June 9, 2010: Pathotype Updates: Latest confirmed race analysis results

Posted on by April 3, 2012

Confirmed results from race analysis completed in the 2009/10 season are now available. The confirmed spread of Ug99 variants carrying combined Sr31 + Sr24 virulence in Africa continues, along with the continued predominance of these variants in Kenya. The absence of Ug99 from samples collected in Pakistan in 2009 was also confirmed.

In Ethiopia, two isolates collected near Meraro in the Rift Valley during October 2007 were confirmed to have combined virulence to both Sr31 and Sr24. Samples were collected by EIAR scientists and analysis undertaken by the Cereal Research Centre, Winnipeg, AAFC, Canada. The race was postulated to be PTKST. This represents the first confirmed occurrence of a Ug99 variant with virulence to Sr24 in Ethiopia.

In Kenya, a total of 55 samples were collected in 2009 by KARI scientists but race analysis was only possible on 12 viable samples. Race analysis was undertaken by the Cereal Research Centre, Winnipeg, AAFC, Canada. Races identified were; TTKST (Ug99+Sr24) (50%), PTKST (34%), and PTKSK (16%). Despite the low sample size, the results did indicate the continued predominance of Ug99 variants with combined Sr31 + Sr24 virulence in Kenya (Wanyera et al 2010).

In Pakistan, samples were collected during the 2009 season from Sindh and lower Punjab. Isolates were analysed at Murree in Pakistan and at the Cereal Research Centre, Winnipeg, AAFC, Canada. All isolates tested were identified as race RRTTF. This race has also been previously identified in Ethiopia (2007) and in Yemen (2007, 2008). RRTTF has reported virulence on Sr13, Sr36 and SrTmp. It is avirulent on Sr8a, 9e, 22, 24, 25, 26, 27, 31, 32, 39, 40. Preserved urediniospores were also sent to PBI, Uni Sydney, Australia for DNA fingerprinting for Ug99 and negative results were obtained. Combined analyses indicate the absence of Ug99 in the 2009 Pakistan stem rust samples (Mirza et al 2010).

May 30, 2010: Algeria rust survey summary – Yellow rust and leaf rust widespread, but stem rust absent

Posted on by October 22, 2014

Wheat rust surveys were undertaken in May 2010 throughout the north-eastern wheat growing areas. A total of 103 wheat fields were surveyed using standard BGRI survey methodology. Forty-four percent of the fields surveyed were Durum Wheat, 30% Bread Wheat and 26% Barley. Stem rust was absent in all the fields surveyed. Yellow rust was the most widespread rust recorded on the survey, present in 65% of the fields visited with moderate or high disease severity (>20%) recorded in 40 of the fields. Leaf rust was also widely distributed, recorded in 56% of the fields visited – although moderate or high disease severity was only recorded in 16 fields.

May 17, 2010: Ug99 Lineage Race PTKST (virulent to Sr31 and Sr24) confirmed in South Africa

Posted on by April 3, 2012

A stem rust sample collected from near Greytown, KwaZulu-Natal, South Africa in Nov. 2009 has been confirmed to be Ug99 lineage race PTKST. Samples from another site – Cedara, KwaZulu-Natal, collected in Dec. 2009 showed similar virulence profiles. The confirmed findings have just been published in Plant Disease by Pretorius et al (2010). Race PTKST was only previously known from Kenya, where it was detected in 2008. Race PTKST is notable in that it carries combined virulence for resistance genes Sr24 and Sr31. The published avirulence/virulence profile of race PTKST is:

Avirulent: Sr13, 14, 21, 22, 25, 26, 27, 29, 32, 33, 35, 36, 37, 39, 42, 43, 44, Em, Tmp, and Satu

Virulent: Sr5, 6, 7b, 8a, 8b, 9a, 9b, 9d, 9e, 9g, 10, 11, 16, 17, 24, 30, 31, 34, 38, 41, and McN.

In seedling tests, 59 out of 103 South African cultivars tested were susceptible to race PTKST. It is believed that PTKST may be an exotic introduction into South Africa rather than a single –step mutation from local stem rust races.

