Question

Which of the following are two cultivated species of cotton used for spinnable fibre?
A. Gossypium hirsutum
B. Gossypium raimondii
C. Gossypium barbadense
D. Gossypium thurberi

• A. B and D only
• B. A and B only
• C. B and C only
• D. A and C only

Hint:

Remember the four cultivated cotton species:
- Diploids ($2n = 26$): G. arboreum and G. herbaceum (Old World).
- Allotetraploids ($2n = 52$): G. hirsutum and G. barbadense (New World).
All other species like G. raimondii, G. thurberi, or G. anomalum are wild species.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The genus Gossypium includes around 50 species, but only four are cultivated globally for their spinnable fibers.
These four cultivated species consist of two diploid species ($2n = 2x = 26$) of Old World origin and two tetraploid species ($2n = 4x = 52$) of New World origin.

Step 2: Detailed Explanation:
Let us analyze the given options:
A. Gossypium hirsutum (Upland Cotton):
This is an allotetraploid species ($2n = 52$, AD1 genome) that accounts for more than 90% of global cotton production.
It is highly valued for its yield, adaptability, and medium-staple spinnable fibers.
Therefore, it is a cultivated species.
B. Gossypium raimondii:
This is a wild diploid species ($2n = 26$, D5 genome) native to Peru.
It is not cultivated for fiber but serves as a crucial donor of the D genome in evolutionary studies of tetraploid cottons.
Therefore, it is not a cultivated species.
C. Gossypium barbadense (Egyptian/Sea Island Cotton):
This is also an allotetraploid species ($2n = 52$, AD2 genome) cultivated for its extra-long staple (ELS), high-strength, and fine spinnable fibers.
It contributes about 5-8% of global cotton production.
Therefore, it is a cultivated species.
D. Gossypium thurberi:
This is a wild diploid species ($2n = 26$, D1 genome) native to North America (Arizona/Mexico) and is not cultivated for fiber.

Step 3: Final Answer:
The two cultivated species used for spinnable fiber are Gossypium hirsutum (A) and Gossypium barbadense (C).
Thus, the correct option is (D).