A genetically engineered variety of brinjal known as Bt brinjal has been developed using genes from the bacterium Bacillus thuringiensis. What is the primary objective of introducing this Bt gene into brinjal plants?

Introduction / Context:
Genetically modified crops are developed to introduce desirable traits such as pest resistance, herbicide tolerance, or improved nutrition. Bt brinjal is a genetically engineered variety where a gene from the soil bacterium Bacillus thuringiensis (Bt) has been inserted into brinjal plants. Understanding the main goal of this modification is important for questions on biotechnology and agriculture. This question asks you to identify the primary objective of introducing the Bt gene into brinjal.

Given Data / Assumptions:

• The crop in focus is brinjal (eggplant).
• The modified version is called Bt brinjal.
• The modification involves a gene from Bacillus thuringiensis (Bt).
• We must choose the main objective from options such as pest resistance, improved taste, drought resistance, longer shelf life, or colour change.
• We assume standard biotechnology explanations taught in biology courses.

Concept / Approach:
Bacillus thuringiensis is a bacterium that produces crystal proteins (Bt toxins) that are toxic to certain insect larvae when ingested. Scientists have isolated the gene coding for such a toxin and inserted it into the genome of various crops, including cotton and brinjal. When insects feed on Bt brinjal, the Bt toxin is activated in their gut and damages the gut lining, leading to the death of the pest. This built in defence reduces the need for external chemical insecticides and helps protect the crop from major insect pests. The goal of this genetic modification is not to alter taste, increase drought tolerance, or extend shelf life, even though these traits might be addressed by other breeding programs.

Step-by-Step Solution:
Step 1: Recall that Bt crops (such as Bt cotton and Bt brinjal) contain a gene from the bacterium Bacillus thuringiensis. Step 2: Understand that this Bt gene produces a protein that is toxic to specific insect pests but generally safe for humans when used correctly. Step 3: Recognise that when target insects eat plant tissues of Bt brinjal, the Bt protein disrupts their digestive system and kills them. Step 4: Note that the principal benefit of this trait is reduced crop damage and lower reliance on chemical insecticides. Step 5: Consider the alternative options: improving taste and nutritive value, increasing drought resistance, or prolonging shelf life are not the main goals of the Bt gene. Step 6: Realise that changing fruit colour for market appeal is also unrelated to the function of Bt toxin. Step 7: Conclude that the main objective of Bt brinjal development is pest resistance.

Verification / Alternative check:
Biotechnology chapters in biology textbooks discuss Bt crops and consistently state that the Bt gene confers resistance against specific Lepidopteran insect pests. For Bt brinjal, the target pests include fruit and shoot borers that cause significant yield losses. Reports about field trials and regulatory debates also emphasise reduced insecticide use and improved yields as the primary benefits. There is no emphasis on taste improvement, drought tolerance, or shelf life extension as the central purpose of the Bt gene in this crop. This confirms that pest resistance is the correct answer.

Why Other Options Are Wrong:
To improve the taste and overall nutritive value of the brinjal fruit: Bt genes are chosen for insecticidal properties, not for flavour or nutrient enhancement. To make the plant highly drought resistant in dry regions: Drought tolerance involves entirely different sets of genes and physiological traits. To significantly increase the shelf life of the harvested brinjal: Shelf life is usually improved by altering ripening processes or storage traits, not by Bt toxins. To change the colour of the fruit for better market appeal: Colour changes involve pigment related genes, not Bt insecticidal genes.

Common Pitfalls:
Students sometimes mix up different objectives of genetic engineering and assume that any genetically modified crop has multiple improvements such as better taste and longer shelf life. In reality, most first generation Bt crops are designed primarily for pest control. Another pitfall is confusing Bt crops with Golden Rice, which was engineered for enhanced vitamin A content. To avoid such confusion, remember that Bt refers specifically to Bacillus thuringiensis and is linked with insect pest resistance.

Final Answer:
The primary objective of Bt brinjal is to make the crop resistant to specific insect pests.