Abstract
Some basic problems related to root-tip checking of chromosome numbers were quantitatively studied in order to establish the most efficient way of aneuploid screening in wheat.
1. The effects of two types of cold treatments on mitosis in root-tips were compared against a check. The cold treatments did not significantly change the number of prophase cells, but increased the number of metaphase cells about three times and reduced the number of anaphase cells. Chromosome length was shortened to about 60 per cent of the check. Chromosome spreading was also improved after the application of cold. The cold treatments apparently intensified chromosome spiralization and disturbed spindle organization.
2. The cold treatment of the detached root-tips accumulated more metaphase cells and more extremely reduced the number of anaphase cells than that of the attached root-tips. The chromosome length was more shortened in the attached root-tips. These results indicate that chromosome spiralization was more intensified in the attached root-tips and spindle organization was more disturbed in the detached root-tips.
3. In application, the cold treatment of the detached root-tips is the best for an efficient screening of aneuploids. However, the treatment of the attached root-tips is recommended whenever anaphase configurations must be studied.
4. Root-tip collections from germinating seeds, transplanted seedlings and growing plants were compared on the per cent success of chromosome counting and the efficiency of plant management. The results indicate that the most satisfactory was root-tip collecting from germinating seeds.
