Line breeding

Line breeding is used for plant varieties that usually breed through self-pollination (e.g. barley, wheat, oats and peas). Such plants are fertilized by their own pollen, even before they leave the flowering stage. However, this does not lead to the increase in genetic diversity that the breeders are looking for, as the genetics are not mixed. To make this possible, breeders use targeted cross-breeding of two parental lines, which complement each other in terms of the desired properties as much as possible.

Next, breeders select those plants that correspond to the desired performance specifications with regard to plant health, yield and quality (selection). After several of these selection cycles, a new variety is built from the best plant, and because this plant is bred through self-fertilization, the plants of this variety are very uniform (homogeneous). This procedure is called line breeding. It eventually results in largely homozygotic and homogenous line-bred varieties with the new, desirable characteristics. These can be identically reproduced through self-pollination for cultivation in agricultural practice.

This often tedious process can be accelerated: The doubled haploid technique involves the isolation of haploid plant cells, e.g. pollen. These only carry male genetic material, i.e. half of the chromosome set. If the chromosome set is subsequently reduplicated, all characteristic attributes are present in homozygotic form.

To do this, breeders create pollen cell cultures, from which tissue and, then eventually, a plant grows. Until then, it only has half of a chromosome set. The so-called homozygotic doubled haploid plants result from a reduplication of the chromosome set. This saves time compared to traditional line breeding with repeated self-fertilization. This allows farmers to quickly see breeding progress.