A biologically perfect system for unlocking wheat’s hybrid vigour

Wheat yield increases have plateaued in many environments because of climate change and slowing incremental genetic gains in yield achievable through plant breeding. Hybrid vigour could significantly improve yield in wheat if efficient and cost-effective systems for overcoming the limitations of self-fertilization are deployed. Here, a two-line wheat hybrid system was developed that produces and maintains male sterility - essential for efficient production of F1 hybrid seed. The system comprises a deletion of the male fertility gene Ms1 on the short arm of chromosome 4B of wheat and an addition chromosome carrying a blue colour locus ( Bla ) from Agropyron elongatum (Syn. Thinopyrum ponticum , 2n = 10x = 70) chromosome 4Ag, and a male fertility restorer gene ( Rf-Ms1 ) from Triticum boeoticum chromosome 4Bo both located on the long arm of the addition chromosome. The addition line comprises 43 chromosomes, is fully fertile and produces blue and white seeds if selfed. There is no recombination between the Bla locus and Rf-Ms1 gene as they are located on alien chromatin. When the 43-chromosome addition line is self-fertilised, the progeny segregated 70:30 on average, white to blue seed. The white seeds carry 42 chromosomes and the homozygous male fertility deletion and are therefore male sterile, whereas the blue seeds carry 43 chromosomes and are male fertile. The blue seed is retained to maintain the system and the white seed is used as a female in F1 hybrid seed production. The system works equally well in red-grained wheat. This study establishes a basis for cost efficient hybrid seed production in wheat.