Contents - Faperta

Genetic Transformation of Crops for Resistance to Insect Pests 221
clones expressing a truncated cryIAb gene has been evaluated in the fi eld. Five elite transgenic
clones showed agronomic and industrial traits similar to the nontransgenic plants of
Ja60-5, but a small number of qualitative traits were different. A total of 51 polymorphic
DNA bands (out of the 1,237 analyzed) were identifi ed by extensive AFLP and RAMP
analysis, showing rare but consistent genomic changes in the transgenic plants as
compared to C 1 and C 2 control plants (Arencibia et al., 1999).
Oilseed Crops
A codon-modifi ed cry1Ac gene has been introduced into groundnut by using microprojectile
bombardment (Singsit et al., 1997). The immunoassay of plants selected with hygromycin
has shown the expression of Cry1Ac protein up to 0.16% of the total soluble protein.
Complete mortality or up to 66% reduction in larval weight has been recorded in the
lesser corn stalk borer, Elasmopalpus lignosellus (Zeller). There was a negative correlation
between larval survival and larval weight of the lesser corn stalk borer with the amount
of Bt protein.
Grain Legumes
A tissue culture and regeneration protocol has been developed for chickpea, which has
been found to be useful for genetic transformation of this crop (Jayanand, Sudarasanam,
and Sharma, 2003). Chickpea cultivars ICCV 1 and ICCV 6, transformed with the cry1Ac
gene, have been found to inhibit the development of and feeding by H. armigera (Kar et al.,
1997). Sanyal et al. (2005) developed transgenic chickpea plants with cry1Ac gene under
the control of CaMV35S promotor and nptII as a selection marker. The transgenic plants
showed protein expression levels of 14.5 to 23.5 ng mg1 of extractable protein. Plants with
Cry1Ac expression levels of 10 ng mg1 showed 80% mortality of the neonate larvae
of H. armigera. Transgenic plants with cry1Ac gene are also being tested for resistance to
H. armigera (Ramakrishna Babu et al., 2005). Pigeonpea plants transformed with cry1Ab,
cry1Ac, and soybean trypsin inhibitor (SBTI) genes have been developed at ICRISAT,
and are being tested against H. armigera (Gopalaswamy et al., 2003; Sree Latha et al., 2005;
K.K. Sharma, Ananda Kumar, and Sharma, 2005; K.K. Sharma, Lavanya, and Anjaiah,
2006). Pigeonpea plants transformed with cryIE-C gene from Bt under the control of
CaMV35S promotor and nptII as a selection marker have shown resistance to the larvae of
tobacco caterpillar, Spodoptera litura (F.) (Surekha et al., 2005).
Tobacco
The fi rst transgenic tobacco plants with Bt toxin genes were produced in 1987 (Barton,
Whiteley, and Yang, 1987; Fischhoff et al., 1987; Vaeck et al., 1987). These plants expressed
full length or truncated Bt toxin genes cry1A under the control of constitutive promoters.
The expression was quite low in tobacco plants, resulting in only 20% mortality of tobacco
hornworm, Manduca sexta L. larvae. Truncated cry1A genes encoding for the toxic N-terminal
fragment provided better protection to tobacco and tomato plants. Plants transformed with
truncated gene expressed about 0.02% of total leaf soluble protein. Gene truncation, use of
different promoters, enhancer sequences, and fusion proteins resulted in only a marginal
improvement in gene expression (Barton, Whiteley, and Yang, 1987; Vaeck et al., 1987).
The cryIIIA gene from B. thuringiensis subsp. tenebrionis has also been expressed in transgenic
tobacco (Sutton, Havstad, and Kemp, 1992), and fi ve classes of sequences that mimic