Contents - Faperta

Applications of Biotechnology in Agriculture: The Prospects 29
Resistance to Insect Pests, Diseases, and Herbicides
The fi rst transgenic plants with Bacillus thuringiensis (Bt) (Berliner) genes were produced
in 1987 (Barton, Whiteley, and Yang, 1987; Vaeck et al., 1987). While most of the insectresistant
transgenic plants have been developed by using Bt d-endotoxin genes, many
studies are underway to use non-Bt genes, which interfere with the nutritional requirements
of the insects. Such genes include protease inhibitors, chitinases, secondary plant
metabolites, and lectins (Hilder and Boulter, 1999; Sharma, Sharma, and Crouch, 2004).
Genes conferring resistance to insects have been inserted into crop plants such as maize,
cotton, potato, tobacco, rice, broccoli, lettuce, walnuts, apple, alfalfa, and soybean. A number
of transgenic crops have now been released for on-farm production or fi eld testing (James,
2007). The fi rst transgenic crop with resistance to insects was grown in 1994, and large-scale
cultivation was undertaken in 1996 in the United States. Since then, there has been a rapid
increase in the area sown with transgenic crops in the United States, Canada, Australia,
Argentina, India, and China. Transgenic crops are now grown in over 25 countries in
the world. Successful control of cotton bollworms has been achieved through transgenic
cotton (Wilson et al., 1992; Benedict et al., 1996; Zhao et al., 1998). Cry type toxins from
Bt are effective against cotton bollworms, Heliothis virescens F. and Helicoverpa armigera
(Hubner), corn earworm, Helicoverpa zea (Boddie), the European corn borer, Ostrinia nubilalis
(Hubner), and rice stem borer, Scirpophaga incertulas (Walker) (Armstrong et al., 1995;
Benedict et al., 1996; Nayak et al., 1997; Mqbool et al., 1998; Alam et al., 1999). Successful
expression of Bt genes against the lepidopterous insects has also been achieved in tomato
(Delannay et al., 1989), potato (Jansens et al., 1995), brinjal (Kumar et al., 1998), groundnut
(Singsit et al., 1997), and chickpea (Kar et al., 1997).
There will be tremendous benefi ts to the environment through the deployment of transgenic
plants for pest management (Sharma and Ortiz, 2000). Deployment of insect-resistant
crops has led to 1 million kg reduction of pesticides applied for pest control in the United
States in 1999 as compared to 1998 (NRC, 2000). Papaya with transgenic resistance to ringspot
virus (Gonsalves, 1998) has been grown in Hawaii since 1996. Rice yellow mottle virus
(RYMV), which is diffi cult to control with conventional approaches, can now be controlled
through transgenic rice, which will provide insurance from total crop failure. Globally,
herbicide-resistant soybean and insect-resistant maize and cotton account for 85% of the
total area under transgenic crops. The area planted to genetically improved crops has
increased dramatically from less than 1 million ha in 1995 to 100 million ha in 2006 (James,
2007). Transgenic plants with insecticidal genes are set to feature prominently in pest
management in both the developed and developing worlds in the future. Such an effort
will play a major role in minimizing insect-associated losses, increase crop production, and
improve the quality of life for the rural poor. Development and deployment of transgenic
plants with insecticidal genes for pest control will lead to:
• Reduction in insecticide sprays.
• Increased activity of natural enemies.
• IPM of secondary pests.
Tolerance to Abiotic Stresses
Development of crops with an inbuilt capacity to withstand abiotic stresses would help
stabilize the crop production and signifi cantly contribute to food security in developing
countries. Plants expressing trehalose phosphate synthase, and trehalose phosphate