Genetic diversity of six isozyme loci in cultivated barley of Tibet.

A random sample of 463 accessions of cultivated barley from the Tibet Hordeum germplasm collection was assayed electorphoretically for genetic diversity at six isozyme loci. Two loci (Acp-1 and Got-1) were found to be monomorphic and extensive variation was detected at the remaining four loci (Est-1, Est-2, Est-3 and Est-4). The allelic composition of Tibetan barley appeared to be distinct as compared to the results of previous studies of barleys from other parts of the world. Partitioning of genetic diversity showed that approximately 96% of the total variation was maintained at the within-subregion level and only about 4% was accounted for by differentiation among the eight subregions. Analysis of multilocus genotypes revealed non-random association of the alleles at the four loci, both in the entire sample and in all the subregions, although the four major multilocus genotypes did not show significant departure from the expectation based on complete random association. The possible causes for the establishment of these multilocus associations were discussed.