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Most bacteria associated with plants are saprotrophic and do no harm to the plant itself. However, a small number, around 100 known species, cause disease, especially in subtropical and tropical regions of the world. [15] [page needed] Most plant pathogenic bacteria are bacilli. Erwinia uses cell wall–degrading enzymes to cause soft rot.
Plant pathogens, organisms that cause infectious plant diseases, include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. [2] In most plant pathosystems, virulence depends on hydrolases and enzymes that degrade the cell wall.
Bacterial soft rots are caused by several types of bacteria, but most commonly by species of gram-negative bacteria, Erwinia, Pectobacterium, and Pseudomonas. It is a destructive disease of fruits, vegetables, and ornamentals found worldwide, and affects genera from nearly all the plant families.
Before the molecular era, the diagnosis of diseases caused by phytoplasma was difficult because the organisms could not be cultured. Thus, classical diagnostic techniques, including symptom observation, were used. Ultrathin sections of phloem tissue from plants with suspected phytoplasma-infections were also studied. [3]
The nitrogen fixing bacteria, and fungi Bradyrhizobium japonicum, infects the roots and establishes a symbiosis. This high magnification image shows part of a cell with single bacteroid (bacterium-like cell or modified bacterial cell) within their symbiosomes. In this image, you can also see endoplasmic reticulum, Golgi apparatus and cell wall.
P. syringae can cause water to freeze at temperatures as high as −1.8 °C (28.8 °F), [26] but strains causing ice nucleation at lower temperatures (down to −8 °C (18 °F)) are more common. [27] The freezing causes injuries in the epithelia and makes the nutrients in the underlying plant tissues available to the bacteria. [citation needed]
All known viroids are inhabitants of angiosperms (flowering plants), [3] and most cause diseases, whose respective economic importance to humans varies widely. [4] A recent metatranscriptomics study suggests that the host diversity of viroids and viroid-like elements is broader than previously thought and that it would not be limited to plants ...
Viruses in wild plants have not been well-studied, but the interactions between wild plants and their viruses often do not appear to cause disease in the host plants. [1] To transmit from one plant to another and from one plant cell to another, plant viruses must use strategies that are usually different from animal viruses. Most plants do not ...