Molecular cytogenetic characterization and stem rust resistance of five wheat-Thinopyrum ponticum partial amphiploids. 
Partial amphiploids created by crossing common wheat (Triticum aestivum L.) and Thinopyrum ponticum (Podp.)  Barkworth & D. R. Dewey are important intermediates in wheat breeding because of their resistance to major wheat diseases.  In this study, we examined the chromosome compositions of five Xiaoyan-series wheat-Th.  ponticum partial amphiploids (Xiaoyan 68, Xiaoyan 693, Xiaoyan 784, Xiaoyan 7430, and Xiaoyan 7631) using GISH, multicolor-GISH, and multicolor-FISH.  We found several chromosome changes in these lines.  For example, wheat chromosomes 1B and 2B were added in Xiaoyan 68 and Xiaoyan 7430, respectively, while wheat chromosome 6B was eliminated from Xiaoyan 693 and Xiaoyan 7631.  Chromosome rearrangements were also detected in these amphiploids, including an interspecific translocation involving chromosome 4D and some intergenomic translocations, such as A-B and A-D translocations, among wheat genomes.  Analysis of the Th.  ponticum chromosomes in the amphiploids showed that some lines shared the same alien chromosomes.  We also evaluated these partial amphiploids for resistance to nine races of stem rust, including TTKSK (commonly known as Ug99).  Three lines, Xiaoyan 68, Xiaoyan 784, and Xiaoyan 7430, exhibited excellent resistance to all nine races, and could therefore be valuable sources of stem rust resistance in wheat breeding.