Contents - Faperta

358 Biotechnological Approaches for Pest Management and Ecological Sustainability
Bt transgenic corn cultivation appears to have no signifi cant infl uence on the nematofauna,
neither at the level of genus composition nor with regard to biodiversity (Manachini
and Lozzia, 2002). Nevertheless, one region did have a change in trophic group composition:
fungal feeding nematodes were more numerous in the soil with Bt corn, while in the fi eld
with the isogenic hybrid, the bacterial feeders were higher than the Bt corn. The Cry1Ab
protein had no consistent effects on nontarget organisms (earthworms, nematodes, protozoa,
bacteria, fungi) in soil or in vitro. The Cry1Ab protein was not taken up from soil by
non-Bt corn, carrot, radish, or turnip grown in soil in which Bt corn had been grown or
into which biomass of Bt corn had been incorporated (Stotzky, 2004). No effects have been
detected in culturable bacteria, fungi, protozoa, and nematodes from the Bt-maize fi elds
(Saxena and Stotzky, 2001). Under fi eld conditions, the microfl ora of Bt transgenic potato
plants has been observed to be minimally different from that of chemically and microbially
treated commercial potato plants (Donegan et al., 1996). It is unlikely that expression
of Bt and any other genes in transgenic plants would have an adverse effect on the soil
microfl ora. There are no signifi cant differences in mortality or weight of the earthworm,
Lumbricus terrestris L., after 40 days in soil planted with Bt maize or after 45 days in soil
amended with Bt maize (Saxena and Stotzky, 2001). Toxin has been detected in the gut and
casts of earthworms, but is cleared in two to three days after being placed in fresh soil.
A 200-day study has been carried out to investigate the impact of Bt transgenic corn on
immature and adult L. terrestris in the fi eld and in the laboratory. No lethal effects of transgenic
Bt corn on immature and adult earthworms were observed (Zwahlen et al., 2003).
Immature L. terrestris in the fi eld had a very similar growth pattern when fed either transgenic
(Bt) or nontransgenic (non-Bt) corn litter. No signifi cant differences were observed in
relative weights of L. terrestris adults fed on transgenic or nontransgenic corn during the
fi rst 160 days in a laboratory trial, but after 200 days, the adult L. terrestris exhibited a
weight loss of 18% when fed transgenic corn litter compared to a weight gain of 4% in
those fed on nontransgenic corn. Further studies are necessary to see whether or not this
difference in relative weight was due to the degradation of Cry1Ab toxin in corn residues
(Zwahlen et al., 2003). Percentage infection of H. virescens larvae by Nomuraea rileyi (Farlon)
was greater on Bt transgenic plants, and higher in the normal larvae than in Bt-resistant
larvae, and might accelerate adaptation to Bt transgenic plants ( Johnson, Gould, and
Kennedy, 1997).
The proteinase inhibitor concentration in the transgenic plant litter after 57 days was
0.05% of the sample at day 0, and was not detectable in subsequent sampling (Donegan
et al., 1997). Although the carbon content of the transgenic plant litter was comparable to
that of the parental plant litter on sample day 0, it became signifi cantly lower over time.
Nematode populations in the soil surrounding the transgenic plant litter bags were greater
than those in the soil surrounding parental plant litter bags and had a different trophic
group composition, including a signifi cantly higher ratio of fungal feeding nematodes to
bacterial feeding nematodes on sample day 57. In contrast, Collembola populations in the
soil surrounding the transgenic plant litter bags were signifi cantly lower than in the soil
surrounding parental plant litter bags, indicating that under fi eld conditions, the proteinase
inhibitor remained immunologically active in buried transgenic plant litter for at
least 57 days and that decomposing parental and transgenic plant litter differed in quality
(carbon content) and in the response of exposed soil organisms (Collembola and nematodes)
(Donegan et al., 1997). Susceptibility of Nosema pyrausta (Paillot)-infected European corn
borer, O. nubilalis, to Bt formulation Dipel ES is greater than to the uninfected larvae. Dipel
ES reduced N. pyrausta spore production in larvae feeding on diet containing Dipel ES,
suggesting that Bt maize might have some adverse effects on the survival and continual