Bt Crops

Bt crops

There have been several misconceptions about Bt cotton, Bt brinjal and other genetically modified  (GM) crops.  Some of these reports emanated because of the basic misunderstanding of the scientific facts related to a bacterium called Bacillus thuringiensis (Bt). As a result the whole gamut of biotechnology applications in agriculture has been under cloud in public perception.

In this article, I seek to dispel some of the misconceptions about Bt crops and emphasize how beneficial these crops would be for the mankind and the environment. Ever since Man domesticated crops ten millennia ago the major problem encountered by the crops is that of insect pests. The crop varieties selected by Man over several centuries do not have natural capability to resist insect attack. Discovery of insecticides in 1940s has brought about a sea change in the way we protected crops from insect damage. However, the adverse effects of many of the pesticides were realized in 1960s as highlighted in the most well known book “Silent Spring” written by Rachel Carson who poignantly described the disappearance of birds because of widespread use of pesticides such as DDT. Protection of environment has got increased attention and research into safe biological pesticides has got a boost.

Even much earlier in 1938, a biological pesticide by name ‘Sporeine’ was used by corn farmers in France to control Corn Borer with good results. This spray pesticide was a crude preparation of a naturally occurring soil bacterium called Bacillus thuringiensis, in short Bt.

Bt is a bacterium that exists all over the globe. It has been in existence for millions of years. A Japanese scientist Ishiwata discovered it in 1901. It was re-discovered by a German scientist Berliner in 1911 who found that the bacterium has insecticidal properties. Extensive research on Bt in 1960s and 1970s revealed that a class of proteins called delta endotoxins are responsible for the insecticidal property and that these proteins do not cause any harm to mammals including human beings. In addition, the endotoxins are harmless to beneficial insects such as honeybees, ladybird beetles, spiders, mites etc. A multi million dollar industry based on Bt spray formulations has come into being in western countries. Since 1970s, Bt spray formulations have been in extensive use for pest management in fruit and vegetable crops, forestry and animal health (control of lice). Certain Bt formulations are used in controlling mosquitoes too.

Extensive research on various aspects of Bt including search for novel Bt strains, safety of Bt proteins, biochemistry and molecular biology of Bt insecticidal proteins has been carried out in 1980s. Bt has been found to be safe for human beings, other mammals, soil dwelling organisms etc. The biochemical nature of Bt proteins makes them safe towards non-target organisms because a counterpart protein called Bt protein-receptor is absent in the guts of such organisms. Receptor protein is essential for Bt protein to act. In addition, the human digestive system is highly acidic in which Bt proteins are instantly degraded. Human volunteers in USA consumed enormous quantities of pure Bt proteins without any adverse effects.

Early 1990s witnessed a revolution in plant biology research. Powerful techniques were discovered by which foreign genes can be introduced and expressed in plant cells. This opened up a plethora of opportunities to make crop plants resistant to pests, diseases etc. The genes responsible for the production of pesticidal proteins were isolated from Bt and expressed in important crops such as cotton, maize and potato. These genetically modified (GM) crops were approved by USA in 1995 after rigorous testing for bisafety and environmental safety. Currently, Bt crops are cultivated in thirteen countries including India. Bt crops occupy about 40% of the global area of GM crops (160 million hectares). Several studies have documented the social, economic and environmental benefits of Bt crops. Protection of environment in terms of reduced pesticide use is the major benefit. Similarly, conservation of biodiversity that includes beneficial insects, non-target organisms such as birds and other wild life has been ensured. There have been several reports of the benefits of Bt cotton in India in the past eight years. No scientifically proven adverse effects of Bt crops have been reported in the past sixteen years around the world.

Bt crops such as Bt cotton are only protected from insect attack. One cannot expect an increase in the yield because of Bt. The Bt crop varieties are as susceptible as other crop varieties to drought, diseases and other environmental factors. The benefits are basically economical and environmental because the pesticide consumption is reduced. Indirectly, Bt crops help protect human health, animal health, food and water quality etc.,

There is an urgent need to develop Bt varieties in vegetables, pulses and staple food crops such as rice primarily to safeguard our health and protect biodiversity and the environment in general. It is all the more important in vegetables because several of them are consumed raw and vegetables laced with pesticides or their residues are highly deleterious to our health. The efforts being made in various public research laboratories should not be jeopardized because of misconceptions about Bt crops. A lot is at stake!

It is generally agreed that GM organisms (GMOs) including Bt crops should be thoroughly tested for their biosafety, environmental safety and protection of biodiversity before their release into the environment. In addition, the GMO regulatory system should be robust, transparent and amenable to public probity.

References:

  1. OECD 2007. Consensus document on safety information on transgenic plants expressing Bacillus thuringiensis derived insect control proteins. ENV/JM/MONO (2007) 14.
  2. WHO 1999. Microbial Pest Control Agent BACILLUS THURINGIENSIS. WHO, Geneva. ISBN 92 4 157217 5
  3. Karihaloo J. L. and Kumar P. A. 2009. Bt-Cotton in India: A Status Report. Asia-Pacific Consortium on Agricultural Biotechnology, New Delhi.
  4. Kumar P A, Sharma R P and Malik V S. 1996 Insecticidal proteins of Bacillus thuringieensis. Advances in Applied Microbiology. 42: 1-43.
  5. Glare, T. R. and O’Callaghan, M. 2000. Bacillus thuringiensis: Biology, Ecology and Safety. John Wiley, Chichester.
  6. NAAS, 2011. Biosafety Assurance for GM Food crops in India. Policy Paper 52. NAAS, New Delhi.
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Author: polumetla

I am a plant molecular biologist and biotechnologist. I worked as Director of National Research Centre on Plant Biotechnology, New Delhi, India; Director, Institute of Biotechnology, Acharya N.G. Ranga Agricultural University, Hyderabad, India; and Director, ICAR-Indian Institute of Rice Research, Hyderabad, India.

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