Submitted to: Canadian Journal of Forest Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/21/2013
Publication Date: 12/16/2013
Citation: Klocko, A., Viswanath, V., Ma, C., James, R.R., Cardineau, G., Skinner, J., Oppert, B.S., Payne, P., Miller, L., Meilan, R. 2013. Bt-Cry3Aa expression reduces insect damage and improves growth in field-grown hybrid poplar. Canadian Journal of Forest Research. 44:28-35. Interpretive Summary: Hybrid poplars are an important source of raw material for the paper and pulp industries, as well as for the emerging biofuel industry. Fiber farm managers and others concerned with tree growth and damage need cultivars that are pest resistant. This study evaluated transgenic poplar expressing a beetle-specific insecticidal protein (Bt). Trees were evaluated for growth and resistance to a major pest, the cottonwood leaf beetle. Overall, trees demonstrated growth as good or better than non-transgenics, with increased resistance to beetle damage. The data suggest that transgenic poplar may provide a resistance management strategy for insect damage and increased biomass production, however, may need to be combined with genetic containment technology to enable regulatory approval.
Technical Abstract: We investigated growth and insect resistance in hybrid poplar expressing the cry3Aa gene in two field trials. An initial screening of 502 trees comprising 51 transgenic gene insertion events in four clonal backgrounds (Populus trichocarpa x P. deltoides, clones 24-305, 50-197, and 198-434; and P. deltoides x P. nigra, clone OP-367) resulted in transgenic trees with reduced insect damage that grew as well as, or better than, non-transgenic controls after a single growing season. A large-scale study of 402 trees from nine insertion events in clone OP-367, conducted over two growing seasons, demonstrated reduced tree damage, and several events had significantly increased growth. Quantification of Cry3Aa protein indicated high levels of expression, which continued after 14 years of annual or biannual coppice in a clone bank. With integrated management, the cry3Aa gene may be a useful tool for protecting against leaf beetle damage and improving yields from poplar plantations.