Molecular Cytogenetic Identification of a Novel Wheat–Thinopyrum ponticum 1J(S) (1B) Substitution Line Resistant to Powdery Mildew and Leaf Rust

Thinopyrum ponticum (2n = 10x = 70) is a wild relative of wheat with high tolerance to both biotic and abiotic stresses; it has been wildly used in wheat genetic improvement. A disomic substitution line named SN19647 was derived from a cross between Triticum aestivum and the wheat–Th. ponticum partial amphiploid SNTE20 (2n = 8x = 56). It was evaluated for disease resistance and characterized via sequential fluorescence in situ hybridization (FISH)-genomic in situ hybridization (GISH) and molecular markers. The results showed that SN19647 carried resistance to both powdery mildew and leaf rust. It contained 42 chromosomes with a pair of wheat chromosome 1B replaced by a pair of J(S) chromosomes from Th. ponticum. In addition to chromosomal substitution events, structural variation also occurred on wheat chromosomes 2A, 5A, 6B, and 7B. Based on marker analysis, 19 markers specific to the J(S) chromosome were obtained, of which seventeen markers belonged to homoeologous group one. These results indicated that SN19647 was a 1J(S) (1B) substitution line. Compared with the known 1J(S) (1D) substitution line CH10A5, it was found that 17 markers generated different specific bands to Th. ponticum, confirming the novelty of the 1J(S) chromosome in SN19647. Therefore, SN19647, resistant to powdery mildew and leaf rust, was a novel 1J(S) (1B) substitution line that can be used in wheat genetic improvement.