[Origin of hybrid dwarfness]

In studies of the hybrid combination (F4 Khar'kovskaya 46 x Triticum dicoccum) x Khar'kovskaya 46, a short-stemmed line, whose progeny exhibited traits of hybrid dwarfism, segregated with a frequency close to 1 : 15. Analysis of this line in F3 and hybrids from crosses of the short-stemmed line from this combination with the long-stemmed accession T. turgidum L. (c-38097) showed that the stem size variability curves of the both lines have two peaks. Since these results cannot be explained by complementary interaction of D genes, hybrid dwarfism is probably controlled by pleiotropic action of two genes that have multiple pleiotropic effect on the D2D2 D3D3 genes. Two or three rounds of selection performed on the progeny of plants higher than 80-100 cm produces stable lines without hybrid dwarfism traits, i.e., the pleiotropic effect disappears.