Molecular characterization of a wheat--Thinopyrum ponticum partial amphiploid and its derivatives for resistance to leaf rust.

Leaf rust (caused by Puccinia triticina Eriks.) occurs annually in most wheat-growing areas of the world. Thinopyrum ponticum (Podp.) Z.-W. Liu & R.-C. Wang has provided several leaf rust resistance genes to protect wheat from this fungal disease. Three chromosome substitution lines, Ji806, Ji807, and Ji859, and two chromosome addition lines, Ji791 and Ji924, with a winter growing habit were developed from crosses between wheat (Triticum aestivum L. em Thell.) and the wheat - Th. ponticum partial amphiploid line 693. These lines were resistant to leaf rust isolates from China. Sequence-tagged site (STS) analysis with the J09-STS marker, which is linked to the gene Lr24, revealed that the partial amphiploid line 693 and all of the substitution and addition lines carried gene Lr24. Genomic in situ hybridization (GISH) analysis was carried out on chromosome preparations using total genomic DNA from Pseudoroegneria strigosa (M. Bieb) A. L?ve (St genome, 2n = 14) as a probe in the presence of total genomic DNA from T. aestivum 'Chinese Spring' wheat (ABD genomes, 2n = 42). The GISH analysis demonstrated that these lines had a pair of chromosomes displaying the typical pattern of a Js genome chromosome. This indicates that the chromosome that carries gene Lr24 belonged to the Js genome of Th. ponticum. In addition to 40 wheat chromosomes, eight Js and eight J genome chromosomes were also differentiated by GISH in the partial amphiploid line 693. Since most sources of Lr24 have a red grain color, the white-colored seeds in all of these substitution and addition lines, together with high protein content in some of the lines, make them very useful as a donor source for winter wheat breeding programs.