Genetic Engineering of Insect Tolerance in Walnut: Isolation and Field Introduction of Transgenic Walnut Plants Containing an Insect Tolerance Gene

Purified insecticidal crystal protein fragments (ICPFs) of Bacillus thurinqiensis encoded by crvIA(c) and cryIA(b) of this organism were shown to be lethal to key target walnut insect pests (codling moth, navel orangeworm and Indianmeal moth). One of these genes, cryIA(c), was used to transform walnut somatic embryos using a binary vector (pWB139) in which this gene was expressed as a protein fusion with the kanamycin resistancegene from bacteria. Transgenic embryos representingindividualtransformationevents were germinated to produce shoots that were maintained as micropropagated shoot clones in the laboratory. Transgenic shoots were then grafted onto seedling rootstocks and introduced into the field. DNA analysis (Southern blotting) is presented here that demonstrates that these shoots are transformed by pWB139 or by the control construct pWB149 (which does not contain the cryIA(c) gene). Insect feeding trials using in vitro grown transgenic shoots were conducted with a test insect cabbage looper, as the target walnut pests do not consume leaf materials. Statistically significant inhibition of feeding and growth was observed in one transgenic line with cabbage looper. Plants from this line have been introduced into the field and further evaluations will be performed with field grown materials.