Burrill did not, however, isolate this bacterium on an artificial medium in pure culture (Burrill, 1882). He named the bacterium causing the disease Micrococcus amylovorus. Two years later, Burrill proved that the introduction of this exudate into healthy apple and pear trees caused the typical symptoms of fire blight. It was not until 1878 that Thomas Burrill, working at the University of Illinois, found that live bacteria were present in the mucous exudate taken from the browned tissues of a pear tree when observed under a microscope (Burrill 1878). At that time, bacteria were not yet known as plant pathogens, and the symptoms of blight were attributed to other factors, such as insects, lightning, ‘bad sap’, frost damage or even God’s punishment (van der Zwet et al. It was discovered in the late 18th century in the United States, near New York, where mass dieback of apple, pear and quince trees was observed, especially of cultivars brought by immigrants from Europe. This work is a review of the studies and achievements in this field from its beginnings focusing on the Gram-negative bacteria and bacteriophages as a biocontrol agents.įire blight, caused by the bacterium Erwinia amylovora, was the first bacterial disease of plants to be detected. Commercial products whose active ingredients are mainly bacteria have already been developed. Currently, it is also carried out in other countries, especially where fire blight causes economic losses. The first research on biological control agents was conducted in the USA about 100 years ago. Limitations related to their use have resulted in an increased interest in alternative methods, including the method of biological protection using various microorganisms. However, the protection of plants against bacteriosis is generally difficult due to the small range of plant protection products and the growing doubts about their safety for the environment. Plant protection against fire blight is aimed at both preventing their infection and controlling the disease. So far, it has been detected in almost all areas of pome fruit cultivation and in some regions it causes economic damage every year. However, seeds usually do not show symptoms.Fire blight caused by bacterium Erwinia amylovora is one of the most damaging diseases of apple and pear trees and many other plant species of the Rosaceae family. Lesions can also occur on the pods causing the seeds to become shriveled and discolored. Generally young leaves are most susceptible to blight infection. Eventually the lesions will fall out of the leaf and the foliage will appear ragged. A yellowish-green "halo" will appear around the edge of water soaked tissue that surrounds the lesions. The centers of the spots will turn a dark reddish-brown and dry out. Symptoms in later growth stages include angular lesions, which begin as small yellow to brown spots on the leaves. Young plants may be stunted and if the infection reaches the growing point, they may die. Disease Symptomsīrown spots on the margins of the cotyledons characterize plants infected early in the growing season. Bacteria can also be spread to uninfected leaves when they rub against infected ones during cultivation, rain, and wind. Seedlings may be infected through infected seed.īacteria that enter the host produce a toxin, which prevents chlorophyll production. In order for infection to occur, the leaf surface must be wet. The bacteria enter the plants through stomata and wounds on leaves. Initial infection of soybeans occurs when wind or splashing water droplets from plant residue on the soil surface to the leaves carry bacterial cells. Bacterial blight ( Pseudomonas savastanoi) of soybeans is typically an early season disease, which over winters in the field on plant residue.
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