Manipulation of the 1RS.1BL Translocation in Wheat by Induced Homoeologous Recombination

Centric translocations of the short arm of rye ( Secale cereale L.) chromosome 1R are useful in wheat ( Triticum aestivum L.) breeding because they confer resistance to several pests and diseases and improve yield. Their major disadvantage is in reduced bread making quality. To remedy this defect, rye chromosome arm 1RS in translocations 1RS.1BL and 1RS.1DL was induced by the ph1b mutation to recombine with the short arms of wheat group‐1 chromosomes. Among 20 234 progeny screened, 139 primary recombinant chromosomes were recovered including 103 with 1BS, 22 with 1AS and 14 with 1DS. The Gli‐1 / Glu‐3 loci of wheat were non‐homoeoallelic to the Sec‐1 locus of rye and were separated by about a 13‐cM‐long segment, which on the rye chromosome contained disease resistance loci Pm8 , Lr26 , Sr31 , and Yr9 Pairs of primary recombinants 1RS‐1BS with breakpoints flanking the storage protein loci were intercrossed and two types of secondary recombinant chromosomes 1RS were produced: a group of over 30 chromosomes where the Sec‐1 locus was replaced by segments of 1BS of various lengths, and two chromosomes where 1.4‐ and 3.2‐cM segments of 1BS introduced the Gli‐1 / Glu‐3 loci. Selected chromosomes from each class were allowed to recombine within the shared segments of 1RS separating the intercalary wheat segments and two tertiary recombinant chromosomes were recovered. Cytologically, these chromosomes appear as normal 1RS arms but each has two intercalary segments of 1BS: one introducing the Gli‐1 / Glu‐3 loci and the second one removing the Sec‐1 locus. Because the protein composition of the resulting translocation lines is identical to that of normal wheat, it is believed that these manipulations could eliminate the quality defect associated with the 1RS.1BL translocation.