Molecular Markers Detect Redundancy and Miss-identity in Genetic Stocks with Alien Leaf Rust Resistance Genes Lr32 and Lr28 in Bread Wheat

Abstract

Ten elite near-isogenic line (NIL) pairs of bread wheat (Triticum aestivum L em Thell) each carrying one of the two alien leaf rust resistance (Lr) genes Lr32 and Lr28, derived from Triticum tauschii and Triticum speltoides, respectively were tested for disease phenotype in controlled conditions. The disease phenotype of the NIL pair detected distinction between the Lr32 donor parent and its derivatives in ten cultivar backgrounds documented as carrying the gene Lr32. The RAPD and SCAR molecular markers identified earlier as linked to Lr32 amplified the critical marker bands identically in eight of the ten NIL pairs as well as the Lr28 donor parent. The critical bands were not amplified in the Lr32 donor parent. A Triticum speltoides specific microsatellite null allele marker located on chromosome 4AL, the genomic region associated with Lr28, expressed in an identical polymorphism as the RAPD and SCAR markers. The PCR product sequenced from a NIL pair revealed 100% homology. It is confirmed that eight of the ten elite Lr32 lines carry the gene Lr28. Molecular marker tools need to be employed to eliminate such miss-identities and reduce redundancy in Indian elite germplasm stocks of wheat possessing the alien Lr genes.