EPWS 310  EXAM 1, Fall 2002


1.  (6 pts) Define nonhost resistance.  How effective is this type of resistance?







2.  (10 pts) Relate the late blight epidemic to the plant disease triangle. What were the important factors contributing to the epidemic?   Would potatoes grown in Arizona or Maine be more likely to get the late blight disease, and why?











3.  (8 pts) Define the following:





      nonhost-specific toxin









4.  (12 pts) What is an compatible interaction?  What states of resistance and virulence can the host and pathogen have that will result in a compatible interaction?  (Hint:  Consider the gene for gene theory.)








5.  (6 pts) List three biochemical defense mechanisms that plants can use to prevent pathogen infection.









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













7.  (14 pts) A farmer has asked you to look at her potentially diseased field of alfalfa which she says are stunted and 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 for next season if you find the alfalfa to be infected with a soil-borne bacteria.  Contrast this with the same control means for fungus-infected strawberries.















9.  (12 pts)  Are all pathogens highly virulent?  Explain the terms “pathogenicity” and “virulence,” differentiating between them.  What factors contribute to pathogenicity or virulence?















10.  (8 pts)   What is fungicide phytotoxicity and what are 3 ways it can be avoided?










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