Contents - Faperta

222 Biotechnological Approaches for Pest Management and Ecological Sustainability
eukaryotic processing signals (which may be responsible for the low levels of transcription
and translation) were identifi ed and eliminated. The GC content of the gene was raised
from 36% to 49%, and the codon usage was changed to be more plant-like. When the
synthetic gene was driven by the CaMV35S promoter and the alfalfa mosaic rymovirus
translational enhancer, up to 0.6% of CryIIIA toxin of the total protein was observed in
transgenic tobacco plants. The transgenic plants showed resistance to the Colorado potato
beetle, Leptinotarsa decemlineata (Say). Another study by Perlak et al. (1993) also confi rmed
that the synthetic cryIII gene in tobacco is effective for the control of Colorado potato
beetle, L. decemlineata. Tobacco plants containing the cryIIa5 gene are also resistant to
H. armigera (Selvapandian et al., 1998), and the effectiveness of this toxin is comparable
to Cry1Ab or Cry1Ac.
Potato
Second-generation transgenic potatoes grown from tubers of transgenic plants expressing
the cryIAc gene showed 10% mortality of fi rst-instar larvae of Phthorimaea operculella (Zeller)
after 48 hours of feeding on leaf discs (Ebora, Ebora, and Sticklen, 1994). The second-instar
larvae were slightly less capable of surviving on leaf discs from transgenic plants than
those fed on the untransformed plants after 24 hours of feeding. Synthetic cryIII gene has
also been expressed in potato plants with resistance to Colorado potato beetle, L. decemlineata
(Jansens et al., 1995). Transgenic potato plants containing the cry1Ab gene (Bt 884) and
a truncated gene cry1Ab6 resulted in less damage to the leaves by the potato tuber moth,
P. operculella. However, the size of the leaf tunnels increased over time in plants containing
only the Bt 884 gene, while no increase was observed in tunnel length in plants containing
the cry1Ab6 gene (Arpaia et al., 2000). Transgenic LT 8 and Sangema tubers remained uninfested
by P. operculella for 6 months. However, no signifi cant effects were observed on the
nontarget species such as Liriomyza huidobrensis (Blanch.), Russelliana solanicola Tuthill, and
Myzus persicae (Sulzer). Damage to the fourth terminal leaf by Epitrix cucumeris (Harris)
was 20 to 31% lower than in nontransgenic plants (Stoger et al., 1999). Davidson et al. (2002)
developed transgenic lines of Ilam Hardy and Iwa with cry1Ac9 gene. A transgenic line from
each cultivar inhibited larval growth of P. operculella by over 40%, and the line derived
from Ilam Hardy prevented pupation of all larvae. A modifi ed gene of B. thuringiensis var
tolworthi (cryIIIB) has shown insecticidal activity toward neonate larvae of Colorado potato
beetle (Arpaia et al., 1997). Picentia and the wild species, Solanum integrifolium (Poir.), have
also been transformed with a wild type (wt) and four mutagenized versions of Bt43 belonging
to the cryIII class (Innacone, Grieco, and Cellini, 1997). Adult males feeding on highlevel
Bt-expressing transgenic potatoes were able to mate and produce mobile sperm, but the
females were impaired in their reproductive ability because their ovaries were not fully
developed (Stewart, Feldman, and LeBlanc, 1999).
New Leaf Bt-transgenic potatoes provide substantial ecological and economic benefi ts to
potato growers (Hoy, 1999). The cry5-Lemhi Russet and cry5-Atlantic potato lines have
shown up to 100% mortality of fi rst instar larvae of the potato tuber moth (Mohammed
et al., 2000). The insertion and expression of the cry1Ab into potato cultivars Sangema,
Cruza 148, and LT 8 have resulted in up to 100% larval mortality of P. operculella (Canedo
et al., 1999). The codon-modifi ed Bt-cry5 gene (revised nomenclature cryIIaI) has been
inserted into the cultivar Spunta to provide resistance to Colorado potato beetle,
L. decemlineata, and potato tuber moth, P. operculella (Douches et al., 2002). Two transgenic
“Spunta” clones, G2 and G3, produced high levels of mortality in fi rst instars of potato
tuber moth in detached-leaf bioassays (80 to 83% mortality), laboratory tuber tests