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Bioscience in brief

Plant genetics and crop breeding

What is genetic diversity?

Genetic diversity of sorghum (left) and millet (right) illustrates the potential of plant breeding.

Genetic diversity within a population refers to the number of different alleles (the alternate forms of genes) of all genes and the frequency with which they appear.

Variation is high when there are many different alleles of all genes and many different combinations of those alleles.

A gene pool is the collective set of alleles found in a population. Usually gene pools refer to a particular species (individuals can interbreed freely). Plant breeders can also make use of the gene pool of closely related species that can cross and produce fertile hybrids (called interspecific hybrids).

Maize ears from CIMMYT’s collection, showing a wide variety of colors and shapes. CIMMYT’s germplasm bank contains about 28,000 unique samples of cultivated maize and its wild relatives.

The level of genetic variation in a population is constantly changing: different alleles of a single gene can appear and disappear from time to time within a population. This means that the gene pool of a population is always dynamic.

For some characteristics, such as maize or sorghum grain colour, there is a great level of genetic variation in nature.

The term “bean” is used to denote the seed of a large number of related plants: broad or fava beans, common beans, runner beans, soybeans, peas, chickpeas, vetches, and lupins. These are in fact different species.

In biology, a species is one of the basic units of biological classification, defined as a group of organisms capable of interbreeding and producing fertile offspring, or as a separately evolving lineage with a single gene pool.

In practice defining a species is not simple (this is known as the “species problem“. Some separately evolving groups (i.e. “species”) may continue to interbreed to some extent, and human intervention has resulted in extraordinary changes in the appearance of plants and animals during their domestication.

Plant breeders define species as populations of organisms that have a high level of genetic similarity.