Line breeding

Line breeding is used for plant varieties that usually breed through self-pollination, for example barley, wheat, oats or peas. Such plants are fertilised by their own pollen, even before they leave the flowering stage. However, this does not lead to the increase in genetic diversity 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 as much as possible in terms of the desired properties.

Next, the breeder selects 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 on the best plant, and because this plant is bred through self-fertilisation, 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 desired new 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, for example 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 eventually a plant grows. Until then, it only has half 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-fertilisation. This allows breeding progress to be conveyed more quickly to farmers.