The overall objectives of the work are to assess the impact on representative elements of the poplar fauna of toxins/protoxins (derived from Bacillus thuringiensis) expressed in transgenic euramerican hybrids.
The overall objective of the project was to assess the impact of toxins and protoxins derived from Bacillus thuringiensis on representative elements of the poplar fauna, expressed in transgenic euramerican hybrids. Attempts to express insecticidal proteins in transgenic poplars of other species were successful and there are real prospects of transgenic approaches towards insect control of different poplar taxa. Preliminary data have been obtained from primary transformants containing single crystal toxins active against either lepidopterans or coleopterans. However, the attempts to transform and regenerate euramerican or transamerican poplar hybrid of commercial significance in Europe were not successful. Poplar genotypes Populus tremuloides x Populus tremula (INRA 35338) and Populus tremula x Populus alba (INRA 717 1B4) contained variable but small amount of detectable Bt toxin/DNA with variable and small effects on poplar feeding insects.
Female poplar clones will be transformed with the DNA sequence directing the production of a Lepidoptera specific protoxin from Bacillus thuringiensis kurstaki (Btk).
Clones expressing the protoxin (which is catabolised in the insect to an active form) will be similarly transformed to constitutively express a second, beetle specific, protoxin using genetic materials from BY tenebrionis. The clones will be propagated for critical reassessment of growth/pathological responses to fungal and bacterial agents as judged against untransformed progenitor material and also clones from the same stock expressing a different introduced gene product; coat protein of poplar mosaic virus. The breeders will supply to Oxford additional female stock with a distinct genetic background. These will be transformed and stock expressing the Lepidoptera specific product will be sent to the collaborating laboratories for bioassay and phenological characterisation.
Field surveys will be done in two contrasting regions, West Germany and the United Kingdom to identify pests and also beneficial insects in the phyllosphere or rhizosphere of euramerican hybrid poplars to facilitate the selection of appropriate species for laboratory/glasshouse tests on the transgenic material.
The West German group will bioassay the transgenic poplar material (particularly using beetles), the Forestry Commission's entomologists will concentrate on soil fauna and, in Oxford, Lepidoptera will be tested in depth.
Cultures of insects that feed on poplar foliage are maintained in each centre and will be used for detailed small scale assessments with the aim of establishing knowledge about whether evolution is forced towards Bt toxin resistance. This will be judged from lethal time extension and percent survival. Field collections will be used to compliment the database concerning impact (behaviour/lethality) of the transgenic stock on poplar associated fauna.
Funding SchemeCSC - Cost-sharing contracts
GU10 4LH Farnham