II. 19. Linkage studies in a gene for high lysine content in Riso barley mutant 1508.
K. E. Karlsson, Swedish Seed Association, S-268 00 Svalof, Sweden. "R"
High lysine content in Riso mutant 1508 is controlled by one recessive gene (Doll 1973). In order to locate this gene, mutant 1508 was crossed to a testerset of translocations covering all the chromosome arms. The F2-populations were grown in the field in 1975. The plants were harvested individually and classified for translocation sterility and shrunken or plump seeds. Screening for the high lysine gene was performed by using a modified prolamine turbidity test (Rhodes 1975), because one of the main characteristics of mutant 1508 is a drastic decrease of prolamines. One seed from each plant was analyzed. The shrunken seed character expresses xenia. Since plump seeds are known to be dominant over shrunken seeds, a plump seed was analyzed from the heterozygous plants.
The obtained figures for segregation of high lysine content and translocation sterility are presented in Table 1. Five different populations were analyzed. T3-7c, T3-7d, and T2-7b were linked to the high lysine gene. The first two showed absolute linkage and the third very close linkage. On the other hand, T2-3f and T4-6e gave free recombination. The high lysine gene in mutant 1508 must accordingly be placed in chromosome 7. The breakpoints of T3-7c and T2-7b are in the long arm, and T3-7d is in the short arm of chromosome 7. This indicates the high lysine gene to be situated in the centromere region.
Free recombination between short rachilla hairs (s) and the high lysine gene was indicated in one combination which segregated for s. Neither does it seem to be any linkage between the high lysine gene in mutant 1508 and the lys-gene from Hiproly.
The simultaneous segregation of the high lysine gene and the shrunken seed character was also studied for the same material as in Table 1. These figures are pooled in Table 2. For 1273 analyzed plants, no recombination at all was found. This is an indication that the high lysine content and the shrunken seeds are expressions of the same gene. We have not found in any population involving mutant 1508 a high lysine plant which does not have shrunken seeds.
Further investigations will be undertaken to make a more detailed localization of this high lysine gene.
Table 1. Segregation of high lysine content
and semisterility in crosses between translocations and Risö mutant
1508.
Table 2. Segregation of high lysine content and
shrunken seeds in crosses between translocations and Risö mutant 1508.
References:
Doll, H. 1973. Inheritance of the high-lysine character of a barley mutant. - Hereditas 74:293-294.
Rhodes, A. P. 1975 A comparison of two rapid screening methods for the selection of high-lysine barleys. - J. Sci. Food Agric. 26:17Q3-1710.
