One of the most common food crops around the world has also had one of the toughest genomes to decipher. On November 28, 2012, scientists reported in the journal Nature that they have finally sequenced the roughly 96 000 genes that that make up the draft genome for wheat.
Did you know? One-fifth (20%) of the calories consumed by the global population come from wheat.
Wheat has an enormous genome. This is because wheat is a hybrid of either two or three different grasses. Pasta wheat (or hard, Durum) is a hybrid of two grasses. Soft, bread wheat is a hybrid of Durum wheat plus a third species of wheat. In each case the full genomes of the ancestors are passed to the next generations, causing the genome of Triticum aestivum (bread wheat) to be arranged as a hexaploid, with three sets of chromosomes of DNA in one nucleus!
Over five times bigger than the human genome, this gigantic genome has presented a real puzzle for the plant genetics community for a number of years.
Do many hands make light work? Well, a little “lighter” work at least. Prior to 2008 an international team of researchers decided to split up and sequence the genome for wheat chromosome by chromosome. The three sets of the wheat genome are known as the A, B and D genomes. In October 2008 plant geneticist Catherine Feuillet from France and a team of plant geneticists mapped wheat’s largest chromosome, 3B (Chromosome 3 of the B genome), and identified over 1000 genetic markers.
Since 2008, ongoing wheat genome sequencing projects have involved scientists in the UK, Germany and three research sites in the USA…and there is still more work to come! Now the draft genome will have to be analyzed in depth and the exact location of genes connected with specific traits identified. The draft genome and its follow-up interpretation is being made available in the public domain so that scientists around the globe can use this information to develop new strains of wheat that can cope with drought, pests and diseases that impact on the productivity of wheat crops.
Plant breeders are currently interested in developing varieties of wheat that are drought-resistant to help combat the effects of climate change. The other big threat to wheat crops worldwide is a fungal disease called Ug99 (wheat stem rust) that has spread rapidly throughout Africa, Asia and the Middle East, causing serious wheat crop losses. The search is on for identifying varieties of wheat that have effective resistance genes to this devastating fungal disease.