Effective introgression of wheat D-genome chromosomes into hexaploid triticale (x Triticosecale Wittm.) using trigeneric hybrids

Given the narrow genetic variability of hexaploid triticale, introgressive hybridization is an efficient means to enrich the available genetic pool. The wheat D-genome chromosomes harbor valuable genes for triticale improvement, such as enhancement of biotic and abiotic stress resistance, bread baking quality, and agronomically useful characters. Introducing the wheat D-genome chromosome into triticale may thus improve its agronomic performance and quality. In the present study, we successfully developed the six hexaploid triticale D-genome chromosome introgression lines derived from wheat-rye-Psathyrostachys huashanica trigeneric hybrids. Genomic and fluorescence in situ hybridization (GISH and FISH) karyotyping revealed that K16-4173-3, K16-1565-6, K16-1565-7, and K16-601-1 were 2D(2R), 3D(3B), 3D, 5D(3B, 5R), and 5D(5B) chromosome substitution lines, respectively. K16-4121-3 was found to be a disomic chromosome addition line having a pair of 6D chromosomes. In addition, line K16-1566-4 carried 28 A- and B-genome, 12 R-genome (lacking two 4Rs), two 4D, and two 7D chromosomes. Analysis of these lines using wheat simple sequence repeats (SSRs) and rye specific molecular markers confirmed that corresponding triticale B or R chromosomes had been replaced by D chromosomes of wheat, an observation perfectly consistent with the FISH and GISH results. Furthermore, these lines except for K16-601-1 were highly resistant to the stripe rust pathogen prevalent in China, than Zhongsi828 plants at the adult stages. Our data suggest that the use of trigeneric hybrids as a bridge between triticale and amphiploid wild-wheat forms is an effect strategy for transferring D-genome chromatin into triticale from other breeding programs. The triticale D-genome introgression lines created in this study may serve as new bridging germplasm for hexaploid triticale breeding and should likewise be useful for enhancing triticale genetic diversity.