Durable Rust Resistance in Wheat

The Durable Rust Resistance in Wheat Project, a collaborative effort begun in April 2008 and ended in 2016, included 22 research institutions around the world and was led by Cornell University.

The objectives of the project sought to mitigate rust threats through coordinated activities to replace susceptible varieties with durably resistant varieties, create accelerated multilateral plant breeding and deliver varieties through optimized developing country seed sectors.

The DRRW was funded by the Bill and Melinda Gates Foundation and the UK Department for International Development.


Human Capacity, Training & Gender
In 2016, the DRRW project engages more than 2000 scientists from 35 international institutions spread over 23 countries, in the global effort to fight wheat rusts. This is up from the handful of scientists and the four original partners (FAO, ICARDA, CIMMYT and Cornell) in 2008.
Since 2008, more than 450 young scientists from around the world have been trained in breeding, screening, pathogen analysis and field survey techniques and methodologies in training courses held in Kenya, Ethiopia, Nepal, India and Mexico. In addition, thirteen graduates students were selected on a competitive basis to deliver plenary presentations at the BGRI technical workshops, 2012-2015.
To help improve the gender balance in the wheat research community, the DRRW instituted the annual Jeanie Borlaug Laube Women in Triticum (WIT) Early Career Awards. Since 2010, 34 women researchers, from 20 countries, have been selected to receive support to participate in the annual Borlaug Global Rust Initiative (BGRI) meeting and in further education and training.
As one indicator of improved gender balance, since 2008, the numbers of women attending the annual BGRI workshop has risen from 15% to 30%.
To further strengthen the pipeline feeding young female scientists into wheat breeding and pathology, the DRRW instituted the annual Jeanie Borlaug Laube Women in Triticum Mentor Award to honor men and women who encourage and mentor female talent. Since 2010, six senior scientists of the DRRW community, working in five countries, have been honoured with the mentor award.
To insure that both men and women farmers are willing to adopt new, improved varieties of rust resistant wheat, the DRRW involves farmers in “participatory variety selection” trials, in which farmers’ input — including input from women who do much of the planting, weeding, and post-harvest use — is considered. Better metrics need to be employed.
Data generation, information sharing and open-access publications are important features of DRRW, and are shared on a robust website, globalrust.org, that is seen as a resource by the entire wheat community. More than 250 peer-reviewed articles have been published in scientific journals, an estimated 170 of which are in open-access publications.

Pre-breeding, Breeding and Seed Delivery
More than 63 varieties of wheat resistant to stem rust Ug99 have been released in 10 at-risk countries since 2008. Those countries — many of which are located in zones that are climate-variable, food-insecure and/or war-torn — are Egypt, Sudan, Ethiopia, Kenya, Iran, Pakistan, Afghanistan India, Bhutan, and Nepal.
During the project period Year-8 (October 2014-September 2015), an estimated 38,000 tons of Ug99 resistance wheat seed were available for planting or will be harvested, which includes 17,600 tons of 12 varieties in Kenya and 17,700 tons of at least 12 varieties in Ethiopia (including 2,000 households that lost their wheat harvest to stem rust epidemics).  Since 2011 an estimated 880,000 tons of rust resistant seed have been distributed to farmers and breeding stations. (In 2012 approximately 750,000 tons of resistant seed were distributed under the USAID Famine Seed Project. Average distribution for other years is 33,000 tons.)  
Since 2008, DRRW scientists have increased the availability of effective race-specific resistance genes and molecular markers for their responsible stewardship. More than 40 plant genes have been identified as sources of resistance to TTKSK (Ug99) and related variants. Of those, 30 have molecular markers and are in wheat breeders’ toolboxes.
To counteract the rust pathogens’ ability to mutate and overcome single resistance genes, the DRRW encourages breeders to use germplasm responsibly, and only release varieties that deploy durable resistant rust gene combinations. To this end, the DRRW instituted the Gene Stewardship Award in 2011. Since then, four national teams have received the award: Nepal, Australia, Ethiopia and Kenya.
Since 2008, breeders have enhanced understanding of complex adult-plant resistance (APR), pleiotropic multi-pathogen resistance genes, QTLs and breeding progress.
The pipeline of high-yielding, Ug99 resistant wheat germplasm developed through Mexico-Kenya shuttle breeding is distributed worldwide through CIMMYT international nurseries and trials. That pipeline has more capacity and is more robust than in 2008.
Systematic technology generation including fast-track variety development & release, and adoption and testing of elite international lines for release or registration have helped replace susceptible varieties with varieties carrying APR genes.

