Contents - Faperta

272 Biotechnological Approaches for Pest Management and Ecological Sustainability
A fusion plasmid pRKC was constructed using pACYC184, RSF1010, and a kanamycinresistance
cartridge from pUC4K to introduce cryIAa gene into Azospirillum spp.
(Udayasuriyan et al., 1995). With the pRKC plasmid, the number of putative transconjugants
obtained in Azospirillum lipoferum (Beijerinck) Tarrand et al. was about 300-fold
greater than in A. brasilense (Tarrand et al.). Expression of the cryIAa gene was not apparent
in SDS-PAGE of the A. lipoferum transconjugants harboring pBTF8. However, E. coli
transformants with the pBTF8 from A. lipoferum transconjugants produced a 135 kDa Cry
protein, indicating that the cry gene was intact in the transconjugants. Production of
molecules with toxic activity in genetically transformed symbiotic bacteria of insect pests
can be used as another tool for biological control. The symbiont Enterobacter gergoviae
Brenner et al. isolated from the gut of the pink bollworm, Pectinophora gossypiella (Saunders)
has been transformed to express cyt1A (Kuzina et al., 2002). The transgenic bacteria can be
used to spread genes encoding insecticidal proteins to populations of agri cultural insects
or as replacement for chemical insecticides.
Entomopathogenic Fungi
More than 700 species of fungi have been reported to be pathogenic to insects, of
which nearly 10 have been deployed for insect control (Hajek and St. Leger, 1994). Species
pathogenic to insect pests are: Metarhizium anisopliae (Metsch.), M. fl avoviride (Metsch.),
Nomuraea rileyi (Farlow) Samson, Beauveria bassiana (Balsamo), Verticillium lecanii (Zimon)
Viegas, Aschersonia aleyrodis Webber, and Paecilomyces farinosus (Holm ex Gray) Brown &
Smith (Aima, 1975; Mohamed, Sikorowski, and Bell, 1977; Abbaiah et al., 1988;
Gopalakrishnan and Narayanan, 1989, 1990; Ferron, Fargues, and Riba, 1991; Hajek and St.
Leger, 1994; Saxena and Ahmed, 1997; Uma Devi et al., 2001). Species belonging to the
Hyphomycetes are pathogenic to a range of insects, particularly against Homoptera.
Commercial products based on B. bassiana, M. anisopliae, M. fl avoviride, N. rileyi, and A.
aleyrodis have a good potential for biological control of insects, and are currently in use or
under development as pesticides. The endophytic nature of B. bassiana offers the potential
for season-long control of insects (Anderson and Lewis, 1991). Sensitivity to solar radiation,
microbial antagonists, host behavior, physiological condition and age, temperature,
relative humidity, and pesticides infl uence the effectiveness of entomopathogenic fungi
(Hajek and St. Leger, 1994). Successful use of entomopathogenic fungi will depend on the
use of the right formulation, dosage, and timing.
Adhesion of fungal spores to host cuticle and their germination is a prerequisite for
effi cacy of fungal pathogens. It is widely accepted that 90% relative humidity (RH) is
required for germination of fungal spores, and this is a big handicap in widespread use of
mycopesticides. However, special formulations of fungi in oil can overcome this problem
by creating high RH microclimates around the spores, enabling entomopathogenic fungi
to function in low RH environments (Bateman et al., 1993). On germination, the fungus
penetrates the cuticle (setae and intersegmental membrane) of the insect, and grows in the
hemocoel of the insect leading to death of the insects. The fungus also grows saprophytically,
and in due course, the hyphae re-emerge and sporulate. Mass production of different
entomopathogenic fungi is quite easy. Glucose-yeast extract–basal salts, agar, and carrot
medium can be used for multiplication of M. anisopliae. Zapek Dox Broth (containing 2%
chitin and 3% molasses) is good for growth and sporulation of most entomopathogenic