Question

After colchicine treatment of a plant regenerated through androgenesis, the derived plant is considered as:

• A. Diploid
• B. Dihaploid
• C. Amphidiploid
• D. Allopolyploid

Hint:

Haploid ($n$) + Colchicine = Dihaploid ($2n$). It is the fastest way to get a 100% pure (homozygous) line in breeding.

Answer 1

The Correct Option is B

Concept: Androgenesis is the process of generating plants from male gametic cells (pollen or anthers), which are naturally haploid ($n$). To restore fertility and stability for breeding, these haploids must have their chromosome number doubled.

Step 1: Understanding Colchicine Action.
Colchicine is an alkaloid that inhibits spindle fiber formation during mitosis. When a haploid ($n$) cell is treated, the chromosomes replicate, but the cell does not divide, resulting in a cell with two identical sets of chromosomes ($2n$).

Step 2: Defining the Product.
A plant that originates as a haploid and subsequently has its chromosome number doubled is specifically called a Dihaploid. While it is technically $2n$ (diploid), the term "dihaploid" emphasizes its origin from a single gamete, ensuring total homozygosity across all genetic loci.

Step 3: Eliminating Other Terms.
Amphidiploids and allopolyploids involve the doubling of chromosomes in a hybrid between two different species. "Diploid" is a general term, but "Dihaploid" is the precise terminology used in the context of androgenic regeneration.