Clean Line in Plant Breeding
The term was introduced in 1903 by W. Johansen. Since self-pollination is a process of combining the same genotypes, therefore, the clean line is a group of organisms homozygous for most genes. In organisms, a mutational process is continuously carried out. Most mutations are recessive and, to a large extent, cause adverse hereditary changes. In cross-pollinated plants, these recessive mutations do not appear externally, since they are in a heterozygous state. With self-pollination, they go into a homozygous state and exert their effect. Most often, adverse mutations in the clean line are eliminated by natural selection. In nature, plants do not have clean lines; they are not viable. But in plant breeding, very often homozygous lines are used to connect with different self-pollinating lines, heterozygous forms are obtained – more viable.