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Bacterial Leaf Streak
Bacterial Leaf Streak – Page 1 of 2
Causal organism
Bacterial leaf streak (BLS) is caused by Xanthomonas oryzae pv. oryzicola. The bacterium is rodshaped
with an average dimension of 1.2 × 0.3 to 0.5 µm. On nutrient agar, bacterial colonies are pale
yellow, circular, smooth, and convex, and have an entire margin (Webster and Gunnell 1992).
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Distribution
Bacterial leaf streak occurs in tropical and subtropical regions of Asia, Africa (including Madagascar),
South America, and Australia (Webster and Gunnel 1992, Niño-Liu et al 2006, Wonni et al 2011).
Symptoms
Symptoms initially appear as small, water-soaked, linear lesions between leaf veins. These streaks are
initially dark green (Fig. 1) and later become light brown to yellowish gray (Fig. 2). BLS lesions are
translucent when held against the light. Entire leaves may become brown and die when the disease is
very severe. Under humid conditions, yellow droplets of bacterial ooze, which contain masses of
bacterial cells, may be observed on the surface of leaves (Fig. 3).
Fig. 1. Water-soaked
and green lesions of
bacterial leaf streak.
Fig. 2. Enlarged and
coalesced lesions of
bacterial leaf streak.
Fig. 3. Bacterial ooze on the surface
of an infected leaf. Photo courtesy of
Dindo King Donayre, Philippine Rice
Research Institute.
Bacterial leaf streak may be confused with narrow brown spot. BLS lesions are usually thinner than
those of narrow brown spot, which is caused by a fungus. When the advancing part of the streaks are
cut and placed in a glass with water, a mass of bacterial cells can usually be seen oozing out of the leaf,
which makes the water turbid after 5 minutes. Moreover, narrow brown spot lesions are not translucent,
nor do they produce bacterial ooze.
Bacterial leaf streak may also be confused with bacterial blight usually at the early stage of infection,
particularly if lesions of both diseases occur on the same leaf. The diseases can be distinguished
through biochemical, pathogenicity, or serological tests. PCR primers were recently developed to
distinguish the two bacterial pathogens (Lang et al 2010).
Epidemiology and ecology
Bacterial leaf streak is a seedborne disease (Xie and Mew 1998) but transmission from seeds to plants
has not yet been clearly demonstrated. Sowing infected seeds may produce infected seedlings, and
contribute to inoculum and disease transfer from one cropping season to another. The pathogen infects
several species of wild rice (Ou 1985) and can survive on infected crop residues, volunteer plants, and
weeds. Frequent rainfall favors the disease (Ou 1985). Rain splash facilitates the dispersal of bacteria
from infected leaves and causes infection on neighboring healthy tissues. Rainfall with strong winds can
For more information, visit the Rice Knowledge Bank: http://www.knowledgebank.irri.org
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Bacterial Leaf Streak – Page 2 of 2
cause water-soaking and wounds, which facilitate the entry of bacteria through stomata. BLS bacteria
may also spread in the field through irrigation water (Ou 1985). The application of excessive amounts of
nitrogen fertilizer favors the disease (Seshagiri Rao and Devadath 1980). The disease is also favored by
warm temperature (25 to 35 °C) and high relative humidity (Webster and Gunnell 1992).
Management
Breeding resistant varieties is the most efficient way to control bacterial leaf streak. Highly resistant rice
varieties are available and have been used as parents in breeding programs. Bacterial leaf streak
resistance appears to be quantitative (Khush 1977), controlled by a number of QTLs (Tang et al 2000,
Han et al 2008). Studies in China show that major genes may also be involved (Han et al 2008).
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Other options for managing bacterial leaf streak include
Keeping fields clean—removing weed hosts and plowing under rice stubble, straw, rice
ratoons, and volunteer seedlings, which may be infected by the pathogen;
Using a balanced amount of plant nutrients, especially nitrogen;
Ensuring good drainage of conventionally flooded fields and nurseries;
Draining the field during severe flooding; and
Drying the field during the fallow period to kill the bacteria and reduce the amount of inoculum
in the soil and plant residues.
References
Han QD, Chen ZW, Deng Y, Lan T, Guan HZ, Duan YL, Zhou YC, Lin MC, Wu WR. 2008. Fine mapping of qBlsr5a,
a QTL controlling resistance to bacterial leaf streak in rice. Acta Agron. Sin. 34:587-590.
Khush GS. 1977. Breeding for resistance in rice. In: Day PR, editor. The genetic basis of epidemics in agriculture.
Academy of Sciences, New York. p 296-308.
Lang JM, Hamilton JP, Diaz MGQ, Van Sluys MA, Burgos MRG, Vera Cruz CM, Buell CR, Tisserat NA, Leach JE.
2010. Genomics-based diagnostic marker development for Xanthomonas oryzae pv. oryzae and X. oryzae pv.
oryzicola. Plant Dis. 94:311-319.
Niño-Liu DO, Ronald PC, Bogdanove AJ. 2006. Pathogen profile. Xanthomonas oryzae pathovars: model pathogens
of a model crop. Mol. Plant Pathol. 7:303-324.
Ou SH. 1985. Rice diseases. Second edition. Commonwealth Mycological Institute, C.A.B. International, Farnham
Royal, Slough, UK. 380 p.
Seshagiri Rao C, Devadath S. 1980. Effect of nitrogen and duration of rice cultivars in relation to bacterial leaf streak
incidence. Oryza 17:42-47.
Tang D, Wu W, Li W, Lu H, Worland AJ. 2000. Mapping of QTLs conferring resistance to bacterial leaf streak in rice.
Theor. Appl. Genet. 101:286-291.
Webster RK, Gunnell PS. 1992. Compendium of rice diseases. American Phytopathology Society, St. Paul,
Minnesota. 62 p.
Wonni I, Ouedraogo L, Verdier V. 2011. First report of bacterial leaf streak caused by Xanthomonas oryzae pv.
oryzicola on rice in Burkina Faso. Plant Dis. 95:72.
Xie GL, Mew TW. 1998. A leaf inoculation method for detection of Xanthomonas oryzae pv. oryzicola from rice seed.
Plant Dis. 82:1007-1011.
For more information, visit the Rice Knowledge Bank: http://www.knowledgebank.irri.org
Developed with input from: N.P. Castilla, S. Savary and A. Sparks
Produced by the International Rice Research Institute (IRRI) • © 2012, IRRI, All rights reserved • Feb 2012
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