Contents - Faperta

Genetic Engineering of Natural Enemies for Integrated Pest Management 303
the mosquito A. stephensi, glutathione S-transferase gene (GST1) from M. domestica, a cytochrome
P450-B1 gene (CYP6A2) associated with dichloro diphenyltrichloroethane (DDT)
resistance in Drosophila, and amplifi cation core and esterase B1 gene from Culex responsible
for resistance to organophosphates (Atkinson, Pinkerton, and O’Brochta, 2001).
Metallothionein genes have been cloned from Drosophila and other organisms that appear
to function in homeostasis of copper and cadmium (Theodore, Ho, and Marni, 1991). These
genes may provide resistance to fungicides containing copper in arthropod natural enemies.
In many crops, fungicides may have a negative impact on benefi cial arthropods
such as phytoseiid predators. The organophoshate-degrading enzymes that confer resistance
to paraoxon and parathion have been expressed in D. melanogaster (Benedict, Scott,
and Cockburn, 1994; Benedict, Salazar, and Collins, 1995), and C. diaphaniae (Presnail and
Hoy, 1996).
Females of M. occidentalis resistant to carbaryl-organophosphate-sulfur lived longer
(25.3 days versus 19.7 days), exhibited a high intrinsic rate of increase (0.243 versus 0.182
individuals per female per day), and shorter generation time (13.9 days versus 17.0 days),
when reared on a diet of 0 to 48-hour-old eggs rather than a diet of mixed actives of
Tetranychus pacifi cus McGregor on bean, Phaseolus vulgaris L., leaf discs (Bruce, Oliver, and
Hoy, 1990). The female to male ratio of the progeny was 2.1:1 when reared on eggs, and 2.0:1
when reared on mixed actives, suggesting that diet infl uences sex ratio. There were no
signifi cant differences in oviposition rates for repeatedly mated and females mated once
reared on a diet of younger eggs (0 to 24 hours old) compared to a diet of older eggs (72- to
96-fold) of T. pacifi cus. The COS strain of M. occidentalis exhibited life-table parameters
comparable to those of other strains, suggesting that the reproductive attributes of this
predator were not altered as a result of artifi cial laboratory selection. Microbial genes conferring
resistance to pesticides can function in arthropods. The opd gene, isolated from
Pseudomonas and conferring resistance to organophosphates, has been inserted, using a
baculovirus expression vector into cultured fall armyworm, S. frugiperda, cells and larvae
(Dumas, Wild, and Rauschel, 1990). Philips et al. (1990) also transferred the opd gene into
D. melanogaster. The opd gene was put under the control of the Drosophila heat-shock
promoter, hsp70, and stable enzyme was produced and accumulated with repeated induction.
It is likely that this gene could be used to confer resistance to organophosphates in
benefi cial arthropod species, as well as serving as a selectable marker for detecting transformation
of insect pests.
Dominant Repressible Lethal Genetic System
Traditionally, sterile insect technique (SIT) has been employed to control several insects
(Knipling, 1955). However, this system depends on large-scale production of the target
insect, and use of irradiation, or chemical sterilization. The SIT has been used against
several insect species, with considerable success. Experience has shown that it works
effectively when suffi cient resources are available or it is applied to geographically isolated
pest populations. To achieve effective control, a high ratio of sterile to normal males has to
be maintained for several generations. The process of rearing the insects under laboratory
conditions and sterilization results in reduced fi tness (Holbrook and Fujimoto, 1970).
Reduced fi tness of the sterile insects requires a high ratio between sterile and wild-type
insect populations. Because the sterile insects die after one generation, the releases have to