We will adopt two inter-specific crossing strategies to add genetic variation to UK bread wheat. Firstly, we will use synthetic hexaploid wheat (SHW) to introduce extensive D genome variation. Secondly, we will make direct crosses between two heaxaploid wheats and a range of diverse tetraploid donors (Hexaploid x Tetraploid Wheat – HxTW). This introduces novel variation in the A and B genomes and saves time, relative to SHW, as it avoids embryo rescue and backcrossing can start as soon as the pentaploid F1 is identified.
We will use Paragon and Robigus as backcross parents for SHW and HxTW. The former is a spring-sown wheat without a vernalization requirement, thus allowing 3 generations per year. In contrast only 2 generations are possible with Robigus as it is an autumn-sown “winter” wheat, representative of the majority of wheat sown in the UK, and needs 6 weeks’ cold treatment for vernalisation. Critically, both varieties work well as parents in our current programme, displaying little hybrid necrosis when crossed with CIMMYT SHWs. In both strands, SNP genotyping will be used to characterize novel genomic blocks transferred into the recipient genotypes and BC1F2-F5 lines prepared for phenotyping and as donor materials for exploitation by commercial breeders.