PLANT PHYSIOLOGY , Vol 112, Issue 1 115-120, Copyright © 1996 by American Society of Plant Biologists
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PLANT-MICROBE AND PLANT-INSECT INTERACTIONS |
Insect Control and Dosage Effects in Transgenic Canola Containing a Synthetic Bacillus thuringiensis cryIAc Gene
C. N. Stewart Jr, M. J. Adang, J. N. All, P. L. Raymer, S. Ramachandran and W. A. Parrott
Department of Crop and Soil Sciences (C.N.S., P.L.R., W.A.P.) and Department of Entomology (M.J.A., J.N.A., S.R.), University of Georgia, Athens, Georgia 30602
Zygotic hypocotyls of canola (Brassica napus L.) cv Oscar, cv Westar, and
the breeding line UGA188-20B were transformed with a truncated synthetic
Bacillus thuringiensis insecticidal crystal protein gene (Bt cryIAc) under
the control of the cauliflower mosaic virus 35S promoter using
Agrobacterium tumefaciens-mediated transformation. Fifty-seven
independently transformed lines were produced, containing 1 to 12 copies of
the transgenes. A range of cry expressors was produced from 0 to 0.4% Cry
as a percentage of total extractable protein. The Brassica specialists, the
diamondback month (Plutella xylostella L.) and the cabbage looper
(Trichoplusia ni Hubner), were completely controlled by low-, medium-, and
high-expressing lines. Whereas control of the generalist lepidopteran, the
corn earworm (Helicoverpa zea Boddie), was nearly complete, the other
generalist caterpillar tested, the beet armyworm (Spodoptera exigua
Hubner), showed a dose response that had a negative association between
defoliation and cry expression. These plants were produced as models for an
ecological research assessment of the risk involved in the field release of
naturalized transgenic plants harboring a gene (Bt) that confers higher
relative fitness under herbivore-feeding pressure.
