BEIJING - Scientists from China and the United States have mapped a key genetic code for bread wheat, a discovery that will help improve the crop's productivity and ability to withstand extreme conditions.

The sequencing and drafting of the A genome, one of the three basic genomes of wheat, was published on the website of the journal Nature on Monday. Researchers present the generation, assembly and analysis of a whole-genome shotgun draft sequence of the genome of wheat T. urartu, the donor of the A genome.

The identification of around 38,000 wheat genes is expected to help provide a valuable resource for accelerating deeper genomic breeding studies and offer a new foundation for the study of wheat evolution, domestication and genetic improvement.

The research, launched by a team from the Institute of Genetics and Development Biology under the Chinese Academy of Sciences (CAS), was conducted by Shenzhen-based BGI, a leading genomics organization, and the University of California, Davis.

Bread wheat (Triticum aestivum) is one of the most widely cultivated and consumed food crops in the world. It feeds about 40 percent of the world's population and provides 20 percent of a human's daily recommended amounts of calories and protein. Major efforts are underway around the world to increase the crop's yield and quality by boosting genetic diversity and resistance to cold, drought and disease.

However, the extremely large size and polyploid complexity of the wheat genome have so far posed substantial barriers for researchers to gain insight into its biology and evolution.