Foreword Norman E. Borlaug Stem rust is a catastrophic disease because of its ability to cause complete annihilation of wheat crops over wide areas. The use of genetic resistance in the major stem rust-prone regions of the world and the organized distribution of resistant germplasm through the International Rust Nursery scheme supported by the USDA and the Rockefeller Foundation, and later replaced by the CIMMYT nursery network, provided ongoing and updated sources of resistant germplasm to the international breeding community. In return, collaborating groups gave feedback on the responses of materials in their respective regions. During the late 1950s and early 1960s, great emphasis was placed on data that came from Kenya, Egypt, and southern Africa. The widespread use of stem rust resistant cultivars such as Red Egyptian, Kenya Farmer, Africa 43 and later, lines like Kenya Page and Africa Mayo, points to the key role of East Africa in the development of genetic resources that led to the global decline of stem rust. The stem rust threat was a primary reason for the establishment of the Rockefeller Foundation- sponsored program in Mexico, the predecessor of CIMMYT. The semi-dwarf, stem rust resistant, widely adapted spring wheat germplasm generated by this program led to the Green Revolution. Much of the material possessed the historically durable “Sr2 complex” from Hope and other well-known stem rust resistance genes. The widespread use of the 1BL.1RS translocation with Sr31 and its continuing stem rust protection on a worldwide basis has led to complacency throughout the wheat community. The discovery of race Ug99 with virulence for Sr31 and other important genes in Uganda in 1999, and possibly earlier in Kenya, was a reminder of the pathogen’s ability to respond, but little seems to have happened in breeding programs until the emergence of current concerns following the continued incidence and spread of race Ug99 in Eastern Africa. A major objective of this report is to assess global vulnerability to stem rust if race Ug99continues to spread. Most of the countries and regions responding to a series of questions relating to their specific situations indicated resistance to stem rust was no longer a leading breeding objective. Several noted that routine surveys were detecting increasing incidences of stem rust, associated with ill-advised use of susceptible varieties. Epidemics occur as a consequence of the use of widely popular very susceptible cultivars. The dynamics of rust epidemics are very much like those of forest or bush fires. The ingredients of fires (and rust epidemics) are fuel (area and distribution of susceptible material, degree of susceptibility), favorable climate conditions (optimum temperatures and moisture), number of ignition points (amount of initial inoculum), air movement, and complacency. Once started, both are difficult to stop. The prospect of a stem rust epidemic in wheat in Africa, Asia and the Americas is real and must be stopped before it causes untold damage and human suffering. i ACKNOWLEDGEMENTS The support of the Rockefeller Foundation in making this assessment possible is acknowledged with appreciation. The team also appreciated the keen interest and availability of the Directors and staff of the Ethiopian Agricultural Research Organization (EARO) and the Kenya Agricultural Research Organization (KARI). The foresight of CIMMYT and ICARDA in commissioning this report is commended and the support of CIMMYT’s offices in both Ethiopia and Kenya is gratefully acknowledged. Dr. Chris Dowswell contributed language for the foreword and other sections of the report. Finally, our Panel and everyone that we encountered during the course of this assessment appreciated the role of Dr. Norman Borlaug in bringing this problem to the attention of the international community. ii CONTENTS Page FOREWORD.............................................................................................................................................. i ACKNOWLEDGEMENTS ..................................................................................................................... ii SUMMARY AND RECOMMENDATIONS...........................................................................................1 CHAPTER 1 – WHEAT STEM RUST....................................................................................................3 1.1 The disease......................................................................................................................................3 1.2 Epidemiology..................................................................................................................................4 1.3 Virulence.........................................................................................................................................4 1.4 Race Ug99.......................................................................................................................................4 1.5 Evolution of new races and dispersal (migration path)...................................................................5 CHAPTER 2 – KENYA AND ETHIOPIA ASSESSMENT...................................................................7 2.1 Ethiopia ...........................................................................................................................................7 2.2 Kenya ..............................................................................................................................................8 2.3 Current and potential economic and social impacts in SSA ...........................................................9 - Ethiopia.......................................................................................................................................11 - Kenya..........................................................................................................................................12 CHAPTER 3 – VULNERABILITY OF OTHER GEOGRAPHICREGIONS ..................................15 3.1 Africa ............................................................................................................................................15 3.2 Asia ...............................................................................................................................................15 3.3 Europe ...........................................................................................................................................16 3.4 The Americas ................................................................................................................................16 3.5 Australia and New Zealand...........................................................................................................17 3.6 Conclusion ....................................................................................................................................17 CHAPTER 4 – STRATEGIES FOR CONTROL.................................................................................18 4.1 Pathogen monitoring .....................................................................................................................18 4.2 Genetic resistance, diversity and utilization..................................................................................18 4.3 Breeding for resistance with emphasis on durable type................................................................19 4.4 Emergency control measures ........................................................................................................20 4.5 Seed multiplication and distribution .............................................................................................20 4.6 Socio-economics ...........................................................................................................................20 4.7 Human resources...........................................................................................................................21 4.8 Infrastructure.................................................................................................................................21 4.9 Reporting and Communication .....................................................................................................21 4.10 Resources for International Agricultural Research Centers..........................................................21 REFERENCES.........................................................................................................................................23 APPENDICES..........................................................................................................................................25 Appendix I -- Panel Members....................................................................................................................25 Appendix II -- Persons Contacted............................................................................................................. 25 Appendix III -- Contributors........................................................................................................26 iii SUMMARY AND RECOMMENDATIONS The rusts (Puccinia spp.) have been a scourge on humankind since the beginning of historical time. Many epidemics have been recorded over the past 150 years, in the near and far east, Europe, and the Americas. Several devastating rust epidemics have resulted in major famines in Asia and grain losses at a massive scale in North America in 1903 and 1905 and 1950-54. For