Nov. 20th, 2012: Ethiopia, Southern Region (SNNPR) survey summary – All 3 rusts widespread, but at low levels of incidence and severity

Posted on by December 4, 2012

Surveys led by Dr Fikre Handero (SNNPR Agricultural Research Institute) with assistance from Dr Getaneh Woldeab (Ambo PPRC) and CIMMYT were undertaken in the mid-altitude / highland areas of SNNPR between Butajeira and Arba Minch during the period 5-10th Nov 2012. A total of 44 fields were surveyed, these were predominantly bread wheat with a few triticale fields included in the Chencha highlands close to Arba Minch. Surveyed crops were mostly at the milk-dough growth stage. Following the 2010 yellow rust epidemic there has been a rapid uptake of the resistant cultivar Digelu. On the survey,  15 out of 38 farmer fields surveyed (40%) were planted with Digelu and the actual proportion of Digelu in the area surveyed was considered to be higher, as there was some avoidance of Digelu on the survey due to the high rust resistance observed.

stem rust was widespread on the survey, but at low incidence and severity (<20% and predominantly trace amounts). Stem rust was present in 21 of the 44 fields surveyed, but moderate (20-40%) severity was only observed at 1 site. Most of the stem rust sites were below 2400m (mean elevation of positive sites 2283m, overall range 1993-2792m). Kubsa and Galema were the cultivars on which stem rust was most often recorded. Digelu had good resistance with very few, tiny pustules observed. The improved cultivars – Dand’a, Hidase, Kakaba and Shorima all had a very low incidence and severity of MSS to S type pustules at the Angacha Research Station. A total of 24 DNA samples and corresponding live samples were collected on the survey. These are undergoing analysis  at the USDA-ARS, Cereals Disease Lab, Minnesota and the Ambo PPRC, Ethiopia.

Yellow rust was observed at 18 of the 44 sites surveyed.  The disease was widespread but generally at low levels of incidence and severity. High incidence of yellow rust was observed at 8 sites in the southern part of the survey area, predominantly on the cultivar Galema. Only 2 sites in the Chencha highlands had high severity (>40%) of yellow rust on the cultivar Galema. The mean elevation of sites with yellow rust was 2364m (range 1993-2795m). Yellow rust was also observed on Triticale in the Chencha highlands. Fourteen samples of yellow rust were sent to the Global Rust Reference Center in Denmark for race analysis.

Leaf rust was recorded at 21 of the 44 sites surveyed. High incidence was observed at 7 sites, but generally there was low to moderate  incidence and severity of  leaf rust within the survey area.

Septoria was the most prevalent and widespread disease recorded on the survey, all cultivars (including Digelu) were affected. This matches observations from other regions of Ethiopia with conditions in 2012 main season being particularly favourable for Septoria development.

Oct. 30th, 2012: Zimbabwe rust survey summary – Stem and Leaf rust at low levels, but indications of possible new leaf rust races

Posted on by December 4, 2012

Credit: Bruce Mutari

Following the widespread distribution of rusts diseases observed in 2011 main season, a survey team co-led by Mr Bruce Mutari (Crop Breeding Institute) and Mrs Mutisi (Plant Protection Research Institute) carried out surveys throughout the key wheat growing areas of Zimbabwe during the period 10th – 16th September 2012. The primary focus of the surveys was to assess the status of wheat stem rust in Zimbabwe compared to the situations in 2009, 2010, 2011 and to monitor the potential spread of virulent races of wheat stem rust (Ug99 race lineage) in Zimbabwe and Southern Africa as a whole. The majority of the crops observed were at dough to maturity, with some crops already harvested. In the survey area, wheat was grown at elevations ranging from 422m to 1605m. A total of 22 wheat fields, distributed throughout the main agro-ecological zones, were surveyed using standard BGRI survey methodology. The highveld region contained the highest density of wheat fields. Surprisingly, wheat stem rust was not widespread and only positively recorded at 1 (4.5%) of the 22 survey sites; Rattray Arnold Research Station, in the middleveld region. Whilst not at the same level of disease pressure as 2010 and 2011, leaf rust was the most widespread disease as it was recorded at 9 (40.9%) of the 22 survey sites (Nyanga 1, Nyanga 2, Sisal farm, Save Valley, Birchnough Bridge, Panmure Research Station, Gwebi Variety Testing Center, Rattray Arnold Research Station and ARTfarm. For the first time in four years, stem rust was not recorded in the Lowveld. At Rattray Arnold Research Station, high levels of stem rust infections were observed in a single experimental line which exhibited highly susceptible reactions. At Birchnough Bridge, high incidence and severity of leaf rust was observed in an irrigation scheme with SC Nduna, Kana and SC Sekuru (improved varieties) showing highly susceptible reactions. Low incidence and very high severity of leaf rust was recorded at GVTC in a Kana breeder’s seed field. Trace amounts of leaf rust were recorded at Agricultural Research Trust farm in contrast to last year where very high incidence and severity was recorded at the same station. In addition to one stem rust sample, nine leaf rust samples were collected and sent to Prof.Z.Pretorius, University of Free State, RSA for race analysis. One stem rust sample was sent to Dr.L. Szabo, Cereal Disease Laboratory (CDL), U.S.A for DNA – molecular diagnostic analysis. As compared to the previous seasons, powdery mildew was much more widespread as it was regularly recorded at survey sites. No stripe rust was observed at any of the survey sites visited.

