Heterosis UPSC NOTE

 What is heterosis

  • Heterosis, also known as hybrid vigor, refers to the phenomenon where the offspring (hybrid) of two different individuals exhibits superior characteristics compared to its parents in one or more aspects.

  • It's like having the "best of both worlds" from the parents, leading to enhanced traits like:

  • Increased size and growth rate.

  • Higher yield: This is important for crop production, leading to more fruits, vegetables, or grains.

  • Improved disease resistance: The hybrid might be better at fighting off infections compared to its parents.

  • Greater stress tolerance: This could involve resistance to drought, heat, or other environmental challenges.

  • Enhanced fertility: This can be beneficial for both plants and animals.

  • Dominance: Sometimes, one parent has "good" genes that mask the "bad" genes of the other parent, leading to a positive outcome in the offspring.

  • Overdominance: In some cases, the hybrid gets a beneficial effect from having different versions of the same gene from each parent, rather than just inheriting one dominant version.

  • Complementation: Different genes from each parent might work together to produce a better outcome than either parent could achieve alone.

Applications of heterosis

  • Agriculture: This is where heterosis is most widely used, with farmers cultivating hybrid crops for better yields and disease resistance.

  • Animal breeding: Crossing different breeds of animals can lead to offspring with improved meat production, milk yield, or disease resistance.

  • Aquaculture: Selective breeding of fish can also benefit from heterosis, leading to faster growth and higher survival rates.

Cabbage basic details

  • Cabbage (Brassica oleracea var capitata) is a small, leafy biennial producing a compact globular mass of smooth or crincled leaves wrapped over each other known as head

  • The outer leaves are generally larger than the inner. 

  • The stem is short and stout. 

  • Plants flower generally after winter.

  • The males of plants as diverse as cabbage, cauliflower, broccoli, tomato, and rice can be made sterile by deleting a very small part of their genome’s DNA

  • This is the take-home message of a paper published in the journal Nature Communications in October by researchers at the State Key Laboratory of Vegetable Biobreeding of the Chinese Academy of Agricultural Sciences, Beijing.

  • The simple deletion resulting in such a drastic outcome brings to mind the story of a kingdom that was lost for want of a horseshoe nail. 

  • But here, instead of loss, the researchers assure us of a gain: that the deletion could lead to an abundant harvest of these plants, thanks to a process called heterosis.

Plant that couldn’t make pollen

  • Round 44 years ago, people found a cabbage plant that contained a natural mutation

  • As a result of this mutation, they found that the plant had lost the ability to make pollen.

  • At first, scientists didn’t know which particular gene in the plant had been mutated

  • They only named the altered gene, whichever it was, Ms-cd1.

  • The mutation’s effect was to make the plant male-sterile, but they had no other defects

  • In fact, the eggs of the mutant plant could be fertilised by pollen from a normal plant, and the fertilised eggs would go on to make normal seeds.

  • In other words, all the seeds from the mutant plants were the result of the plants’ eggs being fertilised by pollen from plants of other strains – a process called out-crossing

  • None of their seeds came from self-crossing. (In a self-cross, an egg is fertilised by pollen of the same strain.)

  • Out-cross seeds – which are also called hybrid seeds – germinate to produce more robust plants than self-cross seeds

  • This is because of a phenomenon called hybrid vigour or, in technical terms, heterosis.



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Learnerz IAS | Concept oriented UPSC Classes in Malayalam: Heterosis UPSC NOTE
Heterosis UPSC NOTE
Learnerz IAS | Concept oriented UPSC Classes in Malayalam
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