Bacterial blight of rice, caused by the pathogen Xanthomonas oryzae pv. oryzae, is one of the most devastating diseases affecting rice crops worldwide, particularly in Asia.
It infects rice plants at all growth stages, leading to wilting of seedlings, yellowing, and drying of leaves, ultimately causing significant yield losses. The disease spreads rapidly under warm, humid conditions and is favored by rain, wind, and poor field sanitation.
Taxonomy of X. Oryzae (
- Domain – Bacteria
- Phylum – Proteobacteria
- Class – Gammaproteobacteria
- Order – Xanthomonadales
- Family – Xanthomonadaceae
- Genus- Xanthomonas
- Species- Xanthomonas oryzae pv. Oryzicola
Xanthomonas oryzae pv. oryzicola is a Gram-negative, rod shaped bacteria with Cell size around 1.0-2.5 x 0.4-0.6 µm. Colonies are fairly slow-growing, usually pale-yellow, round, smooth, entire, domed and mucoid. Spreaded in Asia, Africa, Europe, Australia
Xanthomonas oryzae is transmitted from one location or plant to other by water locally or by infected leaves (visible on naked eye) or by infected seeds ( not visible normally).
Host Range-
Rice is the major host of X.oryzae but it also infect other plants viz. – Leersia sp(p)., Leptochloa filiformis [L. mucronata], wild and cultivated species of Oryza, Paspalum orbiculare, Zizania palustris and Zoysia japonica. The Japonica variety of rice is comperitevely more resistant than Indica variety against this bacteria.
Biology and Spread of Xanthomonas oryzae casused bacterial blight of rice
- Seeds can carry the bacteria, but this is less of a concern in cooler, dry seasons.
- The bacteria survive on leftover crop parts but not in soil. It spreads through irrigation water and is more active in rainy, humid conditions.
- The bacteria enter rice leaves through small openings (e.g. stomata) or wounds, especially from insect damage.
They multiply inside the leaf (sub-stomatal cavity and intercellular spaces in the parenchyma), causing streaks, and can release a sticky bacterial substance on the leaf surface during wet nights.
Showing symptom and pathogenesis of bacterial blight of rice caused by X. oryzae pv. Oryzicola (Source: Shi-Qi An et al., 2019)
Symptoms of bacterial blight of rice
- X. oryzae pv. oryzicola is a bacteria that causes disease in rice plants. At first, it makes long, narrow, dark green streaks between the leaf veins. These streaks are wet-looking and stay on the leaf blades (the flat part of the leaf).
- Later, the streaks grow bigger and change color — they can turn yellow-orange or brown, depending on the type of rice. The streaks can join together to make large damaged areas. You might see tiny amber (orange-yellow) droplets on the damaged parts — this is the bacteria coming out.
- This disease does not affect rice seeds.
- In later stages, it looks similar to another disease called leaf blight caused by X. oryzae pv. oryzae. But one difference is that the streaks from oryzicola stay straight (linear), while oryzae makes wavy edges.
- To be sure which bacteria is causing the problem, scientists may need to look at the bacteria directly under a microscope.
- This disease often spreads more when insects like leaf rollers, leaf-folders, and hispa beetles damage the leaves. The bacteria can easily get into the damaged parts of the plant.
Figure – Symptom of bacterial blight of rice (Source: Jepson, S. B. (n.d.). Bacterial leaf streak of rice. Oregon State University)
Diagnosis and identification bacterial blight of rice
- It is confirmed by testing pathogenicity on rice and/or by complete identification as X. oryzae pv. oryzicola, including positive reactions in starch and gelatin hydrolysis tests
- It can be confirmed by pathogenicity in rice and
- by fully identifying it as X. oryzae pv. oryzicola, including positive results in starch and gelatin breakdown tests.”
- Leaf inoculation
- Serological tests
Control of disease bacterial blight of rice
- To stop the spread of X. oryzae pv. oryzicola,
- it’s very important to use clean, healthy seeds.
- Use of Resistant variety of crop
- Uses of Pesticides – like Fubianezuofeng (FBEZF): Effective in China, but resistance reported. Niclosamide: Effective, environmentally friendl, it disrupts membranes, inhibits biofilm, induces systemic resistance.
- Hot water seed treatment: 52–54°C for 30 min after 8–10h pre-soaking; effective but not widely adopted due to low seed transmission of pathogen.
- Biological control by using other bacterial : It has been investigated and found that some bacterial species compete or inhibit the pathogen- (Limited but promising use) –
- Fluorescent pseudomonads, Bacillus spp., Pantoea spp.
- Bacillus spp. reduced disease by 60% and increased yield 2×.
- Myoviridae bacteriophages: Reduced severity by ~50%, less effective than tecloftalam.
- Bacteriocin-producing X. oryzae pv. oryzae and plant extracts also tested
- Cultural control – Use of clean seed, crop residue management, proper fertilization/ irrigation. Disinfection of equipment, removal of infected plants/weeds. Raise seedlings in boxes to reduce field infection risk
Impact of agricultural losses by bacterial blight of rice
Table – Impact of Xanthomonas oryzae on Production (source: eppo database)
| Region/Country | Time Period | Infested Area / Incidence | Yield Loss | Additional Notes |
| South-East Asia | Since 1960s | Widespread, especially with high-yielding cultivars | Serious losses reported | Most serious rice disease in the region |
| Japan | Various years | Up to 400,000 ha annually | 20–50%; up to 70%+ (kresek form) | |
| Africa | Not specified | Not specified | 2.7–41% | |
| India | First reported 1951 | Major outbreak in 1963 | 17–44% (2006 survey) | |
| Philippines | 1970s | Not specified | Wet season: 22% (susceptible), 9% (resistant); Dry season: 7% (susceptible), 2% (resistant) | |
| China | 1970s–2000s | Epidemics in 1970s; increase since 2000s | Not clearly quantified | 20-year quiet period from 1980s |
| Republic of Korea | 2002–2005 | From <2,700 ha to ~27,000 ha | Substantial (exact % not given) | Epidemic in 2003 due to emergence of new race (K3a) |
| Pakistan | Recent years (2021 report) | Increasing annually | 30–100% | Higher losses in autumn/winter crops; epidemics before panicle initiation are severe |
References:
An, Shi-Qi & Potnis, Neha & Dow, Max & Vorhölter, Frank-Jörg & He, Yong-Qiang & Becker, Anke & Teper, Doron & Li, Yi & Wang, Nian & Bleris, Leonidas & Tang, Ji-Liang. (2019). Mechanistic insights into host adaptation, virulence and epidemiology of the phytopathogen Xanthomonas. FEMS microbiology reviews. 44. 10.1093/femsre/fuz024.
ABI. (n.d.). Xanthomonas oryzae pv. oryzae (bacterial leaf blight of rice). CABI Compendium. https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.56956
EPPO (2025) Xanthomonas oryzae pv. oryzae. EPPO datasheets on pests recommended for regulation. https://gd.eppo.int (accessed 2025-04-12)
Jepson, S. B. (n.d.). Bacterial leaf streak of rice. Oregon State University. Bacterial leaf streak of rice. Assessed on 12/04/2025