Name _____________________





1.  (10 pts)  Define the following:





pathogenicity factor









primary inoculum




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








3.    (8 pts)  List 2 plant growth factors that pathogens used to cause disease and the symptoms associated with an increase in those factors.








4.    (8 pts)  List four defense mechanisms (2 structural and 2 biochemical) mechanisms that plants can use to prevent pathogen infection.




5. (12 pts)  Explain the difference between host-specific and non-host specific toxins.  Give an example of each toxin type and how it works to cause disease.









6. (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?  Would the disease be more common if the crop were grown in Florida or Minnesota?

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












7.  (14 pts)  The local nursery asks you to come look at their grape plants because the leaves are turning brown and dying around the edges.  A search on the internet alerts you that this might be similar to an leafhopper-vectored bacterial disease, Pierces Disease, which has never been found in New Mexico.  Confirmation of the disease in the state would prevent the state from selling any grapevines.  When you go to the nursery 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?












8.  (8 pts)  Compare the use of plant resistance and cultural control for the next season if the grapes have Pierces Disease.  Contrast this with the same 2 types of control for the neighboring field of wheat infected with a soil-borne fungus.

(For 2 extra credit points, explain the benefits and problems with using quarantine for control of Pierces Disease.)









9.  (14 pts)  Diagram a disease cycle  and explain the steps in the cycle that would be different for fungi and nematodes.











10. (12 pts)  Explain how recognition (or the lack of recognition) of a pathogen by a host plant can lead to influence the plant resistance response. (Hint: Consider the gene for gene theory.)