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[1] Stripe rust, wheat - USA (Montana): 1st report
[2] Stripe rust, wheat - Australia (northern New South Wales and Queensland): new pathotype alert

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[1] Stripe rust, wheat - USA (Montana): 1st report
Date: 10 Jun 2007
Source: Great Falls Tribune [edited]
<http://www.greatfallstribune.com/apps/pbcs.dll/article?AID=/20070607/NEWS01/70607017/1002>

A disease that can reduce crop yield has been confirmed on some of the hard white winter wheat at a Montana State University farm west of here, an MSU scientist says. The report of stripe rust on some varieties of hard white winter wheat is believed to be the 1st report in Montana, said Carol Flaherty of the MSU News Service.

"Conditions have been extremely favorable for stripe rust development, and if it remains cool and wet, we may see this disease blow up very quickly," said Mary Burrows, a plant pathologist for the MSU Extension Service. The spores germinate best when the temperature is 41-59 F [5-15 C]. "If we get the cool, wet weather predicted, growers should expect to apply a fungicide to susceptible varieties at the 1st signs of infection," Burrows said. Infected varieties at the MSU farm are Nuwest and Big Sky.

Yellow pustules that occur in stripes are a symptom of stripe rust.
The disease can also affect spring wheat.

[Byline: The Associated Press]

--
Communicated by:
J. Allan Dodds
Former ProMED-mail plant disease moderator <dodds@ucr.edu>

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[2] Stripe rust, wheat - Australia (northern New South Wales and Queensland): new pathotype alert
Date: 29 May 2007
Source: North Queensland Register [edited] <http://nqr.farmonline.com.au/news_daily.asp?ag_id=42799>

The discovery of a new pathotype of wheat stripe rust in southern New South Wales (NSW) and Victorian wheat last year [2006] has prompted a reminder for farmers to be on the alert for the disease in the coming season.

Queensland Department of Primary Industries and Fisheries (DPI&F) plant pathologist Peter Wilkinson of the Leslie Research Centre said the new pathotype has increased virulence against the wheat stripe rust resistance gene Yr17. Mr Wilkinson said several wheat varieties drew their stripe rust resistance from the Yr17 gene and these varieties would be carefully monitored in southeastern Australia in the coming season. The new pathotype was discovered at low levels by the Australian Cereal Rust Control Program (ACRCP) based at Cobbitty, near Sydney.

Mr Wilkinson said there was no sign of the new pathogen in Queensland and northern NSW wheat last year [2006]. "We placed stripe rust probes at 18 sites throughout the area last season. The probes included varieties which could be expected to be more susceptible to the new stripe rust strain," he said. "Results from the testing of samples sent to the ACRP showed none of these stripe rust isolates to be of the new pathotype." Mr Wilkinson said it was possible the rust pathotype could establish in the region in the coming season and urged growers to be on the lookout for stripe rust symptoms. "The risk will be greater if we have higher rainfall than usual," he said.

Grains Research and Development Corporation (GRDC)-supported research will monitor the impact and spread of the new rust as part of the ACRCP. The DPI&F is now placing probes for the disease throughout the wheat growing regions of northern NSW and Queensland for the 2007 season. If any of these probes show the new pathotype, growers will be alerted immediately.

Mr Wilkinson said continuing to use resistant varieties was the best and most economical defense against stripe rust. "If stripe rust is detected, an early spray of a registered foliar fungicide provides good protection. Seed dressings can be effective if there is an early stripe rust epidemic. They can reduce seedlings' coleoptile lengths,
which can cause a problem when using deep sowing."

--
Communicated by:
ProMED-mail <promed@promedmail.org>

[Wheat stripe rust, also called yellow rust, is caused by the fungus _Puccinia striiformis_ var. _striiformis_ and occurs worldwide, mostly in cooler climates. It causes yellow leaf stripes, stunting of plants and reduced grain number and size on developing heads. Yield losses may vary from 40 up to 100 percent. It affects wheat, some
barley varieties, triticale and a number of grass species. Spores are wind dispersed in several cycles during the cropping season.

