Bacterial blight is a disease of

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...

caused by the bacterial pathogen '' Xanthomonas campestris'' pv. ''translucens'' (syn. ''X. translucens''). It has been known as a disease since the late 19th century. It has a worldwide distribution.

Symptoms

The disease is characterized by small, pale green spots or streaks which soon appear water-soaked. The

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

s expand and then appear as dry dead spots. The lesions elongate into linear streaks which may eventually extend the full length of the

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

. Lesions rarely occur on the leaf sheath or culm. In severe infections, a milky gray

exudate An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin ''exsūdāre'' 'to (ooze out) sweat' (''ex-'' 'out' and ''sūdāre'' 'to ...

may be squeezed from the cut end of leaf exhibiting symptoms. Brown spots on the margin of the cotyledon characterized plants

Disease cycle

This disease is caused by a common

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

that persists in soil and water and is spread by wind-driven rains. The bacteria overwinters on crop residue, seed, fall-sown cereals, and Perennial plant, perennial grasses. Spring infection may result from any of these sources. Subsequent infections are spread by splashing of bacterial ooze by rain drops, plant to plant contact and insects. Bacterial blight develops on the upper leaves of during periods of cool, wet weather, after the plants have reached the boot stage. Leaf blight is associated with high relative humidity, wet weather, and cool spring temperatures (15-25 degrees C or 60-75 degrees F). Warm, dry weather stops the disease and new emerging leaves may be relatively free of bacterial infection.

Crop loss

Although detailed studies have not been conducted, damage to the FLAG-tag, flag often occurs suggesting that yield losses may reach 10-15%.

Management

Disease incidence and severity is reducing by rotating to non-grain crops, burying crop residue and using disease free seed. No resistant cultivars are known, some are more susceptible than others.

External links

Bacterial blight (Canada: Manitoba)

References

{{DEFAULTSORT:Bacterial Blight (Barley) Bacterial plant pathogens and diseases Barley diseases