Feb 4, 2011

Glossary

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TILLING

A molecular biological method used to identify point mutations in plant genomes

TILLING (Targeting Induced Local Lesions in Genomes) is based on mutagenesis, a standard method, which it combines with a rapid DNA-analysis method.

In mutagenesis, plants are treated with chemical substances (formerly also with X-rays) that trigger random mutations in the genome. A new DNA-screening process then selects from thousands of mutagenized plants those that display the mutations in a suitable gene. With the TILLING technology, lots of potential mutants can be tested very quickly at the same time. However, researchers have to know the DNA segments being tested.

TILLING is regarded as an acceptable alternative to genetic engineering methods. For instance, it has been used to breed a potato optimized for industrial purposes. A mutation was used to disable a gene responsible for the formation of amylose, an unwanted starch component, in the potato cells. A gene responsible for amylose production was also switched off in Amflora, a potato produced using genetic engineering methods. Amflora is approved for cultivation in the EU but is highly controversial.

TILLING has clear limits compared with genetic engineering. For instance, it can only influence traits governed by the plant’s own genes. It is not possible to introduce genes from other species or from wild relatives to achieve certain plant-breeding objectives, such as insect or fungal resistance, using the TILLING method. When plants are treated with mutagens, a large number of isolated mutations occur affecting lots of genes. This means that the plants can also lose desirable traits like high yield, meaning they have to be back-crossed with high-yielding varieties in a lengthy process.