The emergence of new centres of diversity: evidence from barley.

Statistical analyses of data from a large barley germplasm collection of worldwide origins revealed that material from the USA now contains more variability in toto than material from any other country. In addition trends of overall diversity for other countries suggest that there is little association between high overall variability and what are considered as traditional "centres of origin" or "centres of diversity" for this crop. The five countries of highest overall diversity worldwide were found to be (in descending order): USA, Turkey, Japan, USSR and China. Cluster analyses revealed that relatedness of germplasm was by far strongest between certain European countries, which were also in general of a more intermediate diversity level. The data presented here suggests that the variability present in gene pools still varies substantially by country but according to patterns which appear different from those described previously.