Cloning and mapping of genes involved in wheat-leaf rust interaction through gene-expression analysis using chromosome-deleted near-isogenic wheat lines.

Molecular markers on wheat chromosome 6BL were isolated using mRNA differential display. Two wheat isolines inoculated with Puccinia recondita were analysed: Sinvalocho MA line carrying the Lr3 gene for leaf rust resistance on distal chromosome 6BL, and a rust-susceptible derivative of the Sinvalocho MA line with a deletion at the distal end of chromosome 6BL. Comparison of mRNA fingerprinting profiles, obtained from control and rust-inoculated plants, let to the isolation of 34 differentially displayed cDNAs. All these genes, except TaRr16, were up-regulated in the rust-inoculated resistant line. TaRr16 has constitutive expression in the rust-resistant line while no expression was detected in the rust-susceptible line. A number of those cDNAs revealed homology to genes previously identified in other plant-pathogen interactions. Two out of the 34 cDNAs, mapped in the distal part of chromosome 6BL and TaRr16, was genetically linked to the Lr3 gene. DNA sequence differences and differential expression between non-allelic copies of TaRr16, are also reported.