[Biology Class Notes] on Types of Bt Crops Pdf for Exam

Introduction to Bt Crops

The full form of bt is Bacillus thuringiensis. It is a bacteria that naturally produces a crystal protein that is toxic to many pest insects. These are the crops that are genetically engineered to produce the same toxin as Bt in every cell of the plant so that pests do not destroy the plant. Bt crops are often found safe because Bt is a common organic form of insecticide. When it is used by farmers it degrades within a week and sometimes just in one day. The widespread use of Bt crops, pests became bt resistance. This has become a greater threat to organic agriculture.

Types of Bt Crops

The types of Bt crops are as follows:

• Bt Cotton – The cotton plant is genetically modified with the Bt gene to protect the plants from bollworm which is a major pest of cotton. Bt cotton is a transgenic crop that is an insect-resistant designed to combat the bollworm. It was created by genetically altering the cotton genome to express a microbial protein from the bacterium Bacillus thuringiensis. The genetically modified gene which has been inserted into the plant’s genome produces toxin crystals that the plant would not normally produce at all. When this is ingested by a certain population of organisms it dissolves within the gut lining which leads to the organism’s death.

• The worms which are present on the leaves of Bt cotton become lethargic and sleepy resulting in less damage to the plants. The toxins which are produced by the crops are ingested by the pests which result in their death.

• Bt Brinjal – It is also generated by the genetic transformation of a crystal protein gene cry 1 Ac from the bacterium Bacillus thuringiensis. This crop was developed to provide resistance against insects called Lepidopteron. The proteins which are produced by Bt genes bind to the receptors present on the insect’s membrane which forms pores on the membranes. This damages the digestive process and leads to the death of the insect.

• Bt Maize – The Bt maize was introduced to kill corn rootworm, Diabrotica virgifera which is also known as a billion-dollar bug.  These crops are also derived from the Bacillus thuringiensis so the common name is Bt maize. However, this crop has revolutionized pest control in a number of countries.

About Bt

Bt is a bacterium Bacillus thuringiensis which is a family of proteins originating from strains of the bacterium Bt. To affect the different types of insects there are more than 200 different types of Bt toxins. 

Basically, Bt is a spore-forming bacterium that produces crystals protein known as cry protein which is toxic to many species of insects. It is found almost everywhere in the world. It is also found in all types of terrain, including beaches, deserts, and tundra habitats. It is more significantly used in agriculture, especially in organic farming. 

It is also used in organic spraying programs and in transgenic crops. Bt is used to cause mortality in pests. The toxin of Bt gets dissolved in the high pH insect gut and becomes active. The toxins which were active attack the gut cells of the insect, punching holes in the lining. The spores of Bt dribbles out of the gut and germinate in the insect causing the death of the insect within a couple of days.

 Bt Gene

Bt gene is a gene that is present in the bacterium of Bacillus thuringiensis which is a soil-dwelling bacterium. It naturally produces a toxin that is fatal to certain herbivorous insects. Since 1920, it has been utilized in organic farming in the form of insecticide spray. It is also a source of the gene used to genetically modify a number of crops so that they produce the toxin on their own to destroy various insect pests. Bt genes were first used by the Belgian company Plant Genetic Systems in the year 1985 to develop genetically modified crops with insect tolerance by expressing cry genes from Bt.