Molecular cytogenetic characterization of stem rust and stripe rust resistance in wheat- Thinopyrum bessarabicum –derived doubled haploid lines

Thinopyrum species are potential sources of disease resistance for wheat. Thinopyrum bessarabicum is a well-known source of salt tolerance, but there are very few reports of rust resistance being transferred from this species to wheat. Here, we report wheat- Th. bessarabicum –derived stem rust and stripe rust–resistant doubled haploid (DH) lines and characterized using molecular markers and cytogenetic analyses. We used sequential non-denaturing fluorescence in situ hybridization (ND-FISH) and genomic in situ hybridization (GISH) to determine their genomic compositions. Cytological results were validated by molecular analysis using genome-specific PCR markers. These lines were either alien additions, partial diploids, or partial amphidiploids. Line DH9 was a disomic addition line carrying chromosome 4J b whereas DH1 was a double disomic addition line for chromosomes 6J b and 7J b . Lines DH7 and DH8 were partial diploids that were cytologically unstable due to having ph1ph1 genotype. DH7 also had a pair of T6BL-6J b L.6J b S translocated chromosomes and was monosomic for a T5DS-5J b S.5J b L translocation. The size of the translocated alien segment in chromosome T5DS-5J b S.5J b L was L+(0–0.42)S, whereas the size of wheat chromatin in chromosome T6BL-6J b L.6J b S was S+(0–0.85)L. Lines DH5 (2 n = 50) and DH11 (2 n = 54) were partial amphidiploids with eight and 12 Th. bessarabicum chromosomes, respectively. Lines DH7, DH8, and DH11 expressed an intermediate level of resistance to stem rust with infection types (ITs) varying from 1 + 2 to 23 - , whereas they were immune or near-immune (IT 0 to 0) to stripe rust. Comparison of the rust reactions, genome compositions, and molecular markers of the DH lines along with their parents indicated that the Thinopyrum chromosome conferring resistance to both rusts was 2J b .