLOGY EXAM 1, Fall 2005
1. (10 pts) Define the following:
2. (7 pts) Using vertical plant resistance is much more popular than horizontal resistance with agronomists and most growers. Explain two ways in which the two types of resistance differ and situations where each resistance type would likely work better than the other. Also list one reason why horizontal resistance is so unpopular.
3. (8 pts) List 4 enzymes that pathogens used to cause disease and their modes of action.
4. (4 pts) Phytotoxicity is a potential problem when using chemical control of plant disease. Give two factors that influence whether a chemical will be phytotoxic.
5. (9 pts) List three biochemical defense mechanisms that plants can use to prevent pathogen infection, explain how they work, and state whether they are preformed or induced.
6. (a). (6 pts) Define non-host specific toxin. Give an example of this type of toxin and explain how it works to cause disease.
(b) (4 pts) Give an example of a plant growth regulator and explain how it works to cause disease.
7. (8 pts) Using one of the 3 historical diseases discussed in class ( coffee rust, late blight, or southern corn leaf blight) discuss the disease in relation to the disease triangle. What were the important factors contributing to the epidemic? Would the disease be more common if the crop were grown in New York or Mississippii?
(For 4 extra credit points, answer the question for another of the diseases listed.)
8. (8 pts) Explain how recognition (or the lack of recognition) of a pathogen by a host plant can lead to an incompatible or compatible interaction. (Hint: Consider the gene for gene theory.)
9. (14 pts) A local cotton producer asks you to come look at their field because the plants are wilting and leaves are turning yellow and dying around the edges. A search on the internet alerts you that this might be similar to a new fungal disease caused by Fusarium oxysporum f. sp. vasinfectum Race 4, recently reported from California, which has never been found in New Mexico. Confirmation of the disease in the state would prevent the grower from selling his cotton seed. When you go to the field for the first time what will you look for in diagnosing the problem? What steps will you need to go through to prove what is causing the problem?
10. (8 pts) Compare the use of plant resistance and cultural control for the next season if the cotton has the soil-borne fungus. Contrast this with the same 2 types of control for a local golf course with a fungal leaf spot infecting the hybrid Bermuda on its putting greens.
(For 2 extra credit points, explain the benefits and problems with using quarantine for control of the cotton disease.)
11. (14 pts) Diagram a disease cycle and explain the steps in the cycle that would be different for fungi and viruses.