Email: peng.zhang@sydney.edu.au

Wheat is the world’s second largest crop and is also Australia’s major crop, which contributes more than $6 billion to the Australian economy. There has been an urgent need to increase the productivity of wheat in an increasingly hostile farming environment, mainly due to climate change. In addition, wheat yields have plateaued making it imperative that new avenues for improving the productivity are found. The benefits of hybrid vigour or heterosis in crops such as maize and rice is well known.

However, like rice, wheat is self-fertilizing and therefore not amenable to simple hybrid seed production. Various strategies for overcoming the self-fertilization barrier have been attempted. However, none provided complete sterility and/or fertility restoration besides other shortcomings, making them less attractive for commercialization.

We have implemented the previously reported genetic blue aleurone (BLA) hybrid wheat system in diverse germplasm. The blue seeded materials have an alien chromosome addition with a blue colour gene on the long arm and a fertility restorer on the short arm, and carry a deletion of the male fertility gene Ms1 on chromosome 4BS. When self-fertilized, these materials produce white and blue seed in a 1:1 ratio. The blue seed have 43 chromosomes and maintain the system, whereas the white seed carry a normal complement of 42 wheat chromosomes and are male sterile as they also carry the homozygous Ms1 deletion.

These white seed are used as the female parent in generating F1 hybrid seed, with any wild-type wheat genotype restoring the fertility in the F1 progeny. The monosomic alien chromosome occasionally mis-divides during meiosis and white seed with the fertility restorer are produced.

The overall consequence is that small proportion of the F1 seeds are not hybrid. We have been using different approaches to rearrange the alien chromosome to eliminate/greatly reduce the impact of mis-division.

The BLA chromosome has been sequenced, which allowed us to design oligo-FISH probes to determine the structure of the original BLA chromosome and any rearranged chromosomes. Updates on the progress will be presented.

Once confirmed, this new hybrid wheat system will provide a pathway to more productive, sustainable, and profitable wheat production globally.