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Indians help breach wheat barrier

New Delhi, July 17: An international research consortium with scientists from three Indian laboratories has generated the first draft sequence of the genome of wheat, the world’s third most-produced cereal after maize and rice.

The draft sequence, described in papers to be published tomorrow in the US journal Science, could help crop scientists design smarter breeding strategies for wheat, considered critical because yields have plateaued out over the past decade.

The International Wheat Genome Sequencing Consortium, which produced the draft sequence through a nine-year research effort, has described the work as a “landmark” towards obtaining a complete reference sequence of the wheat genome.

The consortium said it expected the complete reference genome to be completed within three years.

Plant molecular biologist Kuldeep Singh at the Punjab Agricultural University, Ludhiana, coordinated India’s contribution to the research work — sequencing chromosome 2A of wheat’s 21 chromosomes.

Plant biologist Jitender Khurana at the University of Delhi, South Campus, and faculty and research scholars from the Indian Agricultural Research Institute, New Delhi, also participated in the effort.

Although scientists have sequenced dozens of large genomes — including the human, dog and rice genomes among other plants and animals — wheat was viewed as a special challenge because of the size and complexity of its genome.

“In many ways, the wheat genome is a nightmare for analysis,” Frederic Choulet, a senior plant molecular biologist at a government research laboratory in France and a member of the consortium, told The Telegraph.

“The size of the wheat genome is five times that of the human genome, and while a human gene appears as a single pair in each chromosome, each gene is present in wheat as three pairs,” said Choulet, who led a team of scientists that analysed chromosome 3B.

The large genome size also means more repetitive sequences which, Choulet said, makes assembling the sequence difficult.

The consortium has pinpointed the locations of about 124,000 genes on the 21 chromosomes of wheat. Many of these genes are linked to traits such as grain quality, pest resistance and tolerance to environmental stress.

“One emerging concern in India is terminal heat stress — high temperatures during March and April, close to the maturity of wheat crops,” a plant biologist in India who was a member of the consortium told this newspaper.

The wheat genome sequence will allow crop scientists to link genes with specific desirable traits — such as tolerance to heat or resistance to a fungal disease — in certain wheat varieties.

Such varieties could then be crossed with high-yielding varieties to produce new generations of superior wheat, said the Indian scientist who requested not to be named.

India’s department of biotechnology supported the Indian arm of the sequencing effort. Wheat is grown on more land than any other crop — 215 million hectares that are harvested annually worldwide to generate 700 million tonnes.

The wheat genome consortium has said that wheat productivity will need to be increased by 60 per cent by 2050 to meet the growing food demands from a rising population and dietary changes.

The consortium calls wheat “the third most-produced” cereal after maize and rice but the leading source of protein, delivering higher protein content than either maize or rice.