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Bioscience in brief

Plant genetics and crop breeding

Where do plant breeders find genetic diversity?

The source of genetic variation for resistance to a pest or disease, for example, can  be found in cultivated varieties of plants, or among landraces – local varieties of domesticated plant species adapted to the natural and cultural environment in which they are grown. If the required variation cannot be found among cultivars, the plant breeder may look into collections of seed of the wild ancestor of the crop.

If that does not work, the breeder will look into the gene pool of related species which can be crossed with the crop.
If crossing plants is not possible, the genetic engineering route can be examined.

Maize seed samples, CIMMYT germplasm bank. The CIMMYT germplasm bank contains around 28,000 unique samples of maize seed.

A drought-resistant wild wheat, common to Syria and Turkey. Also known as Triticum columnare.

Rice seeds

Cassava brown streak disease, caused by a virus, affects crops in East Africa. This has already infected around 80% of crops in Uganda and around 20% of crops in Rwanda and Burundi. Scientists have not found a source of genetic resistance in the genetic pool of cassava, so it is not possible to develop cassava varieties resistant to this disease by conventional breeding techniques. A number of public research institutions are developing virus resistant GM cassava varieties. Read more…
Bananas and plantains are a hugely important source of food and cash in East Africa. Because cultivated bananas are sterile, introducing resistance to devastating pests and diseases by conventional breeding methods is extremely difficult and time consuming. This is true even in those instances where natural sources of diversity exist in the gene pool of related species. Read more…
Pod borers can wipe out most of a cowpea field.These insects can be controlled with insecticides, but these are not very effective as the insect is buried in the plant and hence protected from contact with chemicals, expensive and toxic. There is no natural source of resistance to this pest in natural cowpea populations. To ensure cowpea remains viable in Africa, GM varieties with an in-built protection to borers have been developed. GM cowpea is being trialled in Nigeria. Read more…