A survey of allozymic alleles and genetic diversity was made for 151 access
ions of the American Barley Core Collection. A total of 25 alleles at ten l
oci were observed. Two loci were monomorphic. The average diversity index f
or individual loci ranged between 0.026 and 0.649. Most significant differe
nces in allelic frequency and genetic diversity value were found between sp
ring and winter barley. Spring barley showed a greatly higher average diver
sity than winter barley (t = 2.124, P = 0.071). The smallest differences in
allelic frequencies and diversity values were observed between the two geo
graphical regions, North and South America. Rare alleles were detected only
in a few accessions. Seven rare alleles were associated with spring barley
. The genetic similarities among the 151 accessions ranged from 0.20 to 1.0
0, which showed that a high level of genetic variability exists in this set
of core accessions. Cluster analysis and principal coordinate analysis did
not give clear-cut separation of different types of barley, but most of th
e winter barley accessions were closely associated.