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The wild species <i>Thinopyrum intermedium</i> (genome JJJ^SJ^SStSt) serves as a valuable germplasm resource providing novel diseases resistance and agronomically important genes for wheat improvement. Two wheat-<i>Th. intermedium</i> partial amphiploids, TAI7045 (2n = 56) and 78784 (2n = 56), exhibit high resistance to stripe rust and powdery mildew, and their chromosome constitutions have been characterized. With the aim to transfer novel resistance genes from <i>Th. intermedium</i>, the crosses of common wheat line MY11 with TAI7045 and 78784 were produced, and their individual F₂-F₅ progenies were characterized using sequential non-denaturing fluorescence in situ hybridization (ND-FISH) and molecular markers. We identified a set of wheat-<i>Th. intermedium</i> addition lines, involving the chromosomes 1St-J^S, 2St, 2St-J^S, 3St, 4J, 4St, 5St, 5J.St, 6J^S.J, and 7J^S. Above all, the stable wheat-<i>Th. intermedium</i> small segmental translocation lines with chromosomes 4DS.4DL-4StL-4DL-4JL and 4DS.4DL-4StL-4DL were selected. Combining data from specific marker amplification and resistance evaluation, we mapped the gene(s) for resistance to powdery mildew and stripe rust in the 233.56–329.88 Mb region of the long arm of the 4St chromosome from the reference <i>Th. intermedium</i> genome. The new wheat-<i>Th. intermedium</i> introgressions will be used as novel germplasm for breeding purposes.