Q.What is bagging technique? How is it useful in a plant breeding programme?
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Let’s begin with something you already know from everyday life.
Imagine you have to make a very important decision — say, which college course to pick. You could ask one friend for advice. But that one friend might be biased (they love their own subject) or misinformed (they heard something wrong). So instead, you ask ten different people — teachers, seniors, parents, counsellors — and then take a majority vote or an average of their opinions. That collective decision is almost always more reliable than any single person’s advice.
That is the core intuition behind Bagging.
What Bagging Does
In data analysis and machine learning, Bagging stands for Bootstrap Aggregating. It is a technique used to make a prediction model more stable and accurate.
Here is the precise meaning: instead of building one single model (like one decision tree or one rule-based classifier) on the entire dataset, you create many slightly different versions of the same model, each trained on a different random sample of the original data. Then you combine all their outputs — usually by taking a majority vote (for classification) or an average (for prediction).
The key word is Bootstrap. A bootstrap sample is created by randomly picking data points from the original dataset with replacement — meaning the same data point can be picked more than once in a single sample, and some points may be left out. Each sample is different, so each model sees a slightly different view of the world.
Why It Matters
The main utility of Bagging is reducing variance — that is, reducing the model’s tendency to change wildly if you give it a slightly different set of data.
Think of it this way: a single model can be “nervous” — it might overreact to a few unusual data points (outliers) or to random noise in the data. But when you average the opinions of many such models, their individual nervousness cancels out. The combined model becomes calm, stable, and more accurate.
Bagging works best when the individual models are unstable — meaning they change a lot with small changes in the training data. Decision trees are a classic example. Bagging turns a shaky tree into a robust forest.
Key Points to Remember (for exams)
- Purpose: To improve accuracy and stability by combining multiple models.
- How it works: Create many random samples (with replacement) from the original data. Train a separate model on each sample. Combine their predictions.
- Why it helps: Reduces overfitting (the model memorising noise) and lowers variance.
- Trade-off: It does not reduce bias much — if the individual model is fundamentally weak, bagging won’t fix that. It only makes a good model more reliable. …
After a flower is emasculated for a planned cross, its stigma must be protected from unwanted pollen until the desired hand-pollination is carried out. …
Bagging protects an emasculated flower from unwanted/foreign pollen until the desired hand-pollination is carried out, which is essential to guarantee a controlled, planned cross.
In artificial hybridization (crossing) programmes in plant breeding, when a bisexual flower is used as the female parent, its anthers must first be removed while still in the bud stage (a process called emasculation) to prevent self-pollination. After emasculation, the emasculated flower is covered with a bag, usually made of butter paper, so that its stigma is not contaminated by unwanted/foreign pollen carried by wind, insects, or other agents — this is called bagging.
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- CBSE 2026Set ANNUAL2 marksQ.Some flowers selected for artificial hybridisation do not require emasculation but bagging is essential for them. Give reason.
›Reveal solutionSolution
Emasculation (removal of anthers) is done only to prevent self-pollination in bisexual flowers; if the selected flower is already unisexual (female, with no anthers of its own), emasculation is unnecessary, but bagging is still essential to stop unwanted foreign pollen from reaching the stigma before the desired artificial cross-pollination is carried out.
In artificial hybridisation (controlled cross-pollination) using bisexual flowers, breeders must first remove the anthers of the flower selected as the female parent while they are still immature (a process called emasculation), so that the flower cannot self-pollinate. The emasculated flower is then covered with a bag (bagging) so that unwanted/foreign pollen carried by insects, wind, etc. does not contaminate the stigma; only the desired pollen is dusted onto the stigma later, and the flower is bagged again till the fruit develops.
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- CBSE 2020Set 57/3/12 marksQ.Name and explain the technique that can be used in developing improved crop varieties in plants bearing female flowers only.(OR)When are the non-flowering plants said to be homothallic and monoecious; and heterothallic and dioecious ? Give an example of each.
›Reveal solutionSolution
Part (a): For plants bearing only female flowers, improved varieties are raised by artificial hybridisation using the bagging technique — hand-dusting selected pollen on the stigma and bagging the flower.
Part (b): A non-flowering plant is homothallic/monoecious when both sex organs are on the same plant (e.g. Funaria) and heterothallic/dioecious when they are on separate plants (e.g. Marchantia).
Part (a)
Developing improved varieties in plants that bear only female flowers
When a plant bears only female (pistillate) flowers, natural self-pollination is impossible, so the breeder must supply pollen and control the cross. The technique used is artificial hybridisation, carried out with the bagging technique.
Steps of the technique
- Selection of parents. Choose the female-flowered plant with good maternal traits (e.g. fruit quality) and a male parent carrying the desired trait (e.g. disease resistance).
- Pollen collection. Collect mature, viable pollen from the anthers of the selected male parent.
- Artificial (hand) pollination. Dust the collected pollen onto the receptive stigma of the female flower with a clean brush. Emasculation is not required, because the female-only plant has no anthers of its own to remove.
- Bagging. Immediately cover the pollinated flower with a butter-paper bag. Bagging prevents contamination by unwanted pollen from the air or insects, so that fertilisation occurs only by the chosen pollen — this is the essence of the bagging technique.
- Raising the new variety. Allow fruit and seed to develop, grow the progeny, select the superior recombinants, and multiply them as an improved variety. …
- CBSE 2019Set ANNUAL2 marksQ.What is bagging technique? How is it useful in a plant breeding programme?
›Reveal solutionSolution
Bagging protects an emasculated flower from unwanted/foreign pollen until the desired hand-pollination is carried out, which is essential to guarantee a controlled, planned cross.
In artificial hybridization (crossing) programmes in plant breeding, when a bisexual flower is used as the female parent, its anthers must first be removed while still in the bud stage (a process called emasculation) to prevent self-pollination. After emasculation, the emasculated flower is covered with a bag, usually made of butter paper, so that its stigma is not contaminated by unwanted/foreign pollen carried by wind, insects, or other agents — this is called bagging.
…
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