The exponential growth of population and demand for food has lead to the development of many methods to increase food productions. The principle cause for decreased yield of agriculture food is due to insect pests. The routine use of pesticides and insecticides though gave good results in the initial decades by increasing crop productive, became failure due to rapid growth of insecticide resistance among insect pests. This leads to the development of alternative methods for insect pest control in agriculture. Bacillus thuringiensis (Bt) Crops, is a category of Genetically Modified (GM) crops, which harbors plasmid deoxyribonucleic acid (DNA) of Bacterial species Bacillus thuringiensis having toxin genes in the host plant. BT crops initiated its commercialization scale with Bt Maize (Corn) in mid-1990's and later to other economical important corps such as Bt Cotton, Bt Potato, Bt Rice, Bt Brinjal, BT Cowpea, etc. The transgenic plants expressing crystal toxins genes from the Bt provides protection against selected insect pests. Bt toxins are effective against insects pest of cotton, rice, maize and many more.
Bacillus thuringiensis (Bt) is a gram positive bacteria present in soil and has its life cycle consists of two phases as vegetative phase and sporulation phase. It is during the sporulation phase, Bt synthesizes parasporal crystals, that are toxic to many agricultural insect pests and vectors on human and animal diseases. The toxin genes of Bt are referred as Cry family genes, which consists of around 300 genes like Cry1A, Cry2A, Cry3A, Cry1C, etc., which exists as clusters in operons. Cry toxins affects through Cadherins receptor molecule occurring in the epithelial cell membrane present in midgut of insects. Binding of Cry toxins to Cadherins receptor triggers Mg2+- dependent signaling pathways culminating in cell death or apoptosis.
Though Bt crops are accepted in many countries for its beneficiary effect of insect resistance, controversies of its disadvantages is a open debate. The developed insecticide resistance in the Bt plant results in avoiding chemical pesticides application, thereby decreasing the cost of agriculture productions and also increase in yields due to less insect damage. Apart from increase in crop yield, Bt crops reduces insecticide poisoning of humans and environment. There are several studies done on Bt crops and its economical impacts and concluded that Bt crops has resulted in sustainable benefits to the farmers.
Everything is not good in Bt crops, there few drawbacks which can't be explained properly. Gene flow from a Bt crop into wild populations and its potential environmental risks is the principle concern for environmental pollution. If the introgressed transgenic gene increases fitness, wild populations are more competitive and become invasive, leading to increased spread of Bt genes, thus increasing the chances of insect getting resistance to the toxin and also change in the genetic makeup of wild populations. Insect pests getting resistance to Bt crops or opportunistic development of other insects as secondary pest might potentially evade the benefit of Bt crop. Other major concerns of Bt crops is its effect on the non-target beneficiary insects like honey bees, butterflies, etc., which acts as natural pollinator of flowers. There are several incidences showing the Bt crops failure to the targeted insect population as the insect accumulating resistance to Cry gene products. Bt crops are associated with seed termination technologies; the seeds produced in the BT crops are not useful for growing next generations, which makes the farmer to purchase the seed for each harvest from companies results in loss of diversity that was existed with traditional seed preservation methods.
New technologies are required to equip human race to face the challenge of food supply in near future. The recent advances in Recombinant DNA technology resulted in developing Bt crops that aids in increasing crop yield has resulted with many concerns. The consequences of Bt crops on non-target species is an important factor that has to be compared with chemical pesticides application, which requires intensive research before going to mainstream agricultural practice. Short timer insect pest control has been achieved through application of insecticides and pesticides, but insect-resistant Bt crops with further research to express toxin genes in conditional manner will go a long way in integrated and sustainable pest management in the commercial and staple crops that are required to satisfy the hunger of bubbling global population.
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