Molecular Cytogenetic Characterization of a New Wheat-<i>Thinopyrum intermedium </i>Partial Amphiploid Resistant to Powdery Mildew and Stripe Rust

A partial amphiploid, TE253, derived from crosses between the common wheat (<i>Triticum aestivum </i>L.) cultivar Yannong 15 and <i>Thinopyrum intermedium</i> (Host) Barkworth &#38; D.R. Dewey was characterized by cytogenetic observations, disease resistance tests and genomic in situ hybridization (GISH). Mitotic observations showed that most plants of TE253 had 56 chromosomes, but a few had 54 or 55 chromosomes. The chromosomes in most pollen mother cells of plants with 2n = 56 formed 28 bivalents. Univalents (0.89 per cell) and tetravalents (0.087 per cell) occasionally occurred at meiotic metaphase I, showing a high degree of cytogenetic stability. After inoculation with the powdery mildew and stripe rust pathogens, Yannong 15 was highly susceptible, whereas TE253 and <i>Th. intermedium</i> were immune to both diseases. This indicated that the resistance of TE253 to powdery mildew and stripe rust was derived from <i>Th. intermedium</i>. GISH analysis using St-genomic DNA from <i>Pseudoroegneria strigosa</i> (M. Bieb) Á. Löve as a probe and ABD-genomic DNA from Chinese Spring wheat as a blocker demonstrated that TE253 consisted of 2 St-genome chromosomes, 8 J^S-genome chromosomes, 2 SAT J chromosomes and 2 J-St translocated chromosomes. Line TE253 is a new partial amphiploid with resistance to both powdery mildew and stripe rust and can be used as a source of resistance genes in wheat improvement.