Name _____________________





1.  (12 pts)  Define the following:








avirulence factor



obligate parasite










2.    (6 pts)  What is vertical plant resistance?  List an advantage and a problem with growing plants that contain this type of resistance.








3.    (8 pts)  List 2 enzymes and 2 plant growth factors that pathogens used to cause disease and the modes of action of the enzymes and symptoms associated with an excess of the plant growth factors.







4.    (8 pts)  Resistance is a potential problem when using chemical control of plant disease.  Explain what fungicide resistance is and give three ways that it can be avoided.









5.    (8 pts)  List four induced defense mechanisms (2 structural and 2 biochemical) that plants can use to prevent pathogen infection and explain how they work.









6.  (6 pts)  Define host specific toxin.  Give an example of this type of toxin and explain how it works to cause disease.









7.  (8 pts)  Discuss late blight 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 Pennsylvania or New Mexico?

(For 4 extra credit points, answer the questions for coffee rust.)










8. (8 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?  (Hint: Consider the gene for gene theory.)











9.  (14 pts)  A local vineyard asks you to come look at their Chardonnay and Pinot Noir grapes because the leaves are turning brown and dying around the edges.  A search on the internet alerts you that this might be a leafhopper-vectored bacterial disease, Pierce’s Disease, which is a major problem in California, and has been recently identified in New Mexico.  Confirmation of the disease in the vineyard would cause a major problem for the grower, including the inability to propagate from the vines.  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 grapes have Pierce’s Disease.  Contrast this with the same 2 types of control for a local wheat field infected with a leaf spotting fungus.

(For 2 extra credit points, explain the benefits and problems with using quarantine for control of the Pierce’s disease.)










11.  (14 pts)  Diagram a disease cycle  and explain the steps in the cycle that would be different for fungi and bacteria.