Ms. Meier et A. Hilbeck, Influence of transgenic Bacillus thuringiensis corn-fed prey on prey preference of immature Chrysoperla carnea (Neuroptera : Chrysopidae), BASIC AP EC, 2(1), 2001, pp. 35-44
Paired-choice assays in a tritrophic system have been carried out to study
the influence of transgenic Bacillus thuringiensis var. kurstaki (Berliner)
corn plants on prey preference of the predator Chrysoperla carnea (Stephen
s). Plants used were a transgenic B. thuringiensis-expressing (Cry1Ab) corn
hybrid and the corresponding isogenic untransformed B. thuringiensis-free
hybrid. Two different prey species were used in the experiments, Spodoptera
littoralis (Lepidoptera: Noctuidae) and Rhopalosiphum padi (Homoptera: Aph
idae). Both species were not lethally affected by the Cry1Ab toxin. C. carn
ea larvae were placed individually in a searching arena together with two g
roups of prey to choose from. One group had eaten transgenic B. thuringiens
is corn (Bt+), the other nontransgenic corn (Bt-). Choice-experiments with
various prey and host plant combinations were performed. The number and typ
e of prey consumed by C. carnea, the time C. carnea larvae spent feeding on
their chosen prey and the number of prey C. carnea only "probed" upon for
one minute or less were recorded. Observations were made for each of the th
ree larval stages of C. carnea. When C. carnea could choose between S. litt
oralis fed transgenic corn (Bt+) and S. littoralis fed non-transgenic corn
(Bt-), they showed a significant preference for S. littoralis fed non-trans
genic corn (Bt-) as 3(rd) instars. Although not statistically significant,
a similar trend was observed for the 2(nd) instar. No preference was observ
ed when C. carnea had the choice between R. padi fed transgenic corn (Bt+)
and R. padi fed non-transgenic corn (Bt-). This lack of preference for R. p
adi fed either transgenic or non-transgenic corn may be due to the absence
of the Bt-protein in the phloem. In prey combinations with S. littoralis an
d R. padi, all three larval stages of C. carnea showed a preference for R.
padi regardless whether they had fed on transgenic or non-transgenic corn.
These findings arc discussed in context with biological control and pest re
sistance development.