Contents - Faperta

236 Biotechnological Approaches for Pest Management and Ecological Sustainability
Black fi eld cricket nymphs, Teleogryllus commodus (Walker) had signifi cantly reduced
growth and survival when fed on lettuce leaves painted with purifi ed avidin. Clover root
weevils, Sitona lepidus Gyllen., adults were unharmed when fed clover foliage painted with
avidin. In contrast, neonate or one-week-old S. lepidus larvae had poor survival when fed
on artifi cial diets containing avidin or streptavidin. Neonate larvae of Argentine stem
weevils, Listronotus bonariensis (Kuschel) had signifi cantly reduced survival when fed with
artifi cial diet containing streptavidin or avidin. Slugs, Deroceras reticulatum (Muller), and
snails, Cantareus aspersus (Muller), were not harmed when fed with avidin-painted lettuce.
Similar numbers of eggs were laid and galls produced by the root-knot nematodes,
M. javanica (Treub) Chitwood, M. hapla, and M. incognita (Kofoid and White) Chitwood
inoculated onto transgenic tobacco plants expressing avidin and nontransgenic controls
(Malone et al., 2002). Transgenic tobacco expressing avidin from 3.1 to 4.6 mM, and from
1.9 to 11.2 mM in apple; and streptavidin from 11.4 to 24.5 mM in tobacco and from 0.4 to
14.6 mM in apple (biotin-binding proteins) conferred a high level of insect resistance in
transformed tobacco plants to potato tuber moth, P. operculella, and in apple plants to light
brown apple moth, Epiphyas postvittana (Walker) (Markwick et al., 2003). More than 90% of
potato tuber moth larvae died on tobacco plants expressing either avidin or streptavidin
genes within nine days of inoculation. Mortality of light brown apple moth larvae was
greater on three avidin-expressing (89.6 to 80.1%) and two streptavidin-expressing (90 to
82.5%) apple plant lines than on nontransformed control plants (14.1%) after 21 days.
Weight of light brown apple moth larvae was also signifi cantly reduced by feeding on
apple shoots expressing avidin and streptavidin at 3.8 mM (Markwick et al., 2003).
Antibodies
Genes that are based on antibody technology can also be exploited for genetic transformation
of crop plants (Hilder and Boulter, 1999). Single chain antibodies (ScFvs) can be used to
block the function of essential insect proteins, which serve as control agents against nematodes,
pathogens, and viruses (Van Engelen et al., 1994; Rosso et al., 1996). This approach
of controlling insects would offer the advantage of allowing some degree of selection for
specifi city effects, so that insect pests, but not the benefi cial organisms are targeted. The
development of a delivery system from transgenic plants to the insect hemolymph will
remove a key constraint in the transgenic approach to crop protection. Mi-mediated resistance
is developmentally regulated, and protects mature plants but not seedlings against
the aphid, Macrosiphum euphorbiae (Thomas) infestation (Goggin et al., 2004). Mi-1.2 is transcribed
in the leaves prior to the onset of aphid resistance, and the transcript levels are
comparable in seedling and fl owering stages. Constitutive overexpression of Mi-1.2 in
transgenic plants did not hasten the onset of aphid resistance in seedlings or boost the level
of resistance observed in fl owering plants. The results suggested that Mi-1.2 transcription
levels did not modulate aphid resistance in tomato leaves (Goggin et al., 2004).
Inducible Resistance
Mechanical wounding and insect damage result in transient increase in activity of polyphenol
oxidase (Dhankher and Gatehouse, 2003). However, there is no systemic induction
of this enzyme following wounding, insect damage, or application of methyl jasmonate.