Name _________________


EPWS 310  EXAM 1, Fall 2003


1.  (4 pts) Define disease escape.  How does it sometimes confuse resistance breeding efforts?







2.  (8 pts) Relate the southern corn leaf blight epidemic to the plant disease triangle. What were the important factors contributing to the epidemic?   Would corn grown in Las Cruces or Georgia be more likely to get the disease, and why?











3.  (8 pts) Define the following:





      host-specific toxin



      virulence factor



      obligate parasite



4.  (12 pts) Which side plant or pathogen is the winner in an incompatible interaction?  What goes on in a plant cell and with a pathogen in an incompatible interaction? What states of resistance and virulence can the host and pathogen have that will result in a incompatible interaction?  (Hint:  Consider the gene for gene theory.)








5.  (8 pts) List four defense (2 preformed and 2 induced) mechanisms that plants can use to prevent pathogen infection.









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













7.  (14 pts) A farmer has asked you to look at her onion field which she thinks may be diseased.  What will you look for initially in diagnosing the problem?  What steps will you need to go through to prove that a fungus is causing the problem?  How would those steps change if you thought the disease was caused by a virus?
















8.  (12 pts) Compare the use of plant resistance and cultural control for next season if you find the onions to be infected with a soil-borne fungus.  Contrast this with the same control means for virus-infected corn.















9.  (12 pts)  Compare the ways that fungi and bacteria penetrate into a plant and cause disease.  How do they get in?  How is that different between fungi and bacteria?  What enzymes do they use, when do they need them, and what is the activity of the enzymes.














10.  (6 pts)   What is fungicide resistance and what are 2 ways it can be avoided?







11.  (4 pts)   What is vertical resistance and what is a benefit and a problem with growing plants with this type of resistance?





(5 pts extra credit)  List 2 plant growth factors that pathogens use to cause disease and the symptoms associated with an increase in those factors