Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating disease that seriously threatens wheat yield and quality. To control this disease, host resistance is the most effective measure. Compared with the resistance genes from common wheat, alien resistance genes can better withstand infection of this highly variable pathogen. Development of elite alien germplasm resources with powdery mildew resistance and other key breeding traits is an attractive strategy in wheat breeding. In this study, three wheat-rye germplasm lines YT4-1, YT4-2, and YT4-3 were developed through hybridization between octoploid triticale and common wheat, out of which the lines YT4-1 and YT4-2 conferred adult-plant resistance (APR) to powdery mildew while the line YT4-3 was susceptible to powdery mildew during all of its growth stages. Using genomic in situ hybridization, multi-color fluorescence in situ hybridization, multi-color GISH, and molecular marker analysis, YT4-1, YT4-2, and YT4-3 were shown to be cytogenetically stable wheat-rye 6R addition and T1RS·1BL translocation line, 6RL ditelosomic addition and T1RS·1BL translocation line, and T1RS·1BL translocation line, respectively. Compared with previously reported wheat-rye derivative lines carrying chromosome 6R, YT4-1 and YT4-2 showed stable APR without undesirable pleiotropic effects on agronomic traits. Therefore, these novel wheat-rye 6R derivative lines are expected to be promising bridge resources in wheat disease breeding.

Rye (Secale cereale genome RR), a close relative of common wheat, possesses valuable resistance genes for wheat improvement. Due to the co-evolution of pathogen virulence and host resistance, some resistance genes derived from rye have lost effectiveness. Development and identification of new, effective resistance genes from rye is thus required. In the current study, wheat-rye line WR56 was produced through distant hybridization, embryo rescue culture, chromosome doubling and backcrossing. WR56 was then proved to be a wheat-rye 2RL ditelosomic addition line using GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization), ND-FISH (non-denaturing FISH), mc-GISH (multicolor GISH) and rye chromosome arm-specific marker analysis. WR56 exhibited a high level of adult plant resistance to powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt). This resistance was carried by the added 2RL telosomes and presumed to be different from Pm7 which is also located on chromosome arm 2RL but confers resistance at the seedling and adult stages. WR56 will be a promising bridging parent for transfer of the resistance to a more stable wheat breeding line. A newly developed 2RL-specific KASP (kompetitive allele specific PCR) marker should expedite that work.