Name _____________________





1.  (16 pts)  Define the following:


hypersensitive response



horizontal resistance









obligate parasite



            penetration peg






secondary inoculum



2.  (12 pts)  List 4 enzymes that pathogens use to cause disease and the modes of action of the enzymes and indicate for each whether they are used early, middle, or late in the infection process.








3. (4 pts)  Resistance is a potential problem when using chemical control of plant diseases.  Explain what fungicide resistance is and give three ways that it can be controlled.

4.  (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?  Give the specifics of each side of the triangle.

Would the disease be more common if the crop were grown in (___) Georgia or in

 (___) Minnesota?

(For 4 extra credit points, answer the entire question for another of the diseases listed.)













5.  10 pts)  Does a compatible interaction end in disease?  What combinations of resistance and virulence can the host and pathogen have that will result in a compatible interaction?  What combination gives an incompatible interaction. (Hint: Consider the gene for gene theory)











6. (6 pts)  Explain the difference between non-host specific toxins and host specific toxins.  Give an example of each type of toxin and explain how it works to cause disease.










7. ((8 pts)  List four defense mechanisms, two structural and two biochemical, that plants can use to prevent pathogen infection and explain how each works.










8.  (8 pts) Diagram a disease cycle and explain which steps in the cycle would differ between fungi and bacteria.











9.  (12 pts)  (12 pts)  The NMSU golf course manager has asked you to come look at his putting greens because he has noticed dead areas on them.  He has heard about a new fungal disease of turf, rapid blight, caused by Labyrinthula terrestris. Confirmation of the disease on the putting greens will cause a huge problem, since fungicides donŐt adequately control the fungus.  Alternatively, the turf may be infected with Fusarium (a commonly collected fungus). When you go to the golf course for the first time what will you look for in diagnosing the problem?   Since you need to be completely sure of your diagnosis, what steps will you need to go through to prove what is causing the problem?















10.  (10 pts)  Compare the use of plant resistance and cultural control for the next season if the turf has Fusarium infection or rapid blight.  Answer the question again (comparing the use of plant resistance and cultural control) for a local field of wheat infected with Fusarium.











11.  (6 pts)  What is vertical resistance?  List an advantage and a problem with growing plants with only this type of resistance.