Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden.
United States Department of Agriculture, Agricultural Research Service, Cereal Disease Laboratory, St. Paul, MN, United States of America.
PLoS One. 2023 Oct 12;18(10):e0292724. doi: 10.1371/journal.pone.0292724. eCollection 2023.
Control of stem rust, caused by Puccinia graminis f.sp. tritici, a highly destructive fungal disease of wheat, faces continuous challenges from emergence of new virulent races across wheat-growing continents. Using combinations of broad-spectrum resistance genes could impart durable stem rust resistance. This study attempted transfer of Sr59 resistance gene from line TA5094 (developed through CSph1bM-induced T2DS·2RL Robertsonian translocation conferring broad-spectrum resistance). Poor agronomic performance of line TA5094 necessitates Sr59 transfer to adapted genetic backgrounds and utility evaluations for wheat improvement. Based on combined stem rust seedling and molecular analyses, 2070 BC1F1 and 1230 BC2F1 plants were derived from backcrossing BAJ#1, KACHU#1, and REEDLING#1 with TA5094. Genotyping-by-sequencing (GBS) results revealed the physical positions of 15,116 SNPs on chromosome 2R. The adapted genotypes used for backcrossing were found not to possess broad-spectrum resistance to selected stem rust races, whereas Sr59-containing line TA5094 showed resistance to all races tested. Stem rust seedling assays combined with kompetitive allele-specific PCR (KASP) marker analysis successfully selected and generated the BC2F2 population, which contained the Sr59 gene, as confirmed by GBS. Early-generation data from backcrossing suggested deviations from the 3:1 segregation, suggesting that multiple genes may contribute to Sr59 resistance reactions. Using GBS marker data (40,584 SNPs in wheat chromosomes) to transfer the recurrent parent background to later-generation populations resulted in average genome recovery of 71.2% in BAJ#12/TA5094, 69.8% in KACHU#12/TA5094, and 70.5% in REEDLING#1*2/TA5094 populations. GBS data verified stable Sr59 introgression in BC2F2 populations, as evidenced by presence of the Ph1 locus and absence of the 50,936,209 bp deletion in CSph1bM. Combining phenotypic selections, stem rust seedling assays, KASP markers, and GBS data substantially accelerated transfer of broad-spectrum resistance into adapted genotypes. Thus, this study demonstrated that the Sr59 resistance gene can be introduced into elite genetic backgrounds to mitigate stem rust-related yield losses.
小麦秆锈病由禾柄锈菌引起，是一种极具破坏性的真菌病害，其在各小麦种植洲不断出现新的毒性更强的菌株，因此对其的防治面临持续的挑战。利用广谱抗性基因的组合可以赋予小麦持久的秆锈病抗性。本研究试图将 TA5094 品系（通过 CSph1bM 诱导的 T2DS·2RL 罗伯逊易位产生广谱抗性而开发）中的 Sr59 抗性基因转移。TA5094 品系的农艺性能较差，因此需要将 Sr59 转移到适应性更强的遗传背景中，并进行小麦改良的利用评估。基于联合的秆锈苗期和分子分析，通过与 TA5094 回交，从 BAJ#1、KACHU#1 和 REEDLING#1 中衍生出 2070 个 BC1F1 和 1230 个 BC2F1 植株。基于测序的基因型分析（GBS）结果揭示了染色体 2R 上 15116 个 SNP 的物理位置。用于回交的适应性基因型被发现不具有对所选秆锈菌系的广谱抗性，而含有 Sr59 的 TA5094 品系表现出对所有测试的菌系的抗性。通过竞争性等位基因特异性 PCR（KASP）标记分析的秆锈苗期测定成功地选择和产生了含有 Sr59 基因的 BC2F2 群体，这通过 GBS 得到了证实。回交的早期世代数据表明存在偏离 3:1 的分离，这表明可能有多个基因对 Sr59 抗性反应有贡献。使用 GBS 标记数据（小麦染色体上的 40584 个 SNP）将轮回亲本背景转移到后续世代群体中，结果导致 BAJ#12/TA5094 群体的平均基因组回收率为 71.2%，KACHU#12/TA5094 群体为 69.8%，REEDLING#1*2/TA5094 群体为 70.5%。GBS 数据证实了 BC2F2 群体中 Sr59 的稳定导入，这表现在 Ph1 基因座的存在和 CSph1bM 中的 50936209 bp 缺失的不存在。将表型选择、秆锈苗期测定、KASP 标记和 GBS 数据相结合，大大加速了广谱抗性向适应性基因型的转移。因此，本研究表明，Sr59 抗性基因可以被引入到优良的遗传背景中，以减轻由秆锈病引起的产量损失。