Results from the DNA analysis indicated that the stem rust race present was TTKSF, although it must be noted that the CDL molecular diagnostic assay used is currently unable to differentiate between races TTKSF and TTKSF+. Conventional race analysis at the University of the Free State confirmed that the stem rust race was TTKSF.

The difference in the incidence and severity of stem and leaf rust between 2010, 2011 and 2012 may be the result of the unfavorable environmental conditions that prevailed during the 2012 season. The 2012 wheat cropping season was characterized by long periods of dry conditions and cool temperatures which are not favorable for rust development. The decline in wheat hecterage in Zimbabwe (from 10 000ha to 5 000ha) might also have resulted in this decrease in rust incidence because of the reduction in suitable hosts. In addition, for the past two seasons, most farmers in Zimbabwe have been adhering to the recommended planting dates which is very important for rust escape. By planting early, the crop escapes stem rust infection since it is common/develops late in the season when temperatures begin to rise.

The breakdown of leaf rust resistance on improved cultivars, SC Sekuru, SC Nduna, Kana and Insiza (highly susceptible reactions) may indicate the presence of new biotypes of leaf rust. However further laboratory analysis needs to be undertaken to confirm if this is the case.

Oct. 19th, 2012: Molecular diagnostics provide updated knowledge on Ugandan stem rust races: Four Ug99 race group members (TTKSK, TTKST, TTTSK and TTKSF) postulated

Posted on by October 19, 2012

Credit: W. Khoury (IFAD)

New molecular diagnostic assays are providing rapid and useful information on the Ug99 race group in Africa. The assays have been developed by the group led by Dr Les Szabo at the USDA-ARS Cereals Disease Laboratory in St Paul, Minnesota, USA. Dr Szabo explains that “The assay consists of two-stages, the first determines if the sample belongs to the Ug99 race group and the second stage predicts the race phenotype based on genotype of a select set of SNP markers”. These assays have been refined over the last 2-3 years and have been validated and correlated against known stem rust isolates. They have been shown to reliably distinguish members of the Ug99 race group (stage 1 assay) and postulate with a high degree of accuracy specific races in the Ug99 race group (stage 2 assay). These molecular diagnostic assays are now being applied to stem rust samples from the field.

A survey team from Buginyanya Zonal Agricultural Research and Development Institute, Uganda led by Dr William Wagoire undertook surveys in the eastern and south-western wheat growing of Uganda during the periods Jan-Feb 2012 and Oct 2012. DNA samples from stem rust recorded on surveys were collected, sent to the Cereals Disease Laboratory and analysed using the molecular diagnostic assays. A total of 53 samples were tested and 62% tested positive for the Ug99 race group. Of the samples that tested positive, it was possible to identify 29 samples that belonged to the following races: TTKSK, TTKST, TTTSK and TTKSF. The results indicated that race TTKST (Ug99 Sr24 variant) predominated with 15 samples, race TTKSK (the original Ug99) was second with 9 samples, race TTTSK (Ug99 Sr36 variant) was third with 3 samples and race TTKSF (Sr31 avirulent) was fourth with 2 samples. Since the original Ug99 isolate (race TTKSK) was first detected in Uganda in 1998/99, little has been known about the stem rust populations now present in Uganda. The latest results from the molecular assays indicate that at least 4 variants of the Ug99 race group are now present in Uganda and the Sr24 variant (race TTKST) predominates. This mirrors the known situation in neighbouring Kenya. Presence of race TTKSF is noteworthy as this Sr31 avirulent race, which dominates in southern Africa, has never been recorded before in East Africa. It must be recognized however that the molecular assays are currently unable to differentiate race TTKSF from the closely related variant TTKSF+ recently identified in South Africa and Zimbabwe (Pretorius et al., 2012).

