An international team has produced the most comprehensive genome map of wheat, which paved the way for more nutritious and climate-adapted varieties of a staple crop that feeds over one-third of the global population.

The study published on Thursday in the journal Science presented the reference genome of the bread wheat variety "Chinese Spring," including its 21 chromosomes, precise locations of 107,891 genes, more than 4 million molecular markers and sequence information between genes.

The wheat has a large, complex genome with 16 billion base pairs or the building blocks of DNA, more than five times larger than the human genome.

Sequencing the bread wheat genome is challenging also due to its complexity, comprising three sub-genomes and more than 85 percent repeated elements in its genome, according to the study.

The repetitive elements means that vast parts of the genome are very similar to each other, making it difficult to distinguish each sub-genome and to put together the genome into its correct order.

More than 200 scientists in 20 countries collaborated to work out the results in 13 years, according to the International Wheat Genome Sequencing Consortium (IWGSC).

"This will greatly speed up our efforts on identification of agriculturally important wheat genes, including those that would help to combat major fungal diseases," said Kostya Kanyuka with the IWGSC.

"Completing this work means we can identify genes controlling traits of interest more rapidly," said Cristobal Uauy, Project Leader in crop genetics at the John Innes Center, one of the 73 research institutes participating in the study.

"This will facilitate and make more effective the breeding for traits like drought or disease resistance," said Uauy.

Wheat accounts for almost 20 percent of the total calories and protein consumed by people worldwide, more than any other single food source. It also serves as an important source of vitamins and minerals.

To meet future demands of a projected world population of 9.6 billion by 2050, wheat productivity needs to increase by 1.6 percent each year. The majority of this increase has to be achieved through crop and trait improvement.

Also, the method of producing the reference sequence and the principles and policies of the consortium provide "a model for sequencing large, complex plant genomes," said Kellye Eversole, Executive Director of the IWGSC.