description
- Bread wheat accounts for a fifth of the world's food, is the main source of protein in developing countries and is second only to rice as a source of calories in those consumers' diets. It is the most widely grown arable crop in the UK, where it is grown on around 1.8 million hectares per year. UK breeders and farmers have been highly successful in developing and growing wheat varieties with higher yield potential: over the period 1948 to 2006, average yields in the UK increased from ~3 tonnes per hectare to ~8.0 tonnes. Unfortunately, wheat production increases have not kept pace with increased demand. Furthermore, wheat productivity is threatened by disease, competition for high quality agricultural land, resource limitations, and adverse environmental conditions that dramatically reduce optimal yields. It has been estimated that in Europe productivity needs to double to keep pace with demand and to maintain stable prices. To help plant breeders improve wheat varieties they have utilised genetics variants, in particular Single Nucleotide Polymorphisms (SNPs), that are linked to known traits such as disease resistance, adaptation to particular environments, bread making quality characteristics and components of yield. Breeders use molecular markers to track linked SNPs as a proxy for these beneficial traits. This has the advantage of screening many thousands of lines quicker, cheaper, and in some cases more accurately than growing in a field to assess the lines conventionally. Wheat evolved from two naturally occurring separate hybridisation events, each creating a genetic bottleneck. Firstly two wild grasses hybridised to form a relative of pasta wheat. Subsequently a third wild grass hybridised to produce bread wheat. As a result, the total genome size is approximately 16,000 Mb or 35 times the size of the rice genome and 5 times the human genome. The relative lack of diversity in bread wheat has led to breeders and researchers crossing wheat varieties with relatives of wheat to increase genetic diversity and specifically to introduce beneficial traits such as disease resistance. Whilst a large number of SNPs have been identified in bread wheat, these have been identified in relatively few varieties and are not always relevant to the particular germplasm that a breeder is working in. In addition, many of the relatives that have been crossed into wheat have not had specific SNPs identified and represent a 'blind spot' to the breeders. This project aims to produce DNA sequence data for wheat genes for 280 wheat varieties, using a technology known as exome capture and 'next generation sequencing'. This is a complexity reduction process, which reduces the genome size and will enable us to produce sequence data for a large number of lines. The lines will be selected to contain key relatives that have been crossed into wheat. This data will enable us to identify the regions that we have been blind to, and to more accurately locate genes of interest so we can then breed for them using molecular markers. Ultimately, this will help us to develop varieties that have key traits for farmers, such as virus resistances, that will enable them to use less pesticides and to farm wheat more reliably.