Molecular cytogenetic characterization of a novel wheat–Psathyrostachys huashanica Keng 5Ns (5D) disomic substitution line with stripe rust resistance

Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) is a valuable genetic resource for improved wheat breeding, because of its high fecundity, vigorous growth, and resistance to diseases. In this study, a novel wheat–P. huashanica 5Ns (5D) disomic substitution line DH66 was isolated from the F6 progeny of the heptaploid hybrid H8911 (2n = 7x = 49, AABBDDNs) and Triticum durum line Trs-372. Mitotic and meiotic observations showed that the chromosome karyotype of DH66 was 2n = 42 = 21II. Genomic in situ hybridization indicated that DH66 contained 40 wheat chromosomes and two P. huashanica chromosomes, which paired stably and were transmitted to the offspring. Fluorescence in situ hybridization showed that chromosome 5D was absent from DH66. Analysis using a 15K wheat chip demonstrated that the genotype of DH66 had strong matches with P. huashanica in terms of many single-nucleotide polymorphism (SNP) loci on the 5D chromosome, but few with line 7182 at the same SNPs. Verification using markers confirmed that a pair of wheat 5D chromosomes in DH66 were substituted by a pair of P. huashanica 5Ns chromosomes, and thus DH66 was characterized as a wheat–P. huashanica 5Ns (5D) disomic substitution line. Agronomic trait evaluations showed that, compared with its wheat parents, DH66 exhibited significant improvements, with reduced plant height and dough stability time, and superior resistance to stripe rust in the adult stage. Therefore, the novel cytogenetically stable substitution line DH66 can be used in wheat disease-resistant and high-quality breeding programs.