Figure 4.

Screening for Spodoptera resistance of transgenic plants. (A) Insecticidal assay with neonate larvae of S. littoralis reared for 2 days on leaves from nontransformed alfalfa (M. sativa, Upper) and NS7 transgenic (Lower) plants. (B) Free choice bioassays with leaves from wild-type and transgenic alfalfa plants. In the plate to the left, 10 larvae of S. exigua (third instar) were placed on the red line located between leaves of wild-type (Left) and NS7 transgenic (Right) alfalfa plants. In the plate to the right, the larvae were placed between leaves from wild-type (Left) and NS6 (Right; Fig. 3D, lane 6) transgenic alfalfas. For 5 days, the larvae failed to colonize leaves from the transgenic plants in both assays. (C and D) Leaves from tobacco (C) and alfalfa (D) plants were used for feeding of five fifth instar larvae of S. exigua for 10 hr. Petri dishes to the left in C and D contained leaves from nontransformed plants. Leaves shown in Petri dishes to the right in C and D were collected from a NS7 tobacco transgenic line producing 0.2% of soluble proteins as CryIC toxin (Fig. 3D, lane 2) and from a NS6 alfalfa transformant producing 0.1% of leaf proteins as CryIC toxin, respectively. (E) Transgenic NS7 (Left; Fig. 3D, lane 2) and nontransformed alfalfa (Right) plants were infested with 15 larvae of S. exigua (third to fourth instar stage) for 6 days.