Prior to the experiments, each plant was tested for the
expression of Bt-toxin in a bioassay with L. decemlineata
larvae. This procedure was necessary as a certain proportion
of the transgenic eggplants segregated as non-
Bt. For the bioassays, one leaf disc of 1.25 cm diameter
was cut from each plant using a cork borer, and placed
on a wet filter paper in a plastic petri dish (diameter
5 cm). Four neonate larvae of L. decemlineata were
added to each dish. Dishes were placed into a climate
cabinet at 25 ± 1 C and 70% R.H. Leaf discs from
the same plant individual were renewed after two days
in each dish. After four days, L. decemlineata larvae
were checked for consumption of leaf tissue and survival.
Only plants from dishes with high mortality of
beetle larvae and a low rate of consumption were regarded
as Cry3Bb-toxin expressing and used in the subsequent
experiments. This bioassay was sensitive enough
to reveal the most actively expressing plants. Cry3Bb
toxin levels were found to range from 800 to
1400 ng per g fresh weight in such plants while low
amounts of the toxin, still detectable with immunochemical
methods, did not prevent L. decemlineata larvae
from damaging plants (Arpaia et al., 1997).
Prior to the experiments, each plant was tested for theexpression of Bt-toxin in a bioassay with L. decemlineatalarvae. This procedure was necessary as a certain proportionof the transgenic eggplants segregated as non-Bt. For the bioassays, one leaf disc of 1.25 cm diameterwas cut from each plant using a cork borer, and placedon a wet filter paper in a plastic petri dish (diameter5 cm). Four neonate larvae of L. decemlineata wereadded to each dish. Dishes were placed into a climatecabinet at 25 ± 1 C and 70% R.H. Leaf discs fromthe same plant individual were renewed after two daysin each dish. After four days, L. decemlineata larvaewere checked for consumption of leaf tissue and survival.Only plants from dishes with high mortality ofbeetle larvae and a low rate of consumption were regardedas Cry3Bb-toxin expressing and used in the subsequentexperiments. This bioassay was sensitive enoughto reveal the most actively expressing plants. Cry3Bbtoxin levels were found to range from 800 to1400 ng per g fresh weight in such plants while lowamounts of the toxin, still detectable with immunochemicalmethods, did not prevent L. decemlineata larvaefrom damaging plants (Arpaia et al., 1997).
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