[A change in dominance of a mutation in barley, combined with suspension of the pleiotropic action of the gene].

In order to demonstrate change of dominance of mutants in altered genetic environments, a mutant of spring barley type Haisa II was used as the experimental material. This mutant is inherited as a single gene dominant. It differs from the original type by length of the grain, the rachis segment and the straw. The complex of characteristics of this mutant is pleiotropically inherited.Referring to these three characteristics the following plant types were analyzed: plants of the mutant, of the type Haisa II (from which the mutant is derived), seven other spring barley types serving as crossing partners of the mutant, and finally F1-plants of the MS-, MH- and SH-crossings.A change of dominance could be demonstrated in the case of the F1-plants of certain MS-crosses. With the F1-plants of several of these MS-crosses it could be shown, that the change of dominance is combined with suspension of pleiotropic gene action.In the discussion it is pointed out how little is known at the present time about the mechanisms which underlie a change of dominance and of pleiotropism. For a deeper understanding of these phenomena experiments on a moleculargenetic level, similar to those performed in other experimental systems, are necessary.