Latest Survey Data
- Rust Issues: All 3 rusts are potential constraints, but widespread chemical control is undertaken.
- Ug99 Status: Race TTKSK (Ug99) was detected in Egypt in 2014.
Situation Updates:
Combined results from race analysis undertaken at several different labs indicate that five new variants in the Ug99 lineage were detected from samples collected in East Africa during 2013 or 2014. Probably most significant were the two new SrTmp variants (Races TTKTK and TTKTT) previously reported (see “16 April 2015: BGRI report two new Ug99 variants with virulence to SrTmp detected in Kenya” and Patpour et al. 2015). Further analysis has revealed the presence of three additional new Ug99 lineage races. Details of these additional new races are:
- Race TTHST: Similar to race TTKST (Ug99 + Sr24 vir) but avirulent on Detected in Kenya in 2013 (1 isolate). Source lab: USDA-ARS Cereals Disease Lab, USA (Newcomb et al in prep)
- Race TTHSK: Similar to race TTKSK (Ug99) but avirulent on Detected in Kenya in 2014 (2 isolates). Source lab: AAFC Morden Research Centre, Canada (Fetch et al 2016)
- Race PTKTK: Similar to race PTKSK (Ug99 but avir on Sr21) but virulent on SrTmp. Detected in Kenya in 2014 (5 isolates). Source lab: AAFC Morden Research Centre, Canada (Fetch et al 2016)
These latest results bring the total of known variants within the Ug99 lineage to 13, with yet another SrTmp variant being detected in Kenya. All five of the new variants were detected in Kenya, but as previously reported race TTKTK was also detected in Uganda, Rwanda, Eritrea and Egypt in 2014. The results indicate that the Ug99 race group continues to evolve at a rapid rate.
Mehran Patpour (Global Rust Reference Center in Denmark) and co-authors have just published details of the emergence and spread of virulence to SrTmp in the Ug99 race group in Africa. The note is now available as a First Look in Plant Disease (see http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-06-15-0668-PDN). The report details the results of combined race analysis undertaken by the GRRC, Denmark and the USDA-ARS Cereals Disease Lab, Minnesota on 84 stem rust samples collected in 2014 from Kenya, Uganda, Rwanda and Egypt.
Seedling reaction of Race TTKTK on selected differentials (Photo: GRRC, Denmark)
The presence of two new Ug99 race group variants – race TTKTK (Ug99 + virulent on SrTmp) and race TTKTT (Ug99 + virulent on SrTmp and Sr24) were confirmed in Kenya. Race TTKTK was also confirmed in Uganda, Rwanda and Egypt. Detection of these new variants in the Ug99 race group across several countries in a single year indicates the relevance of coordinated surveillance activities and also indicates potentially very rapid geographical dispersal of race TTKTK.
Fig 1: Modeled spore dispersal based on a source location in the central Nile Delta, Egypt for March, April, May 2014. Pink areas indicate where 95% of released spores are predicted to be deposited. Given high seasonal consistency, similar dispersal patterns would be expected to occur in March-May 2015.
Following the confirmed detection of Ug99 (race TTKSK) in Egypt in 2014 (BGRI special newsletter report April 2015) increased vigilance is needed for stem rust in the eastern Mediterranean. Although no confirmed reports of race TTKSK have been obtained from Egypt in 2015, trace amounts of stem rust (race unknown) were detected in the central delta of Egypt in early March 2015. No further reports of stem rust outbreaks have been reported from Egypt in 2015. Crops in Egypt are now approaching maturity, with harvesting occurring between mid April to mid May. However, if any stem rust inoculum were to build up in Egypt then spore deposition models run jointly by the UK Met Office and Cambridge University indicate that there is a risk of onward movement of spores to the eastern Mediterranean basin. Model results show consistent seasonal deposition patterns over the last 12 years, indicating a higher risk, relative to other areas, of spore deposition for Israel, Lebanon, Jordan, eastern Syria and southern Turkey. During the months April and May typically there is a large spatial variation of deposition patterns, with long-distance dispersal of spores that reach eastern Mediterranean countries (see Fig 1 – Data from March, April, May 2014 used as an illustrative example of typical spore dispersal patterns). The most recent spore deposition forecast maps for the period 8 – 14 April 2015, based on confirmed sites for Ug99 (race TTKSK) in Egypt in 2014 agree well with the long-term dispersal trends. Increased surveillance and monitoring is advised in Israel, Lebanon, Jordan, eastern Syria and southern Turkey. Sampling of any stem rust detected in the eastern Mediterranean and rapid race identity confirmation is recommended (either by race analysis on live samples or through the USDA CDL SNP assay for the Ug99 race group). Please contact Dave Hodson, CIMMYT (d.hodson@cgiar.org) for more details on sampling options.
Wheat rust surveys were undertaken during the period mid February to the end of April 2011. The surveys covered the wheat growing areas of the Nile Valley from Aswan to the Delta. A total of 32 wheat fields were surveyed using standard BGRI survey methodology. Stem rust was absent in all the fields surveyed. Leaf rust was widespread and the predominant rust recorded on the survey. Leaf rust was observed in 90% of the fields visited, but mainly the disease was at low severity. Only 4 fields (all in the Delta) were observed to have high disease severity (>40%). Yellow rust was only observed in trace amounts. Only 2 fields were recorded with the disease, one of which had high severity.
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.