Contents - Faperta

238 Biotechnological Approaches for Pest Management and Ecological Sustainability
and L235-4 (glandular trichomes), along with the cryV-Bt-transgenic lines of each genotype,
were tested for resistance to potato tuber moth, P. operculella. Nearly 54% mortality
was observed when fi rst-instar larvae were fed on the leaves of USDA8380-1. High levels
of expression occurred in cryV-Bt transgenic lines, with up to 96% mortality. Walker et al.
(2002) combined a QTL conditioning corn earworm resistance in soybean PI 229358, and
cry1Ac transgene from the recurrent parent Jack-Bt into BC 2F 3 plants by marker-assisted
selection. The segregating individuals were genotyped and SSR markers linked to an
antibiosis/antixenosis QTL on linkage group M, and were tested for the presence of
Cry1Ac. Few larvae of corn earworm and soybean looper survived on leaves expressing
the Cry1Ac protein. Though not as great as the effect of Cry1Ac, the PI 229358-derived LG
M QTL also had a detrimental effect on larval weights of both species, and on defoliation
by corn earworm, but did not reduce defoliation by soybean looper, indicating that combining
transgene- and QTL-mediated resistance to lepidopteran pests may be a viable
strategy for insect control.
Transgenic plants of cotton with Bt GNA conferred resistance to bollworm, H. armigera
and the cotton aphid, A. gossypii (Z. Liu et al., 2003). Segregation of resistant and susceptible
plants in F 2 and BC 1 populations fi tted the 3:1 and 1:1 ratios, respectively, indicating
that resistance to bollworm was controlled by one pair of dominant genes and inherited in
Mendelian manner with no cytoplasmic effects. Allelic tests showed that the resistance
gene in transgenic line TBG and that of insect-resistant transgenic cotton strains Zhongxin
94, R 19, Shanxi 94-24, Shuangkang 1, and Xinmian 33B might be inserted in different chromosomes.
The Bt gene and OC gene have been co-transformed to tobacco chloroplast with
the particle bombardment method. Transgenic tobacco containing both genes had enhanced
toxicity to the larvae of corn earworm, H. zea, as compared to plants containing only the
Bt or OC gene alone. The Bt and OC genes were inherited maternally (Su et al., 2002).
Sugarcane plants transformed with both the GNA and a proteinase inhibitor from Nicotiana
alata Link and Oho. caused a signifi cant negative effect on the weight gain of Dermolepida
albohirtum (Waterhouse) larvae (Nutt et al., 2001). Transformed entomopathogenic virus
that produces chitinase displayed enhanced insecticidal activity (Chit Kramer and
Muthukrishnan, 1997). Chitinase also potentiates the effi cacy of the toxin from B. thuringiensis.
Gahakwa et al. (2000) studied the stability of transgene expression in 40 independent
rice plants representing 11 diverse cultivated varieties. Each line contained three or four
different transgenes delivered by particle bombardment, either by co-transformation, or in
the form of a co-integrate vector. Approximately 75% of the lines showed Mendelian inheritance
of all transgenes, suggesting integration at a single locus. The levels of transgene
expression varied among different lines, but primary transformants showing high-level
expression of the GNA, gusA, hpt, and bar genes were transmitted to the progeny. Six transgenes
(three markers and three insect resistance genes) were stably expressed over four
generations of transgenic rice plants. Transgene expression was stable, and this represented
a step toward genetic engineering from model varieties to elite breeding lines grown in
different parts of the world.
Conclusions
The ideal transgenic technology should be commercially viable, environmentally benign
(biodegradable), easy to use in diverse agroecosystems, and have a wide spectrum of