Question

Which of the following shows very high inbreeding depression on selfing?

• A. Spine gourd
• B. Lettuce
• C. Carrot
• D. Pea

Hint:

Inbreeding Depression: Loss of vigor when closely related individuals are bred. More severe in naturally cross-pollinating species.
Carrot: Cross-pollinated, shows strong inbreeding depression.
Lettuce & Pea: Mostly self-pollinating, show little inbreeding depression.
Spine Gourd: Dioecious (obligate outcrosser), would show depression if inbreeding were forced.

Answer 1

The Correct Option is C

Inbreeding depression is the reduced biological fitness (e.g., vigor, yield, fertility) in a given population as a result of inbreeding, or breeding of related individuals. It is more pronounced in species that are naturally outcrossing (cross-pollinated).
(1) Spine gourd (Momordica dioica): This is a dioecious plant (separate male and female plants), making it obligately outcrossing. Selfing is not naturally possible in the strict sense, but forced close breeding would likely show depression.
(2) Lettuce (Lactuca sativa): Primarily self-pollinating, so it generally shows little to no inbreeding depression upon selfing.
(3) Carrot (Daucus carota): Naturally cross-pollinated by insects (protandrous flowers promote outcrossing). Carrots are known to exhibit very severe inbreeding depression upon forced selfing, leading to significant loss of vigor, yield, and increased abnormalities in subsequent generations. This is why hybrid carrot varieties are popular.
(4) Pea (Pisum sativum): Primarily self-pollinating (cleistogamous flowers). It shows very little inbreeding depression. Mendel famously worked with peas due to their true-breeding nature upon selfing. Therefore, among the options given, carrot is well-known for showing very high inbreeding depression on selfing. Carrot