Molecular dissection of Secale africanum chromosome 6R afr in wheat enabled localization of genes for resistance to powdery mildew and stripe rust

摘要

Introgression of chromatin from Secale species into common wheat has for decades been a successful strategy for controlling the wheat diseases. The wild Secale species, Secale africanum Stapf., is a valuable source for resistance to foliar disease of wheat. A wheat-S. africanum chromosome 6Rafr substitution line displayed resistance to both powdery mildew and stripe rust at the adult-plant stage. Wheat-S. africanum chromosome 6Rafr deletion and translocation lines were produced and identified by sequential non-denaturing fluorescence in situ hybridization (ND-FISH) using multiple Oligo-based probes. Different ND-FISH patterns were observed between S. cereale 6R and S. africanum 6Rafr. With reference to the physical map of the draft genome sequence of rye inbred line Lo7, a comprehensive PCR marker analysis indicated that insertions and deletions had occurred by random exchange between chromosomes 6R and 6Rafr. A survey of the wheat- S. africanum 6Rafr lines for disease resistance indicated that a powdery mildew resistance gene(s) was present on the long arm of 6Rafr at FL0.85–1.00, and that a stripe rust resistance gene(s) was located in the terminal region of 6RafrS at FL0.95–1.00. The wheat-S. africanum 6Rafr introgression lines also displayed superior agronomic traits, indicating that the chromosome 6Rafr may have little linkage drag in the wheat background. The combination of molecular and cytogenetic methods allowed to precisely identify the chromosome rearrangements in wheat- S. africanum 6Rafr substitution, deletion and translocation lines, and compare the structural difference between chromosomes 6R and 6Rafr. The wheat- S. africanum 6Rafr lines containing gene(s) for powdery mildew and stripe rust resistance could be used as novel germplasm for wheat breeding by chromosome engineering.