TILLING (Targeting Induced Local Lesions In Genomes) is a reverse genetic method. It combines chemical mutagenesis, a method used in plant breeding since decades, with modern techniques allowing screening of large populations on molecular level. It uses the fast growing knowledge of plant genomes and is applicable on every plant, since it does not require plant tissue culture techniques. It mostly uses the chemical EMS to introduce point mutations into plant genomes, mimicking natural mutations caused by sunlight although at a much higher frequency, followed by a high-throughput screening for induced mutations in target gene.

Many plant genomes are sequenced or are just being sequenced and many biosynthetic pathways are known. Based on this steadily growing knowledge interesting target genes can be identified and TILLING may be used to prevent the production of unwanted components or to modify biosynthetic pathways in a desirable manner.

For potato we developed a modified TILLING technique taking into account the plant-specific features of potato (autotetraploidy, heterozygosity, vegetative propagation). The gbssI gene (granule bound starch synthase I) that leads to the production of amylose, was used as a model and first target gene. The resulting inactive gbssI allele is now being used in breeding of high-amylopectin potato varieties.