A quick method of producing pure lines in crops that are inbreeding, and seed-propagated, such as many cereals and grain legumes. A breeding population may contain many individuals that are both genetically diverse and heterozygous. A single self-pollinated seed is taken from each individual and is grown to maturity. This process is repeated up to six times. Each individual becomes more or less homozygous, but the population is still diverse. The best individuals are selected and kept as new pure lines, or as the parents of the next generation of recurrent mass selection . The idea behind SSD is to save time. There is no screening until the process is complete. With perhaps three generations of SSD each year, with the aid of hydroponics and a greenhouse, it is possible to produce homozygous lines in two years, or less. The more traditional method would require screening under field conditions in each generation of selfing and, in a temperate climate, with only one screening season each year, this would require up to six years.
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