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Unformatted text preview: PPPodcast: Week 6 Welcome to the PPPodcast for week 6. The Major Issue for this week is exotic vs. endemic pathogens. You may think that all plant pathogens are a little exotic, but really, just some of them are. The plant disease epidemics that we have studied so far have either been the result of introducing a new host plant into an area containing a virulent pathogen, as with fire blight of apples and pears, or introducing a new pathogen into an area with a susceptible host, as with downy mildew of grapes. In the first case, where a new host is introduced to an area, and becomes infected by a pathogen that already exists there, we say that the pathogen is endemic to that area, and the new host is exotic . In the second case, where a new pathogen is introduced, we say that the pathogen is exotic and the host is endemic to the area. Endemic means that that organism is native to an area, or has existed there for a long time. Exotic means that that organism is a relative new comer to that area. Most of the historically important plant disease epidemics have been the result of a virulent exotic pathogen being introduced into an area with a susceptible endemic host, or a susceptible exotic host being introduced into an area with a virulent endemic pathogen. In both of these cases the host and the pathogen evolved separately, thus the host did not have a chance to develop resistance to the pathogen, With little or no disease resistance, the host is easily infected by the pathogen, and a major epidemic can result. In some cases, such as we saw with coffee rust and South American leaf blight on rubber trees, the host and the pathogen originally evolved together, but the disease resistance was lost when humans selectively bred plants for other...
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This note was uploaded on 04/01/2012 for the course PLPA 200 taught by Professor Darcy during the Spring '08 term at University of Illinois, Urbana Champaign.
- Spring '08