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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 ]
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]
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]
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.
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
Infections begin when a spore lands on the plant surface, germinates, and invades its host. Infection is limited to plant parts such as leaves, petioles, tender shoots, stem, fruits, etc. [ 3 ] Plants with severe rust infection may appear stunted, chlorotic (yellowed), or may display signs of infection such as rust fruiting bodies.
Leaf spots are visible symptoms of virus infections on plants, and are referred to as systemic symptoms. [7] In systematic virus infections leaf spots caused by viruses show a loss of green colour in leaves, due to chlorosis which is a repression of chlorophyll development. [ 1 ]
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.