Contents - Faperta

220 Biotechnological Approaches for Pest Management and Ecological Sustainability
Cnaphalocrosis medinalis (Guen.) (Fujimoto et al., 1993). Scented varieties of rice (Basmati 370
and M 7) have also been transformed with cryIIa, confering resistance to yellow rice stem
borer, Scirpophaga incertulas (Walker) and the rice leaf folder, C. medinalis (Mqbool et al.,
1998). Truncated cry1Ab gene has been introduced into several indica and japonica rice
cultivars by microprojectile bombardment and protoplast systems (Datta et al., 1998). Rice
lines transformed with the synthetic cry1Ac gene are highly resistant to yellow stem borer,
S. incertulas (Nayak et al., 1997), and those with the cry1Ab gene are resistant to the striped
stem borer, C. suppressalis and the yellow stem borer, S. incertulas (Ghareyazie et al., 1997).
The cry1Ab gene has also been inserted into the maintainer line, R 68899B with enhanced
resistance to yellow stem borer, C. suppressalis (Alam et al., 1999). Khanna and Raina (2002)
developed Bt transgenics of elite indica rice breeding lines (IR 64, Pusa Basmati 1, and
Karnal Local) with synthetic cryAc gene. Selected Bt lines of IR 64 and Pusa Basmati 1, having
Bt titers of 0.1% (of total soluble protein) showed 100% mortality of yellow stem borer
larvae within four days of infestation in cut stems as well as at the vegetative stage in
whole plant assays. Husnain et al. (2002) expressed cry1Ab in Basmati rice under the
control of three promoters (PEPC, ubiquitin, and pollen specifi c promotor derived from the
Bp10 gene of Brassica napus L. in pGEM 4Z). Toxin protein expression was 0.05% of the total
protein in stems under the control of the PEPC promotor alone or in combination with the
pollen specifi c promotor, but was nearly 0.15% of the total protein under the control of the
ubiquitin promotor, suggesting that a specifi c promotor can be used to limit the expression
of cry1Ab gene in desired plant parts. There were no signifi cant differences in the progenies
of either the indica japonica or japonica japonica crosses, indicating that transgenic
Bt rice can be used in crossbreeding elite cultivars with resistance to insects (Cui et al.,
2001). Zhu et al. (2003) observed that a dominant locus, and the linkage between the cryIAb
and bar gene, followed 3:1 segregation in T 1, was stably homozygotic in T 2, and followed 1:1
and 3:1 segregation in BC 1-BC 4 and BCF 2 (self-cross of BC), respectively.
Sorghum
Toxins from B. thuringiensis var morrisoni have shown biological activity against the
sorghum shoot fl y, Atherigona soccata (Rondani). Cry1Ac, Cry1C, Cry1E, and Cry2A are
moderately effective against the spotted stem borer, C. partellus, while Cry1Ac is effective
against H. armigera (H.C. Sharma et al., 2004). Sorghum plants having the cry1Ac gene have
been developed for resistance to spotted stem borer, C. partellus (Harshavardhan et al.,
2002; Seetharama et al., 2002; Girijashankar et al., 2005). Feeding by the neonate larvae
of C. partellus on the leaf discs from transgenic plants was 60% lower compared to that on
the nontransgenic control plants, and the weight gain by the larvae was reduced by 36%.
The larval mortality was 40% more in the larvae fed on leaf discs from transgenic plants
compared to that on the nontransgenic control plants.
Sugarcane
The truncated cry1Ab gene in sugarcane has shown signifi cant activity against the sugarcane
borer, D. saccharalis despite low expression of the Bt protein (Arencibia et al., 1997).
Transgenic cane tissue incorporated into artifi cial diet caused low body weights, prolonged
development time, and high mortality in Mexican rice borer, Eoreuma loftini (Dyar) (Samad
and Leyva, 1998). Larvae that survived to adulthood laid fewer eggs compared to larvae
fed on artifi cial diet with nontransgenic sugarcane or artifi cial diet alone. Egg hatch was
also poor in the transgenic treatment. A population of 42 transgenic sugarcane ( Ja60-5)