II.34 Three-point tests on barley chromosome 3.
Bodil Søgaard, Department of Physiology, Carlsberg Laboratory, G1. Carlsbergvej 10, DK-2500 Valby, Copenhagen, and Danish Atomic Energy Commission Research Establishment Risø, DK-4000 Roskilde, Denmark.
Four three-point tests were made with chromosome-3 marker genes. The markers employed were the eceriferum loci cer-r, cer-zd and cer-zn, the erectoides locus ert-c, and the semi-brachytic locus uz.
The four cross combinations were as follows:
The double mutants with the genes listed in columns m and c were used as the female parents. The pollen parents had the genes listed in column r. The F1 generation was grown and selfed in the phytotron in Stockholm. The F2 generation was grown in the field at Risø.
The genotypes of all F2 plants were determined by scoring the F2 plant progenies in the field. Twenty-seven genotypes could be distinguished in this way; number of plants for each genotype are given in Table 1. From these data the order of the loci in each cross was determined and the recombination percentages were calculated by the maximum likelihood method (Figure 1).
Table 1. Observed number of F2 plants of the 27 genotypes.
Figure 1. The recombination percentages from each cross.
A linkage map comprising the 5 genes was determined by a method described by Jensen and Jørgensen (1975). The best fit is the sequence shown in Figure 2 that also shows the distances and their standard deviation (in per cent recombination).
Figure 2. The sequence of the five loci on chromosome 3.
The coefficient of coincidence was less than 1, corresponding to a positive interference, in all four cases.
The details of the analysis will be published in: Søgaard, B. The localization of eceriferum loci in barley. V. Three-point tests of genes on chromosomes 1 and 3 in barley (in preparation).
References:
Jensen, J. and J.H. Jørgensen, 1975. The barley chromosome 5 linkage map. I. Literature survey and map estimation procedure. - Hereditas 80: 5-16.
