Releasing natural variation in bread wheat by modulating meiotic crossovers

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In bread wheat, important agronomical traits are distributed along chromosomes. Traditionally, plant breeders cross high yielding parental lines and then select for progeny in subsequent generations that carry desirable attributes whist removing undesirable traits. However, the process of 'gene-shuffling' (meiotic recombination) is non-random and skewed towards the ends of the chromosomes. Therefore, desirable traits are often transmitted as a block together with undesirable traits. This is analogous to dealing a deck of cards where a significant proportion of the cards are tethered by an elastic band. In this case a desirable hand cannot be achieved until the elastic band is severed and the cards are able to segregate freely. In this proposal we aim to understand why desirable and undesirable traits in bread wheat are often tethered together, so that we can break this bond, and release the full potential of available natural variation. Then, we aim to modulate this process so that the plant breeder can decide which traits can be 'dealt' together in the same variety. This unlocking of wheat's natural variation will lead to the production, via classical plant breeding, of superior varieties with favourable agronomic traits such as increased yield and improved nutrient acquisition. To provide direct evidence that our research has application we will work with two of the UK's largest wheat breeders KWS and RAGT to target chromosomal regions, which are known to be transmitted as blocks. We will show that by using novel procedures, we can increase the amount of recombination in these blocks. Increasing the amount of recombination in any of these regions will enable breeders to generate new gene combinations which will lead to new varieties with, for instance, increased protein content or pathogen resistance. Further down the breeder's pipeline our research will directly translate to new varieties with superior characteristics that will help maintain farm incomes and improve sustainability of the UK arable and milling industries. In addition high yielding varieties will reduce dependence on imported grain and associated transport and environmental costs and improved pipelines for the generation of new UK varieties that will enhance reliability and competitiveness in overseas markets.