Characterization of wheat-Secale africanum chromosome 5R(a) derivatives carrying Secale specific genes for grain hardness.

Main conclusion New wheat- Secale africanum chromosome 5R a substitution and translocation lines were developed and identified by fluorescence in situ hybridization and molecular markers, and chromosome 5R a specific genes responsible for grain hardness were isolated. The wild species, Secale africanum Stapf. (genome RaRa), serves as a valuable germplasm resource for increasing the diversity of cultivated rye (S. cereale L., genome RR) and providing novel genes for wheat improvement. In the current study, fluorescence in situ hybridization (FISH) and molecular markers were applied to characterize new wheat–S. africanum chromosome 5Ra derivatives. Labeled rye genomic DNA (GISH) and the Oligo-probes pSc119.2 and pTa535 (FISH) were used to study a wheat–S. africanum amphiploid and a disomic 5Ra (5D) substitution, and to identify a T5DL.5RaS translocation line and 5RaS and 5RaL isotelosome lines. Twenty-one molecular markers were mapped to chromosome 5Ra arms which will facilitate future rapid identification of 5Ra introgressions in wheat backgrounds. Comparative analysis of the molecular markers mapped on 5Ra with homoeologous regions in wheat confirmed a deletion on the chromosome T5DL.5RaS, which suggests that the wheat–S. africanum Robertsonian translocation involving homologous group 5 may not be fully compensating. Complete coding sequences at the paralogous puroindoline-a (Pina) and grain softness protein gene (Gsp-1) loci from S. africanum were cloned and localized onto the short arm of chromosome 5Ra. The S. africanum chromosome 5Ra substitution and translocation lines showed a reduction in the hardness index, which may be associated with the S. africanum- specific Pina and Gsp-1 gene sequences. The present study reports the production of novel wheat–S. africanum chromosome 5Ra stripe rust resistant derivatives and new rye-specific molecular markers, which may find application in future use of wild Secale genome resources for grain quality studies and disease resistance breeding.