The Example of Winter Cereals

Winter cereals are temperate cultivars that can be sown, and allowed to germinate, in the fall. They are cold-tolerant, and they survive the winter, often under snow. In the spring thaw, they start growing, and they then have an advantage of several weeks over the spring-sown cereals, mainly because they can start growing when the ground is still too wet to allow tractors on the land.

When plant breeders want to produce new cultivars of a winter cereal, they sow a segregating mixture of seeds in the fall, and wait for the winter to kill off all the cold-susceptible seedlings. The survivors are cold-tolerant and the best of them can be screened for other characters. Obviously, the colder the winter, the fewer the survivors, and the greater their cold tolerance. This cold tolerance can be further increased by transgressive segregation, in which the best survivors are used as parents in a recurrent mass selection program.

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