- Spontaneous :
- chromosome doubling occurs occasionally in somatic tissues and unreduced gametes are produced in low frequencies.
- Production of adventitious buds :
- Decapitation in some plants leads to callus development at the cut ends of the stem.
- Such a callus has some polyploid cells and some of the shoot buds regenerated from the callus may be polyploid.
- In Solanaceae 6-36% of adventitious buds are tetraploids.
- The frequency of polyploid buds may be increased by the application of 1% IAA at the cut ends as it promotes callus development.
- Treatment with physical agents:
- Heat or cold treatment centrifugation , x-ray or gamma ray irradiation may produce polyploids.
- Exposing the plants or ears of maize to a temperature of 38-45 oC at the time of the first division of zygote produce 2-5 % tetraploid progeny.
- Regeneration in vitro:
- polyploidy is a common feature of the cells cultured in-vitro.
- Colchicine treatment:
- Colchicine treatment is the most effective and the most widely used treatment for chromosome doubling.
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