18-BTT: Induction of double haploids in wheat using CENH3 mutants and genome editing

Traditional wheat breeding requires six to seven generations of self-pollination to deliver highly homozygous and stable cultivars. An alternative approach is the production of doubled haploids (DH) which reduces the generation time to deliver true-breeding lines to a single generation. Current DH technologies in wheat (based on maize pollination) are laborious and require a high level of expertise and well-equipped laboratories. These are expensive resources and severely limit DH use even in developed countries. Amino acid changes in a gene called CENH3 result in haploid inducing (HI) lines in the model species Arabidopsis. We propose a strategy to combine mutants and gene-edited versions of this gene to alter CENH3 in wheat and develop haploid inducer lines. Our final goal is to accelerate wheat breeding by developing efficient haploid inducer lines that will produce doubled haploids (DH) as seeds

Our goal is to accelerate wheat breeding by developing efficient haploid inducer lines that will produce doubled haploids (DH) as seeds. Current DH technologies in wheat are laborious and expensive, limiting their use. Here, we propose to modify the centromere specific histone 3 (CENH3) to develop a simpler technology of haploid production in wheat. In Arabidopsis, single amino acid changes that result in high haploid inducing efficiency have been identified. However, the translation of these results to wheat has been complicated by the buffering effect of wheat polyploidy and the presence of tightly linked CENH3 paralogs. In this project we will combine mutations in CENH3 that will result in a haploid inducer line that is viable, fertile, and genetically stable on self-fertilization, but prone to loss of its own genome on outcrossing, producing paternally derived haploids. Once mutant haploid inducer lines are established, they will produce haploids as seeds without tissue culture. This will result in a low-tech, high throughput, and inexpensive approach. The generation of DH from seeds will democratize the use of DH technology and accelerate wheat breeding cycles in both developed and developing countries.

Beneficiaries of this work will be UK wheat breeding companies, which will be able to develop homozygous doubled haploid lines in a much more cost effective and timely manner than current practices. Roughly 30% of advanced lines within a UK breeding programme are derived from doubled haploid. This number is not larger due to the costs involved in their production. The technology developed within this project will allow a higher percentage of advanced lines to be derived from doubled haploids, accelerating the rate at which cultivars are tested in the field. This will help accelerate genetic gains in the UK and elsewhere as the multiple generations of selfing that are traditionally required for normal cultivar develop are circumvented with this technology. This means that BBSRC investment in wheat will reach the field more quickly than possible before.

Farmers will benefit from this impact as they will be able to grow wheat cultivars which are developed using the latest technology and that reach field more quickly compared to traditionally bred cultivars.

UK consumers will benefit from this impact as wheat constitutes a main staple in British diets. On average, each person consumes roughly 60 kg of wheat flour per year and 99.8% of UK households purchase bread at least once yearly. This is equivalent to nearly 11 million loaves of bread consumed each day in the UK alone. Being able to breed and grow local varieties with improved characteristics will help keep food prices low and at a more stable price over the year. This is especially relevant for lower income households, which assign a larger percentage of their food budget to basic groceries (such as bread and milk) than higher income households.