Molecular and Cytogenetic Identification of Stem Rust Resistant Wheat–Thinopyrum intermedium Introgression Lines

Thinopyrum intermedium (JJJ s J s StSt, 2n = 6x = 42), a wild relative of common wheat, possesses many desirable agronomic genes for wheat improvement. The production of wheat–Thinopyrum intermedium introgression lines is a key step for transferring these beneficial genes into wheat. In this study, we characterized three wheat–Thinopyrum intermedium introgression lines TA3681, TA5566, and TA5567 using non-denaturing fluorescence in situ hybridization, genomic in situ hybridization, PCR-based landmark unique gene, and intron targeting markers. Our results showed that TA3681 is a wheat–Thinopyrum intermedium 1St disomic addition line, TA5566 is a wheat–Thinopyrum intermedium non-Robertsonian translocation line carrying two pairs of 3A-7J s translocation chromosomes, and that TA5567 is a wheat–Thinopyrum intermedium non-Robertsonian translocation line carrying a pair of 3A-7J s translocation chromosomes. We developed 13, 36, and 15 Thinopyrum intermedium chromosome-specific markers for detecting the introgressed Thinopyrum chromosomes in TA3681, TA5566, and TA5567, respectively. Stem rust assessment revealed that TA3681 exhibited a high level of seedling resistance to Chinese-prevalent Puccinia graminis f. sp. tritici pathotypes, and both TA5566 and TA5567 were highly resistant to Australian P. graminis f. sp. tritici pathotypes, indicating that Thinopyrum intermedium chromosomes 1St and 7J s might carry new stem rust resistance genes. Therefore, the new identified introgression lines may be useful for improving wheat stem rust resistance.