Surveillance and Monitoring
Creation of a surveillance & monitoring network unprecedented in scope or scale for crop pathogens. As of 2015, scientists from 37 countries are participating in rust surveillance through a globally coordinated, online surveillance community. In 2007, scientists from only two countries were involved in the network. Today this network covers all major wheat growing countries of Africa, Middle East and South Asia. Over 23,000 geo-referenced survey records and 5000+ rust isolates records have been collected, resulting in one of the most comprehensive plant disease databases. For the first time, important stem rust race groups, e.g., the Ug99 race group, have been successfully tracked in space and time. The successful system is now being applied to other crops and diseases. The rust surveillance and monitoring system for wheat is being used as a model for other crop / pathogen systems, notably Maize Lethal Necrosis.
Partnerships & Community Building. A dynamic community has been built around the surveillance activities. Annual surveillance meetings have attracted 60+ scientists from 30+ countries. A network of partnerships spanning the entire spectrum from advanced to basic research has contributed to the overall success of the surveillance system.
Improved knowledge through increasing use of cutting-edge technologies. Expanded use of molecular diagnostics and genomics is providing new insights into pathogen population genetics, evolution and migration. Advanced spore dispersal and epidemiology modeling are providing an improved understanding of migration pathways and permitting improved early warning.
Rust surveillance and monitoring capacity in Ethiopia.
Ethiopia is on the way to having one of the most comprehensive rust monitoring systems in the world. Surveillance and pathotyping facilities are fully functional. Advanced early warning systems are being developed. Early detection and rapid response to race TKTTF (Digalu race) illustrated the functionality of the surveillance system.
With the improved capacity of the international pathogen surveillance and monitoring network, an outbreak of stem rust was detected in late December 2014 in Ethiopia. Because of early detection and subsequent rapid identification, it was confirmed that this was a new stem rust race, labelled TKTTF or Digalu race, and not part of the Ug99 race group. Nonetheless, wheat varieties in the international breeders’ pipeline with resistance to TKTTF were identified and subsequently distributed to at-risk zones in Ethiopia to be deployed in time for the 2015 planting season. This rapid response effectively thwarted what could have been a major epidemic and protected farmers’ yields in parts of Ethiopia in 2015 and 2016. The world cannot afford to be complacent because the threat is still there: this new race is currently confirmed in nine countries — Turkey, Iran, Lebanon, Egypt, Ethiopia, Georgia, Azerbaijan, Eritrea and Yemen.

East Africa Screening Facilities
A world-class phenotyping platform has been established at the Kenya Agriculture & Livestock Research Organization (KALRO), in Njoro, Kenya, for screening against stem rust races of the Ug99 lineage. This facility plays a vital role in evaluating global wheat germplasm; facilitating pre-breeding, testing and release of Ug99 resistant varieties in the CIMMYT-Kenya shuttle breeding program; pathogen surveillance; and gene discovery and characterization studies.
Since 2006, over 400,000 accessions of bread wheat, durum wheat and barley from 25 countries have been screened in international screening nurseries in Kenya and Ethiopia. The capacity of these East African “Ground Zero” nurseries was virtually non-existent in 2005. Screening operation are carried out twice a year with a capacity of evaluating 50,000 lines annually from 25 countries and institutions worldwide with information provided to collaborators.
Phenotyping platforms are an integral component in the development and release of stem rust resistant germplasm globally.
29 partners from 24 countries currently screen cereal germplasm in the East African rust nurseries:
North America: USDA, NDSU, Cornell, AAFC, University of Alberta, CIMMYT
Europe: Hungary
Australia: University of SYDNEY, CSIRO
South America: Argentina, Uruguay, Paraguay, Brazil
Africa: Kenya, Ethiopia, South Africa, Uganda, Egypt, Morocco
Asia: India, China, Nepal, Bangladesh, Pakistan, Afghanistan, Bhutan
Middle East: Iran, Turkey, ICARDA
During the project, Central Asian countries also have submitted germplasm for screening: Tajikistan, Kazakhstan, and Uzbekistan.
Facilities at the Wheat Research Center of Excellence at the Kulumsa Agricultural Research Center in Ethiopia have been improved to include the mechanization of the wheat breeding program with tractors, combines and the human capacity for their maintenance and upkeep and the establishment of irrigation infrastructure that enables off-season seed multiplication. These improvements are in collaboration with EAAP, CIMMYT, and EIAR.
A greenhouse and head house at the Ambo Plant Protection Center in Ethiopia has been constructed with the concurrent development of routine pathoytpe analyses, and the rearing of clean, uncontaminated inoculum for field screening activities.
A seed cold-room storage has been constructed to enable long-term, safe storage of germplasm resources for the breeding programs at KARC and at the Debre Zeit Agricultural Research Center in Ethiopia, and for the safe storage of nuclear (pre-breeding, etc.) quantities of seed for multiplication.

Opportunities for the Future
To bring the power of well-managed collaboration, which was so effective in the DRRW, to all the major objectives of wheat improvement.
To establish effective collaborative screening platforms for other major constraints to wheat, such as heat and wheat diseases like Septoria and Helminthosporium (Spot Blotch), and to allow us to deliver genetic gains in the face of climate change.
To harness the revolutionary exponential expansion of computing power to drive genetic gain in wheat, the world’s most widely grown food crop.
To survey and monitor wheat varieties in fields using DNA analysis to accurately determine farmer adoption and seed dissemination.
To build scientific and leadership capacity in national programs in order to retain talent in country.