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Genetics | Generation of the CAUT lines | Verification of the CAUT lines

2. Seed irradiation and sector analysis.

In a typical experiment 10 batches each of 20 Mg of seeds are irradiated with unfiltered X-rays. Various doses can be used in these experiments but the highest level that can routinely be used is 16 kilorad. This dose delays leaf emergence by 3 days. Each batch of seed is broadcast to a filled seed tray in 10 gm of dry sand. It is important to keep the humidity high until the true leaves emerge, as the irradiated plants tend to dry out and die. Sectors are found on up to 1% of plants and sectored plants are picked off to new trays.

The ch-42 sectors are a characteristic yellow colour and sectors with other phenotypes are usually the result of unrelated events and should be discarded. The sectors tend to green up over time but this effect can be reduced by increasing the light intensity. Once branches with yellow L₂ and L₃ tissue have been generated by cutting back they can be marked with waterproof ink. This allows the seeds to be collected from the sector even though the dry silique has no chlorophyll and the sector cannot be seen. Sector phenotypes can be scored at whatever time and/or stage they normally appear. It is a good idea to retain a few yellow mutant homozygotes and a few green non-sectored plants as controls