Fine Mapping of Wheat Stripe Rust Resistance Gene Yr26 Based on Collinearity of Wheat with Brachypodium distachyon and Rice

Xiaojuan Zhang,Zhensheng Kang,Jianhui Wu,Fengping Yuan,Dejun Han,Lili Huang,Qingdong Zeng,Jingdong Shi,Qilin Wang,Yinghui Duan,James C Nelson

doi:10.1371/journal.pone.0057885

Xiaojuan Zhang, Zhensheng Kang + Show 9 more

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https://doi.org/10.1371/journal.pone.0057885

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Journal: PloS one	Publication Date: Mar 5, 2013
Citations: 71	License type: CC BY 4.0

Affiliation: North West Agriculture and Forestry University

Abstract

The Yr26 gene, conferring resistance to all currently important races of Puccinia striiformis f. sp. tritici (Pst) in China, was previously mapped to wheat chromosome deletion bin C-1BL-6-0.32 with low-density markers. In this study, collinearity of wheat to Brachypodium distachyon and rice was used to develop markers to saturate the chromosomal region containing the Yr26 locus, and a total of 2,341 F2 plants and 551 F2∶3 progenies derived from Avocet S×92R137 were used to develop a fine map of Yr26. Wheat expressed sequence tags (ESTs) located in deletion bin C-1BL-6-0.32 were used to develop sequence tagged site (STS) markers. The EST-STS markers flanking Yr26 were used to identify collinear regions of the rice and B. distachyon genomes. Wheat ESTs with significant similarities in the two collinear regions were selected to develop conserved markers for fine mapping of Yr26. Thirty-one markers were mapped to the Yr26 region, and six of them cosegregated with the resistance gene. Marker orders were highly conserved between rice and B. distachyon, but some rearrangements were observed between rice and wheat. Two flanking markers (CON-4 and CON-12) further narrowed the genomic region containing Yr26 to a 1.92 Mb region in B. distachyon chromosome 3 and a 1.17 Mb region in rice chromosome 10, and two putative resistance gene analogs were identified in the collinear region of B. distachyon. The markers developed in this study provide a potential target site for further map-based cloning of Yr26 and should be useful in marker assisted selection for pyramiding the gene with other resistance genes.

Highlights

Wheat (Triticum aestivum L.) is an important crop and a primary food source for humans
Among the 551 F2:3 families tested with the same race, 147 of 409 families derived from resistant F2 plants were homozygous resistant, 262 segregated and 142 families derived from susceptible F2 plants were homozygous susceptible
The responses were consistent with earlier F2 phenotypes; that is, 49 F2:3 families derived from susceptible F2 plants were homozygous susceptible, 7 of 43 families derived from resistant F2 plants were homozygous resistant and 36 were segregating

Summary

Introduction

Wheat (Triticum aestivum L.) is an important crop and a primary food source for humans. Most of these genes have been mapped on chromosomes and/or specific chromosomal regions, and many of them have been used in wheat breeding programs worldwide. With the spread of Pst race CYR32, a large number of known resistance genes are no longer effective in China [1]. Yr26 has been widely used in wheat breeding programs in China for developing stripe rust resistant cultivars [4,5], varieties with Yr26 are grown on more than 3.4 million hectares in China. As the gene is still effective against the current Pst populations, cloning Yr26 is important for understanding the molecular mechanisms of resistance. The gene was previously mapped near the centromere region, putatively on the short arm of wheat chromosome B with SSR markers Xgwm, Xgwm and Xgwm413 [6]. Several markers have been mapped to the Yr26 region, the number of the markers is still limited, and more are needed for more efficient marker-assisted selection, fine mapping and map-based cloning of Yr26

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