- Also called:
- bacterial blight of rice
- Related Topics:
- Plant disease
- Rice
- Bacterial disease
- Xanthomonas
Rice bacterial blight
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What is rice bacterial blight?
Rice bacterial blight is a destructive bacterial disease affecting cultivated rice, capable of causing yield losses as high as 75% in severe epidemics. The disease manifests as water-soaked streaks on leaves, which expand and release a milky ooze that dries into yellow droplets. Grayish-white lesions appear as the infection progresses, eventually leading to the leaves drying out and dying. In seedlings, this can cause a fatal condition known as kresek.
The bacterium Xanthomonas oryzae pathovar oryzae (Xoo) causes bacterial blight and thrives in warm, humid conditions, spreading through water in rice paddies and also via wind and water to other plants.
Control methods include cultivating rice varieties with resistance genes, such as Xa21, which have been integrated into commercial strains to reduce yield losses. Other methods include crop rotation, destroying diseased plants, and disinfecting tools.
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What causes rice bacterial blight?
Rice bacterial blight is a destructive disease affecting cultivated rice, capable of causing crop losses as high as 75 percent. The disease is caused by the bacterium Xanthomonas oryzae pathovar oryzae (Xoo).
Bacterial blight starts as water-soaked streaks on leaves, spreading from the tips and margins. These streaks enlarge and release a milky ooze that dries into yellow droplets. Grayish-white lesions appear, and in seedlings, leaves dry out and wilt, a condition known as kresek, often killing the plant. Adult plants may survive but with reduced yield and quality.
Xoo spreads easily in flooded rice paddies, moving from infected plants to neighboring ones through water. Wind and water can also spread the bacteria to other crops and paddies. The bacteria can survive in rice seeds, straw, other hosts, water, or briefly in soil during nongrowing seasons.
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How does rice bacterial blight affect rice plants?
Rice bacterial blight is a destructive disease affecting cultivated rice, leading to potential crop losses of up to 75% in severe epidemics. The disease manifests initially as water-soaked streaks on leaves, progressing to grayish-white lesions as the infection advances. In seedlings, this blight causes leaves to dry out and wilt, a condition known as kresek, often resulting in the death of the plant. Adult plants can survive, but their yield and quality are diminished. The bacterium Xanthomonas oryzae pathovar oryzae (Xoo) spreads easily in flooded rice paddies, moving from infected plants to neighboring ones through water. While chemical controls are limited, cultivating rice varieties with resistance genes is an effective defense.
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What are the common symptoms of rice bacterial blight?
Rice bacterial blight is a destructive affliction of cultivated rice. The disease initially manifests as water-soaked streaks on leaves, spreading from the tips and margins. These streaks enlarge and release a milky ooze that dries into yellow droplets. As the infection progresses, characteristic grayish-white lesions appear, and leaves eventually dry out and die. In seedlings, the leaves dry out and wilt, a condition known as kresek, which usually results in the death of the seedling within a few weeks. Adult plants may survive, but their yield and quality are diminished.
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How can rice bacterial blight be spread between plants?
Rice bacterial blight, a destructive disease of cultivated rice, spreads easily among crops in flooded rice paddies. The bacteria Xanthomonas oryzae pathovar oryzae (Xoo) travels through the water from infected plants to the roots and leaves of neighboring rice plants. Wind and water may also spread Xoo bacteria to other crops and rice paddies.
Xoo can also infect other plants, such as rice cut-grass, Chinese sprangletop, and common grasses and weeds. In nongrowing seasons, Xoo may survive in rice seeds, straw, other living hosts, water, or, for brief periods, soil.
Control methods include cultivating rice varieties with resistance genes to Xoo infection. Proper sanitation is also key to stopping the spread.
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What methods are used to prevent or control rice bacterial blight in fields?
Rice bacterial blight is a destructive disease impacting cultivated rice, leading to potential crop losses of up to 75% in severe cases.
Control methods include cultivating rice varieties with resistance genes to Xanthomonas oryzae pv. oryzae (Xoo). Over 30 resistance genes have been identified, some integrated into commercial strains, which has dramatically reduced yield losses. Other methods include crop rotation, destroying diseased plants, eliminating alternate host plants, pruning, disinfection, and heat treatments. Also, fixed copper or streptomycin can be effective antibiotics against bacterial blights if applied weekly during damp weather when leaves and shoots are expanding.
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Rice bacterial blight, deadly bacterial disease that is among the most destructive afflictions of cultivated rice (Oryza sativa and O. glaberrima). In severe epidemics, crop loss may be as high as 75 percent, and millions of hectares of rice are infected annually. See also list of plant diseases.
The disease was first observed in 1884–85 in Kyushu, Japan, and the causal agent, the bacterium Xanthomonas oryzae pathovar oryzae (also referred to as Xoo), was identified in 1911, at that time having been named Bacillus oryzae. Thriving in warm, humid environments, bacterial blight has been observed in rice-growing regions of Asia, the western coast of Africa, Australia, Latin America, and the Caribbean. Although not commonly found in the United States, a bacterial strain related to Xoo has been listed as an agricultural select agent by the U.S. Department of Agriculture, a designation that places it under strict regulations.
Bacterial blight first becomes evident as water-soaked streaks that spread from the leaf tips and margins, becoming larger and eventually releasing a milky ooze that dries into yellow droplets. Characteristic grayish white lesions then appear on the leaves, signaling the late stages of infection, when leaves dry out and die. In seedlings, the leaves dry out and wilt, a syndrome known as kresek. Infected seedlings usually are killed by bacterial blight within two to three weeks of being infected; adult plants may survive, though rice yield and quality are diminished.
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Since rice paddies are flooded throughout most of the growing season, Xoo may easily spread among crops; bacteria travel through the water from infected plants to the roots and leaves of neighboring rice plants. Wind and water may also help spread Xoo bacteria to other crops and rice paddies. Various mechanisms of disease, including quorum sensing and biofilm formation, have been observed in rice bacterial blight and Xoo. In addition to rice, Xoo may infect other plants, such as rice cut-grass (Leersia oryzoides), Chinese sprangletop (Leptochloa chinensis), and common grasses and weeds. In nongrowing seasons, Xoo may survive in rice seeds, straw, other living hosts, water, or, for brief periods, soil.
Methods of controlling rice bacterial blight are limited in effectiveness. Chemical control has been largely ineffective in minimizing bacterial blight because of safety concerns, practicality, and bacterial resistance. Biological control methods, which rely on the use of bacterial antagonists of pathogens (disease-causing organisms), can reduce bacterial blight, though their use has been limited. The most-common method of defending against rice bacterial blight is the cultivation of rice varieties with genes that confer resistance to Xoo infection. More than 30 resistance genes, termed Xa1 to Xa33, have been identified in rice plants, and some, such as Xa21, have been integrated into the genomes of commercial rice strains. These resistant rice varieties have been largely successful, dramatically reducing yield losses in many rice-producing countries.