Genetic Maps of Stem Rust Resistance Gene Sr35 in Diploid and Hexaploid Wheat

Puccinia graminis f. sp. tritici is the causal agent of stem rust of wheat. A new race designated TTKSK (also known as Ug99) and its variants (TTKST and TTTSK) are virulent to most of the stem rust resistance genes currently deployed in wheat cultivars worldwide. Therefore, identi! cation, mapping, and deployment of effective resistance genes are critical components of global efforts to mitigate this threat. Multipathotype seedling tests demonstrated that resistance gene Sr35 is effective against the three TTKS variants and another broadly virulent race from Yemen, TRTTF. Two genetic maps of Sr35 are presented in diploid (Triticum monococcum) and two in hexaploid wheat (T. aestivum). The Sr35 resistance to TRTTF and RKQQC races was mapped in diploid wheat within a 2.2 to 3.1 cM interval on the long arm of chromosome 3Am between markers XBF483299 and XCJ656351. This interval corresponds to a 174-kb region in Brachypodium that includes 16 annotated genes. The Sr35 map location was con! rmed in two backcross-derived hexaploid populations segregating for Sr35. Recombination between diploid and hexaploid chromosomes was 10-fold lower than between homologous chromosomes, but was suf! cient to reduce the introgressed diploid segment. These maps provide markers closely linked to Sr35 that will be useful to accelerate its deployment and pyramiding with other stem rust resistance genes. Wenjun Zhang, Zewdie Abate, and Jorge Dubcovsky, Univ. of California, Dep. Plant Sciences, Davis, CA 95616. Eric Olson, Cyrille Saintenac, and Eduard Akhunov, Kansas State Univ., Dep. Plant Pathology, Manhattan, KS 66506. Matt Rouse and Yue Jin, Univ. of Minnesota, Dep. of Plant Pathology, St. Paul, MN 55108. Yue Jin, USDA-ARS, Cereal Disease Lab., Univ. of Minnesota, St. Paul, MN 55108. Mike Pumphrey, Washington State Univ., Dep. Crop and Soil Sciences, Pullman, WA 99164. Wenjun Zhang and Eric Olson contributed equally to this work. Received 13 Apr. 2010. *Corresponding author ( [email protected]). Abbreviations: EST, expressed sequence tag; RIL, recombinant inbreed lines; SSR, simple sequence repeat; TTKS-complex: TTKSK, TTKST, and TTTSK stem rust races. Published in Crop Sci. 50:2464–2474 (2010). doi: 10.2135/cropsci2010.04.0202 Freely available online through the author-supported open-access option. Published online 27 Sept. 2010. © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.