Plant pathology or phytopathology is the scientific study of caused by (infectious organisms) and environmental conditions (physiological factors).
Plant pathogenicity
Plant pathogens, organisms that cause infectious
, include
fungus,
oomycetes,
bacterium,
plant virus,
,
virus-like organisms,
phytoplasmas,
protozoa,
and
.
In most plant , virulence depends on and enzymes that degrade the cell wall. The vast majority of these act on (for example, pectinesterase, pectate lyase, and ). For microbes, the cell wall are both a food source and a barrier to be overcome. Many pathogens grow opportunistically when the host breaks down its own cell walls, most often during fruit ripening.
To colonize a plant, pathogens have specific pathogenicity factors, of five main types: uses of cell wall–degrading enzymes, toxins, effector proteins, , and exopolysaccharides.
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Cell wall-degrading enzymes: These are used to break down the plant cell wall in order to release the nutrients inside and include esterases, glycosyl hydrolases, lyases and oxidoreductases.
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Toxins: These can be non-host-specific, which damage all plants, or host-specific, which cause damage only on a host plant.
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Effector proteins: These can be secreted by pathogens such as bacteria, fungi, and oomycetes
-
are chemicals used by plants for signaling; pathogens can produce these to modify plant growth to their own advantage.
-
Exopolysaccharides are mostly small chains of sugars that help pathogens to adhere to a plant's surface, enabling them to begin the process of infection.
Physiological plant disorders
Some abiotic disorders can be confused with pathogen-induced disorders. Abiotic causes include natural processes such as
drought,
frost,
snow and
hail;
and poor drainage; nutrient deficiency; deposition of mineral salts such as
sodium chloride and
gypsum;
and breakage by storms; and
.
Epidemiology
Epidemiology is the study of factors affecting the outbreak and spread of infectious diseases.
A disease triangle describes the basic factors required for plant diseases. These are the host plant, the pathogen, and the environment. Any one of these can be modified to control a disease.
Disease resistance
Plant disease resistance is the ability of a plant to prevent and terminate infections from plant pathogens. Structures that help plants prevent pathogens from entering are the cuticular layer, cell walls, and stomata guard cells. Once pathogens have overcome these barriers, plant receptors initiate signaling pathways to create molecules to compete against the foreign molecules. These pathways are influenced and triggered by genes within the host plant and can be manipulated by genetic breeding to create resistant varieties.
Management
Detection
Ancient methods of leaf examination and breaking open plant material by hand are now augmented by newer technologies. These include molecular pathology assays such as polymerase chain reaction (PCR),
RT-PCR and loop-mediated isothermal amplification (LAMP).
Although PCR can detect multiple molecular targets in a single solution there are limits.
Bertolini et al. 2001, Ito et al. 2002, and Ragozzino et al. 2004 developed PCR methods for multiplexing six or seven plant pathogen molecular products and Persson et al. 2005 for multiplexing four with RT-PCR.
More extensive molecular diagnosis requires
.
The primary detection method used worldwide is enzyme linked immunosorbent assay.
Biological
Crop rotation is a traditional and sometimes effective means of preventing a parasitic population from becoming well-established. For example, protection against infection by
Agrobacterium tumefaciens, which causes gall diseases in many plants, by dipping cuttings in suspensions of
Agrobacterium radiobacter before inserting them in the ground to take root.
History
Plant pathology has developed from antiquity, starting with
Theophrastus in the ancient era, but scientific study began in the
Early Modern period with the invention of the
microscope, and developed in the 19th century.
Notable People in Plant Pathology
-
George Washington Carver
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Anton de Bary
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Erwin Frink Smith
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Agnes Arber
-
Harold Henry Flor
See also
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American Phytopathological Society
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Australasian Plant Pathology Society
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British Society for Plant Pathology
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Forest pathology
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Gene-for-gene relationship
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Global Plant Clinic
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Glossary of phytopathology
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Horsfall-Barratt scale
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List of phytopathology journals
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Microbial inoculant
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Phytopharmacology
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Plant disease forecasting
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Stunting
External links
