2 Germ Theory and Its Evolution - Copy

2 Germ Theory and Its Evolution - Copy - PP 315 / 590J...

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PP 315 / 590J  Lecture 2 Germ Theory and Its Evolution Objectives Understand the factors that are necessary for disease to occur and how that relates to the Disease  Triangle and the Disease Pyramid. Learn of the fathers of Plant Pathology and how their contributions  lead to the development of the field. What factors are necessary for disease to occur?  Pathogen  - an entity (microorganism) that can cause a disease Parasite  - an organism that lives on or in another living organism (host) and obtains its food from the  latter most pathogens are parasites but not all parasites are pathogens  Host  - susceptible to pathogen that is present - not all pathogens can attack all plants -  Host range -  plants that a given pathogen can use as a source of nutrients and, in the case of pathogens,  cause disease Disease  - any condition that is detrimental to the growth or reproduction of a plant (interference with  normal physiology), is caused by continuous irritation by a primary causal agent (biotic and sometimes  abiotic) and results in production of symptoms  1)  Detrimental effects  resulting in symptoms  2)  Primary causal agent  – generally refers to biotic agent (organism), but may be abiotic; this is the topic  of next lecture. If biotic, it also implies contagious nature of disease. Infectious disease can grow and 
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2 Germ Theory and Its Evolution - Copy - PP 315 / 590J...

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