Exploiting the ZIP 4 homologue within the wheat Ph 1 locus has identified two 1 lines exhibiting homoeologous crossover in wheat - wild relative hybrids 2 3

34 Despite possessing related ancestral genomes, hexaploid wheat behaves as a diploid 35 during meiosis. The wheat Ph1 locus promotes accurate synapsis and crossover of 36 homologous chromosomes. Interspecific hybrids between wheat and wild relatives are 37 exploited by breeders to introgress important traits from wild relatives into wheat, 38 although in hybrids between hexaploid wheat and wild relatives, which possess only 39 homoeologues, crossovers do not take place during meiosis at metaphase I. However, 40 in hybrids between Ph1 deletion mutants and wild relatives, crossovers do take place. 41 A single Ph1 deletion (ph1b) mutant has been exploited for the last 40 years for this 42 activity. We show here that selection of chemical induced mutant lines possessing 43 mutations in TaZIP4-B2 exhibit high levels of homoeologous crossovers when 44 crossed with a wild relative. Exploitation of Tazip4-B2 mutants rather than mutants 45 with whole Ph1 locus deletions may improve introgression of wild relative 46 chromosome segments into wheat. Such mutant lines may be more stable over 47 multiple generations, as multivalents causing accumulation of chromosome 48 translocations are less frequent. 49 50 . CC-BY-NC 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/142596 doi: bioRxiv preprint first posted online May. 26, 2017;