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Systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen.SAR is analogous to the innate immune system found in animals, and although there are many shared aspects between the two systems, it is thought to be a result of convergent evolution. [1]
Hypersensitive response (HR) is a mechanism used by plants to prevent the spread of infection by microbial pathogens.HR is characterized by the rapid death of cells in the local region surrounding an infection and it serves to restrict the growth and spread of pathogens to other parts of the plant.
Viburnum lesquereuxii leaf with insect damage; Dakota Sandstone (Cretaceous) of Ellsworth County, Kansas. Scale bar is 10 mm. Knowledge of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defense (such as spines) or herbivory-related damage; the observation of plant debris in fossilised animal feces; and the structure of herbivore mouthparts.
However, disease control is reasonably successful for most crops. Disease control is achieved by use of plants that have been bred for good resistance to many diseases, and by plant cultivation approaches such as crop rotation, pathogen-free seed, appropriate planting date and plant density, control of field moisture, and pesticide use.
Plant disease triangle. Epidemiology is the study of factors affecting the outbreak and spread of infectious diseases. [11] 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. [12]
Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves. [2]
Given the lack of knowledge of human infectious diseases at this time (and well into the 19th century) this was not an unusual conclusion, [15] but what is surprising is that while tulip mosaic disease has a far more impressive and documented history than any other plant virus, the realization that it was a communicable plant disease, let alone ...
Bacterial leaf scorch (commonly abbreviated BLS, also called bacterial leaf spot) is a disease state affecting many crops, caused mainly by the xylem-plugging bacterium Xylella fastidiosa. [1] It can be mistaken for ordinary leaf scorch caused by cultural practices such as over-fertilization.