GENETIC STUDIES OF A 6x-DERIVATIVE FROM AN 8x TRITICALE

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Abstract
A hexaploid strain named "Salmon" (2n=42) was obtained in the progeny of octoploid Triticale (2n=56). This strain was crossed to common wheat. The F1 hybrid showed 21II in a majority of PMC''s. Apparently, octoploid Triticale was converted to hexaploid wheat by the elimination of the rye chromosome complement. From chromosome configurations in meiosis of the F1 hybrid and karyotypes of its parents, it was found that the satellited arm of one of the wheat Sat-chromosomes was replaced in Salmon by an arm of a rye chromosome. Monosomic analysis on waxiness, also, indicated that a segment of chromosome XIII, comprising W locus, was lost in Salmon. Therefore, it has been concluded that the remaining wheat chromosome complement is slightly modified. The nucleus substitution line of Salmon was superior to Salmon itself, while those of some other wheats were inferior to the corresponding normal lines. The frequencies of haploids and twin seedlings in the substitution line of Salmon were much higher than in other wheats. These peculiar behaviors of Salmon''s nucleus substitution line seems to be due to the modification of the wheat chromosome complement. All those facts furnish a strong support for Kihara''s old view that the genome is a functional unit in heredity.