Geographical distribution of isozyme alleles for phosphogluconate dehydrogenase in barley.

The Ak and Tj alleles at the Pgd1 locus and the Ps and Tn alleles at the Pgd2 locus were detected for phosphogluconate dehydrogenase in barley. The Ak allele at the Pgd1 locus was widely distributed around the world, while the Tj allele was found only in two accessions from Nepal and one from India. At the Pgd2 locus, the Ps allele was abundant everywhere, whereas the Tn allele was occasionally found in Caucasus, Turkey, and Europe, and scarcely or none in Korea, China, Nepal, India, and Ethiopia. The Tn allele was also detected in Japanese accessions. Among them, six-rowed varieties carrying the Tn allele were principally grown in northern parts of Japan and characterized by covered kernel, the Occidental type for nonbrittleness of rachis, and resistance to Japanese races of powdery mildew. However, the loci responsible for these characteristics were independent of the Pgd1 locus.Key words: barley, isozymes, phosphogluconate dehydrogenase, geographical distribution.