• Preparation of a DNA sample in the laboratory
    Crossing and selection

Crossing and selection

Overview

In a nutshell

Parental plants bearing the desired characteristics are cross-bred with each other.

The grains of the largest and most productive plants are sown again.

Advantages

Original and fundamental type of plant breeding

Disadvantages

Requires a lot of time to achieve the desired result

Development

Selection since about 12,000 BC in modern-day Anatolia and the Zagros Mountains (modern-day Iran). Research on cross-breeding from about 1855 by Gregor Mendel (Mendel’s laws).

Crossing

Breeders want to provide agrarians with optimally adapted crops. This requires combining many positive characteristics in one single variety. The desired properties include a very good yield; resistance to pathogens; a high starch, protein or sugar content; and good standability in the field. To be able to combine all these properties in one single variety, parent plants carrying the desired characteristics are cross-bred. This creates a filial generation.

In the best-case scenario, this will include a few individual plants that carry the positive traits of both parents. Only then does the crossing experiment achieve the desired result. In a next step, breeders cross-breed this offspring with other plants that have other desired properties. Several cross-breeding stages later, a new line is created that ultimately combines all beneficial characteristics and, after several test phases, can be registered as a new variety. This process is time- and labor-intensive. It must be carefully planned and implemented over several years.

After the first crossbreeding of two parent plants (far left), breeders crossing new plants into the offspring again and again. In the end—often only after many years—a plant with the desired properties is finally obtained.

After the first crossbreeding of two parent plants (far left), breeders crossing new plants into the offspring again and again. In the end—often only after many years—a plant with the desired properties is finally obtained.

Selection (screening)

Selection (also called screening) is the oldest form of plant breeding. Around 12,000 years ago, humans initially cultivated wild cereal grains. Early farmers purposefully held back the grains of the largest and most productive plants. These seeds were then sown again the following year, while all other plants were excluded from the breeding process. This allowed the desired properties of the plants to assert themselves more and more over time. Among other things, yield was increased.

If this selection process is repeated often enough, eventually only almost homozygotic plants (with regard to the selected characteristic) remain that have the desired properties. Without knowing the genetic principles, the first farmers managed to carry out selective breeding through accurate observation and their experience. One of the first cultivated cereal crops was wild einkorn (Triticum urartu). It grows only a few small grains and its ears are brittle. Constant selection of the best individual plants then led to cultivated einkorn (Tritium monococcum) with larger grains and solid ears.

The principle of selection: For example, breeders retain the grains of the largest plants in a crop. They sow this seed the following year. Over the course of years or decades, the desired, larger plants continue to prevail.

The principle of selection: For example, breeders retain the grains of the largest plants in a crop. They sow this seed the following year. Over the course of years or decades, the desired, larger plants continue to prevail.

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Thilo Resenhoeft
Thilo Resenhoeft
Corporate Communications
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