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Plant pathology, or phytopathology, is the science that deals with plant health. Keeping plants healthy requires an understanding of the organisms and agents that cause disease, as well as an understanding of how plants grow and are affected by disease.
The interaction between plant pathogenic fungi and their host plants is extremely complex and should be viewed from the perspectives of both the fungus and the plant. The biology of pathogenic fungus that needs to be understood includes factors such as how the fungus reproduces and if alternate hosts or special over wintering conditions are necessary. Other factors include the means by which the fungus reaches the host, such as wind, insect vectors like beetles (they carry the conidia of Ophiostoma ulmi which causes Dutch elm disease), or inappropriate storage conditions where the fungus can remain until a new crop is stored. These are examples of potential points to stop the spread of pathogenic fungi.
From the perspective of the host plant, its physiology and metabolism must be understood. Mineral nutrient requirements and ion uptake, water conditions like water related stress, internal transport processes for the manufacture and distribution of nutrients, the role of plant hormones, inhibitors, and phytochromes in the regulation of plant growth and development, must be understood. The effects of the physical environment where the plant is growing and how this impacts the plant's growth, development, and the correlation of biochemical changes that are occurring within the plant are likewise important. Some fungus-plant interactions are exceptionally specific. For example, the wheat rust fungus Puccinia graminis is classified into different races based upon how the genetic systems of the rust interact with the genetics of the host plant cultivars.
Disease management is addressed once the diagnosis of a plant disease has been made and the causal agent is identified. An analysis of the host and its symptoms, the identification of the fungal pathogen present, an understanding of how it caused the disease, and any environmental factors that may have contributed to the development of the disease and spread of the fungus are determined. Once this information is known, management approaches can be considered, which include:
- Preventing additional plant disease by planting genetically resistant plants
- Using antifungal agents like propiconazole (brand name Tilt)
- Modifying the pre-storage processes or the storage conditions
It is interesting to note that azole antifungal agents are used in human mycology, veterinary mycology, and plant pathology. They are used because the same groups of fungi cause disease in humans, animals and plants. The implications of this for development of resistance are unknown.
An exciting area of plant pathology is understanding at the molecular level how plant diseases develop. This includes plant physiology, fungal physiology, biochemistry, and the genetics of the host-pathogen relationship. Areas of special interest are the specificity of the fungus-plant interaction, how the fungus recognizes the plant host, how the fungus gains entrance into the plant, the role of fungal toxins during disease development, how plant metabolism is modified, plant resistance mechanisms, and gene expression during host-pathogen interactions.
Plant Pathology Internet Guide Book
American Phytopathological Society
National Agriculture Library's AGRICOLA database
Phytopathogenic Fungi from South Africa