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Wheat Draft Genome Sequence Cracked
Jul 30, 2014

An international consortium of scientists, including some from India, has put together a draft genome sequence for ‘bread wheat,’ providing an overview of the genetic make-up of a key crop that feeds almost a third of the world’s population.

Bread wheat (Triticum aestivum), which produces the grain used for chapatis and pooris, arose from a series of hybridisation events that ultimately resulted in chromosomes from three ancestral species being merged. Consequently, the plant has ended up with three sets of seven pairs of chromosomes, each set forming a distinct sub-genome.

Working out the plant’s genome required disentangling the sub-genomes with very similar chromosomes. The International Wheat Genome Sequencing Consortium accomplished the task by first physically separating the chromosomes. One chromosome from each of the 21 pairs was then sequenced to establish the exact order and location of units of DNA, known as bases, that it possessed. 

The bread wheat genome, 17 billion bases in size (five time larger than that of humans), has been analysed and some 124,000 genes identified, according to papers published last week in Science. It also turned out that none of the sub-genomes is dominant with more of its genes being utilised to turn out proteins.

India’s Contribution: Indian scientists, supported by funding from the Department of Biotechnology, were given the responsibility for sequencing chromosome 2A. This chromosome alone has about 900 million bases, about two and a half times bigger than the entire rice genome.

At present, only a ‘draft sequence’ is available for 20 pairs of chromosomes. A finished version, with minimal gaps, is ready for only one pair of chromosomes. The aim is to get the other chromosomes to that stage within three years, according to the International Wheat Genome Sequencing Consortium.

The chromosome-based sequence will help plant breeders learn how genes controlled complex traits such as yield, grain quality, disease, pest resistance and the ability to withstand various kinds of stress, according to a press release issued by the consortium. 

India is the world's second largest wheat producer (after the United States) and also the second biggest wheat consuming nation (after China. Having the complete wheat genome sequence in hand will allow scientists to activate genes that the plant possesses to create varieties producing better quality grain, which are more heat tolerant as well as capable of withstanding changing climatic conditions.

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