Effects of transgenic petunia expressing Bacillus thuringiensis toxin on selected lepidopteran pests

Toxicity of 11 transgenic petunia lines expressing the CryIA (c) insecticidal crystal protein of Bacillus thuringiensis subsp. kurstaki was investigated using lepidopteran neonates Spodoptera exigua, Trichoplusia ni and Manduca sexta. Mortality of S. exigua, T. ni and M. sexta varied within and among transgenic petunia lines. Bioassay results demonstrated that levels of CryIA (c) expression obtained in 7 out of the 11 transgenic petunia lines produced at least 50% mortality in S. exigua and T. ni, and all 11 transgenic lines produced more than 80% mortality in M. serta. Demographic analysis of the biological impact of transgenic petunia on S. exigua revealed that sub-lethal feeding on transgenic petunia significantly reduced larval weight and prolonged larval and pupal development times. Continuous feeding on transgenic petunia significantly reduced lifetime fecundity, egg hatch and longevity in female and male moths. Compared with insects fed continuously on non-transgenic petunia, lifetime fecundity and net reproductive rate were reduced by 58 and 84% in insects fed continuously on transgenic petunia respectively. Mean generation time was 8 days longer for insects fed continuously on transgenic petunia than for insects fed on non-transgenic petunia. Ovipositional attractiveness of transgenic petunia to S. exigua with respect to non-transgenic tomato or lettuce plants was similar, suggesting that petunia/tomato and petunia/lettuce may not be effective trap-cropping combinations. The potential and implications of using transgenic petunia as trap plants interplanted with crop plants for management of lepidopteran pests in the field are discussed.