Scientists from Germany, the United States, the Czech Republic and Canada have assembled a draft of a genetic blueprint of bread wheat, also known as common wheat.
A significant advancement for wheat genetics and the breeding community, the genetic blueprint allows plant science researchers and breeders to locate specific genes on individual chromosomes throughout the genome. By identifying genes that control traits such as yield, pest resistance, quality, water stress, etc the researchers can produce new generations of wheat with desired qualities.
The food plant is grown on more than 531 million acres around the world and produces nearly 700 million tons of food each year. Decoding the genome will afford ways to boost yield of this staple crop.
The genome of bread wheat contains a staggering 100,000 or so genes (the human genome contains roughly 20,000). This does not make wheat a more complicated organic unit than a human because complexity does not stem from the absolute number of genes, but how and when the genes are activated and also the interplay between genes and tissues.
The genome's unusual size and form made the sequencing especially difficult for the team.
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The huge wheat genome can be traced directly to three ancient, closely related grasses that underwent a hybridisation process in which multiple excess copies of genes are passed along to offspring. Wheat essentially combines three grasses in one genetic package. While the process is relatively common in plants (but rare in animals), what's unusual about wheat is that some strains went through the hybridisation more than once.
A second paper in Science details the first reference sequence of chromosome 3B, the largest chromosome in common wheat.
"The wheat genome only has 21 chromosomes, but each chromosome is very big and therefore quite complicated," Eduard Akhunov, associate professor of plant pathology and a collaborator with the International Wheat Genome Sequencing Consortium said.
"The largest chromosome, 3B, has nearly 800 million letters in its genetic code. This is nearly three times more information than is in the entire rice genome. So trying to sequence this chromosome -- and this genome -- end-to-end is an extremely complicated task."
The sequencing approach developed for the 3B chromosome can now be applied for sequencing the remaining chromosomes in wheat. The consortium estimates the full genome sequence will be available in three years.
A draft still, the sequence gives an idea of the genes in the right order along the respective chromosome. The next step will be to understand the genes' orientation and the sequences of the regions between the genes.
Work on the bread wheat genome began in 2011, while the genomes for rice and corn were published in 2002 and 2009.