Cytological and genetic analyses of a wheat-rye 2RL ditelosomic addition line with adult plant resistance to powdery mildew

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.