Molecular Markers Of Wheat Leaf Rust Resistance Gene Lr45 Based On AFLP And SSR

Wheat leaf rust is one of the most destructive diseases on wheat production throughout the world. Therefore the exploitation of marking, location of leaf rust resistance (Lr) genes would facilitate MAS (marker assisted selection) and benefit breeding the effective leaf rust resistant cultivars, and the gene cloning.Lr45 was a resistant gene against wheat leaf rust disease originated from Secale cereale and was localized onto the chromosome 2A. No virulent races to the gene have been found so far, and molecular markers have not been reported for the gene based on our knowledge at the present time. Segregation ratio of resistance vs. susceptibility from TcLr45 ×Thatcher F₂ progenies in greenhouse test showed that the resistance of Lr45 to the disease is controlled by a single dominant gene. The successful marking of this gene would pave a solid way to MAS and cloning of the resistance gene.AFLP (amplified fragment length polymorphism) analysis were carried out in Thatcher, near isogenic lines (NILs) carrying different genes conferring resistance against wheat leaf rust and TcLr45×Thatcher F₂ progenies to develop markers for Lr45. 304 AFLP primer combinations were screened and PCR-amplified products were isolated on urea denaturing 6.0% poly-acrylamide gel, and then were visualized by silver straining. Most of them provided clear amplification products, and 84 primer pairs displayed polymorphism in NILs. Five AFLP markers closely linked to gene Lr45 were acquired. P-AGG/M-GAG261 bp was found closely linked to the Lr45 locus at a distance of 0.6cM on one side, and P-ACA/M-GGT₁₀₅ bP at a distance of 1.3cM on the other. The specific bands were cloned and sequenced subsequently. The fragment of 261bp produced by P-AGG/M-GAG was 86 percent similarity with the sequence of Vulgare HortI gene. The 105bp produced by P-ACA/M-GGT was 96 percent with the phosphatidylserine decarboxylase gene of the Triticum monococcum. Both of them included an open reading frame (ORF).SSR protocol was also used to marks Lr45. A total of 31 microsatellite primer combinations specific to the chromosome 2A of wheat genome were used to detect polymorphism between the four NILs located on chromosome 2A. Of them nine primer...