The fungus needs living plants to survive between seasons, it cannot survive on seed, stubble or in soil. Volunteer plants generate a "green bridge" providing the main source of rust inoculum to infect new crops. Only one infected leaf per 30 ha of re-growth is needed to produce severe epidemics. The susceptibility of available volunteer wheat cultivars influences the quantity of inoculum generated. Use of resistant varieties, control of volunteer plants and fungicide applications are part of disease management.

Pathogens can mutate spontaneously and randomly, and mutants are referred to as pathotypes, races or strains. In plants, they may differ in their ability to infect host cultivars, depending on what resistance gene or genes are present in the host. If a new strain has developed the ability to overcome a particular resistance gene, the resistance in the respective host cultivars is said to have "broken down." However, it is the pathogen that has changed, not the resistance gene in the host cultivar.

Stripe rust was introduced to eastern Australia in 1979, most likely from Europe. A number of strains with increased virulence on more wheat varieties developed over time. These strains did not spread to Western Australia. The pathogen was then introduced again to Western Australia in 2002, probably from the USA. The WA strain had spread to eastern Australia by 2003, where it is now dominant. The ACRCP monitors the occurrence of cereal rust pathotypes throughout Australia each year. The pathotypes are identified by glasshouse tests on seedlings of known susceptible and resistant cultivars, which can also be used as field probes. Surveys of rust pathotypes in 2003, for example, identified 6 pathotypes of stripe rust, 9 pathotypes of wheat stem rust ( _P. graminis_), and 6 pathotypes of wheat leaf rust (_P. triticina_).

Maps:
Map of US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>
Australia:
<http://www.ga.gov.au/image_cache/GA4073.jpg>

Pictures
Stripe rust, leaf symptoms:
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>

Links
Information on wheat stripe rust:
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>,
<http://www.hgca.com/hgca/wde/diseases/Yellow%20rust/Yrhost.html> and
<http://www.oznet.k-state.edu/path-ext/factSheets/Wheat/Wheat%20Stripe%20Rust.asp>
Pathogen taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=427989>
GRDC media release:
<http://www.grdc.com.au/whats_on/mr/north/northern_region07028.htm>
Stripe rust management, Victorian Department of Primary Industries 2006:
<http://www.dpi.vic.gov.au/dpi/nreninf.nsf/childdocs/-22C871BE2A0105794A2568B30004D413-3C5B474B480825C8CA256BC700824574-78F1BBD6496F89034A256DEA00274EEC-A1EF0A69F9553BA2CA256F85008022E0?open>
General information on wheat diseases and pathogens:
<http://www.apsnet.org/online/common/names/wheat.asp>
Explanation of strains, pathotypes and races of rusts:
<http://www.grdc.com.au/growers/gc/gc53/rust.htm>
GRDC:
<http://www.grdc.com.au>
- Mod.DHA]

[see also in the archive:
Fungal pathogens, wheat - United Kingdom: new races 20070523.1652
Wheat diseases - USA (KS): crop loss 20070518.1574
Wheat stripe rust, wheat - China 20070413.1230
2005
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Stripe rust, wheat - Australia 20051031.3173
Wheat stripe rust - USA (FL) 20050601.1521
2004
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Wheat stripe rust - Australia (NSW) 20040928.2683
Wheat stripe rust - Australia (NSW): alert 20040810.2215
Wheat stripe rust - China 20040429.1191
2003
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Wheat stripe rust, new strains - Australia (SA) 20030930.2465
Wheat stripe rust - Australia (WA) 20030624.1553
Wheat stripe rust, 1st report - USA (Florida) 20030516.1220
2002
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Wheat stripe rust - Australia (Western): alert 20020831.5198
2001
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Wheat stripe rust - USA (Great Plains) 20010715.1366
Wheat stripe rust - USA (Central) 20010629.1236]

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