US and Chinese scientists say mapping a key genetic code for bread wheat could improve the crop's productivity and ability to withstand extreme conditions. Their sequencing and drafting of the A genome, one of the three basic genomes of wheat, has been published in the journal Nature, China's state-run Xinhua News Agency reported Monday. The findings could further the study of wheat evolution, domestication and genetic improvement, the researchers said. The identification of around 38,000 genes in bread wheat, Triticum aestivum, was accomplished by a team of researchers including scientists from the Institute of Genetics and Development Biology under the Chinese Academy of Sciences and the University of California, Davis. Researchers said their goal is to increase the crop's yield and quality by boosting genetic diversity and resistance to cold, drought and disease. Bread wheat, one of the world's most widely cultivated and consumed crops, feeds about 40 percent of the world's population.