Adopting new technology always involves advantages and risks; Bt cotton (
Gossypium hirsutum
L.) is a new
technology well known in developed countries for its many advantages, such as reduced pesticide application, better
insect pest control, and higher lint yield. However, its success in developing countries is still a question mark. Global
adoption of Bt cotton has risen dramatically from 0.76 million ha when introduced in 1996 to 7.85 million ha in the 2005
cotton-growing season where 54% of the cotton crops in the USA, 76% in China, and 80% in Australia were grown with
single or multiple Bt genes. Bollworms are serious cotton pests causing 30-40% yield reduction in Pakistan and 20-66%
potential crop losses in India. The major advances shown in this review include: (1) Evolution of Bt cotton may prove
to be a green revolution to enhance cotton yield; (2) adoption of Bt cotton by farmers is increasing due to its beneficial
environmental effects by reducing pesticide application: however, a high seed price has compelled farmers to use illegal
non-approved Bt causing huge damage to crops because of low tolerance to insect pests; and (3) some factors responsible
for changes in the efficiency of the Bt gene and Bt cotton yield include internal phenology (genetics), atmospheric changes
(CO
2 concentration), nutrition, insect pests, boll distribution pattern, disease and nematodes, removal of fruiting branch
and/or floral bud, introduction of Bt gene, and terpenoids and tannin production in the plant body.
