Molecular cytogenetic analyses of two new wheat-rye 6RL translocation lines with resistance to wheat powdery mildew

Rye (Secale cereale) is a valuable gene donor for wheat improvement, especially for its resistance to diseases. Developing rye-derived resistance sources is important for wheat breeding. In the present study, two wheat-rye derivatives, designated JS016 and JS110, were produced by crossing common wheat cultivar Yangmai 23 with Pakistani rye accession W2A. Using sequential genomic in situ hybridization (GISH) and multicolor fluorescence in situ hybridization (mc-FISH), JS016 and JS110 were identified as a T6BS.6RL translocation line and a T6BS.6BL6RL translocation line, respectively. Ten newly 6RL chromosome arm-specific markers were developed and used to confirm the 6RL translocation. The wheat 55K single-nucleotide polymorphism (SNP) array further verified the molecular cytogenetic identification results above and clarified their breakpoints at 430.9 and 523.0 Mb of chromosome 6B in JS016 and JS110, respectively. Resistance spectrum and allelism test demonstrated that JS016 and JS110 possessed novel powdery mildew resistance gene(s) that was derived from the 6RL translocation but differed from Pm20. Moreover, JS016 and JS110 had better agronomic traits than the previously reported 6RL translocation line carrying Pm20. To efficiently transfer and detect the 6RL translocation from JS016 and JS110, one 6RL-specific Kompetitive allele specific PCR (KASP) marker was developed and validated in high throughput marker-assisted selection (MAS).