Towards consumer-friendly cisgenic strawberries which are less susceptible to Botrytis cinerea

This thesis describes the development of genetically modified (GM) strawberries which are less susceptible to fruit rot caused by the fungus Botrytis cinerea. To achieve Botrytis resistance, a polygalacuronase inhibiting protein (PGIP) gene has been isolation from strawberry and was characterised. It was shown that the natural expression of this gene is probably insufficient to restrict colonisation of the fruit by Botrytis . Next to this, the activity of different promoter sequences has been tested in strawberry. A fruit-specific promoter from the strawberry Expansin gene was selected as a suitable candidate to provide enhanced expression of the strawberry PGIP gene in strawberry fruits. Furthermore, the development of a transformation method is described which enables the elimination of selection genes. Selection genes are essential for the production of transgenic plants, but have no function after the GM plants have been produced. After introduction of the combined Expansin promoter and PGIP gene in GM strawberries and subsequent removal of the selection gene, the ultimate GM strawberry plant will contain no gene sequences from foreign species. For this reason, these plants are called cisgenic rather than transgenic. The improved acceptance of such cisgenic strawberries by consumers and producers of strawberries is discussed