Question:
Which of the following shows very high inbreeding depression on selfing?
Which of the following shows very high inbreeding depression on selfing?
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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.
Updated On: Jul 2, 2026
- Spine gourd
- Lettuce
- Carrot
- Pea
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The Correct Option is C
Approach Solution - 1
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
(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
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Approach Solution -2
Breeding-system approach:
Inbreeding depression is severe mainly in naturally cross-pollinated (outcrossing) crops, because they carry a heavy load of hidden recessive alleles that selfing exposes. Lettuce and pea are both predominantly self-pollinating crops that are effectively "selfed" generation after generation already, so forcing self-pollination changes little and depression stays minimal. Spine gourd is dioecious and outcrossing, but it is less classically cited for this effect than carrot. Carrot, by contrast, is an obligate cross-pollinator with protandrous flowers, and forced selfing collapses its vigour and yield so severely that hybrid seed production is now the industry standard specifically to avoid this depression. This makes carrot the crop showing the highest inbreeding depression among the options.
Inbreeding depression is severe mainly in naturally cross-pollinated (outcrossing) crops, because they carry a heavy load of hidden recessive alleles that selfing exposes. Lettuce and pea are both predominantly self-pollinating crops that are effectively "selfed" generation after generation already, so forcing self-pollination changes little and depression stays minimal. Spine gourd is dioecious and outcrossing, but it is less classically cited for this effect than carrot. Carrot, by contrast, is an obligate cross-pollinator with protandrous flowers, and forced selfing collapses its vigour and yield so severely that hybrid seed production is now the industry standard specifically to avoid this depression. This makes carrot the crop showing the highest inbreeding depression among the options.
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