Telocentric chromosomes obtained from calluses of nulli-5B tetra-5D of Chinese Spring wheat

T. SHIMADA¹⁾, N. INOMATA²⁾, M. OKAMOTO³⁾ and H. ASAMI⁴⁾

Callus tissues in the fifth successive culture of calluses obtained from seeds of nulli-5B tetra-5D were studied cytologically. The results obtained are summarized in the following table.



The above table shows that callus tissues from seeds of Chinese Spring similarly studied had no telocentric chromosomes. Callus tissues from seeds of nulli-5B tetra-5D at the fifth culture, however, had one telocentric chromosomes in 20% of the cells observed and two telocentric chromosomes in 2% of the cells observed.

Observation of telocentric chromosomes in the fifth culture of callus tissues of nulli-5B tetra-5D may be explained as follows.

Since there were no telocentric chromosomes at the initial step of the experiment, the telocentric must be due to misdivision of centromeres at mitosis of callus tissues.

The causes for misdivision of centromeres of chromosomes are tentatively explained by assuming (1) presence of a gene or genes for suppressing centromere misdivision on the chromosome 5B, (2) presence of a gene or genes for promoting centromere misdivision on the chromosomes 5D, and (3) interaction between absence of chromosome 5B and presence of extra dosage of chromosome 5D.

Either of the above hypothesis is correct cannot be said at the present stage of our experiments.

(Received August 25, 1974)