ENGINEERED INSECT RESISTANCE IN TOMATO

The American bollworm, Helicoverpa armigera, is a polyphagous insect with one of the widest distributions of any agricultural pest. In many area's this insect is a major pest on processing tomatoes (Albajes et al. 1988). The larvae feed mainly on the fruit, causing extensive damage and promoting decay.

Bacillus thuringiensis produces a crystalline parasporal inclusion composed of one or several proteins which are toxic to lepicopteran, coleopteran and dipteran larvae (Höfte & Whiteley, 1988). Using Agrobacterium mediated transformation, transgenic tomato plants have been obtained which are expressing the toxic fragment of a B.t. insecticidal crystal protein gene, cryIAb either under the control of the woundstimulated TR2' or the constitutive 358 promotor.

Significant, but incomplete control of Helicoverpa armigera was observed in a greenhouse trial. Tomato plants expressing the cryIAb gene under the control of the TR2' promotor were artificially infested with H. armigera eggs. Percentage fruit injuries as well as number and size of larvae were significantly reduced on the CRYIAb containing plants.

A second generation expressing a cryIAb gene optimalized for expression in plants is actually under investigation. Based on expression data improved insect control is expected.