II. 17. Location of the high-lysine locus Lys4d on barley chromosome 5.
Jens Jensen, Agricultural Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark. "R"
The Risø high-lysine mutant 8 is induced in the variety 'Bomi' by an EMS treatment (Doll et al. 1974). The shrunken endosperm character of mutant 8 was found to be located on chromosome 5 by trisomic studies (Ullrich and Eslick 1978). Jensen (1979) showed that the high-lysine character of mutant 8 was conditioned by a dominant or semidominant gene. Furthermore, the shrunken endosperm character of mutant 8 was a pleiotropic character of the high-lysine gene, and by translocation studies the gene was found to be on chromosome 1 or chromosome 5. It was proposed that the high-lysine gene of mutant 8 be called Lys4d (Jensen and Doll 1979).
Mutant 8 was crossed with a line containing the marker genes necla, ert-b, and Ml-at. Unfortunately, only a limited number of F2 seeds from a single F1 plant were available. The F1 plants were grown in the greenhouse and the F2 plants in the field. The erectoides (ert-b) character was scored on the F2 plants. The high-lysine (Lys4d) character was determined by the shriveled seed character scored on the seed in the F2 spike. About 25 F3 seedlings from each F2 plant were grown in a greenhouse where they were scored for the powdery mildew resistance (Ml-at) character after inoculation with powdery mildew culture JEH30 (201176-7). The same F2 progeny was scored for the necrotic leaf spotting (nec1a) character.
Table 1 presents the segregation data of the six possible two-point combinations. It also gives the recombination percentages (rec %) with their standard deviations, the crossing-over frequencies in centimorgans (cM) as obtained by the Kosambi mapping function, and chi-squares (c2 fit) with their respective degrees of freedom (df). The chi-squares test the observed segregations against the segregations expected at the recombination estimate. The Lys4d gene is linked with the ert-b gene with 30.5% rec. To the nec1a gene the Lys4d gene is linked with 40.8% rec., and as ert-b and nec1a are only 18.4% rec. apart, the genes must be in the order nec1a, ert-b, Lys4d. The recombination frequencies between these three genes and the Ml-at gene were high in all cases.
Table 1. The F2 segregation and the linkage estimates from the cross Lys4d x nec1a, ert-b, Ml-at.
The small material of the present experiment gives rather high standard deviations; however, the data clearly indicate in which region of chromosome 5 the Lys4d gene is located. Furthermore, the linkage data are in agreement with the current barley chromosome 5 map (Jensen 1980). The additivity of cM obtained by the Kosambi transformation may be seen from Figure 1 showing a map with the loci nec1, ert-b, and Lys4.
Figure 1. Map distances in centimorgam (cMO)between the loci nec1, ert-b, and Lys4 on chromosome 5.
References:
Doll, H., B. Køie, P. O. Eggum. 1974. Induced high-lysine mutants in barley. Radiation Botany 14:73-80.
Jensen, J. 1979. Chromosomal location of one dominant and four recessive high-lysine genes in barley mutants. In proc.: Int. Symp. of Seed Protein Improvement in Cereals and Grain Legumes. Vol. I. IAEA, Vienna, p 89-96.
Jensen, J. 1980. Coordinator's report of Chromosome 5. Barley Genetics Newsletter 10:88-90.
Jensen, J. and H. Doll. 1979. Gene symbol for barley high-lysine mutants. Barley Genetics Newsletter 9:33-37.
Ullrich, S. E. and R. F. Eslick. 1978. Chromosome location evidence for Risø-induced high-lysine shrunken endosperm mutants of barley. Barley Genetics Newsletter 8:114-125.