Aug 17th, 2012: Latest version of Mehtaensis newsletter published by DWR, Flowerdale, Shimla: Comprehensive, updated information on rusts in India and South Asia

Posted on by August 17, 2012

The latest version of the Mehtaensis newsletter (a 6 monthly newsletter named after Prof. K.C. Mehta) has just been published by the DWR, Regional Station, Flowerdale, Shimla. Compiled by Dr. S.C. Bhardwaj, Mehtaensis contains a detailed summary of all the rust activities and race analysis results from India and neighbouring South Asian countries during the period Jan – July 2012. The executive summary is reproduced here:

“During 2011-12 crop year, there was scanty rainfall early in the season. Wheat rusts appeared almost one month late than previous year. Except for some localized incidences of yellow rust in northern India, it was comparatively less rust year. Inoculation of aecial stages from Berberis on wheat, barley and oat showed that these were not related. Likewise, rust samples from grasses could not infect wheat, barley however, one sample infected oat. This year 1655 samples of wheat and barley rusts were collected and 1006 were analyzed. Pathotype 46S119 of yellow rust was most predominant followed by 78S84 in northern India. In Nilgiri hills pathotype I(38S102) was common. In Ladhakh pathotype CI, followed by CII and CIII were observed. These pathotypes do not occur anywhere else in India. In Black rust pathotype 40A followed by 40-1 were common in Nilgiri hills. In Ladhakh area, pathotype 34-1 was identified in all the samples. This pathotype is very primitive and does not occur in other parts of India. In brown rust pathotype 77-5 was observed in most of the samples from India, Nepal, Pakistan and Bangladesh. During this year 1625 wheat and barley lines were evaluated at seedling stage against different pathotypes of three rusts. None of the wheat AVT lines showed resistance to all the rusts however, three lines of barley were resistant to three rusts. Ten Lr genes were characterized in 151 lines, 5 Yr genes in 117 and 13 Sr genes in 159 lines. Wheat disease monitoring nurseries was planted at 38 locations distributed in all the wheat growing areas of India. Likewise SAARC nursery was planted in 23 locations in five SAARC nations.”

Aug 15th, 2012: Short (“Belg”) season surveys undertaken in the Bale zone of Ethiopia

Posted on by August 16, 2012

A survey team co-led by Dr Bekele Hundie (Sinana Research Station) and Dr Getaneh Woldeab (Ambo Plant Protection Center) carried out surveys in the Bale zone of southern Ethiopia during the period 4-6th Aug 2012. A total of 54 fields were surveyed, covering a range of bread wheat varieties, local emmer wheat and durum wheat. The majority of the “Belg” season crops observed were at dough to maturity, with some crops already harvested. This region represents a classic “green-bridge” area with the main season crops already emerged; green freshly emerged crops adjacent to crops close to maturity and infected with rust were a common sight. Both stem and leaf rust were observed on the survey. Stem rust was recorded in 33 of the fields surveyed (61%) and leaf rust in 25 of the fields (54%).

July 3, 2012: Eighth new Ug99 variant identified – Race TTKSF+ confirmed in South Africa and Zimbabwe

Posted on by July 4, 2012

Photo Credit: ZA Pretorius

stem rust samples collected from Afrikaskop, Eastern Free State, South Africa in Dec. 2010 and Birchenough, Eastern Zimbabwe in Sept. 2010 have been confirmed to be a new variant in the Ug99 lineage. The confirmed findings have just been published in Plant Disease by Pretorius et al. (2012). The new variant has been designated as race TTKSF+, this is the eighth race detected in the Ug99 group. The new race was collected from the winter wheat cv. Matlabas in South Africa. This was the first time this cultivar had been observed to be infected with stem rust. Microsatellite analysis showed that all single pustule isolates established from the original Matlabas isolate formed part of the Ug99 group. Race analysis using the 20 North American (NA) stem rust differential lines and letter code system classified the new race as TTKSF. However, cv. Matlabas is resistant to race TTKSF and characterization with selected single nucleotide polymorphisms (SNPs), revealed that all single pustule isolates of the Matlabas race shared an identical genotype that differed from race TTKSF. The Zimbabwe isolate was identical and was also classified as race TTKSF+. Studies are under way to determine the identity of the defeated Sr gene in Matlabas. Since no other cultivars or advanced lines were found to carry the Matlabas gene, it is unlikely that race TTKSF+ will threaten wheat production in South Africa. However, the occurrence of a new Ug99-related race emphasizes the variability within this internationally important group.

