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| High-resolution mapping of SrTm4, a recessive resistance gene to wheat stem rust |
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Race Ug99 of Puccinia graminis f. sp. tritici (Pgt), the causal agent of wheat stem (or black) rust is one of the most serious threats to global wheat production. The identification, mapping, and deployment of effective stem rust resistance (Sr) genes are critical to reduce this threat. In this study, we generated SrTm4 monogenic lines and found that this gene confers resistance to North American and Chinese Pgt races. Using a large mapping population (9522 gametes), we mapped SrTm4 within a 0.06 cM interval flanked by marker loci CS4211 and 130K1519, which corresponds to a 1.0-Mb region in the Chinese Spring reference genome v2.1. |
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Hongna Li, Jing Luo, Wenjun Zhang, Lei Hua, Kun Li, Jian Wang, Binyang Xu, Chen Yang, Guiping Wang, Matthew N. Rouse, Jorge Dubcovsky & Shisheng Chen
Theoretical and Applied Genetics May 2023; vol. 136, Article number: 120
Key messageThe diploid wheat recessive stem rust resistance gene SrTm4 was fine-mapped to a 754-kb region on chromosome arm 2AmL and potential candidate genes were identified. AbstractRace Ug99 of Puccinia graminis f. sp. tritici (Pgt), the causal agent of wheat stem (or black) rust is one of the most serious threats to global wheat production. The identification, mapping, and deployment of effective stem rust resistance (Sr) genes are critical to reduce this threat. In this study, we generated SrTm4 monogenic lines and found that this gene confers resistance to North American and Chinese Pgt races. Using a large mapping population (9522 gametes), we mapped SrTm4 within a 0.06 cM interval flanked by marker loci CS4211 and 130K1519, which corresponds to a 1.0-Mb region in the Chinese Spring reference genome v2.1. A physical map of the SrTm4 region was constructed with 11 overlapping BACs from the resistant Triticum monococcum PI 306540. Comparison of the 754-kb physical map with the genomic sequence of Chinese Spring and a discontinuous BAC sequence of DV92 revealed a 593-kb chromosomal inversion in PI 306540. Within the candidate region, we identified an L-type lectin-domain containing receptor kinase (LLK1), which was disrupted by the proximal inversion breakpoint, as a potential candidate gene. Two diagnostic dominant markers were developed to detect the inversion breakpoints. In a survey of T. monococcum accessions, we identified 10 domesticated T. monococcum subsp. monococcum genotypes, mainly from the Balkans, carrying the inversion and showing similar mesothetic resistant infection types against Pgt races. The high-density map and tightly linked molecular markers developed in this study are useful tools to accelerate the deployment of SrTm4-mediated resistance in wheat breeding programs.
See https://link.springer.com/article/10.1007/s00122-023-04369-z
Figure 2: High-density genetic maps for stem rust resistance locus SrTm4. a Genomic region containing SrTm4 (marked in gray) on the long arm of wheat chromosome 2A. b Genetic map based on 811 F2 plants and 14 molecular markers; c High-density genetic map based on 4761 F2 plants and 10 molecular markers; d Physical map of Chinese Spring. Coordinates are based on CS RefSeq v2.1 |
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.png "High-resolution mapping of SrTm4, a recessive resistance gene to wheat stem rust")
.png "High-resolution mapping of SrTm4, a recessive resistance gene to wheat stem rust")
