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Identification and characterization of Sr13, a tetraploid wheat gene that confers resistance to the Ug99 stem rust race group

  1. Jorge Dubcovskya,d,2
  1. aDepartment of Plant Sciences, University of California, Davis, CA 95616;
  2. bDepartment of Plant Pathology, University of Minnesota, St. Paul, MN 55108;
  3. cUS Department of Agriculture-Agricultural Research Service, Cereal Disease Laboratory, University of Minnesota, St. Paul, MN 55108;
  4. dHoward Hughes Medical Institute, Chevy Chase, MD 20815
  1. Contributed by Jorge Dubcovsky, September 25, 2017 (sent for review April 24, 2017; reviewed by Paul Schulze-Lefert and Brian J. Staskawicz)

Significance

Wheat provides a substantial proportion of the calories and proteins consumed by humans, but further production increases are necessary to feed a growing human population. Reducing yield losses caused by pathogens can contribute to these increases. In this study, we report the identification of Sr13, a gene from pasta wheat that confers resistance to the new virulent races of the stem rust pathogen that appeared in Africa at the beginning of this century. We identified three different resistance forms of Sr13 and developed a diagnostic marker to accelerate their deployment in wheat breeding programs. In addition, Sr13 can be a useful component of transgenic cassettes including multiple resistance genes.

Abstract

The Puccinia graminis f. sp. tritici (Pgt) Ug99 race group is virulent to most stem rust resistance genes currently deployed in wheat and poses a threat to global wheat production. The durum wheat (Triticum turgidum ssp. durum) gene Sr13 confers resistance to Ug99 and other virulent races, and is more effective at high temperatures. Using map-based cloning, we delimited a candidate region including two linked genes encoding coiled-coil nucleotide-binding leucine-rich repeat proteins designated CNL3 and CNL13. Three independent truncation mutations identified in each of these genes demonstrated that only CNL13 was required for Ug99 resistance. Transformation of an 8-kb genomic sequence including CNL13 into the susceptible wheat variety Fielder was sufficient to confer resistance to Ug99, confirming that CNL13 is Sr13. CNL13 transcripts were slightly down-regulated 2–6 days after Pgt inoculation and were not affected by temperature. By contrast, six pathogenesis-related (PR) genes were up-regulated at high temperatures only when both Sr13 and Pgt were present, suggesting that they may contribute to the high temperature resistance mechanism. We identified three Sr13-resistant haplotypes, which were present in one-third of cultivated emmer and durum wheats but absent in most tested common wheats (Triticum aestivum). These results suggest that Sr13 can be used to improve Ug99 resistance in a large proportion of modern wheat cultivars. To accelerate its deployment, we developed a diagnostic marker for Sr13. The identification of Sr13 expands the number of Pgt-resistance genes that can be incorporated into multigene transgenic cassettes to control this devastating disease.

Footnotes

  • ?1W.Z. and S.C. contributed equally to this work.

  • ?2To whom correspondence may be addressed. Email: matthew.rouse{at}ars.usda.gov or jdubcovsky{at}ucdavis.edu.
  • Author contributions: M.N.R. and J.D. designed research; W.Z., S.C., Z.A., J.N., and M.N.R. performed research; W.Z., S.C., J.N., M.N.R., and J.D. analyzed data; W.Z., S.C., M.N.R., and J.D. wrote the paper; and J.D. supervised the project.

  • Reviewers: P.S.-L., Max Planck Institute for Plant Breeding Research; and B.J.S., University of California, Berkeley.

  • The authors declare no conflict of interest.

  • Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. KY825225KY825235 and KY924305).

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1706277114/-/DCSupplemental.

Online Impact

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