Wheat is the most important crop in the world in terms of area harvested (220 million hectares in 2014). The main types of cultivated wheat are the hexaploid bread wheat (T. aestivum), and tetraploid durum wheat (T. turgidum). Other types of wheat, such as einkorn, emmer and spelt, are still grown on a more limited scale in some regions, though interest has been increasing of late.
The earliest forms of domesticated wheat originated in southeast Turkey. From there, the crop spread to the Near East (9000 BP). The dispersal of the crop into Europe occurred through Greece (8000 BP). It reached the Balkans, the Danube, and southern Europe by 7000 BP. Wheat was brought to China through Iran and Central Asia (3000 BP), and it entered Africa through Egypt. The Spanish introduced the crop to Mexico in the 16th century.
Wheat is conserved as seeds. Over 560,000 accessions are held among 40 different collections, as described in the global ex situ conservation strategy for wheat, rye and triticale.
Almost 320,000 wheat accessions are visible on Genesys. Nearly 23% of these are landraces, and about 7% are wild relatives. The International Maize and Wheat Improvement Center (CIMMYT) hosts the largest wheat collection in the world, followed by the USDA-ARS genebanks, the Australian Grains Genebank and ICARDA.
Wheat is expected to be negatively impacted by climate change. Due to its importance in diets and livelihoods, a global effort led by CIMMYT is harnessing the genetic diversity of wheat to produce more resilient, productive and nutritious varieties.