- Xanthomonas oryzae pv. oryzae
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Xanthomonas oryzae pv. oryzae Scientific classification Kingdom: Bacteria Phylum: Proteobacteria Class: Gamma Proteobacteria Order: Xanthomonadales Family: Xanthomonadaceae Genus: Xanthomonas Species: X. oryzae Variety: X. o. pv. oryzae Trinomial name Xanthomonas oryzae pv. oryzae Xanthomonas oryzae pv. oryzae is a bacterium which causes a serious blight of rice, other grasses and sedges.
Contents
Background
The genus Xanthomonas, which mostly comprises phytopathogenic bacteria, is a member of the family Pseudomonadaceae. Among xanthomonads, Xanthomonas oryzae pv. oryzae causes bacterial blight (BB) of rice which is one of the most important diseases of rice in most of the rice growing countries.[1]
Bacterial blight of rice has high epidemic potential and is destructive to high-yielding cultivars in both temperate and tropical regions especially in Asia. Its occurrence in the 70s in Africa and the Americas has led to concerns about its transmission and dissemination.[2]
Research on bacterial blight of rice was commenced in Japan as early as in 1901, and the efforts were focused mainly on ecological studies and chemical control. Since then, significant gains have been made in understanding BB through analysis of the interactions between X. oryzae pv. oryzae and rice at many levels, including studies focused on the epidemiology, population biology, physiology, cell biology, biochemistry, and molecular genetics of the host pathogen interaction. It is very notable that BB became the first case where the genome sequencing of both host plant and pathogen was completed.[3]
Hosts
There is a very large host range for Xanthomonas oryzae pv. oryza.[4]
Among the grasses, hosts include:
- Cenchrus ciliaris (buffelgrass)
- Cynodon dactylon (Bermuda grass)
- Echinochloa crus-galli (barnyard grass)
- Leersia hexandra (southern cut grass)
- Leersia oryzoides (Rice cutgrass)
- Leptochloa chinensis (Chinese sprangletop)
- Oryza (species of rice), including
- Oryza sativa (rice)
- Panicum maximum (Guinea grass)
- Paspalum scrobiculatum (ricegrass paspalum)
- Poaceae (Meadow grasses)
- Urochloa mutica (Tall panicum)
- Zizania aquatica (Annual wildrice)
- Zizania palustris (Northern wild rice (USA))
- Zoysia japonica (zoysiagrass)[4]
Among the Cyperaceae (Sedges), hosts include:
- Cyperus difformis (Small-flowered nutsedge)
- Cyperus rotundus (Purple nutsedge)[4]
Symptoms
Symptoms appear on the leaves of young plants as pale-green to grey-green, water-soaked streaks near the leaf tip and margins. These lesions coalesce and become yellowish-white with wavy edges. The whole leaf may eventually be affected, becoming whitish or greyish and then dying. Leaf sheaths and culms of more susceptible cultivars may be attacked. Systemic infection results in wilting, desiccation of leaves and death, particularly of young transplanted plants.[5]
In older plants, the leaves become yellow and then die. In its advanced stages, the disease is difficult to distinguish from leaf blight caused by Xanthomonas oryzae pv. oryzicola, but lesion margins are wavy rather than linear as for the former. Damage is often associated with lepidopteran leaf rollers, leaf-folders and hispa beetles, since bacteria readily enter the damaged tissue caused by insect infestation.[5]
References
- ^ Hopkins, C.M.,White, F.F., Choi, S.-H., Guo, A., Leach, J.E., "Identification of a Family of Avirulence Genes from Xanthomonas oryzae pv. oryzae", Molecular Plant-Microbe Interactions, Vol. 5, No. 6, pp.451-495,1992.
- ^ AFFRC - Xanthomonas
- ^ AFFRC.go.jp - Genome Sequence of Host and Pathogen
- ^ a b c NAPPFAST: Xanthomonas oryzae hosts, NAPPFAST, 2007.
- ^ a b Invasive: Symptoms of Bacterial Blight, "USDA", May 04, 2010.
Categories:- Xanthomonadales
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