Somatic embryos of Jack, a Glycine max (1.) Merrill cultivar, were transformed using microprojectile bombardment with a synthetic Bacillus thuringiensis insecticidal crystal protein gene (Bt crylAc) driven by the 35s promoter and linked t o the HPH gene.Approximately 10 g of tissue was bombarded, and three transgenic lines were selected on hygromycin-containing media and converted into plants. The recovered lines contained the HPHgene, but the Bt gene was lost in one line. The plasmid was rearranged in the second line, and the third line had two copies, one of which was rearranged. The CrylAc protein accumulated up to 46 ng mg-' extractable protein. I n detached-leaf bioassays, plants with an intact copy of the Bt gene, and t o a lesser extent those with the rearranged copy, were protected from damage from corn earworm (Helicoverpa zea), soybean looper (Pseudoplusia includens), tobacco budworm (Heliothis virescens), and velvetbean caterpillar (Anticarsia gemmatalis). Corn earworm produced less than 3% defoliation on transgenic plants, compared with 20% on the lepidopteran-resistant breeding line CatlR81-296, and more than 40% on susceptible cultivars. Unlike previous reports of soybean transformation using this technique, all plants were fertile. To our knowledge, this is the first report of a soybean transgenic for a highly expressed insecticidal gene.

bean pests including the soybean looper (Pseudoplusia includens Walker) (All et al., 1989). In more than 25 yr since the discovery of soybean [Glycine maxThere are several reasons for the difficulty experi-(L.) Merr.] resistance to defoliating insects, attempts to introgress enced in breeding for PRI in soybean. Resistant germthis trait into elite germplasm have been relatively unsuccessful. Resisplasm is of low agronomic quality. Insect resistance is tance to defoliating insects in soybean is expressed as a combination of antibiosis (toxicity) and antixenosis (nonpreference). Both of these inherited quantitatively in all three resistant PIs (Sisson resistance modes are inherited quantitatively in soybean. The objecet al., 1976; Luedders and Dickerson, 1977; Rufener et tives of this study were (i) to use restriction fragment length polymoral., 1989; Kenty et al., 1996), making full introgression phism (RFLP) maps to identify quantitative trait loci (QTLs) in soydifficult and increasing the potential for inferior yield bean for antibiosis against corn earworm (CEW) (Helicoverpa zea through linkage drag (Zeven et al., 1983; Young and Boddie), (ii) to determine the relative magnitude, gene action, and

The seeds of a number of Brassica L. species are cultivated for the production of oil. Collectively, the oilseed Brassica sp., generally referred to as rapeseed, supply more than 13% of the world's supply of edible oils and rank third behind soybean and oil palm in importance. The term "canola" was adopted by the Canadians in 1979 and used to describe oilseed Brassica cultivars that produce oils containing less than 2% erucic acid and to describe defatted seed meals with less than 30 pmol g-' of aliphatic glucosinolates. Brassica napus L. canola cultivars are currently dominant in U.S. production, although canola-quality Brassica rapa (synonymous with Brassica campestris) cultivars also exist (Raymer et al., 1990).Production of canola in the U.S. has grown at a modest rate during the last 10 years from virtually O in 1985 to 165,000 ha in 1995 (C. Boynton, U.S. Canola Association, personal communication). As production of canola continues to grow, insect problems are expected to become more serious (Lamb, 1989). This may be particularly true as canola production expands in the southeastern United States and California, where mild winter temperatures are likely to lead to increased herbivory, as compared with the much cooler areas (e.g. Canada), where canola has historically been produced. Ubiquitous lepidopteran Brassica specialists, such as the DBM and the CBL, and generalist lepidop-terans, such as the BAW and CEW, may increase in importance where canola is grown in warmer regions (Buntin and Raymer, 1994). This scenario may be especially viable with regard to generalist herbivores, since glucosinolates, a hypothesized antiherbivorant to generalist insects (Giamoustaris and Mithen, 1995), have been bred out of canola-quality rapeseed. Transgenic canola cultivars with insecticidal properties will certainly play a major role in integrated pest management strategies for canola pests (Talekar and Shelton, 1993;Evans and Scarisbrick, 1994). The objectives for this study were 2-fold. (a) To determine the effect of Bt expression in B. napus on antibiosis for severa1 lepidopteran insects. Unlike the related Bt soybean study (Stewart et al., 1996), in which only few, low-expressing synthetic Bacillus thuringiensis insecticidal crystal protein ( B t crylAc) plants were produced, the likelihood of obtaining a wide range of B t expression is greater using a species that is more amenable to genetic transformation, such as B. napus. (b) To develop biological tools to test models pertaining to biotechnological risk assessment. It is possible that a plant species, such as B. napus, that is able to persist in nonagricultural environments could become more weedy in a transgenic form if the transgene confers an increment of fitness and the plant is naturalized in areas of its cultivation. Thus, we developed the B t canola to ultimately test population-leve1 ecological hypotheses.

Rapeseed Brassica napus L. transgenic for a Bacillus thuringiensis (Bt) transgene was developed and was shown to be insecticidal towards certain caterpillars including the diamondback moth Plutella xylostella L. and the corn earworm Helicoverpa zea Boddie. To simulate an escape of the transgenics from cultivation, a field experiment was performed in which transgenic and nontransgenic rapeseed plants were planted in natural vegetation and cultivated plots and subjected to various selection pressures in the form of herbivory from insects. Only two plants, both transgenic, survived the winter to reproduce in the natural‐vegetation plots which were dominated by grasses such as crabgrass. However, in plots that were initially cultivated then allowed to naturalize, medium to high levels of defoliation decreased survivorship of nontransgenic plants relative to Bt‐transgenic plants and increased differential reproduction in favour of Bt plants. Thus, where suitable habitat is readily available, there is a likelihood of enhanced ecological risk associated with the release of certain transgene/crop combinations such as insecticidal rapeseed. This is the first report of a field study demonstrating the effect of a fitness‐increasing transgene in plants.

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