Question:
The following statements about onion are given below
(A). Temperature is comparatively more important for bulb formation
(B). Photoperiod is more important for flowering
(C). Long day onion varieties do not bulb under short day conditions
(D). Genetic constitution of the male sterility maintainer is Nmsms.
Choose the correct answer from the options given below:
The following statements about onion are given below
(A). Temperature is comparatively more important for bulb formation
(B). Photoperiod is more important for flowering
(C). Long day onion varieties do not bulb under short day conditions
(D). Genetic constitution of the male sterility maintainer is Nmsms.
Choose the correct answer from the options given below:
(A). Temperature is comparatively more important for bulb formation
(B). Photoperiod is more important for flowering
(C). Long day onion varieties do not bulb under short day conditions
(D). Genetic constitution of the male sterility maintainer is Nmsms.
Choose the correct answer from the options given below:
Show Hint
Remember the rule of opposites for onion:
- Bulbing $\rightarrow$ regulated by Photoperiod
- Flowering $\rightarrow$ regulated by Temperature (Vernalization)
- Bulbing $\rightarrow$ regulated by Photoperiod
- Flowering $\rightarrow$ regulated by Temperature (Vernalization)
Updated On: Jul 10, 2026
- (A), (B) and (D) only.
- (A) and (D) only.
- (A), (B), (C) and (D).
- (C) and (D) only.
Show Solution
Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Successful onion cultivation requires an understanding of how photoperiod (daylength) and temperature regulate bulb formation and flowering, as well as the genetic mechanisms used in hybrid seed production.
Step 2: Detailed Explanation:
Let us analyze each statement:
- Statement (A) is false: Photoperiod (daylength), rather than temperature, is the primary factor regulating bulb initiation and formation in onion.
- Statement (B) is false: Temperature is the primary factor regulating flowering. Exposure to low temperatures (vernalization, typically $4\text{--}10~^\circ\text{C}$) is required to induce bolting and subsequent flower development.
- Statement (C) is true: Long-day onion varieties require daylengths of 14 hours or more to initiate bulbing. Under short-day conditions (10–12 hours), they continue vegetative leaf growth without forming bulbs.
- Statement (D) is true: In onion hybrid seed production using cytoplasmic-genetic male sterility (CGMS), the maintainer line (B-line) must have normal fertile cytoplasm ($\text{N}$) and be homozygous recessive for the male sterility gene ($\text{msms}$), designated as $\text{Nmsms}$. This allows it to produce pollen and maintain the male-sterile A-line ($\text{Smsms}$) when crossed.
Hence, only statements (C) and (D) are correct.
Step 3: Final Answer:
The correct option is (D).
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