A Smaller, Compensating Version of the Lr59 Translocation of Common Wheat.

Transfer of the leaf rust (caused by Puccinia triticina Eriks.) resistance gene Lr59 from Aegilops peregrina (Hackel) Maire et Weiler to common wheat (Triticum aestivum L.) produced a complex, non-compensating translocation chromosome with the composition 1AS.1L^P.6S^P.6BS. At its proximal end the alien insert has homoeology with the group 1L chromosome arms whereas its distal end has group 6S homoeology (with Lr59 occurring within 6S^P region). The telomere of the translocation chromosome derives from wheat chromosome arm 6BS. Displacement of homoeologous group 1L distal chromatin with chromatin having group 6 homoeology resulted in a sizeable group 6S duplication and a comparable group 1L deletion.

An allosyndetic pairing induction experiment to reduce the amount of alien chromatin resulted in 160 translocation recombinants; eight of which retained Lr59 in association with the smallest amounts of alien chromatin. In seven of the eight recombinants Lr59 got relocated to chromosome arm 6BS whereas in the eighth recombinant it most likely got relocated to either 6AS or 6DS. Of the eight recombinants, Lr59-151 appears to be the shortest. It is a compensating, intercalary translocation with composition 6BS.6S^P.6BS.6BL.

The seven shortest recombinants on 6B were most likely produced from a low frequency of quadrivalents involving 1A, the 1A translocation, and two 6B chromosomes.  Crossover within the 6BS satellite region of such quadrivalents apparently resulted in comparatively small compensating alien chromatin inserts on 6B. Characterization of the recombinants with previously mapped simple sequence repeat loci suggested that the crossovers occurred distally from the Gli-B2 storage protein locus on 6BS and the translocations are therefore not expected to affect baking quality. Marker DUPW217 detects an alien homoeo-allele within each recombinant that can be used for marker-assisted selection of Lr59-151.