Wheat stem (or black) rust, caused by Puccinia graminis f. sp. tritici (Pgt), has been historically among the most devastating global fungal diseases of wheat. The recent occurrence and spread of new virulent races such as Ug99 have prompted global efforts to identify and isolate more effective stem rust resistance (Sr) genes. Here, we report the map-based cloning of the Ug99-effective SrTm5 gene from diploid wheat Triticum monococcum accession PI 306540 that encodes a typical coiled-coil nucleotide-binding leucine-rich repeat protein. This gene, designated as Sr22b, is a new allele of Sr22 with a rare insertion of a large (13.8-kb) retrotransposon into its second intron. Biolistic transformation of an ~112-kb circular bacterial artificial chromosome plasmid carrying Sr22b into the susceptible wheat variety Fielder was sufficient to confer resistance to stem rust. In a survey of 168 wheat genotypes, Sr22b was present only in cultivated T. monococcum subsp. monococcum accessions but absent in all tested tetraploid and hexaploid wheat lines. We developed a diagnostic molecular marker for Sr22b and successfully introgressed a T. monococcum chromosome segment containing this gene into hexaploid wheat to accelerate its deployment and pyramiding with other Sr genes in wheat breeding programmes. Sr22b can be a valuable component of gene pyramids or transgenic cassettes combining different resistance genes to control this devastating disease.

中文翻译：

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小麦茎锈病抗性基因 Sr22 的新等位基因 Sr22b 的鉴定和表征对 Ug99 种族组有效

小麦茎（或黑色）锈病，由Puccinia graminis f. 引起。sp。tritici ( Pgt ) 在历史上一直是全球最具破坏性的小麦真菌病害之一。最近出现和传播的新毒株如 Ug99 促使全球努力识别和分离更有效的茎锈病抗性 ( Sr ) 基因。在这里，我们报告了来自二倍体小麦Triticum monococcum登记号 PI 306540​​ 的 Ug99 有效SrTm5基因的基于图谱的克隆，该基因编码典型的卷曲螺旋核苷酸结合富含亮氨酸的重复蛋白。该基因命名为Sr22b，是 Sr22 的一个新等位基因在它的第二个内含子中罕见地插入了一个大的 (13.8-kb) 反转录转座子。将携带Sr22b的~112-kb 环状细菌人工染色体质粒基因枪转化到易感小麦品种 Fielder 中足以赋予对茎锈病的抗性。在对 168 种小麦基因型的调查中，Sr22b仅存在于栽培的T中。 单球菌亚种 单球菌种质，但在所有测试的四倍体和六倍体小麦系中均不存在。我们为Sr22b开发了一种诊断分子标记，并 成功渗入了一个T。单球菌包含该基因的染色体片段进入六倍体小麦，以加速其在小麦育种计划中的部署和与其他Sr基因的整合。Sr22b可以是基因金字塔或转基因盒的重要组成部分，结合不同的抗性基因来控制这种破坏性疾病。