The stability and value of transgenic pest resistance for promoting tree growth are poorly understood. These data are
essential for determining if such trees could be beneficial to commercial growers in the face of substantial regulatory and
marketing costs. We investigated growth and insect resistance in hybrid poplar expressing the cry3Aa transgene in two field
trials. An initial screening of 502 trees comprising 51 transgenic gene insertion events in four clonal backgrounds (Populus
trichocarpa × Populus deltoides, clones 24-305, 50-197, and 198-434; and P. deltoides × Populus nigra, clone OP-367) resulted in
transgenic trees with greatly reduced insect damage. 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 significantly increased volume growth (mean 14%).
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 appears to be a highly effective tool for protecting against
leaf beetle damage and improving yields from poplar plantations
