Progress in breeding for resistance to Ug99 and other races of the stem rust fungus in CIMMYT wheat germplasm

Abstract

Races belonging to the Ug99 (TTKSK) lineage of the wheat stem rust fungus, carrying complex virulence combinations, and their migration to countries in Africa, Middle East and Asia continue to pose a significant threat to global wheat production. The rapid spread of additional races, e.g., TKTTF or the Digalu lineage, in several countries causing localized epidemics reminds us of the vulnerability of wheat germplasm to stem rust disease, a formidable foe referenced as early as biblical times. A global rust monitoring system reflecting increased surveillance efforts has identified 13 races within the Ug99 lineage in 13 countries and unrelated lineages are emerging, spreading and posing serious threats to wheat production. Race TKTTF has caused localized epidemics in Ethiopia and its variants have been recently implicated in stem rust outbreaks in Europe. Concerted research efforts have resulted in the identification of several new resistance genes and gene combinations for use in breeding. Combining multiple adult plant resistance (APR) genes in high-yielding backgrounds and discovery of new quantitative trait loci conferring stem rust resistance has progressed in the recent years, enhancing the durability of resistance. Effective gene stewardship and new generation breeding materials and cultivars that combine multiple race-specific or minor to intermediate effect APR genes, complemented by active surveillance and monitoring, have helped to limit major epidemics and increase grain yield potential in key target environments.

Keywords

adult plant resistance / black rust / race-specific resistance / Triticum aestivum

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Acknowledgements

We gratefully acknowledge the support of partnering institutions and financial support particularly from the DGGW Project managed by Cornell University and funded by the Bill and Melinda Gates Foundation and the UK Department for International Development, as well as the Indian Council of Agricultural Research, USAID, USDA-ARS and GRDC-Australia. We also thank Greg Grahek (Vice President of Publishing, The American Phytopathological Society) for Phytopathology’s permission (Ref. 25).

Compliance with ethics guidelines

Sridhar Bhavani, David P. Hodson, Julio Huerta-Espino, Mandeep S. Randhawa, and Ravi P. Singh declare that they have no conflicts of interest or financial conflicts to disclose.

This article is a review and does not contain any studies with human or animal subjects performed by any of the authors.

RIGHTS & PERMISSIONS

The Author(s) 2019. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)