Bacterial diseases in plants pdf

As with viruses, many diseases caused by fastidious bacteria are named after the most important host plant or the one where the disease was first discovered, but some can also infect many other plants. For example, the aster yellows phytoplasma also affects other ornamentals, such as gladiolus and phlox or tomato, spinach, onion, lettuce, celery, carrots and strawberry, and many weeds. As the name implies, members of plants belonging to the family Asteraceae are vulnerable to infection, though the disease can also affect a variety of common vegetables, cereals, garden plants, and wild species.

Causes: The bacteria are spread by rain and wind so the disease can occur after long cool wet periods which penetrates into the plant through damaged leaves.

Warm dry weather proves to curb the spread of bacterial blight. Symptoms: Small brown spots on the upper leaves which eventually grow bigger as they cover the whole leaf. In some cases, the infected leaves can turn brown and become watery. Treatment: infected part of the crop which happens to be the leaves, stems and branches should be cut off; make sure to disinfect the pruning tools after use.

Avoid the use of overhead irrigation system for watering to avoid further spreading. When applicable, practice crop rotation to avoid overwintering of the bacterial blight. Use disease free seeds and practice antibiotic seed treatment. Causes: Black rot can be caused by wet and warm weather conditions. The bacteria can infest the plant through natural openings or wounds of the leaf. Once the bacterium is in the plant, it can infect the entire plant traveling through its water conducting system.

Symptoms: Yellow to dark brown discoloration appears on the margins of the leaves. As the disease spreads it infects the whole leaf which turns dark brown. Use bactericides to treat the infected plants but beware that most of the bactericides may impose harm on the plant and its fruit or vegetables.

One method of prevention is to use disease-free seeds or to wash them properly before planting them. Causes: Wet and cool conditions hepls in the spread of bacteria. Once it has infected the plant, the leaf spot bacteria can multiply very quickly. In some extreme cases, these dark necrotic spots can spread to the whole leaf and kill it. The cells can be rod-shaped, spherical, spiral-shaped or filamentous. Only a few of the latter are known to cause diseases in plants.

Most bacteria are motile and have whip-like flagella that propel them through films of water. Phytoplasmas and spiroplasmas are bacteria that lack rigid cell walls, and infect plants. Phytoplasmas are round or ovoid.

As with viruses, many diseases caused by fastidious bacteria are named after the most important host plant or the one where the disease was first characterized, but some can also infect many other plants. For example, the aster yellows phytoplasma also affects other ornamentals, such as gladiolus and phlox or tomato, spinach, onion, lettuce, celery, carrots and strawberry, and many weeds. The taxonomy of plant pathogenic bacteria is currently in flux based on recent advances on how bacteria are classified.

Plant pathogenic bacteria cause many different kinds of symptoms that include galls and overgrowths, wilts, leaf spots, specks and blights, soft rots, as well as scabs and cankers. In contrast to viruses, which are inside host cells, walled bacteria grow in the spaces between cells and do not invade them. The means by which plant pathogenic bacteria cause disease is as varied as the types of symptoms they cause. Some plant pathogenic bacteria produce toxins or inject special proteins that lead to host cell death or they produce enzymes that break down key structural components of plant cells and their walls.

An example is the production of enzymes by soft-rotting bacteria that degrade the pectin layer that holds plant cells together.

Still others colonize the water-conducting xylem vessels causing the plants to wilt and die. Agrobacterium species even have the ability to genetically modify or transform their hosts and bring about the formation of cancer-like overgrowths called crown gall. Bacteria that cause plant diseases are spread in many ways—they can be splashed about by rain or carried by the wind, birds or insects.

People can unwittingly spread bacterial diseases by, for instance, pruning infected orchard trees during the rainy season. Water facilitates the entrance of bacteria carried on pruning tools into the pruning cuts. Propagation with bacteria-infected plant material is a major way pathogenic bacteria are moved over great distances.

No matter how the bacterial pathogens are disseminated, they require a wound or natural opening, such as stomata, to get inside a plant host. Once inside they then kill host cells, by the means described above, so that they can grow. Between hosts they may grow harmlessly on plant surfaces and then can overwinter or survive unfavorable environmental periods or the absence of a susceptible host by either going dormant in infected tissue, infested soil or water, or in an insect vector. Bacterial diseases in plants are difficult to control.

Emphasis is on preventing the spread of the bacteria rather than on curing the plant. Integrated management measures for bacterial plant pathogens include:. CFAES provides research and related educational programs to clientele on a nondiscriminatory basis.

For more information, visit cfaesdiversity. For an accessible format of this publication, visit cfaes. Skip to main content. Bacterial Diseases of Crop Plants. Authors: Suresh G. Borkar, Rupert Anand Yumlembam. Food and agriculture is an important component in the development and survival of civilizations. Plant diseases take as much as a 30 percent toll of the crop harvest if not managed properly and efficiently.

Phytopathogenic Bacteria and Plant Diseases.