Nicola.walter@nottingham.ac.uk, Surbhi.grewal@nottingham.ac.uk

Wild relatives of bread wheat (Triticum aestivum) are often utilised to increase wheat’s genetic diversity. For example, Aegilops sharonensis contains gene Sr62 that confers stem rust resistance. However, some wild relatives including Ae. sharonensis contain gametocidal genes, also known as cuckoo chromosomes.

These selfish genes ensure preferential transmission to offspring through inducing chromosomal breakages in gametes that lack them, resulting in agronomically unstable lines with shrivelled seeds, unhealthy plants and significant yield reductions. Due to the selfish nature of these genes, they are extremely difficult to remove through traditional methods of breeding, preventing useful germplasm from being used in breeding programmes.

Using molecular markers and skim-sequencing we characterised a previously generated gametocidal gene (Gc2) containing translocation line, T4B-4Ssh. This line was shown to carry a 9Mb chromosome 4Ssh segment from Ae. sharonensis introgressed into chromosome 4B of wheat. We developed an F1 population by crossing this line with wheat cv.

Chinese Spring and treatment of 4800 F1 seeds with 0.3% and 0.4% ethyl methane sulfonate (EMS) resulted in 67 M1 plants with potential loss-of-function in the Gc2 locus. Ten progeny from each M1 plant were genotyped to verify the normal segregation of the 4Ssh segment. Mendelian segregation was observed in two families, confirming mutations in the gametocidal locus. Two additional mutants demonstrated abnormal segregation patterns.

Chromosome flow sorting was used as a means of complexity reduction to isolate the recombinant chromosome 4B-4Ssh prior to short-read sequencing of the wild-type T4B-4Ssh and mutant lines. Sequencing data were analysed using the MutChromSeq pipeline to identify candidates in the introgressed segment for further downstream analyses and targeted mutagenesis.

Ultimately, this research has taken great steps towards identification of the long sought-after gametocidal gene, Gc2. Additionally, these mutant lines can be used within breeding programmes to remove Gc2 from wheat-Ae. sharonensis introgression lines, allowing valuable germplasm with potentially advantageous traits to be released to breeders.