Question

Chemical most widely used for chromosome doubling in haploid culture is-

• A. Sorbitol
• B. Mannose
• C. Colchicine
• D. Mannitol

Hint:

Directly associate the word {Colchicine} with {Chromosome doubling}. It is the classic and most famous antimitotic agent used in plant breeding to induce polyploidy.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Haploid plants produced through techniques like anther culture are sterile because they lack homologous chromosomes for proper meiosis. To make them fertile and create homozygous diploid lines for breeding, their chromosome number must be doubled. The question asks for the chemical used for this purpose.
Step 2: Detailed Explanation:
Colchicine is an alkaloid chemical extracted from the autumn crocus (Colchicum autumnale). It is a potent mitotic inhibitor.
Its mechanism of action is to bind to tubulin, the protein subunit of microtubules. This disrupts the formation of the spindle fibers during metaphase of mitosis. As a result, the sister chromatids fail to separate and move to opposite poles. The cell proceeds through the cell cycle but fails to divide, resulting in a nucleus with double the original chromosome number (e.g., a haploid 'n' cell becomes a diploid '2n' cell).
The other options—Sorbitol, Mannose, and Mannitol—are sugars or sugar alcohols commonly used as carbon sources or as osmotic stabilizers in plant tissue culture media to prevent cell lysis; they do not induce chromosome doubling.
Step 3: Final Answer:
The chemical most widely used for chromosome doubling in haploid cultures is colchicine.