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Genetic blueprint for wheat genome decoded

July 19, 2014

Rapid fire

Draft sequence of wheat bread genome ready

DNA markers generated can help produce wheat variety of better quality

First time that draft sequence results are made available to the research community

India played a major role through research work of three institutions supported by DBT

Science Wheat cover July 17 2014 140718HR

Scientists have successfully brought out the draft sequence of the wheat bread genome. The work which was carried out by a consortium of scientists from 14 countries who sequenced isolated chromosome arms has been published in a paper in the journal Science (July 18, 2014 issue).

India has played a major role as three Indian institutionsPunjab Agricultural University, Ludhiana, National Research Centre on Plant Biotechnology (NRCPB) and University of Delhi, South Campus, New Delhi sequenced the 2A genome with the support of the Department of Biotechnology.

The decoding of wheat genome may help in identifying more than 125,000 genes of which about 50 percent have been assigned to individual wheat chromosomes.  This four years effort by the International Wheat Genome Sequencing Consortium (IWGSC) has opened gates for understanding the biological function of each of these genes.The current draft sequence would generate thousands of DNA markers which could be used as ‘tag’and eventually help track particular genes responsible for certain traits of  interest. It will help plant breeders to produce new high quality cultivars, with better yield, disease and pest resistance, abiotic stress tolerance and richer in essential micronutrients.

For each gene in wheat there are three copies, one from each of the three genomes, and in most cases only one copy expresses. How the plant decides which copy of the gene to express is most intriguing question in wheat biology. Availability of chromosome based sequence has opened new horizons for researching this issue.

While earlier private companies have claimed to have decoded the raw wheat genome sequence data, this is the first time that the sequence results are available to the public through IWGSC. It has been called a draft sequence because the blue print at present assembles only about 60 per cent of the genome and the team expects to assemble the complete genome in next 3-4 years.

Completion of the wheat genome reference sequence is essential to accelerate breeding and the rapid identification of genes underlying complex traits such as yield, disease and pest resistance, or a-biotic stress tolerance. The genome sequence will aid breeders by enabling new strains to be developed, including new “stacked” trait combinations, and by allowing the development of accelerated and smarter breeding schemes. This in turn will decrease the time from discovery to commercialisation of new varieties for farmers.

In nature, bread wheat evolved after cross hybridization of three different but closely related species. This evolutionary feature made it to accumulate largest content of DNA among all the food crops, making wheat genetics more complex in comparison. Ten years ago, wheat was considered one of the toughest crops to decode due to its huge genome size of 17000 million base pairs, and presence of three sets of highly similar chromosomes in the genome and a very large proportion of repetitive DNA (ranging from 80-90%).

Technological advances in DNA sequencing made in recent years and availability of specialized wheat lines, each having one chromosome arm added in duplicate to the normal chromosomes complement, developed during 1950s in wheat variety ‘Chinese Spring’ made it possible to isolate individual chromosomes for sequencing. The chromosome-based draft sequence provides new insight into the structure, organization, and evolution of the large, complex genome of the world’s most widely grown cereal crop.

The genome reference sequence will act as a benchmark point for understanding the differences between varieties that are associated with different traits, and provide breeders and plant scientists with a molecular toolkit for marker-based selection, high throughput screening, and the association of traits with specific genes and proteins. It holds the key to the production of a new generation of wheat varieties that will enable higher yields and improved sustainability of wheat production systems.

Chief Editor
DBT Communications cell

From → Uncategorized

One Comment
  1. Great work! Kudos to all the students, postdocs and faculty who worked hard to achieve this goal!

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