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Source: Grainews [abridged, edited]
Of cereal diseases to worry about, bacterial leaf streak [BLS] is likely to become a major issue across the Canadian Prairies [Alberta, Saskatchewan, Manitoba] over the coming years. "The first time I saw bacterial leaf streak was 2012 and it was only a couple of fields," says Michael Harding, Alberta Agriculture and Forestry. "Each year, it has been ratcheting up."

Alongside increased incidence and severity, the disease is now hitting economic levels with 20 to 30 per cent yield losses reported in some fields. It has [also] been affecting wheat across the United States and beyond. [In the US] it's being considered "the" cereal leaf disease -- even more important than any fungal disease. Some regions have fields with up to 50 per cent yield losses.

"BLS is emerging in multiple places right now," says Harding. He thinks it's here to stay. "For us, it's an emerging disease. It's going to get more and more common until we can come up with a good way to manage it," he says. Large storms, which have been unusually common in the last few years, may also be contributing to the disease's spread.

Bacterial leaf streak is caused by _Xanthomonas translucens_ pv. _undulosa_. Bacterial leaf spot, caused by _Pseudomonas syringae_, has appeared in crops at less than economic levels for two decades or more. Some confusion still remains between the two diseases.

[byline: Madeleine Baerg]
communicated by:

[_Xanthomonas translucens_ is a bacterial complex. Members can cause major diseases of cereal crops and also affect other grasses (Poacea). Most pathovars have a narrow host range. Pathovar _undulosa_ affects wheat, triticale (wheat/rye hybrid), rye and barley. BLS diseases of cereals mainly affect leaves and spikes. Symptoms may include water-soaked streaks on leaves which become translucent and necrotic; bacterial ooze on leaf surfaces; in severe cases, the whole leaf area may be affected, leading to reduced photosynthesis and, hence, plant vigour.

_Xanthomonas_ pathogens can survive between seasons on volunteer crop plants or plant debris. They can be seedborne, depending on the host; they can also be spread with infected plant and other materials, by water and mechanical means (including human and insect activity). Disease management is difficult and may include phytosanitation (control of reservoir hosts, removal of contaminated materials), cultural measures (crop rotations with non-hosts), bacteriocides (such as copper compounds) and use of resistant crop varieties, if available. Genome sequencing of species and pathovars of _Xanthomonas_ is providing information on mechanisms of bacterial virulence.

Related species in the genus cause, for example, bacterial leaf blight of rice, bacterial leaf streak (BLS) of rice, BLS of maize, leaf scald of sugar cane, as well as a range of important diseases of non-cereal crops, including bacterial blight of banana, citrus canker and black rot of brassica vegetables (see previous ProMED-mail posts in the archives).

The other cereal disease mentioned above refers to bacterial leaf blight of wheat, caused by _Pseudomonas syringae_ pv. _syringae_.

Canada (with provinces): and

BLS symptoms in wheat:,,, and

Information on BLS of wheat:,,, and
_X. translucens_ complex, pathovars:
Genus _Xanthomonas_ taxonomy:
Classification of _Xanthomonas_ species:
- Mod.DHA]


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