II. 6. Linkage of a trypsin inhibitor locus (Itc1) and two esterase loci (Est1 and Est4) with marker loci on barley chromosome 3.
G. Nielsen, Agricultural Research Department, Riso National Laboratory, DK-4000 Roskilde, Denmark. Jorn Hejgaard, Department of Biochemistry and Nutrition, Technical University of Denmark, DK-2800 Lyngby, Denmark.
The locus Itc1 coding for the protein trypsin inhibitor TI-1 (Mikola and Suolinna, 1969) has previously been located to chromosome 3 by means of wheat-barley addition lines (Hejgaard et al., 1984). The esterase locus Est1 has been located to the telocentric chromosome of 3L-telotrisomic plants (Nielsen and Hvid, 1976).
The linkage relationship between Itc1, Est1, Est4 and seven chromosome 3 marker genes has now been studied by F2-segregation analysis in three crosses involving the following genes:
Cross A: Itc1, Est4, f2, vst2 (77 plants)
Cross B: Itc1, Est1, gs2, wst (164 plants)
Cross C: Itc1, Est4, als, uz, cu2 (71 plants)
The calculated recombination percentages <50 have been transformed to distances in centimorgan (cM) ± standard deviation and are drawn to relative scale (Figure 1). Recombination percentages >50 are indicated by broken lines. The order of the genes and the distances shown at the top of the figure are calculated by means of a maximum likelihood method (Jensen and Jorgensen, 1975) on the basis of the combined linkage data from the three crosses.
The standard deviation of some distances is relatively large due to the low number of plants. It has been reported that Est1 and Est4 are very closely lined (Kahler and Allard, 1970) and that Est1 and f2 are linked with a distance of 11.7 ± 2.2 cM (Nielsen and Hvid, 1976). From our data we conclude that the group Est1, Est4, f2 is located distally to the other marker genes. The Itc1 locus is positioned between the group als, wst, gs2 and the group yst2, uz, cu2.
References:
Hejgaard, J., S.E. Bjorn and G. Nielsen. 1984. Localization to chromosomes of structural genes for the major protease inhibitors of barley grains. Theor. Appl. Genet. 68:127-130.
Jensen, J. and J.H. Jorgensen. 1975. The barley chromosome 5 linkage map. I. Literature survey and map estimation procedure. Hereditas 80:5-16.
Kahler, A.L. and R.W. Allard. 1970. Genetics of isozyme variants in barley. I. Esterases. Crop Sci. 10:444-448.
Mikola, J. and E.M. Suolinna. 1969. Purification and properties of a trypsin inhibitor from barley. Eur. J. Biochem. 9:555-560.
Nielsen, G. and S. Hvid. 1976. Location of the esterase locus Est1 on
barley chromosome 3. BGN 6:45-46.
