GEOGRAPHIC DIFFERENTIATION IN ISOZYME GENOTYPES OF HIMALAYAN BARLEY (HORDEUM-VULGARE)

Isozyme variation among Himalayan barley (Hordeum vulgare L.) landraces was surveyed at seven loci, using 650 accessions collected from different regions. Large genetic diversities were detected at the Est1, Est2, and Est4 loci for esterase and at the Aat3 locus for aspartate aminotransferase. However, only a few variations were observed at the Pgd1 and Pgd2 loci for phosphogluconate dehydrogenase, and no variation was found at the Aat2 locus. The allelic combinations observed were not randomly distributed in the Himalayas: a geographic trend was closely related to covered and naked types of barley. The covered barleys were frequently distributed in southern regions of the Himalayas and were characterized principally by the Al-Fr-At genotype at the Est1-Est2-Est4 multilocus, combined with the Mo allele at the Aat3 locus. The naked barleys were found mainly in northern regions, and most of them possessed the genotypes Ca-Un-Nz or Pr-Fr-At, together with the Eg allele. Such a nonrandom allelic distribution provides useful information for further analysis aimed at considering the history of cultivated barley in the Himalayas.