The use of primary trisomics for the localization of genes on the seven different chromosomes ofPetunia hybrida. I. Triplo V

Data on 3n×2n and 2n×3n crosses as a source of trisomics inPetunia are given. The delayed germination and retarded growth ofPetunia trisomics, in comparison with diploids, is mentioned. The application of recent fluorescence staining techniques to enzymatically macerated roottips made it possible to distinguish the seven chromosome pairs ofPetunia hybrida. With the aid of the standard karyogram, a number of primary trisomics could be identified. The origin of two primary trisomics is discussed. With these trisomics, some genetic factors, placed in linkage groups, have been localized on one of the chromosomes. This first localization concerns the linkage group, containing the geneUn (=Undulata) for flower shape. In a primary trisomic with the undulate flower shape, chromosome V proved to be present in triplicate. From the deviating ratios for the undulata character in crosses with this trisomic, it was concluded that the location of the linkage group containing the geneUn is on chromosome V.