On the resistance of Bt and CpTI dually transgenic tobacco to larvae of oriental tobacco budworm and black cutworm.
Bioassays and tissue section examinations were conducted to determine the resistance of 931 (a Bt and CpTI transgenic tobacco line), to oriental tobacco budworm (Helicoverpa assulta) and black cutworm (Agrotis ypsilon [A. ipsilon]). After feeding on 931 for 2-3 days, the mortalities of all larval instars of H. assulta were up to 100%, while those of 1st- and 2nd-instars of A. ipsilon were 48 and 28%, respectively. No deaths were recorded in A. ipsilon larval stages older than the 2nd-instar, but the villi on the midgut epithelia of surviving larvae were dissolved, and most of the epithelial cells had collapsed. Following the feeding of A. ipsilon larvae with 931, the villi of the midgut were dissolved, the epithelial cells were shortened and cell walls became thinner, but cell collapse was negligible.