Genetic control and mechanism of chromosome elimination in the hybrids between Hordeum bulbosum(4X) and Hordeum vulgare(4X)

Two strains of Hordeum bulbosum (4X), #191 and #487, were reciprocally crossed to a strain of H. vulgare (4X), D8/55, and their hybrid embryos were cytologically examined in order to know time, pattern and genetic control of somatic chromosome elimination occurred in the tetraploid hybrids between these species. Fourty hybrid embryos from each cross were sampled at 6 different times from 3 to 13 days after pollination. In all of the crosses, chromosome elimination occurred very frequently by about 9 days after pollination and a number of dihaploid cells were observed. The maximum rate of chromosome elimination was observed in the period of 3 to 5 days after pollination. It was cleary indicated that degree of chromosome elimination or dihaploid frequencies were quite different between the crosses with #191 and #487 but not different between reciprocals. This strongly suggests that the chromosome elimination is mainly controlled by nuclear gene (s) involved in bulbosum parents, but affected little by cytoplasms of these two species