II.21 Chromosome location of Est-l by analysing F1 trisomic plants.
Gunnar Nielsen and Ove Frydenberg. Danish Atomic Energy Commission, Research Establishment Riso, DK-4000 Roskilde, and Department of Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark.
In plants heterozygous for the Est-1 alleles Pr and Ca the relative densitometric strength of the electrophoretic zones is about 1:2 (left part of Figure), and the strength of the individual zone is only about half the strength of the same zone in homozygous plants.
In order to locate the Est-1 locus, plants homozygous for the allele Ca were crossed as males to seven lines of Betzes barley, each of which was trisomic for one chromosome. The trisomic lines were all homozygous for the allele Pr. F1 progeny was cytologically classified in disomics and trisomics and the relative strength of the Pr and Ca electrophoretic zones was determined by densitometri. The ratio between Pr and Ca activity was identical in disomics and trisomics for all chromosomes (left part of Figure) except for trisomics for chromosome 3. In chromosome 3 trisomics the activity of the Pr-allele, coming from the maternal parent, is greatly increased in comparison with the Ca activity (right part of Figure).
It is concluded that the Est-1 locus is located on chromosome 3. Since Est-1 locus is closely linked to Est-2, this latter locus is also on chromosome 3.