April 29, 2010: Stem Rust at Very Low Incidence in Sudan and Egypt

Posted on by April 3, 2012

Extensive field surveys undertaken in Sudan (Feb 2010) and Egypt (Feb-Apr 2010) revealed a very low incidence of stem rust in farmers fields. Stem rust was not observed on-farm in Sudan and only trace amounts were recorded at three locations in Egypt (see country maps). A total of 83 locations were surveyed in Egypt and 34 locations in Sudan. Stem rust was present at research stations in both countries. Initial trap plot observations in Egypt gave no indication of the presence of the Ug99 lineage at any sites.

April 27, 2010: Race TTKSF (presumed Ug99 progenitor) confirmed in Zimbabwe

Posted on by April 3, 2012

stem rust samples collected near Harare in Sept 2009 have been confirmed as race TTKSF, the presumed progenitor of Ug99. Analysis undertaken by the University of the Free State, South Africa and the USDA-ARS, Cereals Disease Lab, Minnesota, USA confirmed the presence of this race. TTKSF is similar to Ug99 except for avirulence on Sr31. TTKSF had only previously been known from South Africa, where it has become the most prevalent stem rust race since its detection in 2000.

March 5, 2010: Situation Update Ethiopia, Kenya & Yemen Feb 2010

Posted on by April 3, 2012

Ethiopia: Results of the field surveys undertaken in Sep-Dec 2009 were received. Very comprehensive surveys were undertaken covering virtually all the main wheat growing areas. A total of 877 locations were surveyed. Thirty-five percent of the locations were infected by stem rust. Highest incidence of stem rust occurred in the southern areas, notably the Arsi/Bale region, and the disease was widespread in the Rift Valley area south of Addis. Stem rust was infrequent in northern and western areas. No information on races present is currently available.

Kenya: Field surveys were undertaken in the Mount Kenya and Central Rift Valley regions in Jan-Feb 2010. A total of 90 locations were surveyed. Fifty-nine percent of the locations were infected with stem rust and the disease was widespread throughout the regions surveyed. Approximately 77% of the locations surveyed had been sprayed with fungicides. Confirmation of races present is not yet available.

Yemen: Moderate to high incidence of stem rust was recorded in the screening nursery at Al Kedan on the Red Sea coast in the first week of Feb 2010. Samples are under going race analysis.

Dec 17, 2009: Additional Wheat Stem Rust Reports – Africa & Yemen

Posted on by April 3, 2012

Additional reports of wheat stem rust were received from several African countries.  In August, wheat stem rust was reported to be widespread in Tanzania. Wheat growing areas in Northern provinces and the Southern highlands both reported the presence of wheat stem rust. In South Africa, wheat stem rust was reported to be widespread in the Southern and Eastern Cape regions during Sept-Oct. One 160 ha field reportedly suffered complete yield loss to stem rust. In Zambia, trace amounts of wheat stem rust were found on 3 breeding lines at Golden Valley Research Station in late October. In all countries, the identity of stem rust races present remains unknown.

In Yemen, reports were received indicating higher incidence of wheat stem rust, compared to 2008, in highland areas during October. No race information is currently available.

Sep 20, 2009: Wheat Stem Rust Widespread in East Africa

Posted on by April 3, 2012

East Africa:

In Uganda, high incidence and severity of wheat stem rust have been reported in late August throughout the wheat growing regions. In Kenya, despite drought in many areas, wheat stem rust has been recorded throughout the wheat areas. Unsprayed fields in the North Rift province surveyed in September had high severity of stem rust. The variety KS Mwamba was highly affected.  In both countries, there is no confirmation of races involved but presence of the Ug99 lineage is highly likely. Late rains in Ethiopia delayed planting, surveys will be undertaken in Oct.

Southern Africa:

Surveys were undertaken in Zambia in late August and Zimbabwe (7-11 Sept. 2009). In Zambia, no stem rust was observed in farmer fields during the survey. Intensive use of fungicides (up to 3 sprays) was reported for commercial farmers. Stem rust was however detected at one research station on 17th Sept. Race identity is currently unknown. In Zimbabwe, stem rust was recorded at 5 locations: Gwebi, Birchenough, Mutare, Nyanga and Harare. Races involved are currently unknown, but race analysis is underway. At Gwebi, this was the first report of stem rust since 2003. At Nyanga, high levels of stem rust infections were observed on small-holder plots.