Engineered Versions of the Wheat Lr62 Translocation

Leaf rust resistance gene Lr62 was transferred from Aegilops neglecta Req. ex Bertol. to chromosome 6A of common wheat (Triticum aestivum L.) in 2008. After homoeologous chromosome pairing induction, smaller translocations that retained Lr62 were derived from it. This study compared the original translocation and the four apparently shortest recombinants to determine which would be the best suited for breeding. The translocations were analyzed using chromosome 6A and 6B simple sequence repeat (SSR) markers and genomic in situ hybridization. Recombined translocations 133, 135, and 136 were found to occur at the 6AS telomere. In addition to the wheat Xdupw217(aest) SSR locus on chromosome arm 6BS, the three recombinants also expressed an Ae. neglecta-derived homoeolocus (Xdupw217(negl)) that could be used to detect the presence of the Ae. neglecta chromosomal segment. The Lr62-129 translocation was relocated to 6BS in an allosyndetic recombination event that replaced the Xdupw217(aest) locus with Xdupw217(negl). Lr62-129 retained the least Ae. neglecta chromatin and is therefore recommended for use in wheat breeding.