[Photo Legend: Left to right: race TTKSF+ on Matlabas; race TTKSF on Matlabas; race TTKSF (original isolate) on Matlabas, Susceptible Control]

July 2, 2012: Several new rust resistant varieties released in Ethiopia and Kenya

Posted on by July 3, 2012

Photo Credit: Meredith Braden

Breeding for rust resistance in East Africa is moving forward at a rapid pace. National research programs in both Ethiopia and Kenya have recently announced the formal release of several new rust resistant varieties in both countries. The Ethiopian Institute of Agricultural Research (EIAR) have released two new varieties – Hidase and Ogolcho. Both originate from CIMMYT germplasm and have resistance to both stem rust (Ug99) and yellow rust. Hidase is targeted towards highland environments and Ogolcho to lowland environments. Full details are given on the Ethiopia Rust Resistant Cultivars page.

In Kenya, the Kenyan Agricultural Research Institute (KARI) have released six new rust resistant varieties – Kenya Tae, Kenya Sunbird, Kenya Wren, Kenya Korongo, Kenya Kingbird, and Kenya Hawk12. All of these are derived from CIMMYT germplasm selections and have resistance to stem rust Ug99 and yellow rust. Full details are given on the Kenya Rust Resistant Cultivars page.

The fantastic progress achieved by the wheat breeding programs in both Ethiopia and Kenya is a wonderful achievement. It reflects the ever-increasing national capacity in both countries and the strong partnerships with the international wheat community, notably – CIMMYT, ICARDA and the DRRW project.

June 25, 2012: Azerbaijan rust survey summary – very low incidence of yellow rust

Posted on by June 26, 2012

Wheat rust surveys were undertaken by staff from the Azerbaijan Institute of Crop Husbandry throughout most of the wheat growing regions of Azerbaijan during early June 2012. A total of 8 sites were surveyed using standard BGRI survey methodology, the sites were representative of  the wheat growing areas of the country. Conditions in 2012 did not appear favourable for rust development and the only record was yellow rust at low incidence and severity on the Gobustan Research Station. The survey did however record very high incidence and severity of Tan Spot at virtually all the survey locations. The cultivar Bezostaya was severely affected by Tan Spot.

June 1, 2012: South Africa – Latest race analysis results. Race TTKSF continues to be the predominant stem rust race in South Africa

Posted on by June 26, 2012

Analysis undertaken by the Small Grains Institute, Agricultural Research Council (ARC), South Africa indicated the continued predominance of stem rust race TTKSF in South Africa. Race TTKSF is one of the Ug99 lineage races, although it is avirulent on Sr31. This race was first detected in South Africa in 2000 by Prof Z.A. Pretorius, University of the Free State and was identified in Zimbabwe in 2007. Of the 40 South African stem rust isolates analysed in 2011, 35 were typed to be race TTKSF. Additional races detected in 2011 were BPGSC+Sr27, Kw, Satu (2SA105) [n=4] and BPGSC+Sr27 (2SA102) [n=1].

June 1, 2012: Eritrea – Latest race analysis results. “J races” predominate, but PTKST still present

Posted on by June 26, 2012

Analysis undertaken by AAFC, Canada on stem rust samples collected by NARI, Eritrea in Oct. 2011 has confirmed the continued presence of Ug99 lineage race PTKST in Eritrea, but only 1 sample out 15 was typed to this race. All other samples analysed were found to be “J races”  (JRCSC  (n=2), JRHSC (n=4), JRHSF (n=8)) these are all virulent on Sr13 and probably came from durum wheat. A set of samples of stem rust from Oats was collected and analysed. The Oat results were interesting,  two races were identified NHFC (n=11) and NKFC (n=3), all the isolates were clearly high on genes Pg10 and Pg16. It is believed that this virulence is not present anywhere else in the world except Australia.