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[1] Black chaff and bacterial stripe - South Dakota
[2] _Heterodera filipjevi_ - Oregon, first report


[1] Black chaff and bacterial stripe - South Dakota
Date: Wed 16 Jul 2008
Source: Dakota Farmer, South Dakota State University College of Agriculture and Biological Sciences (SDSU AgBio) report [edited] <http://dakotafarmer.com/index.aspx?ascxid=fpStory&fpsid=34835&fpstid=2>

Bacterial diseases infecting South Dakota wheat

There's an outbreak of bacterial disease in wheat in South Dakota this year, says Lawrence Osborne, SDSU Extension plant pathologist. The main problems are black chaff and bacterial stripe.
"Infection occurs through wounds or natural openings in the leaf, which may develop into streaks and water-soaked tissue, usually accompanied by yellowish to whitish ooze," he says. "In dryer parts of the day, the ooze appears shiny or scaly on leaf surfaces on or near the dark, sunken streaks within the affected leaves."

Some leaves may have an orange cast, but this bacterial disease's appearance should not be confused with tan spot, a fungal disease. "Tan spot typically produces small diamond- or lens-shaped, tan lesions on leaves, bordered with bright yellow halos," Osborne says. "Stagonospora blotch, another fungal leaf blight, may most closely resemble the bacterial symptoms. Neither fungal disease produces shiny or slimy ooze like the bacteria, and the fungicides used against tan spot will not help with bacterial disease."

Crop rotation, resistant cultivars, and proper nutrient management are the primary means for stopping black chaff. "Residue removal or burial will help limit inoculum in a field, but for some areas, may be impractical or undesirable," he says. "Rainy weather, especially when high winds are involved, tends to favor plant wounding and thus, bacterial infection."

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[2] _Heterodera filipjevi_ - Oregon, first report
Date: July 2008
Source: The American Phytopathological Society, Plant Disease 2008; 92(7): 1136 [edited] <http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-7-1136B>

[Ref: R. W. Smiley et al: 1st record of the cyst nematode _Heterodera filipjevi on wheat in Oregon. Plant Dis 2008; 92(7): 1136; DOI:
10.1094/PDIS-92-7-1136B]

Plant and soil samples from an irrigated winter wheat (_Triticum aestivum_) field near Imbler (Union County), Oregon, were evaluated for root diseases during April 2007. The field exhibited patches with as much as 90 percent plant mortality. Previous crops were winter wheat (2004), chickpea (_Cicer arietinum_, 2005), and spring wheat (2006). Stubble was baled and removed, and the field was cultivated before replanting to winter wheat in October [2006].
Patches of stunted seedlings (3- to 5-leaf stage) appeared in March 2007. Stunted seedlings exhibited chlorotic or necrotic lower leaves, healthy younger leaves, few or no tillers, rotting of lower culms and crowns, and light brown roots with little or no branching. Signs and symptoms of fungal pathogens were present on affected plants.

Most small grain fields in Union County are infested with _Heterodera avenae_ [cereal cyst nematode] but none of the roots, on either healthy or stunted plants, exhibited the bushy branching pattern typical of sites where _H.
avenae_ females penetrate and encyst. Extraction of motile nematodes from soil revealed high populations of _Pratylenchus neglectus_, _Tylenchorhynchus_ spp., and a species initially thought to be _H. avenae_. Cysts were also extracted.

During PCR (polymerase chain reaction)-restriction fragment length polymorphism identification of _H. avenae_ collected in Oregon, Washington, and Idaho, 4 restriction enzymes applied to amplified DNA of cysts from the Imbler field consistently revealed a pattern identical to that of a _H. filipjevi_ DNA standard and distinct from patterns of _H. avenae_, _H. schachtii_, and _H. latipons_.
Morphological evidence confirmed that the specimens were _H. filipjevi_, a member of the '_H. avenae_ Group'’ of cereal cyst nematodes.
Cysts were lemon shaped and light brown. As described for _H. filipjevi_, cysts hatched much more readily and at lower temperatures than populations of _H. avenae_.

Detection of _H. filipjevi_ in Oregon represents a new record for the occurrence of this species in the United States and for North America. The pathotype and resistance genes for incorporation into wheat, barley, and oat are being identified.

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[Black chaff and bacterial stripe of wheat are both caused by _Xanthomonas campestris_ pv. _translucens_. The site and extent of the symptoms depend on the strain of the bacterium, the affected cultivar, and environmental conditions. Black chaff occurs primarily on the glumes [ears], bacterial stripe primarily on the leaves and/or leaf sheaths. The bacterium can be seed borne and persists on crop residues in the soil, tolerating warm as well as freezing temperatures.

Cereal cyst nematode, _H. avenae_, can cause significant yield losses on most cereal crops when populations are high. All wheat cultivars are susceptible, but some do not support cyst formation. Other species in the genus affect a range of different crops. Disease management for cyst nematodes includes crop rotation and the use of partly resistant cultivars to keep populations low. Elimination of cyst nematodes from infected fields is usually not possible.

For more information on these diseases please see links below.

Maps
USA:
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html> and
<http://healthmap.org/promed?v=40,-97.6,4>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>

Pictures of wheat diseases, including black chaff, bacterial stripe, and cereal cyst nematodes, via:
<http://cril.cimmyt.org/gallery/main.php?g2_itemId=934>

Links:
Information on black chaff/bacterial stripe:
<http://wheatdoctor.cimmyt.org/index.php?option=com_content&task=view&id=131&Itemid=43>,
<http://scarab.msu.montana.edu/HpIPMSearch/Docs/BacterialStreakBlackChaff-SmallGrains.htm>,
and
<http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm2384>
Genus _Xanthomonas_ taxonomy:
<http://www.bacterio.cict.fr/xz/xanthomonas.html>
Information on cereal cyst nematode:
<http://wheatdoctor.cimmyt.org/index.php?option=com_content&task=view&id=76&Itemid=43>
&
<http://soilquality.org.au/fact_sheet_documents/7/Biol_-_Cereal_Cyst_Nematode.pdf>
Genus _Heterodera_ species taxonomy via:
<http://plpnemweb.ucdavis.edu/nemaplex/Taxamnus/G060mnu.htm>. - Mod.DHA]