Question

Choose the correct option for the chromosome number in ascending order in the following crops :
(A) Rice
(B) Pigeon pea
(C) Groundnut
(D) Wheat
Choose the correct answer from the options given below :

• A. (A), (D), (C) and (B)
• B. (A), (B), (C) and (D)
• C. (B), (A), (C) and (D)
• D. (B), (A), (D) and (C)

Hint:

To remember crop chromosome numbers:
- Pigeon pea: $2n = 22$.
- Rice: $2n = 24$.
- Groundnut: $2n = 40$.
- Bread Wheat (hexaploid): $2n = 42$.
- Maize: $2n = 20$.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This question focuses on the somatic chromosome numbers ($2n$) of major agricultural crops.
Comparing ploidy levels and chromosome counts is essential in cytogenetics and crop breeding.

Step 2: Detailed Explanation:
Let us determine the somatic chromosome numbers ($2n$) for each of the given crops:
(A) Rice (*Oryza sativa*):
Rice is a diploid species with a basic chromosome number of $x = 12$.
Its somatic chromosome number is:
\[ 2n = 2x = 24 \]
(B) Pigeon pea (*Cajanus cajan*):
Pigeon pea is a diploid pulse crop with a basic chromosome number of $x = 11$.
Its somatic chromosome number is:
\[ 2n = 2x = 22 \]
(C) Groundnut (*Arachis hypogaea*):
Cultivated groundnut is an allotetraploid species with a basic chromosome number of $x = 10$.
Its somatic chromosome number is:
\[ 2n = 4x = 40 \]
(D) Wheat (*Triticum aestivum*):
Common bread wheat is an allohexaploid species containing three distinct genomes (AABBDD), with a basic chromosome number of $x = 7$.
Its somatic chromosome number is:
\[ 2n = 6x = 42 \]
Arranging these somatic chromosome numbers in ascending order (smallest to largest):
Pigeon pea ($2n = 22$) $<$ Rice ($2n = 24$) $<$ Groundnut ($2n = 40$) $<$ Wheat ($2n = 42$).
This sequence corresponds to: (B) $\rightarrow$ (A) $\rightarrow$ (C) $\rightarrow$ (D).

Step 3: Final Answer:
The correct ascending sequence of chromosome numbers is (B), (A), (C), and (D).
This corresponds to Option (C).