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Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). [1] Organisms that cause infectious disease include fungi , oomycetes , bacteria , viruses , viroids , virus -like organisms, phytoplasmas , protozoa , nematodes and parasitic plants . [ 2 ]
Plants can show many signs or physical evidence of fungal, viral or bacterial infections. This can range from rusts or molds to not showing anything at all when a pathogen invades the plant (occurs in some viral diseases in plants). [9] Symptoms which are visible effects of diseases on the plant consist of changes in color, shape or function. [9]
In most plant pathosystems, virulence depends on hydrolases and enzymes that degrade the cell wall. The vast majority of these act on pectins (for example, pectinesterase, pectate lyase, and pectinases). For microbes, the cell wall polysaccharides are both a food source and a barrier to be overcome.
Bacterial diseases; Bacterial leaf blight and stalk rot: Pseudomonas avenae subsp. avenae. Bacterial leaf spot: Xanthomonas campestris pv.holcicola. Bacterial stalk rot: Enterobacter dissolvens = Erwinia dissolvens
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. [1] Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are: [citation needed]
Plant disease resistance is crucial to the reliable production of food, and it provides significant reductions in agricultural use of land, water, fuel, and other inputs. Plants in both natural and cultivated populations carry inherent disease resistance, but this has not always protected them.
Injury in plants is damage caused by other organisms or by the non-living (abiotic) environment to plants. Animals that commonly cause injury to plants include insects, mites, nematodes, and herbivorous mammals; damage may also be caused by plant pathogens including fungi, bacteria, and viruses.
In agriculture, disease management is the practice of minimizing disease in crops to increase quantity or quality of harvest yield.. Organisms that cause infectious disease in crops include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants.