Effective introgression of wheat D-genome chromosomes into hexaploid triticale (× 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repeats (SSRs) and rye specific molecular markers confirmed that corresponding triticale B or R chromosomes had been replaced by D chromosomes of wheat, an observation perfectly consistent with the FISH and GISH results.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.