During half a century world food production has more than doubled from 700 million tons to about two billion as of now.

However, to meet the increasing needs of the growing population, it would be required to produce 50 per cent more food by 2025. Therefore, crop varieties with higher yields are required. Several biotic and a biotic stresses are threatening the sustainability and yield stability of crops. These stresses cause approximately 40 per cent of loss in agricultural production.

From 1960 to 2000 there has been an excessive use of chemical fertilizers and pesticides which has become a matter of concern on account of its adverse effect on environment and human health. Thus, there is a challenge how to sustain the productivity by using traditional agricultural methods.

To increase the yield, improved disease-resistant varieties have been developed through conventional plant breeding through which the shuffling of genes in the resulting offspring is at random and the desired objective (trait) may or may not be achieved. Moreover, it is a very labourious and highly time-consuming process.

Recent advances in molecular biology have opened new avenues for the production of genetically engineered pants with the new genetic properties. The refinement in plant regeneration with the defined marker genes selected for expression of desired traits, mediated by a vector (carrier) for transferring the genes have resulted in the production of 90 species of genetically-engineered plants.

When genes of an organism is transferred into the genome of another organism, the resulting plant is called transgenic. The transgenic plant is created by means of genetic engineering. This is done to achieve certain objectives.

It could be to create new varieties of crop plants with higher yields, better nutritional values, better taste and flavour and self-protective measures from diseases and pests. Transgenic plants have been produced in several major crop plants such as wheat, barley, rice, maize, cotton, tomato, potato, soybean etc. The area under-transgenic crops had increased from 2.8 million hectares in 1996 to 12.8 million hectares in 1997 (James, 1997).

Agrobacterium tumefaciens (A. t.) mediated gene transfer is the most common system used for the transformation in higher plants. The soil bacterium (A.t.) infects a wide range of plants to produce crown galls by introducing DNA into the plant at the site of infection. The bacterium is capable of transferring a piece of DNA (T-DAN) into the genome of host plant. The foreign genes inserted into T-DNA through Ti plasmids are co-transferred and integrated into the host genome. Agrobacterium rhizogenes harbouring Ri plasmids are also now being used in gene transfer.

A series of genes governing agronomically important traits have been transferred through A.t. and various other transfer techniques such as direct gene transfer, microinjection, micro-projectile bombardment, electroporation and polyethylene glycol (PEG) mediated gene transfer.

For the management of pests and parasites, several agronomically important genes for viral, bacterial, fungal resistance and herbicide tolerance have been transferred through genetic engineering techniques in transgenic plants. Bacillus thuringtensis (B.t.) produces a number of insect toxins. The toxin is specifically toxic to Lepidopteran insects by disrupting the gut cells of the insects.

The gut-cell swells and eventually bursts. The microbial preparations of B.t. as commercial insecticides are in use to resist attack of insects on cotton, corn etc. for the last 20 years.

Transgenic plants carrying B.t. genes are stably inherited in the progeny without detrimental effects on the recipient plant and are eco-friendly and sustainable under diverse agro-ecosystem.

At the end, it may be pointed out that any genetic change occurring via traditional breeding or by genetic engineering will have some measurable impact on the environment. The important criterion for evaluating transgenic (genetically modified) plants should be whether the benefit (biotech food fighting hunger) outweighs the risk (toxins and allergens) in the environment.