Abstract
It seemed difficult to obtain tetraploid plants of rice by the soaking of seed into colchicine water solution. The following method was found to be good: to germinated seed on moistened sand in a dark incubator, and after the elongation of first internode out of the hull, to apply lanoline paste containing 3% of colchicine on the first note, or a drop of 0.1% water solution on a small piece of absorbent cotton winded round the first node (4 times a day for 3 days). Thus, seedlings thickened by the effect of colchicine were selected after a week, and were cultured in pots with sterilized soil.
A half or more of them died during the seedling stage; the percentage of death was found to be different with the variety. Varieties of “Continental” group seemed somewhat higher in the percentage of death than “Insular” varieties.
After the heading, panicles (or chimaeral parts of a panicle) showing some characteristics of tetraploid are found in some 10% to 25% of the thickened plants. And the plants raised from the seemingly tetraploid seeds were found to be tetraploids in 40% to 50% of cases. The lower the fertility of seemingly tetraploid panicles, the higher the frequency to gain tetraploid plants in the second generation.
By the above mentioned method, 120 varieties of various districts of Eastern Asia were treated, and tetraploid strains were obtained from 74 varieties.
