Molecular cytogenetic characterization of wheat-Secale africanum amphiploids and derived introgression lines with stripe rust resistance

Two amphiploids, AF-1(Triticum aestivum L. cv. Anyuepaideng-Secale africanum Stapf.) and BF-1 (T. turgidum ssp. carthlicum-S. africanum), were evaluated by chromosomal banding and in situ hybridization. The individual S. africanum chromosomes were identified in the BF-1 background by sequential C-banding and genomic in situ hybridization (GISH), and were distinguishable from those of S. cereale, because they exhibited less terminal heterochromatin. Fluorescence in situ hybridization (FISH) using the tandem repeat pSc250 as a probe indicated that only 6R(a) of S. africanum contained a significant hybrid signal, whereas S. cereale displayed strong hybridization at the telomeres or subtelomeres in all seven pairs of chromosomes. Extensive wheat-S. africanum non-Robertsonian translocations were observed in both AF-1 and BF-1 plants, suggesting a frequent occurrence of chromosomal recombination between wheat and S. africanum. Moreover, introgression lines selected from the progeny of wheat/AF-1 crosses were resistant when field tested with widely virulent strains of Puccinia striiformis f. sp. tritici. Three highly resistant lines were selected. GISH and C-banding revealed that resistant line L9-15 carried a pair of 1BL.1RS translocated chromosomes. This new type of S. africanum derived wheat-Secale translocation line with resistance to Yr9-virulent strains will broaden the genetic diversity of 1BL.1RS for wheat breeding.