EPWS 310  EXAM 1, Fall 2001


1.  (8 pts) Define tolerance as a type of resistance.  What are the benefits and problems with using this?











2.  (10 pts) Relate the late blight epidemic to the plant disease triangle. What were the important factors contributing to the epidemic?   If potatoes were grown in Las Cruces, would you expect the disease to be a problem?  Explain your answer.











3.  (8 pts) Define the following:


      abiotic disease






      host range






4.  (10 pts) What is an incompatible interaction?  List the major phenomena that this induces in the plant.






5.  (6 pts) List three structural defense mechanisms that plants can use to block fungal invasion.










6.  (12 pts)  What are the ways in which a disease cycle would differ between a fungus and a virus?













7.  (12 pts) A farmer has asked you to look at her potentially diseased field of seedless watermelon which she says are wilting.  What will you look for initially in diagnosing the problem?  What steps will you need to go through to prove what is causing the problem?
















8.  (12 pts) Compare the use of plant resistance and cultural control if you find the watermelon to be infected with a fungus.  Contrast this with the same control means for virus-infected walnut trees.















9.  (14 pts) Describe the enzymatic process a fungus would use to infect a plant and gain nutrition from it.  Which types of enzymes would it use and what is the activity of those enzymes?















10.  (8 pts)   Explain how an organism carrying an avirulence gene can still cause disease.










(5 pts extra credit)  List a nonhost specific toxin, the pathogen that produces it and its mode of action.