Contents - Faperta

322 Biotechnological Approaches for Pest Management and Ecological Sustainability
No. of Jassids/plant
18
16
14
12
10
8
6
4
2
0
Bt NBt Bt NBt Bt NBt Bt NBt Bt NBt Bt NBt
UP CP UP CP UP CP
Mech 12 Mech 162 Mech 184
FIGURE 10.5 Cotton leafhopper, Amrasca biguttulla biguttulla, incidence in three cotton cry1Ac transgenic
hybrids under protected and unprotected conditions. UP, unprotected; CP, completely protected.
fusca Fuller in southern Africa (van Rensburg, 1999), sugarcane borers, Diatraea grandiosella
(Dyar) and Diatraea saccharalis F. (Bergvinson, Willcox, and Hoisington, 1997), fall armyworm,
Spodoptera frugiperda (J.E. Smith), and Southwestern corn rootworm, Diabrotica undecimpunctata
howardi Barber (Williams et al., 1997). Insecticidal crystal protein from B. thuringiensis
strain PS149B1 provides effective control of western maize rootworm, Diabrotica
virgifera virgifera Leconte (Herman et al., 2002). Field studies indicated signifi cantly greater
resistance to insect feeding in Tex6 plants as compared with nontransgenic B 73 plants,
primarily to fl ea beetles, Chaetocnema spp. (Dowd and White, 2002) and corn earworm, H.
zea (approximately three- fold). At harvest, similar trends in reduction of numbers of damaged
kernels as well as infection by Fusarium spp. were noted. Transgenic Bt maize is now
grown in fi ve countries in Europe. Transgenic hybrids with cryIAb gene showed less insect
feeding and Fusarium ear rot than their nontransgenic counterparts (Munkvold, Hellmich,
and Rice, 1999). Good control of major stem borer species, C. partellus, Eldana saccharina
Walker, and Sesamia calamistis Hampson has been observed in controlled fi eld trials in
Kenya (Mugo et al., 2005). In South Africa, genetically modifi ed white maize with the
cry1Ab gene gave greater yields and resulted in less damage by the stalk borers, B. fusca
and C. partellus than the nontransgenic cultivars (Keetch et al., 2005). The total gain from
borer-resistant maize was estimated to be over 15.5 million Euros.
Transgenic rice cultivars with resistance to insects have not been released for cultivation,
although in several events Bt genes have been developed for resistance to the striped stem
borer, Chilo suppressalis (Walker) (Fujimoto et al., 1993), yellow rice stem borer, Scirpophaga
incertulas (Walker) (Mqbool et al., 1998), and rice leaf folder, Cnaphalocrosis medinalis
(Guenee). Rice varieties with cry1Ac gene have shown better resistance to yellow stem
borer (Nayak et al., 1997), while those with the cry1Ab are resistant to striped stem borer
and the yellow stem borer (Ghareyazie et al., 1997). Plants of the cry1Ab-transformed line
827 were more resistant to young larvae of S. incertulas, C. suppressalis, and C. medinalis than
the control plants at the vegetative stage, but not at the fl owering stage (Alinia et al., 2000).
Sorghum plants with the cry1Ac gene with resistance to spotted stem borer, C. partellus, have
been identifi ed (Girijashankar et al., 2005). 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). None of these transgenic plants have been